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#736544 - 07/10/09 02:40 AM Old Amp I Found On craigslist  
Joined: Aug 2004
Posts: 988
Tony Whitehead Offline
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Tony Whitehead  Offline
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Louisville Ky
This is my first tube amp. I bought this thing off my local craigslist. It's a c 1960 or so all tube, dual chassis, point to point, hand wired, yada yada. This model was designed to use with an accordion, but has Guitar and Instrument inputs as well. 1x15" and 2x8" speakers. That speaker configuration, and the "stereophonic" accordion inputs are what designates it as an accordion amp. But the Guitar and Inst. inputs have gain pots, and it sounds fine with both electric and acoustic guitars. Crank the guitar gain knob and hit it with a high output humbucker, and it get's real nasty in a good way. The EL84 power tubes it has in it are suited for guitar amps from what I gather. I managed to find the schematics, and the amp originally had 8417 power tubes. From what I've gathered from searching the net, the switch to EL84's requires a mod. I have to believe the tech did well, because the amp sounds pretty good, despite the 8's missing from it. It appears to have had a good servicing recently. New caps and some wiring.

Anyhow, I saw the ad, called, and figured for 225.00, I'd take a chance on it instead of buying one of the Chinese 5 watt tube amps that sell for the same or more. It just looks so dang Retro cool. The splatter design on the grill - even has it on the back, the vintage corner guards, and the features galore. And the "side-throw" 8's. Like a built in stage monitor ? grin

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

Pre amp bottom

[Linked Image]

Pre amp tube-side

[Linked Image]



EDIT: The power tubes are el34's, not el84's


Last edited by Tony Whitehead; 08/26/09 04:53 AM.
#736555 - 07/10/09 03:16 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
Joined: Aug 2004
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Tony Whitehead Offline
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Tony Whitehead  Offline
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Louisville Ky
So, my questions at this point are :

- since the speaker output is an RCA, can I use an RCA to 1/4" female adapter, thus enabling me to run a guitar or even a bass cabinet ?

- if I can, then how do I determine what load this amp wants to see ? 8 ohm, 4 ohm ? Is this something I have to let a tech determine, or can I do it myself with the right meter and instruments/tools ?

btw, I know this amp can kill me if I go "poking around" in it wink

- I realize there is an extension cab output, but to run a bass cab, I'd need to disconnect the internal speaker. I don't think that old alnico 15" would last long in an open back cab being hit with a bass. Also, I'd just like to know if I can run an extension guitar cab without the internal 15. The extension output doesn't disengage the internal speakers on this amp.

Until I find the proper specs 8's to restore the original configuration, I'm concerned that using the extension output may not be a good idea. I'm not sure if the missing 8's are causing an impedance issue yet. If the 8's were gone before it was last serviced, I'm sure the tech would have dealt with it. But if the 8's were removed after it was last serviced, impedance may be an issue. I just don't want to hurt the amp, and the seller didn't know who serviced it last.

I'm just eager to hear it drive the right cab to get an idea of what it's capable of. Until I get the 8's back in it, I'm settling for a poorly suited cab to run the 15". open back/open side cabs probably don't quite cut it lol.

So, someone who knows, did these old amps have a standard minimum load range ?

It sounds good anyway, and the warm overdrive and breakup it has should really shine with the right cab.




Last edited by Tony Whitehead; 07/10/09 03:29 AM.
#736567 - 07/10/09 04:38 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
Joined: Feb 2004
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Jerry Jakala Offline
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Jerry Jakala  Offline
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Check out the web site below to get schematics etc for your Sano amp.

www.musicparts.com



http://www.jerryjakala.com
http://cdbaby.com/cd/jakalajerry2

The difference between genius and stupidity is that there is a limit on genius.-Albert Einstein
#736575 - 07/10/09 05:22 AM Re: Old Amp I Found On craigslist [Re: Jerry Jakala]  
Joined: Aug 2004
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Tony Whitehead Offline
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Tony Whitehead  Offline
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Louisville Ky
Originally Posted by Jerry Jakala
Check out the web site below to get schematics etc for your Sano amp.

www.musicparts.com



Thanks Jerry. I found the schematics for it already. I can read them well enough to tell they are the right ones for my amp. That's about as far as I can go with them though. I'm new to the electronics stuff, but I'm learning a lot. I think I've ID'd the 15. I think it's a Misco. The numbers and letters on the speaker are faded and tough to read. Even when zooming in on hi res macro photos of them. It's alnico though, and works fine smile


#736591 - 07/10/09 08:25 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Colin Ward Offline
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Has the ungrounded cord been replaced with a three wire, three prong cord and plug? Has the death cap been removed and the polarity switch disabled? Those are pretty important safety modifications.

