Amplifier repair shops closing down

[Joey Voltage]

Re: Amplifier repair shops closing down

Thank you. It sounded quite deep from what I recall. It must have been 12oHz than. I assumed 6oHz, since I could only hear it when I plugged AC supplied effects in the loop.

It’s not uncommon to hear both frequencies riding on top of each other, making it hard to decern what the true culprit is. But from what you are telling me, it sounds like you are getting some unwanted coupling between the fx unit, and the loop return. It could also be like you suspected, a ground loop, especially if your fx unit is an old one that plugs directly into the wall like some old mxr’s did, and doesn’t have a lift to ensure no loop exists. Do your typical battery operated fx do the same thing? That said, the loop is a very sensitive spot in the amplifier, particularly the return - it’s just as sensitive and prone to noise pickup as an input stage, it essentially is a separate input stage.

 

[jimman]

Re: Amplifier repair shops closing down

Exactly.

Back in the day, a group played the bars as a starting point to "pay their dues"; to sharpen their band & playing skills and hope eventually someone in the crowd was a big record co. man with a contract in hand, so they could move on to an actual professional gig (hit the "Big Time") with an album in tow... but since those days are gone and since kids have little to no interest (mainly because of lack of discipline, ADHD with their smartphones and the piss poor state the music biz is in) in playing guitar, the bar band scene is, apparently, now the lofty pinnacle of "professional" rock band "success". :lol:

The times they are a changin'...

I will just throw my perspective out here as a millennial who attempted to do something with music at one point. I started out playing for youth groups at churches and we tried to expand to playing at bars and other gigs. We had some success finding gigs, but getting paid anything was hard. I actually knew a few bands that found themselves having to pay for a gig or the owners would force them to sell a certain amount of tickets to the gig to play in it, at the time I refused to do that as I felt it was taking advantage of us and I still feel that way. After a certain point we realized we were putting so much time and effort into just getting gigs it wasn't even worth our time if we wanted to make a career out of music. I am sure there are a lot of mistakes we made and a more business savvy person could have done better, but we were 18-19 year old kids at the time we didnt know what we were doing. If I was a kid trying to get started now, I would absolutely be using Youtube to get started. It takes a lot less time to get started, and you can reach a much larger audience. The traditional bar scene is demoralizing to anyone who wants to make a serious career out of music and all of the people my age who do it are just doing it as a hobby, not trying to make a career.

 

[ehdwuld]

Re: Amplifier repair shops closing down

If it stops with a cable.in the loop
It's a bad jack in the loop

The jack does a switching function
Probably just needs cleaning

 

[Joey Voltage]

Re: Amplifier repair shops closing down

If it stops with a cable.in the loop
It's a bad jack in the loop

The jack does a switching function
Probably just needs cleaning

It would depend on how the jacks are wired, some loops do not use switching jacks, and the ones that do typically break the connection on both ends when something is inserted anyway, so if the switching terminal was the problem, you would most likely have the issue when nothing was connected, not the other way around. He also said the problem only happens when he is using AC supplied effects only.

 

[LLL]

Re: Amplifier repair shops closing down

I will just throw my perspective out here as a millennial who attempted to do something with music at one point. I started out playing for youth groups at churches and we tried to expand to playing at bars and other gigs. We had some success finding gigs, but getting paid anything was hard. I actually knew a few bands that found themselves having to pay for a gig or the owners would force them to sell a certain amount of tickets to the gig to play in it, at the time I refused to do that as I felt it was taking advantage of us and I still feel that way. After a certain point we realized we were putting so much time and effort into just getting gigs it wasn't even worth our time if we wanted to make a career out of music. I am sure there are a lot of mistakes we made and a more business savvy person could have done better, but we were 18-19 year old kids at the time we didnt know what we were doing. If I was a kid trying to get started now, I would absolutely be using Youtube to get started. It takes a lot less time to get started, and you can reach a much larger audience. The traditional bar scene is demoralizing to anyone who wants to make a serious career out of music and all of the people my age who do it are just doing it as a hobby, not trying to make a career.

Yeah agree 1000%.

(my statement about playing in the bars as being the "pinnacle" of "professional" rock band "success" was entirely tongue-in-cheek, entirely sarcastic and designed to make a point to a very select few members here who incorrectly assume that they've "made the big time" or have accomplished some major musical achievement by playing in a bar...)

Yep YouTube kicks ass! And it costs nothing to get your stuff out to a quite huge audience.

I mean, this is the 21st century, after all... :lol:

Venue owners that ask a band to pay for the "privilege" to play can go ******** themselves in the *******... get real.

 

[67Mopar]

Re: Amplifier repair shops closing down

It’s not uncommon to hear both frequencies riding on top of each other, making it hard to decern what the true culprit is. But from what you are telling me, it sounds like you are getting some unwanted coupling between the fx unit, and the loop return. It could also be like you suspected, a ground loop, especially if your fx unit is an old one that plugs directly into the wall like some old mxr’s did, and doesn’t have a lift to ensure no loop exists. Do your typical battery operated fx do the same thing? That said, the loop is a very sensitive spot in the amplifier, particularly the return - it’s just as sensitive and prone to noise pickup as an input stage, it essentially is a separate input stage.

