Sho Bud single channel- Cain amplifier advice

[Ron la Villa]

Hello- I'm in the UK and have bought a "Cain" pedal steel amplifier, which I understand is from a short run Kevin, or Kenneth(sorry) Cain made himself, basically a Sho Bud single channel. I have a few questions and would greatly appreciate any advice on restoring it to its' best, original (if possible) condition).It's running at 110volts with a transformer as we're 240v out here.

I want to make it as close to new as possible without altering it's original tone.

1st) the noise floor sounds quite high- I've read that could be caused by one of the RCA transistors needing to be replaced. If this is the case, are there modern equivalents to these RCA transistors that will not change the tone of the amp? is there a specific transistor in the schematic that is usually the culprit?

2)Would changing some of the carbon composite resistors lower the noise floor, (I know this is a topic that can induce nausea, I've tried to read through the opinions on this and I'm aware changing some resistors in specific parts of the signal path could reduce noise floor and some believe it does/ doesn't have an impact on tone) , I guess I'm asking- if you wanted to lower the noise floor and preserve the original tone, what would you do?

3) I understand these were made with JBLD130's, what would be a good equivalent speaker? When I bought it it had an Eminence ME15 300,which weren't made till the mid 1990's, so it's not original, (though weirdly it has an "Eminence" plastic badge nailed to the top of the cabinet as if it were).

4) I want to confirm the reverb pan is the correct one, (I'm using the Sho-bud single channel schematic to try to ascertain the pan hasn't been changed over the years and I'm not great at this. Either the drive or return channel (or both) are out as there is no reverb.

God only knows how this amp got out here to the UK, hardly anyone knew/knows what it is and I have to take in in to get serviced- any advice/ feedback would be greatly appreciated- fingers crossed- Thanks!

[Nick Fryer]

I’m a big fan of the Sho-Bud single channel amps. I have one that is basically mint and I love it. I’d be interested in seeing some pics of your “Cain”.

[Ron la Villa]

Will do soon as soon as I get home, glad to get feedback from people who love this amp as well.

[Nick Fryer]

I can compare the pics to mine and see if anything looks different. Mine is in great working order but I do need to do a little maintenance on it. I’d like to redo the thermal paste in and around some of the components. Some are getting hot and it worries me a little. Also would like to check the bias on it.

[Ron la Villa]

I hadn't even thought about the thermal paste!Even with the speaker which i'm sure isn't the correct one I love the way this amp sounds on an E9 steel.

[Ron la Villa]

as the reverb isnt working I take it the 1/4 jack on the front panel is a reverb on/off?

[Ron la Villa]

[Lee Jeffriess]

Ron, could you pull back and take a picture of the whole of the amps circuitry please. Are the power transistors 2N3055's ?
Cheers
Lee

[Donny Hinson]

Changing the components of the amp will change the tone somewhat, and you can’t get around that. How much it will change is basically a crapshoot, as all components have a certain tolerance when they are made, and as a rule, their actual values drift farther and farther as they age. The tone it has now is the sum total of all those values. All this to say that the tone you’re hearing now (the tone you’re probably in love with), is probably not exactly the way it sounded when it was new.

As the old adage goes, “you never know until you try”.

[Ron la Villa]

Ron, could you pull back and take a picture of the whole of the amps circuitry please. Are the power transistors 2N3055's ?
Cheers
Lee

Finally got it back- Thank you so much, here's what the tech said:
"There seem to be two identical power amplifiers, so it would be useful to know what configuration these are in, for example bridged.

One of the driver transistors on one power amp seems to be shorted. I've not invetsigated this further.

The pre-amp has some chips in it (difficult to see any writing on these), implying it is different from what I assume is the discreet JFET pre-amp of the schematic I have. (The Sho Bud Single Channel).
Any advice would be greatly apreciated or pointing towards someone who may know- it's sad to have such a great amp in stotage useless.

Signal is coming out of the pre-amp into the power amp, so that part is nominally working.One of the driver transistors on one power amp seems to be shorted. I've not invetsigated this further".

(More observations from the tech):

Pre-amp:

The pre-amp board has some ICs on it.
I can only see writing on the top of one of these as it has come off the others.
The schematics we have indicate that the pre-amp JFETs are used.
I assume that these would be discreet and thus there would have been transistors on the board rather than IC, although it could be that one of the chips could be a JFET array, although these are generally used for switching rather than audio
There is also evidence of a previous repair on the pre-amp PCB.

Power amp:

The power amp seems to be two identical sections, using only NPN output transistors.
The voltages on the side nearest the mains switch don't look correct and I think at least one of the transistors on that side of he power amp has shorted.
I'm not 100% convinced that the power transistors are original; I think they may be a modern equivalents.

[Chance Duhon]

I have extensive knowledge on these amplifiers and the sho bud single channel amps. I will tell you it is not a transistor that’s causing the high floor noise. I own Magnolia Amplification. If you are interested in having this amp serviced, send me a message. A lot of people send me the chassis to these amps and I fix them

[Chance Duhon]

Also a Cain amp and a Sho Bud single channel are not the same amps. There are a good bit of differences.