Fender amps from that era were very forgiving relative to speaker impedance. If you plug in an extension speaker to my twin reverb, it simply adds the load to the built in speakers. Hasn't hurt it so far and it's 40 years old! The RCA connector is just a two wire connector, as is a 1/4" phone plug. You could make a converter pigtail or replace the RCA socket with a 1/4". The design speaker impedance should be on the schematic alongside the output transformer. If you add an external speaker, use speaker wire to connect it, not a guitar cable which will have the wrong impedance and therefore sound bad and possibly damage the amp.

I don't know how many EL84s are in it but you will get about 7 watts of output per EL84. My guess is it should be pretty loud!

Old Ampeg guitar amps had a second input marked accordion. They had a larger input resistor on the accordion input for slightly less gain but otherwise were the same, if memory serves.

I have a book called the Guitar Amp Handbook by Dave Hunter which I recommend.

Have fun!

PS - I just recorded an instrumental ditty on my recently acquired 1967 Gibson Skylark after I replaced the filter caps. It's cranked and dirty.

Skylark



Colin

I try to critique as if you mean business.....

http://colinwardmusic.com/

http://rosewoodcreekband.com/


#736626 - 07/10/09 10:59 AM Re: Old Amp I Found On craigslist [Re: Colin Ward]  
Joined: May 2001
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Ray E. Strode Online content
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Ray E. Strode  Online Content
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Hi Tony,
I looked in my tube substitution list but can't find a listing for the 8417 tubes. The EL-84 output tubes will put out about 12 watts in a two tube push-pull configuration. The EL-84 tubes are the equivelent of RCA 6BQ5 tubes. There are only a small list of power tubes that are used in guitar amps.

If you want to do a basic check of the speaker impedenance you can use an OHM Meter that you can purchase at Radio Shack for not much money. Just unplug a speaker wire and measure the resistance. There most likely is an impedenance matching transformer already in the amp that matches the extra speakers for the correct impedenance that you have.

Some amps will have the option of switching a wire to match the speaker impedenance of a different speaker setup.

Substuting a speaker of a different impedenance than what the amp calls for will not make much difference as long as the speaker is sturdy enough to handle the output of the amp.


Ray E. Strode
#736703 - 07/10/09 05:45 PM Re: Old Amp I Found On craigslist [Re: Colin Ward]  
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Tony Whitehead Offline
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Tony Whitehead  Offline
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Louisville Ky
Originally Posted by Colin Ward
Has the ungrounded cord been replaced with a three wire, three prong cord and plug? Has the death cap been removed and the polarity switch disabled? Those are pretty important safety modifications.

Hi Colin, thanks for taking time to offer some info. Yes, it's been updated to a 3 prong cord. As far as the cap, I'm not sure. The polarity switch doesn't have any audible effect when I switch it back and forth, so it may have been disconnected.

Quote

Fender amps from that era were very forgiving relative to speaker impedance. If you plug in an extension speaker to my twin reverb, it simply adds the load to the built in speakers. Hasn't hurt it so far and it's 40 years old! The RCA connector is just a two wire connector, as is a 1/4" phone plug. You could make a converter pigtail or replace the RCA socket with a 1/4". The design speaker impedance should be on the schematic alongside the output transformer. If you add an external speaker, use speaker wire to connect it, not a guitar cable which will have the wrong impedance and therefore sound bad and possibly damage the amp.

I don't know how many EL84s are in it but you will get about 7 watts of output per EL84. My guess is it should be pretty loud!

Old Ampeg guitar amps had a second input marked accordion. They had a larger input resistor on the accordion input for slightly less gain but otherwise were the same, if memory serves.

I have a book called the Guitar Amp Handbook by Dave Hunter which I recommend.

Have fun!

PS - I just recorded an instrumental ditty on my recently acquired 1967 Gibson Skylark after I replaced the filter caps. It's cranked and dirty.

Skylark



The schematics don't have impedance info that I can tell, but I may be missing it. It's loud alright. I've got speaker cables to use with the extension cabs though.

The stereophonic inputs on this one are for accordion. As far as wattage, I don't understand enough electronics theory yet, but the guy I got it from said it does 50 watts. A guy at a local shop told me the 2 EL84's should give an honest 35 watts total, but he was guessing. I didn't have the amp with me. There are 10 tubes total in the amp.

The Skylark sounds good. Gotta love that tremolo smile I still have to get a foot switch to use the tremelo on my amp. It works if I plug into the stereophonic input, but that jack is a TRS and I'm not getting the reverb yet. I won't know if the reverb even works until I get a footswitch. As you mentioned, that input has less gain than the guitar and instrument ins.

