Tech near upstate NY to service my Marshall?

[Vintagelove]

Hello and thanks for reading. I’m looking for someone within a couple hour drive from Albany New York who would be interested in doing some work on my JMP. Long story short, looking to have the "Larry ground scheme" implemented. If this sounds like something you’re interested in, or you have the contact of someone who might, feel free to message me. Thanks again and have a great day.


PS, why don’t I just do it myself? I’m considering it, but this amp has considerable sentimental value to me. It was a gift from my late father and I’d like to have it done by someone more experienced than me.

[thetragichero]

I'm in Cairo/greene county, moving to canajoharie/Montgomery county sometime in October

so does it have a problem or are you wanting to do it "just 'cause"? i tend to try to talk folks out of unnecessary work (especially on vintage amps)

[Stevem]

I have that same question, why do you want it reworked?

What is it not doing to your liking now?

[Vintagelove]

I have that same question, why do you want it reworked?

What is it not doing to your liking now?

I'm in Cairo/greene county, moving to canajoharie/Montgomery county sometime in October

so does it have a problem or are you wanting to do it "just 'cause"? i tend to try to talk folks out of unnecessary work (especially on vintage amps)

Hi guys, thanks for replying. Here’s the deal.


About 10 years ago (before I knew anything about amps/electronics) I had FJA mod the amp with an extra gain stage (and recap it while he was in there). Unfortunately the amp was returned with a bit of a hum. I didn’t know enough then to know it was an issue (it’s not an overwhelming hum, but it’s there). I’ve been looking for someone to do this for a while as my usual tech is pretty much retired at this point. I had a gentleman who was going to help me out with it, but shipping it safely was going to be like 300 each way. So…

In talking with him, he suspects it is likely the result of upping the gain, but keeping their original ground scheme in place. Of course, there is a chance that it’s not the cause, and that’s also why I wanted to have someone with more experience than me do the work.

Basically, I would like someone to confirm that is the source of the hum, then improve the ground scheme (or fix whatever they find). I might have a little thing or 2 done while it’s on the bench (switchable bright cap etc), but for the most part, that’s it.


Canajoharie would be fine. Even farther would be fine too. Again, many thanks for your time and consideration.

[thetragichero]

shot you a PM with contact information, etc. be aware that the forum's software tends to not notify of messages

[pdf64]

Just to eliminate the obvious, but are you sure it isn’t just the buzzy hum of a valve with imperfect heater - cathode insulation, eg fitted into V1?
The 2k7 // 0.68uF partial cathode bypass opens the door to that issue.
Heater elevation can eliminate it (as can fitting a different valve).

[Vintagelove]

Just to eliminate the obvious, but are you sure it isn’t just the buzzy hum of a valve with imperfect heater - cathode insulation, eg fitted into V1?
The 2k7 // 0.68uF partial cathode bypass opens the door to that issue.
Heater elevation can eliminate it (as can fitting a different valve).

Yes, I’ve swapped various tubes. Thanks anyway.