Peavey Deuce VT Series: UPDATE*

[plexi50]

Very low and distorted volume. Cant get any volume until the pot is on at least #8. Bias is perfect and power are good. SS preamp problem. This has the Automix circuit as well. All inputs produce low volume and distorted level. I have never had much luck with these amps

[Platefire]

Har! Nobody is diving in on this one  Know how you feel, because I put out post sometimes nobody wants to touch 

So you think it's a SS preamp problem. Have you checked all the normal stuff---power tubes, chop sitcked for cold solder joints, good solid ground points, looked for burnt components and checked voltages? Platefire

[plexi50]

These amps are a D. If i only had a layout with part numbers on it i would be done already. I have probed the entire preamp board using the listening device and it is loud and proud. The preamp signal is fine but not making a connection to the pre out or to the power tube coupling. I can see the part values on the schematic i need to check but cant find them on the board itself. I am tracing the best my eyes will let me at this moment.

I have a hum at the preamp out and amp out jacks. I pulled the connector that joins the preamp and power amp on the board 1 mile to the east of the pre and power jacks and also have hum on pins 2&3 of the connector that mate the pre & power amp.

I just found a bad JRC4558 chip (replaced) and now have pre & power signal at the jacks and resistors surrounding the pre & power connector. Still no preamp coupling to the power amp itself. Bypass patch makes no diff. So close. Got to stop for today.
If i can find the PI coupling cap and resistors IR13 4.7K & IR14 IK & IC18 cap i think that will do it.

Without this listening device/probe i would be completley blind and wasting my time  

[Platefire]

I haven't contacted Peavey lately but use to everytime I would contact them regarding an amp, they would send me a complete schematic and layout. Last time they sent electronic files by e-mail. If you haven't tired them, it would be worth a try. Platefire

[plexi50]

Worth a try i suppose Platefire. Usually dont need a schematic much anymore. But of course this amp with the SS preamp will through you off your normal thinking and ease. The schematics i have show different OP amps and i think some of them are actual switching chips and opto. RCA 945 & Texas Instruments TL604

[plexi50]

Amp done and sounds good. The problem was a 22K 2 watt resistor that was the 130VDC feed for the drivers. It was open. The other 22K measured 49K. Happy dance*

The amp kicked my amp. It was the obvious and yet i suspected the worst case in transistor problems. It wasnt.
Amen! Shamalama Ding Dong  

[Willabe]

Yes but why was 1 open and the other had drifted to over double it's value?

Could be more going on?


             Brad     

[plexi50]

Yes but why was 1 open and the other had drifted to over double it's value?

Could be more going on?


             Brad     

Good question. The PS caps have been changed recently so i suspect it may have been the old caps or bad power tubes in the past. They were 2 watt CC resistors

[smackoj]

Senor Plexi; well done and kudos on your success. when one succeeds, we all succeed.

 

[Platefire]

Glad you got it!! Ye haw

[plexi50]

Senor Plexi; well done and kudos on your success. when one succeeds, we all succeed.

 

Thats the truth. Ive been tinkering with electronics since 1971,mostly Ham & CB radio modifications as a kid. But this is a whole new bird in electronics. This is the most rewarding thing next to SX. 

Yehaw! Platefire! I have a Classic VT Series that i just brought in the house. When i get more time i want to fiddle with it and get it going. Maybe i can learn more about repairing these

[Platefire]

I've have a LANEY VH 100R head in that looses power but when you beat on it, it comes back. I'll be hollering for help when i open that up.  Plate

[guitardude57]

The Laney should be easier.  If it is IWT, (intermittent when tapped) sounds like a loose connector, part, or a bad solder spot.