I can get a similar dirty tone as with your Skylark, It will get dirtier as well.

As soon as I find an extension cab, I'll know more. I do have 8 ohm(2x10) and 4 ohm(2x12) bass cabs. I'm curious to see how it sounds with a bass. Both cabs are 500 watt cabs.

#736705 - 07/10/09 05:58 PM Re: Old Amp I Found On craigslist [Re: Ray E. Strode]  
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Tony Whitehead Offline
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Tony Whitehead  Offline
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Joined: Aug 2004
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Louisville Ky
Originally Posted by Ray E. Strode
Hi Tony,
I looked in my tube substitution list but can't find a listing for the 8417 tubes. The EL-84 output tubes will put out about 12 watts in a two tube push-pull configuration. The EL-84 tubes are the equivelent of RCA 6BQ5 tubes. There are only a small list of power tubes that are used in guitar amps.

If you want to do a basic check of the speaker impedenance you can use an OHM Meter that you can purchase at Radio Shack for not much money. Just unplug a speaker wire and measure the resistance. There most likely is an impedenance matching transformer already in the amp that matches the extra speakers for the correct impedenance that you have.

Some amps will have the option of switching a wire to match the speaker impedenance of a different speaker setup.

Substuting a speaker of a different impedenance than what the amp calls for will not make much difference as long as the speaker is sturdy enough to handle the output of the amp.


Hi Ray, I assume the impedance matching transformer you mentioned would be part of the extension cab circuit ? That would make sense.

I'll do as you say and get a meter and check the speaker.

So am I right to assume that "minimum load" is the crucial thing ? In other words my bass head says 4 ohm minimum. So 4 or 8 is ok, but not 2 ohms, right ?

As far as switching to the EL84's, I remember seeing some info mentioning what modifications are needed. At any rate, it's been done, and they sound pretty good to my ears.

Thanks for the info smile

#736720 - 07/10/09 06:59 PM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
Joined: May 2001
Posts: 7,072
Ray E. Strode Online content
Top 30 Poster
Ray E. Strode  Online Content
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Posts: 7,072
Brunswick, Ga. USA
Hi Tony,
The tube information is right out of my RCA TUBE Manual. True you shouldn't use lessor Ohm Speakers. They used to make 4, 8 and 16 Ohm Speakers. I think 2 Ohm Speakers may be a later invention. The Polarity Switch on the Amp is used (I Think) to adjust for hum if you hear any from the amp due to electricial current from the electric company. That is probably not much of a problem today as the system is much improved.

If everything sounds good I wouldn't do anything else. From the pictures, it looks like it has a full wave tube rectifier. In later amps solid state diodes were used. It also looks like some of the filter caps have been replaced, the blue caps in the picture. Have fun!


Last edited by Ray E. Strode; 07/10/09 07:00 PM.

Ray E. Strode
#736740 - 07/10/09 07:37 PM Re: Old Amp I Found On craigslist [Re: Ray E. Strode]  
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Minneapolis
Tony, that's a marvelous score! I poked around and found more info, and it sounds like you'll nail one of my favorite amp sounds, the Ampeg Reverberocket:

http://www.myrareguitars.com/robergesano.html

And here's another cool link by someone else who just scored a Sano, a New Jersey Company. Does yours have old Telefunken tubes??

http://www.gearslutz.com/board/inst...ano-guitar-accordian-tube-amplifier.html

Quote
- since the speaker output is an RCA, can I use an RCA to 1/4" female adapter, thus enabling me to run a guitar or even a bass cabinet ?
But your picture shows a 1/4 inch External Speaker jack...so wouldn't it just be standard 1/4 inch to 1/4 inch...as in a guitar cord?

#736870 - 07/11/09 04:37 AM Re: Old Amp I Found On craigslist [Re: Mark Kaufman]  
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Tony Whitehead Offline
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Tony Whitehead  Offline
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Joined: Aug 2004
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Louisville Ky
Originally Posted by Mark Kaufman
Tony, that's a marvelous score! I poked around and found more info, and it sounds like you'll nail one of my favorite amp sounds, the Ampeg Reverberocket:

http://www.myrareguitars.com/robergesano.html

And here's another cool link by someone else who just scored a Sano, a New Jersey Company. Does yours have old Telefunken tubes??

http://www.gearslutz.com/board/inst...ano-guitar-accordian-tube-amplifier.html

Quote
- since the speaker output is an RCA, can I use an RCA to 1/4" female adapter, thus enabling me to run a guitar or even a bass cabinet ?
But your picture shows a 1/4 inch External Speaker jack...so wouldn't it just be standard 1/4 inch to 1/4 inch...as in a guitar cord?


