Peavey Delta Blues

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Peavey Delta Blues

Postby pchilson » Fri Aug 15, 2008 6:30 am

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?

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Its made in Mississippi. Are they all?

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It has a little "use" but not bad.

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The back...

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Postby cartoonweirdo » Sun Aug 17, 2008 10:52 am

Hi Mr Chilson,
I have no idea about the year of manufacture of your Peavy.

Having been inside many an old Peavy however I have something to say about your noise.

If it is humming (60 Hz or 120 Hz) that indicates the electrolytics. It wouldn't be a bad idea to replace them on principle if they are more than ten or fifteen years old.

If it is crackling, popcorn kind of noise you need to check for a couple of things.

Peavy puts the tubes in TERRIBLE places as far as venting the heat goes. There is a reason that Fender quit building them that way (tweed style) and that most makers of tube amps put the tubes on the top of the chasis instead of the bottom. If you open it up and see any signs of heat buildup (darkening of circuit board or componants) replace your resistors. Most likely to go are the plate load resistors.

Peavy began using snap together connectors at a certain point. If you have them they are almost certainly dirty. Those cause 85% of Peavy problems. You must spray contact cleaner (not tuner cleaner) in the connector and plug/unplug it from it's pins on the circuit board to clean them both. Some of the connectors are polarized, but some will go on either way so it might not hurt to mark them before you remove them.

Before you do any of this switch the tubes for known good ones. It might solve your problem and it might not but it's fast, and easy to reverse.

Good luck
Carl
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Postby pchilson » Mon Aug 18, 2008 6:28 am

Thanks for your thoughts cartoonweirdo.

I have found the amp to be a 2002 model so I less suspect the electrolytics although they are not ruled out. I did swap one of the EL84s that was very noisy and the amp started behaving much better. There is still a hum that comes from the reverb when the "boost" is engaged, it disappears if you turn down the reverb knob, strum the guitar or disengage the "boost". I've yet to track this one down. I will do the cleaning you have suggested as a routine maintainence and good practice measure.

Thanks
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Postby dhuebert » Mon Aug 18, 2008 7:51 am

not tuner cleaner


I am very interested to hear your reason for this. I use it to clean everytihing, but I know from experience that not all of my ideas are good ones.

At work we use something called Stabilant 22A, seems to do the job.

Gar Gillies hated Peaveys.

I see Tweed style amps all the time and have yet to see a combo with the tubes on top of the chassis. I agree that puting the tubes on top is a better cooling strategy but this means the chassis has to be in the bottom of the amp. Am I misunderstanding something here?

Peavy began using snap together connectors at a certain point. If you have them they are almost certainly dirty


Funny thing, medical electronics uses tons of these things, and just normal Mode etc, nothing exotic, to good effect. You do have to clean them once in a while tho. The big difference with guitar amps is the cigarette smoke they are exposed to, a real enemy of electronics.

Don
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Postby mesherm » Mon Aug 18, 2008 5:30 pm

The big difference with guitar amps is the cigarette smoke they are exposed to


or other types of paper-wrapped organic materials Yellow_Light_Colorz_PDT_07 Yellow_Light_Colorz_PDT_04 Yellow_Light_Colorz_PDT_09 Yellow_Light_Colorz_PDT_08
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Postby cartoonweirdo » Mon Aug 18, 2008 7:50 pm

Mr Huebert,
As regards your tuner cleaner/ contact cleaner question. I realize the terms may be interchangeable.

To my knowledge, however, there exists a family of spray cleaners designed to clean pots (tuner cleaner in my vocabulary).

These cleaners contain a lubricant designed to keep your moving parts moving and a detergent designed to scrub the beer, oxidation, and cigarettes out of the moving parts. Variations exist for conductive plastic, and of course everyone claims their product is different and better, but they are pretty similar in my experiance.

A different family of cleaners exist that contain a desicant and slightly abraisive solution. These are for maximum scrubbing power in contact items (switches and sockets and etc). I know them as contact cleaners.

The differences are small but important. A lubricant tends to attract dust, and/or dry out making it unsuitable outside of pots by way of gumming up non moving parts. Hence my caveat against tuner cleaner for multi-pin connectors. In fact I prefer to replace pots in my personal gear rather than "cleaning" them, as they eventualy gum up and must be "exercized" before use to free them of crackles. The problem can, however, be easily fixed for a while with more tuner cleaner.

A heavy duty cleaner (contact cleaner) can dry out the lubrication in moving bits making them "scratchy" or ,in extreme cases, like a period of submersion in cleaner, freezing them entirely.

Combos with the tubes on top are rare but not unheard of. The most famous would be the AC-30. Check out the new "AC-30" which vents heat quite well and is manufactured for Marshall/Korg/Vox.

Mr Chilson,
All the Peavys with dirty connector problems I have repaired were of mid '90's and earlier vintage. My guess would be that your amp is too new to have developed this problem.

Good luck with your Delta Blues
Carl
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Postby dhuebert » Tue Aug 19, 2008 7:41 am

Wow, good answer. Exactly what I was hoping for.

In fact I prefer to replace pots in my personal gear rather than "cleaning" them


I agree completely, others say they get good results with cleaners but not me. I have never had a cleaned pot last as long as a new one. Mechanical devices wear out and electro-mechanical ones (pots) especially cause no end of trouble when they do.

I started using tuner cleaner on the bullet connectors in my 1970 Triumph TR6. The lubricant was nice because it made it easy to get them together and apart later. These connectors are exposed to the road and have shown no failures in six years. Based on this I started using it everywhere but I will definitly review this practice.

Don
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Postby nyazzip » Thu Sep 25, 2008 9:00 am

i played one of these the other day. very tasty sounds...! doesn't clean up very well though. i wonder if the circuit employs diode clipping?
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Postby Gingertube » Thu Sep 25, 2008 9:52 pm

Here is the schematic.
Its a typical designed down to a price and not up to a standard offering from the mid 1990's.

The "concertina" phase splitter is a little unusual for a 1995 amp. That was probably the "blues" part of the design.

http://www.schematicheaven.com/newamps/ ... ablues.pdf.

There is no way to set or adjust bias or bias balance. A matched quad of output tubes is a MUST.

Caps should be OK - its not that old but worth a visual inspection.
I would suspect 1 or more duffed Output Tubes.

Cheers,
Ian
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Postby EWBrown » Fri Sep 26, 2008 10:48 am

The reverb picking up hum indicates some grounding or shielding problems, probably a loose or corroded connection. An amp of this size probably rode around in a car's trunk and got bounced around a lot...

The output EL84s are probably shot, they would take a beating as compared to the normal duty cycle a "hi fi" amp. BEst to replace the group of them with matched quad - Sovteks should be just fine here, or the generic 6P14Ps or 6P14P-EVs.

/ed B
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