Peavey Delta Blues

[pchilson]

Hi,

Couldn't resist picking up this DB today. A pawnshop find.

When turning it on, after about a minute when the tubes get heated up it will make some awful noise. Volume or channel buttons in any position, no diff.
It will do this, on and off, the whole time its on.
I'm assuming electrolytics but I don't know the age of the amp so thats a guess.
The inside looks kinda difficult to work on.

I've emailed Peavey about the Date of Manufacture but that may take days to hear back if ever.
Anyone able to date this one from the serial?



Its made in Mississippi. Are they all?



It has a little "use" but not bad.



The back...

[Enzo]

WHy assume caps? I'd be far more suspicious of the tubes. SOmething tells me no one invested in a new set of tubes just before pawning it.

Sorry waiting a few days for the age is holding things up. Look at date codes on the speaker, the transformers, and the pots. That will tell you the approximate age.

[pchilson]

Hi Enzo,

Thanks for your info.
Peavey emailed me back stating the amp is a 2002. That took the caps out of the thinking for me. Your experience is shining through. After finding out the amp is only 6 years old I quit thinking caps and started thinking solder joint or tube. I did a chopstick test and found one tube being cranky. Replaced it with another and problems went away. I'm no pro at this so I don't have the experience to fall back on... You thought tubes right off.
I still get a bit of noise out of it a times and the reverb will start humming loudly after a time. I don't know if the reverb is tube driven in this amp or not. From what I see now a new set of tubes would probably do wonders for the amp.

Thanks

[Enzo]

The reverb is solid state, drive and recovery - a single 4558 chip handles it.

[pchilson]

What would be a reason for it to go to humming loudly after a while being on?
Is that 4558 a socketed chip? There was one, I think 6 leg, socketd chip half out of the socket when I first took a look inside.

Thanks

[Enzo]

8 legs. Only IC in the amp.

Reason? Failing chip I would imagine.

I can't guarantee it is the IC, but it would be suspect. Does the reverb work OK until the hum?

[pchilson]

Yes it does work ok then it just starts a steady loud hum that goes away when you turn the reverb knob to 1.
Bad chip huh?

[pchilson]

Ok, new findings on the reverb issue.
The hum seems to be only there when the boost button is applied. It is quite ok whilst the boost is off.
Does this suggest anything?

Thanks

[Steve A.]

Ok, new findings on the reverb issue.
The hum seems to be only there when the boost button is applied. It is quite ok whilst the boost is off.
Does this suggest anything?

Thanks

Yes- don't push the boost button.

Steve Ahola

P.S. I've had my brand new one for almost 6 weeks now and like it more every day!

[pchilson]

Yes- don't push the boost button.

Steve Ahola

P.S. I've had my brand new one for almost 6 weeks now and like it more every day!

Haha, funny guy...

I went to Radio Shack and picked up a TL082 Op Amp and also one just called a 741 Op Amp.

Can't get a 4558 without ordering it.
Will either of the ones I picked up work? Would one be better than the other?

Thanks

Edit: Ooops, I was doing my research when I posted this question. Seems that the 741 in not a "dual" op amp. Is that correct? If so, then that won't work then.

[Albert Kreuzer]

TL082 will work.
Doubt it's the chip though.

Cheers,
Albert

[Don Moose]

TL082 will work.
Doubt it's the chip though.

Prob''y not, but the phrase 'half out of its socket' concerns me a bit.

Since the hum is more boost related than reverb ... if I read that right, then I'm probably look at the boost switching, the components that get switched and any rails that feed it.

The Delta Blues is not in my Peavey pile, so I'm working from generalities.

Hope this helps!

[pchilson]

Prob''y not, but the phrase 'half out of its socket' concerns me a bit.

Since the hum is more boost related than reverb ... if I read that right, then I'm probably look at the boost switching, the components that get switched and any rails that feed it.

The Delta Blues is not in my Peavey pile, so I'm working from generalities.

Hope this helps!

Thanks for the responses guys.

Albert, when you say "doubt its the chip though" can you expand on that? What comes to your mind?

Don, you are suggesting looking for bad caps, resistors that have drifted...? What about the rails? Look at the voltages for high or low?

Give me a bit to chew on.

Thanks

[Amp Kat]

So your saying if you turn the reverb down the hum is still there ? Try using the send out to another amp and see if the hum is still there or try another preamp into the return. Hum can be caused from preamp or power amp or bad tubes or badly mismatched power tubes.

[pchilson]

The way its doing now. If I don't have the boost initiated the reverb is fine. If I initiate the boost or run any kind of boost through the effects loop then the reverb will start to produce a loud and continuous hum that wont quit until I turn the reverb down or disengage the "boost".
When I got the amp it was loaded with 4 Sovtek EL84s and 2 Sovtek 12AX7s and 1 EH 12AX7. One of the EL84 went ballistic and I swapped it out with another Sovtek EL84 that I had. That one I replaced was definitely bad, it shows the same symptoms in another amp. The other 3 would have to be considered questionable. I pulled the 2 Sovtek 12AX7s and replaced them with 2 more EH 12AX7s so now there is a full complement of EH 12AX7s in the preamp.
I need to get a matched quad of EL84s before I can rule out the tubes as causing any of the niggles at this point.
I have had a few tube amps up to this point but have never had bad tubes in any of them so the problems that bad tubes can cause are new to me.

I appreciate the input you guys provide. School me...

Thanks