Hey Mark, thanks. The model the other guy has is a later one from what I gather. Thanks for posting the link, it looks like it has the same 15, so mine probably had the same 8's as his. Plus I can see how the 8's were wired. Cool.

Mine still has the mounting hardware and that cap for the 8's

[Linked Image]

Mine doesn't have all the original tubes.
The extension speaker out works, but I'm talking about the output to the internal speakers having an RCA jack.

[Linked Image]

I want to hear it push a bass cab and also a guitar cab sans the 15. The extension cab jack doesn't disengage the internal speakers.

They made a lot of models. The LJM site has a slide show. Hit replay at the end to see the second batch.
http://www.flickr.com/photos/11903466@N08/sets/72157604662830084/show/with/2432572781/


#737091 - 07/11/09 11:37 PM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Andy K Online content
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Andy K  Online Content
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I think those are EL34 output tubes. EL34s are usually used as replacements for 8417s, which are very rare, even back in the 1960s. EL34s and 8417s have 8 pin plastic bases, called octal bases, while EL84s have 9 pin glass bases and are much smaller, though still taller than 12AX7As, another common 9 pin glass tube. EL34s would put out at least 35W. EL34s can also handle the extra high voltages (over 600V) that many 8417 amps have. EL84s can't handle much more than about 350V (only rated for 300V).

I presently own a couple EL34 and EL84 powered amps. One EL34 amp is 50W, the other is 80W. The 80W amp (a modified McGohan PA amp) was originally designed to use 8417s but I modified it to use EL34s since I had them around, haven't had any 8417s since the 1980s, and didn't want to pay hundreds of dollars for some 8417s. With 8417s, the amp was rated at 100Wrms.

My three EL84 amps are about 17W, 15W, and 5W, with the 5W amp only using a single EL84 output tube and being pure class A.

The schematic may be at http://www.schematicheaven.com/bargainbin.htm. I suspect it is a 30/50WRT. You should be able to find a model number somewhere on the chassis.

If it is a 30/50WRT, it looks like the highest voltage is 500V. The schematic doesn't give the output impedance. It is possible to determine the output impedance by measuring the turns ratio of the transformer and dividing that ratio into the ideal 8417 output tube plate load impedance as listed in a tube data book (somewhere between 2800 and 4200 ohms in my RCA tube data book). This is not a simple thing to measure without frying something and not recommended for the novice (though I do it often, but I'm an electronics engineer).

Note that EL34s work best at around 6500 ohms plate load impedance, about twice what 8417s like. So you would want the speaker load on this amp to have twice the impedance that you would use for 8417s. In other words, if the amp was originally designed to drive a 4 ohm speaker load with 8417s in it, you should hook up an 8 ohm speaker load when using EL34s.

You could assume that the person who originally modified the amp knew what he was doing and purposely disconnected the 8 inch speakers to double the speaker load impedance so that it was better matched to the EL34 tubes. If so, just measure the 15 inch speaker resistance with an ohmmeter. That measurement will be a little less than the actual impedance. For example, if you measure the 15 inch speaker to be about 6 to 8 ohms, then it is an 8 ohms speaker. Then just disconnect the 15 inch speaker and hook up the same impedance external speaker to the same leads.


Stone Marmot
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Check out our latest song, "Black Hole Jezebel"
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#737252 - 07/12/09 12:33 PM Re: Old Amp I Found On craigslist [Re: Andy K]  
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Well Andy,
When I looked at the pictures I though the output tubes looked more like EL-34's as the EL-84 is a minature size tube. Assuming the output tubes are EL-34's this puts a whole new light on the subject. The EL-34/circa 6CA7 tube has a maximum plate dissapation of 25 watts and I think about 40 plus watts in a 2 tube configuration. The EL-34 also requires the supressor grid bias to be set for maximum efficency via a pot in the power supply circut. I think in all other power tubes the supressor grid is tied to ground. The output transformer may have taps to match different impedenance speakers.


Ray E. Strode
#737444 - 07/13/09 12:23 AM Re: Old Amp I Found On craigslist [Re: Ray E. Strode]  
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Thanks Andy. Yes, they are el34's. Sorry, I should have looked harder before I posted.

Good info, and lot's to take in there. This stuff is fascinating. I'm coming across some pretty cool info, both as offered here by all, and via google.

I just found out yesterday a guy who I'll be collaborating with on an Americana project, also happens to be an amp tech, and he's eager to check it out. I'll post an update when he's had time to do so.

Thanks again, I'm saving all the info you guys have offered. I may have to take some electronics courses and dig into this stuff. smile

#737450 - 07/13/09 12:43 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Hi Ray, sorry about mis-naming the power tubes and wasting your time looking for info. I should have made sure first.