I didn't get a chance to try the loop with battery powered effects, as I don't have any. Rockman chorus, delay, and a Lexicon PCM 7o only. I dropped the amp off yesterday, and will be picking it up tomorrow. The repair cost was more expensive than I hoped for, but I don't care. I just love the tone of the GVT15. The fix as a Ampeg factory update, but they would not give the mod to me... Authorized Ampeg repair techs only.

 

[67Mopar]

Re: Amplifier repair shops closing down

It would depend on how the jacks are wired, some loops do not use switching jacks, and the ones that do typically break the connection on both ends when something is inserted anyway, so if the switching terminal was the problem, you would most likely have the issue when nothing was connected, not the other way around. He also said the problem only happens when he is using AC supplied effects only.

The amp does have a separate input jack for switching the loop and reverb on/off via remote foot-switch. Someone on the Tele forum said something about "15 VDC on the rails", but I don't think that is the issue. I tested the return using a DMM. No 15VDC, but I did read some capacitance. Starts at 1oVDC (sorry, my zero key is busted] and slowly drains to zero volts. I did get some popping when I toggled the loop switch, but the popping dissipated after about 7 or 8 toggles, then was quiet. I assume this is related to the DC on the return line?

Schematics link: https://ampeg.com/support/files/Schematics/G Series/GVT15H/GVT15H Combover Schematics.PDF

 

[dave74]

Re: Amplifier repair shops closing down

It's a 4hr round trip in either direction for any reputable service that I might trust with my Mesa heads, and then another 4hrs to pick it up.
Rather than waste all that time and driving expense and still not being sure of the outcome I've decided to just send them home when/if needed. (Petaluma)

I have a 95 Dual Rectifier (blacked-out totally, early revG in almost perfect condition cosmetically) that needs a filter/bias-cap job, serial-loop mod, and possibly some new tube-sockets while it's there anyways. Of course the shipping-charge will suck, even only sending the chasis might be around $50 each way just guessing. I do trust Mesa much more than some guy I don't really know about, so for my situation I think it's the wiser choice.

 

[67Mopar]

Re: Amplifier repair shops closing down

It's a 4hr round trip in either direction for any reputable service that I might trust with my Mesa heads, and then another 4hrs to pick it up.
Rather than waste all that time and driving expense and still not being sure of the outcome I've decided to just send them home when/if needed. (Petaluma)

I have a 95 Dual Rectifier (blacked-out totally, early revG in almost perfect condition cosmetically) that needs a filter/bias-cap job, serial-loop mod, and possibly some new tube-sockets while it's there anyways. Of course the shipping-charge will suck, even only sending the chasis might be around $50 each way just guessing. I do trust Mesa much more than some guy I don't really know about, so for my situation I think it's the wiser choice.

I had one of the first DR heads back in '92. It was actually a custom build, that was not suppose to be sold. MESA had sent it to Akron Ohio as a demo unit for a set of clinics. Who the player was, I do not know? After about 1 month, it developed an issue of popping coming through the speakers. I called MESA in regards to sending it in for repairs... After giving them the serial number, they refused to work on it! WTF? They asked; "Where did you get the amp from?" I told them that I had purchased it from a guy in Cleveland, who was also a Cleveland cop. This was when they informed me of its provenance. MESA said that the circuit board was a one-off custom design, and that it could not be replaced. I told them that I did not want it replaced, just repaired. She replied again that they would not service the amp. I was f-ing pissed! I tried others, but none sounded like my original. I ended up trading it at Lentine's Music. Actually, I got to meet Steve Morse that same day. What an awesome guy!

 

[dave74]

Re: Amplifier repair shops closing down

I had one of the first DR heads back in '92. It was actually a custom build, that was not suppose to be sold. MESA had sent it to Akron Ohio as a demo unit for a set of clinics. Who the player was, I do not know? After about 1 month, it developed an issue of popping coming through the speakers. I called MESA in regards to sending it in for repairs... After giving them the serial number, they refused to work on it! WTF? They asked; "Where did you get the amp from?" I told them that I had purchased it from a guy in Cleveland, who was also a Cleveland cop. This was when they informed me of its provenance. MESA said that the circuit board was a one-off custom design, and that it could not be replaced. I told them that I did not want it replaced, just repaired. She replied again that they would not service the amp. I was f-ing pissed! I tried others, but none sounded like my original. I ended up trading it at Lentine's Music. Actually, I got to meet Steve Morse that same day. What an awesome guy!

