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Ampeg SVT-3 Pro noisy and cuts out

Mas Fuego

Mas Fuego

There is more
May 31, 2013
105
8
carlthomas.net
#1
I am not sure what happened to my amp.

When I turn it on, it sounds noisy, not quite like static, just noisy. When I play it, if it hits a peak it cuts out almost like it restarts. I have to wait for that lag time like at startup and then it plays again. But again, if I drive it at all it cuts out.

Any suggestions? The only repair place I know nearby is Sam Ash.
 
#2
There are two jacks with an internal interrupt from preamp to power amp, the effects return and poweramp in. Use an instrument cable or pedal board jumper to loop the effects send to return and preamp out to power amp in. If you troubles are gone (which the chances are very good they will be) those two jacks need cleaning (yes, especially if you don't use them).
 
#3
Mine used to crackle.
These have had some history with bad traces on the board.
Mine had the traces touched up and worked fine for a year.
It did the same thing and other traces were reinforced.
If the effects send /return idea doesn't work it is highly likely to be traces on the board or possibly a tube.
 
#4
I think it's the loop or a tube myself. Bad traces were sometimes found on earlier 3 Pros, but that was more about getting used to the lead-free solder they had to switch to to sell in Europe. They're pretty well over that hump since the mid 90's, though. At least that's what Jerrold Tiers said.
 
#6
Sorry for the lack of reply. I have been out of town.

B-string said:
There are two jacks with an internal interrupt from preamp to power amp, the effects return and poweramp in. Use an instrument cable or pedal board jumper to loop the effects send to return and preamp out to power amp in. If you troubles are gone (which the chances are very good they will be) those two jacks need cleaning (yes, especially if you don't use them).
Click to expand...

I am back with a can of compressed air to clean the jacks and see what happens.

Jim C said:
To the OP: how old is yours; mine wasn't that old but bad traces can happen regardless of solder type.
Click to expand...

How do i date it?
 
#7
Serial number. Dating Ampeg Amplifiers and scroll down for date info about any SVT 3 Pros made before 2008. For any made since 2008, it's a little more complicated since the place of the digit will move around depending on the model, but the process pretty much repeats itself with A: 2008, B: 2009, etc.
 
#10
Here is my issue. Now that I plugged in the jumpers, played, unplugged the jumpers and played, it stopped cutting out. It sounds noisy but I don't know if it always sounded noisey or not. I used to keep it in a practice space and now have it in a bedroom where it first started the cut out.

I will continue to work with it and see what happens but for right now it seems to be not cutting out.

Thanks all.

B-string said:
DeoxIT is the answer if the jumpers clear the problem.
Click to expand...

should I get the spray can or the finger nail polish looking bottle?
 
#13
JimmyM said:
Serial number. Dating Ampeg Amplifiers and scroll down for date info about any SVT 3 Pros made before 2008. For any made since 2008, it's a little more complicated since the place of the digit will move around depending on the model, but the process pretty much repeats itself with A: 2008, B: 2009, etc.
Click to expand...

Serial ATKDL6XXXX
Digits 1, 2, 3 = Model ???

Digit 4 = Country Code where:
D = domestic U.S.

Digit 5 = Year where:
K=1998

Digit 6 = Month where:
6=June

So US amp made in June 1998, right?
 
#14
More like $70-75 since there's 5 tubes in it. But it probably isn't necessary to order a full set. Usually it's just one tube that's ka-flooey.

And yes, that's exactly right about the date.
 
#16
The trouble with trying to clean an effects loop jack with the 'spray the plug and insert/remove several times' technique is that the plug doesn't touch the switching contacts at all. All you're doing is opening and closing the connection but nothing is touching or wiping it. To clean it properly you must open the amp and get in between the contacts with a thin, soft cloth. A spritz of cleaner there doesn't hurt either.
 
Last edited:
#17
David Jayne said:
The trouble with trying to clean an effects loop jack with the 'spray the plug and insert/remove several times' technique is that the plug doesn't touch the effects loop contacts at all. All you're doing is opening and closing the connection but nothing is touching or wiping it. To clean it properly you must open the amp and get in between the contacts with a thin, soft cloth. A spritz of cleaner there doesn't hurt either.
Click to expand...

That will be the plan. This thing is crackeling like a bowl of rice crispies.
 
#18
Mas Fuego said:
Sorry for the multiple replies. How does one isolate the offending tube?
Click to expand...
A couple different ways...

---Switch each tube with a known good tube one at a time.

---Take a chopstick or similar wooden stick and lightly tap each tube while it's on and listen for weirdness. A good tube should make a solid thunk whereas bad tubes can make static sounds and/or pinging sounds. NOTE: Only use wood for obvious reasons.
 
#19
Mas Fuego said:
That will be the plan. This thing is crackeling like a bowl of rice crispies.
Click to expand...

Not an uncommon issue with the effects return or power amp in jacks as well. If you bought the spray, with the amp unplugged spray a shot into a kleenex first to start the flow then a VERY FAST shot into the effects return and/or power amp in jacks. Work a plug in and out several times then allow at least 20 minutes to make sure any solvents had "dried out". Plug it back in and play.
 
#20
Mas Fuego said:
Here is my issue. Now that I plugged in the jumpers, played, unplugged the jumpers and played, it stopped cutting out. It sounds noisy but I don't know if it always sounded noisey or not. I used to keep it in a practice space and now have it in a bedroom where it first started the cut out.

I will continue to work with it and see what happens but for right now it seems to be not cutting out.

Thanks all.



should I get the spray can or the finger nail polish looking bottle?
Click to expand...

The bottle is less handy to get a drop inside the jacks but better to treat pots (don't spray down the shaft of a pot) and to get a good film on plugs or wet a "QTip" to wipe inside jack contacts.
 

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