Anyhow I appreciate the info, including what you added to Andy's post. I'm having a tech look at it soon.


#737530 - 07/13/09 11:18 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Ray, with proper design, you can get more than twice the power out of an amp as the rating of the output tubes. For example, most Marshalls with two EL34s in them are rated at 50 Wrms but usually measure closer to 70 Wrms. The RCA data book also says the maximum plate dissipation for the 8417 is 35 W, but one of the design examples in the same data sheet has a 100 Wrms rating for a two tube class AB amplifier using this tube.

Remember, the maximum theoretical efficiency for a class B amp is 78.5%. So two tubes with a maximum plate dissipation of 25 W should be able to theoretically put out:

2 x 25 W / (1 - 0.785) = 232.5 Wpeak,

or about 116 Wrms. Of course, in the real world, it would be very difficult to get this theoretical maximum efficiency. But 80 W out of two EL34s is not unreasonable. Remember, the tubes aren't dissipating ALL the amplifier power, just the power that is not going to the load, i.e., the waste power (the inefficiency).


Stone Marmot
nouveau retro pop-rock music
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Check out our latest song, "Black Hole Jezebel"
Video at Black Hole Jezebel
#737555 - 07/13/09 12:45 PM Re: Old Amp I Found On craigslist [Re: Andy K]  
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Well Andy it's been a while,
Tha maxium you can put thru a tube measured at RMS and peak are two different things. This is usually measured at a percent of distortion. Stated in the RCA Tube Manual the maximum plate dissipation for the EL-34/6CA7 running 800 volts is 25 watts per tube at 5.1 percent total harmonic distortion.

A typical 2 tube push pull configuration with 450 volts on the plate puts out 40 watts maximum. So the amp Tony has is most likely a 40 watt amp. Disregarding a peak of power with increased distortion. The max power an amp can produce is limited by the Power Supply and the associated components.

Tube designs are probably designed to give a good margin for longivity.

The Marshall's you mention are probably overly optimistic in their power ratings.

The RCA Tube Manual I have gives actual ratings for the tubes and a typicial useage.

The intresting thing is that they are still making Guitar Tube Amps brand new. I had a Traynor 85 watt amp at one time, the equivelent of a Fender 65 Twin Reverb. That Fender is now selling for about $1400.00. Ouch!


Ray E. Strode
#737627 - 07/13/09 05:58 PM Re: Old Amp I Found On craigslist [Re: Ray E. Strode]  
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I think a lot of players are going for tube amps these days.

Musicians Friend has more tube combos listed than solid state right now. 193 to 187. That surprised me.

#738757 - 07/17/09 10:48 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Ray, you are right that Tony's amp probably puts out only about 40 Wrms max due to its low plate supply voltage. The amp I have that measures at over 80 Wrms has over 600 Vdc plate supply.

The Marshall data was measured by a number of people. Marshall back in the 1960's and 1970's, like Ampeg, tended to be rather conservative in their advertised power ratings.


Stone Marmot
nouveau retro pop-rock music
www.stonemarmot.com
Check out our latest song, "Black Hole Jezebel"
Video at Black Hole Jezebel
#745098 - 08/14/09 02:46 AM Re: Old Amp I Found On craigslist [Re: Andy K]  
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Can anyone tell by this preamp schematic(pg 2) if the guitar channel is part of the tremolo circuit ?

http://www.schematicheaven.com/bargainbin/sano_30_50_WRT.pdf






#745151 - 08/14/09 11:26 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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There is a Tremelo Circut in the schematic that I assume works with all inputs.


Ray E. Strode
#745154 - 08/14/09 11:40 AM Re: Old Amp I Found On craigslist [Re: Ray E. Strode]  
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I know enough to be dangerous, but I am pretty sure the tremolo should work on all inputs but you may need the footswitch (or a jumper plug) to turn it on.


Colin

I try to critique as if you mean business.....

http://colinwardmusic.com/

http://rosewoodcreekband.com/


#745177 - 08/14/09 01:13 PM Re: Old Amp I Found On craigslist [Re: Colin Ward]  
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Colin you are probably correct. The Scematic, of which I printed out to study it a bit does show the Tremolo Circut going to a Jack. This is most likely for a foot switch. There is also an Echo Device that appears to also be in the Tremelo Circut. The Tremolo appears to work with all inputs as long as it is turned on thru the jack.


Ray E. Strode
#745970 - 08/18/09 02:42 AM Re: Old Amp I Found On craigslist [Re: Ray E. Strode]  
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Ok, thanks guys. The reason I asked, is because the tech who has the amp thought the guitar and instrument channels didn't utilize the tremolo and reverb. But he was looking at the schematic I gave him, which was very light and hard to read. I told him to check the SH site and he now has a more readable copy.