Yeah that would be frustrating.
From what I understand they still only do the simplest of mods, like the serial loop. They won't deviate much from their standard production-run specs.
They did setup this page though as a general guide, but it's still required to call-in first for a return/service# before sending the chasis.

https://mesaboogie.zendesk.com/hc/en-us/articles/218929987-MESA-Factory-Service-Warranty-Maintenance

 

[67Mopar]

Re: Amplifier repair shops closing down

Okay, I picked the Ampeg up today. The tech said that the GVT15 loop hum is caused by the heater and effects return traces being placed too close to each other. The amp sounds great, no more hum in the loop. Woo-hoo! I had an issue with attenuation when the remote was plugged-in, but it's fine now. I think I need to clean the sockets with some DeoxiT.

1. Would it be possible to install a trim pot in place of R1 for adjustability to the effects loop return?
2. Instead of rewiring the amp, is it possible to convert the heater voltage from AC to DC? If yes, would this take care of the hum?

Something like this: https://www.mouser.com/datasheet/2/54/266-776573.pdf

 

[dave74]

Re: Amplifier repair shops closing down

The parallel effects loop may have been my fault. I was hanging-out at Ohio Guitars back in 1989/90. A friend who worked there (Mike) was on the phone with Randall Smith. I heard Mike say; "Let me ask someone I know..." Mike asked; "I'm on the phone with Randall Smith of Mesa/Boogie. He wants to know what you would like to see in an amplifier." I replied; "A parallel effects loop." Randall Smith asked why I would want that? I said that I wanted to be able to blend the amp dry tone with the effected tone. The next year series amplifier (Dual Rectifier, I think?) included a parallel loop. I had not considered phasing issues due to latency, but then I wasn't using digital effects either. I naturally assumed any such design would include a serial loop as well. I had stopped playing Boogie, as I moved back to playing Marshall and also had an SLO100. Maybe there were other amplifiers that featured a parallel loop, prior to MESA. If there were, I was unaware of it.

It's not really as terrible as it's reputation IMO, and if a guy was just using a single modulation and the amp's mix-knob was on the front of the head it would be OK.
Series does make everything less complicated when running a bunch of pedals together through the loop, and then there's no "reach-around" problems. lol

 

[Joey Voltage]

Re: Amplifier repair shops closing down

Okay, I picked the Ampeg up today. The tech said that the GVT15 loop hum is caused by the heater and effects return traces being placed too close to each other. The amp sounds great, no more hum in the loop. Woo-hoo! I had an issue with attenuation when the remote was plugged-in, but it's fine now. I think I need to clean the sockets with some DeoxiT.

1. Would it be possible to install a trim pot in place of R1 for adjustability to the effects loop return?
2. Instead of rewiring the amp, is it possible to convert the heater voltage from AC to DC? If yes, would this take care of the hum?

Something like this: https://www.mouser.com/datasheet/2/54/266-776573.pdf

View attachment 91231

yeah, sounds about right. that's the coupling of the sensitive return stage to the un-rectified source I mentioned earlier in this thread.

So for your other questions.
1) Yes, but I wouldn't replace the 10K with a pot, I would just add a 100K pot to ground after the jack, and connect the 10K to the wiper, or I would place a pot wired like a rheostat in the return opamp's feedback loop in series with r7, and reduce the value of r7.
2)possible, but not easily. you would have to have room for it, and high current DC supplies can be a lot of trouble if you already have proximity issues. You could more easily elevate the AC heater to a DC potential, but you would still have the AC component present on top of it.

 

[67Mopar]

Re: Amplifier repair shops closing down

yeah, sounds about right. that's the coupling of the sensitive return stage to the un-rectified source I mentioned earlier in this thread.

So for your other questions.
1) Yes, but I wouldn't replace the 10K with a pot, I would just add a 100K pot to ground after the jack, and connect the 10K to the wiper, or I would place a pot wired like a rheostat in the return opamp's feedback loop in series with r7, and reduce the value of r7.
2)possible, but not easily. you would have to have room for it, and high current DC supplies can be a lot of trouble if you already have proximity issues. You could more easily elevate the AC heater to a DC potential, but you would still have the AC component present on top of it.

Thank you so much for your help. You were dead-on about the heater line causing the hum! :beerchug:

 

[Aceman]

Re: Amplifier repair shops closing down

Youtube wanted to compensate me {$$$} for some of my videos

May I see evidence of that?

 

[LLL]

Re: Amplifier repair shops closing down

To make $$$ doing YouTube vids:

Provided you meet the (now stricter) requirements (1K followers, 4K watch hours), all you have to do is setup an AdSense account
and a few incidentals.

https://support.google.com/youtube/answer/72857?hl=en

You set the pay threshold - once you hit the threshold, they mail you a check.

 

[Securb]

Re: Amplifier repair shops closing down

Not sure what bar bands or YT have to do with amp repairs but back to the op. Boston always has been and always will be a live music city. There is no shortage of guitar players or broken guitar amps. The 3 or 4 amp techs in Boston proper have been around for decades. The one I have always used, Aztech Electronics is so busy you have to make an appointment to get your amp in there.