He now says what you both said, and now he's got to figure out why the foot switch isn't working and allowing the tremolo and reverb to work with those channels. I'm betting the reverb tank is the culprit. It's not the original one, and a tech who happened to walk by at a shop while I was trying to find a footswitch was kind enough to check the reverb tank with his meter. He said the readings were very high for an old tube amp, and suspects the tank is the wrong one for the amp. The tech that has it said he has a few old hammond tanks in storage, so we'll see.

The good news so far is that no harmful mods have been done to the amp as far as he can tell, and he's determined the amp is self biasing. All I need to do when replacing the el34's is put a matched set in it and turn it on.

The last person who worked on it, probably the one who replaced the caps, did some sloppy wiring ans soldering, so he's taking care of that. Also, the control knob on the power amp chassis is the hum balance. He set it and got it quieted down.

Right before I took it to him, I tried pulling the preamp tubes to see if I could track down the hum issue, and I got lucky. The first one I pulled was the CU10. The amp quiet down a lot. He's got a few used ones in stock, so no problem there.

Hopefully I'll have the amp back this week. He's had it almost a month now, but he has a valid excuse. His shop is in his basement and the flood we had a couple of weeks ago left him with a few inches of water down there. Thankfully, my amp wasn't sitting on the floor. And his parts stock are stored high and dry.

#745997 - 08/18/09 09:26 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Hey Tony,
I have been tearing my hair out trying to determine how a Tremelo Circut works. I believe it is a basic oscillator circut that should run all the time and is connected to the output by a foot switch. You can see the Gain and Frequency Pots on the Schematic. If the Hammond Echo Device is a spring that makes the reverb work it should be OK as long as it is not open somewhere.

Not sure what the 2n2497 Transistor does but it is in the Tremelo Circut and could be faulty. The drawing of the 2N2497 may be an early way to draw a transistor. I cold not find a listing for it in my substution guide. If the 12AX7 tube is worknig OK then a capacitor may be open if everything is still wired correctly.

If you are getting hum out of the amp an easy to check it is to turn the volume controls down. If it disappears it is in a circut some where, If it is still there a filter capacitor in the power supply is weak and needs to be changed, maybe all of them.


Ray E. Strode
#746147 - 08/19/09 04:14 AM Re: Old Amp I Found On craigslist [Re: Ray E. Strode]  
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Originally Posted by Ray E. Strode
Hey Tony,
I have been tearing my hair out trying to determine how a Tremelo Circut works. I believe it is a basic oscillator circut that should run all the time and is connected to the output by a foot switch. You can see the Gain and Frequency Pots on the Schematic. If the Hammond Echo Device is a spring that makes the reverb work it should be OK as long as it is not open somewhere.


Hi Ray, the echo device is the spring tank. It's mounted to the side of the cabinet. Left side in this photo...

[Linked Image]

If you look at the schematic, you'll see the rectangular symbol marked ac with an input and and output. That is the tank. The schematic is labeled "echo device ", I think, because that is where the reverb control is. You should see the 500 k pot on the schematic. And just as we see in the photo in my first post, the reverb control is right next to the foot switch jack, same as the schematic. The black wire plugged into the tank is the input, and the gray one is the output. The gray wire goes to the "canon connector" marked on the schematic. That is the stereophonic accordion input with the pins.

[Linked Image]

The pot to the left is the reverb control. Above that pot in the photo is the stereophonic accordion TRS input. And to the right of that, you can see the foot switch input.

The yellow wire on the cannon connector goes to the guitar input in this photo. It's the one coming from the top of the photo, and it's emerging from where it's tucked under the accordion TRS input. I had a cable plugged in the guitar input when the photo was taken. The yellow wire coming off the guitar input goes to the instrument input, which can't be seen in this photo. I can't read the schematic well enough to be sure, but the reverb tank output wiring is going to that connector, and wiring is going to the guitar and instrument inputs from that connector. The yellow wire does not look like the original wire, it looks newer.

[Linked Image]

Quote


Not sure what the 2n2497 Transistor does but it is in the Tremelo Circut and could be faulty. The drawing of the 2N2497 may be an early way to draw a transistor. I cold not find a listing for it in my substution guide. If the 12AX7 tube is worknig OK then a capacitor may be open if everything is still wired correctly.

The tremolo works fine if I use the stereophonic TRS input, so the problem may be elsewhere.

Quote


If you are getting hum out of the amp an easy to check it is to turn the volume controls down. If it disappears it is in a circut some where, If it is still there a filter capacitor in the power supply is weak and needs to be changed, maybe all of them.


Turning the volume down quieted the hum. The tech said the control knob on the power amp chassis was a hum control, and he has is set now where it should be. I did try to see if I could find a preamp tube causing the hum by pulling them one by one. The first one I pulled was the CU10, and the amp quieted down a lot. The tech knows this, and has CU10's in stock, so he'll see if it was the tube itself. Also, the reverb could be heard very faintly if I plugged into the accordion input, but after I pulled that tube, I couldn't hear it.

I'm banking on the reverb tank or at least the reverb circuit being the culprit. A tech I bumped into at a shop where I was trying to find a footswitch was curious about the amp and he checked the input and output of the tank. He thought the input reading on his meter was quite high, but added that didn't mean it wasn't the right one or it was faulty. He just wasn't familiar with Sano amps. He'd never seen one.

At any rate, the tech that has it will figure it out hopefully. I'm going nuts waiting to get it back, because I've acquired a couple of strats, and I'm stuck using a Crate acoustic amp in the mean time. I've also acquired a Barber Launch Pad which is a sort of "swiss army knife" type pedal. It does several things.
- clean boost
- a/b box
- corrects phase issues when driving parallel channels on an amp at the same time
- buffer to put at the end of a pedalboard
- it can "cook" the amp, which is something I don't have a grasp on yet, but info is on the Barber site forum.
- can be used to add channel switching capability to an amp with two channels that was built before channel switching was a feature of amps

As soon as the amp is healthy I should be able to use it for anything from clean country twang to dirty overdrive. I'm not a heavy metal/ distortion player, but I did try a Barber high gain distortion pedal with it, and even with the issues the amp had before I shopped it, it sounded like a Marshall stack lol.

I'm going to have some fun with it for sure.

#746190 - 08/19/09 10:57 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Hey Tony,
I found out what the 2N2497 Transistor is. It is a FET Transistor. It is the Equivalent to a Sylvania ECG 326 in case it is defective. One problem with this schematic is it doesn't identify each tube. Usually there is a V number for each tube on the Schematic. It shouldn't be too hard to fix anything that is wrong with the Amp. If some Plate Voltage on a tube is reading high, say 500 Volts, as that is what is coming out of the Power supply, off the 5U4 tube, then something is most likely open and needs to be replaced.


Ray E. Strode
#746273 - 08/19/09 05:45 PM Re: Old Amp I Found On craigslist [Re: Ray E. Strode]  
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Originally Posted by Ray E. Strode
Hey Tony,
I found out what the 2N2497 Transistor is. It is a FET Transistor. It is the Equivalent to a Sylvania ECG 326 in case it is defective. One problem with this schematic is it doesn't identify each tube. Usually there is a V number for each tube on the Schematic. It shouldn't be too hard to fix anything that is wrong with the Amp. If some Plate Voltage on a tube is reading high, say 500 Volts, as that is what is coming out of the Power supply, off the 5U4 tube, then something is most likely open and needs to be replaced.


Ok, thanks Ray. I'll just email him a link to this thread in case he's having trouble tracking down the problem. There is some good info offered here by everyone.

I'll post an update after he's done with it.

#747559 - 08/26/09 04:56 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Got it back !

-The "stereophonic" channel, which is a TRS jack, works fine with a mono guitar cable, and the reverb, while not up to par with the Fender reverb works fine. The tremolo is very nice though. No volume control for that channel. It's clean as can be. I'll know more when I get a stereo instrument cable and plug my strat into an old Zoom 404 w/stereo out. The 404 is an acoustic pedal, but two of the 6 banks are for electric guitar. I imagine that channel will work fine for my Gibson jumbo run through the Zoom as well.

- Guitar channel is hot ! If I dime the volume/gain on that channel, I can get a great lower gain OD, and with the main volume at 1 or 2, I get a very nice lower volume OD tone. With the main volume at about 6, forget it. It's a Marshall killer. I had a blast holding the Squire CV in it's face lol. I'll put it up against any stock Marshall combo. Cleans up well by rolling back the volume on the guitar, and does it without that much difference in volume.

- Instrument channel isn't as hot gain-wise, but sounds very good clean or dime'd.


And it's going to get better. As much as I'm digging this amp, all of this great tone I'm finding is coming through a totally screwed up cabinet configuration. The amp has an old Eminence 15, and did have two 8's in it, mounted on the side. The 8's are gone, so I'm basically running a 15 in an open back/open side cab. Definitely not an ideal configuration. Until I find original specs 8's to put back in it, I'm going to cover the holes with something, and today, I'm buying an extension cab. Just sealing off the 8's holes should improve the sound, but that and an extension cab should really let this amp do it's magic. I'll also disconnect the internal 15, and run the extension cab off the power amp output and see how that sounds. That may be the way to go if it sounds great, and will free the tubes of being tortured by the cab resonance coming from the 15. We'll see.

The only shortcoming of the amp is the bass and treble controls. Lack of midrange without rolling the bass way back. Then I'm loosing a tad too much low end. No problem though, I can get a Barber Barb EQ if need be. But first I'm going to deal with the speaker issue. The right extension cab might bring the mids to the mix.

Anyhow, I'm very excited, and the tech did a good job. It sounds better than it did when I dropped it off, and it only cost me 35 bucks and a pizza lol. He said 50, but he knows I run pizzas for Papa Johns, and said 35 and a pizza would work. (I work a mile from his house, so he got it steamin hot )

As soon as I get everything lined out, I'll record some clips. I've got to figure out how to use this Zoom H2 gizmo I bought.

#748152 - 08/28/09 10:20 PM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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That is very cool!

#753969 - 09/22/09 12:05 AM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Tony... what did the tech tell you about the output ohms coming from the EL34 setup. Is it 8 ohms?

I've had one of the same amps kicking around my house for ten years.

I've had a couple techs do some bad work on it.. one removed the capacitor from the 8's and then loaded a the wrong speaker ohms into it.. another converted it to the 6L6 tubes but didn't follow thru with all the modifications.

Anyhow.. it's running pretty good now. but I'd like to disconnect the 8's and just run a 15'.. I have an 8ohm 1969 Eminence.

Also what did he say about the external output? What's the ohm output of the external? Is it okay to disconnect the internal speaker and run the external only?? Makes me nervous.. don't want to blow up the output transformer.

thanks - Liam

#760349 - 10/15/09 07:35 AM Re: Old Amp I Found On craigslist [Re: LiamFitz]  
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Originally Posted by Jack Swain
That is very cool!


Thanks Jack, I've been patiently waiting for the right deal on a nice cabinet. I did score an old 90's Sonic 212 cheap which originally had Sonic 16 ohm V30 copies in it. Vertical slant cab in burgundy tolex. I didn't know this when I bought it and the store staff member assumed it was the original 8 ohm cab w/the V30 clones. Much to my delight someone put two 8 ohm Celestion G12L's in it rated at 35 watts each. The cab was wired 16 ohms and I now have them in parallel at 4 ohms. I clipped the neg lead to the internal 8 ohm 15" and just plug the cab into the extension jack.

Originally Posted by LiamFitz
Tony... what did the tech tell you about the output ohms coming from the EL34 setup. Is it 8 ohms?

I've had one of the same amps kicking around my house for ten years.

I've had a couple techs do some bad work on it.. one removed the capacitor from the 8's and then loaded a the wrong speaker ohms into it.. another converted it to the 6L6 tubes but didn't follow thru with all the modifications.

Anyhow.. it's running pretty good now. but I'd like to disconnect the 8's and just run a 15'.. I have an 8ohm 1969 Eminence.

Also what did he say about the external output? What's the ohm output of the external? Is it okay to disconnect the internal speaker and run the external only?? Makes me nervous.. don't want to blow up the output transformer.

thanks - Liam


Hi Liam, mine has El34's in it. According to the schematic, it originally had 8417's. The tech that had it was ok to leave the EL34's in it, so I assume it was modded right. He said the amp is self biasing and that it was fine to run it at 8 ohms or 4 ohms. Mine had a 15 " Eminence 8 ohm in it as well, and the 8's are gone. The external jack is wired parallel to the internal speaker, and since I have a cab with 2 8 ohm 12's, I just wired them parallel and clipped the neg lead going to the internal 15 between the output on the power amp and the speaker. Using the ext jack, I'm showing the amp a 4 ohm load.

On yours, an external 8 ohm cab will give you a 4 ohm load if running both the internal and the cab. Whether that is ok with yours modded for the 6L6's, I can't say.

Perhaps one of the more knowledgeable folks will know. Ray, Colin, Andy ?

#760726 - 10/16/09 12:52 PM Re: Old Amp I Found On craigslist [Re: Tony Whitehead]  
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Speaker Impedenance is determined by the Output Transformer. Some transformers will have taps to match the impedenance of a different speaker. I don't know how the output impedeance is determined. It could be that the average resistance of the output transformer and the speaker is about the same.

It probably won't make much difference if a higher impedenance speaker is used there will just be less volume. If replacing a speaker be sure it is for the corosponding amp and not for a home audio system. Speakers are usually designated as such whereever they are sold.


Ray E. Strode

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