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Author Topic: Peavey 212 VTX classic  (Read 4894 times)

freecrowder

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Peavey 212 VTX classic
« on: March 19, 2014, 12:07:05 PM »
I had lots of problems getting this up and running after setting in attic for years.  Replaced quite a few bad components but working ok now.  One last problem.  When I turn up the saturation pot I start to hear cracking sounds on hard strumming.  The more I turn it up the more cracking I get but not louder.  It sounds like a voicecoil bottoming out but I don't think that is what it is.  Tried it on another external speaker and it does the same cracking.  One thing I'm not using any footpedal not sure if it is needed to turn on and off.  When the Sat pot is all the way down everything sounds fine.

g1

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Re: Peavey 212 VTX classic
« Reply #1 on: March 19, 2014, 04:21:56 PM »
  Did you try cleaning the Sat pot?

nashvillebill

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Re: Peavey 212 VTX classic
« Reply #2 on: March 19, 2014, 09:03:43 PM »
You must have the footswitch to engage the Normal channel, by the way. (for testing, you can ground Pin 5 on the DIN socket).

The manual is available for download on the Peavey website, under Classic VTX.
« Last Edit: March 19, 2014, 11:15:58 PM by nashvillebill »

J M Fahey

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Re: Peavey 212 VTX classic
« Reply #3 on: March 20, 2014, 01:46:45 PM »
In some amps when you rise Distortion/Saturation/Gain pots it still generates strong distortion, even with distortion switched off.
Simply its *output* is switched off.
*Sometimes* this distortion finds a way to jump ahead anyway, either jumping the not_so_perfect switch (FET or logic gate such as CD4066) or through imperfect grounds or supply rails or simply because 2 tracks run parallel and relatively close, and distorted sound "jumps" from one to the other.
Proper troubleshooting would be to feed an audio tone at the input, say 100mV 1KHz, set amp as normal, raise Saturation with Distortion switched off and when it appears where it shouldn't, scope nearby points to find the leak.
But it's not easy ;)
Sometimes when customers bring amps for repair and say "it burnt"I smile.
Obviously they get angry, but I explain: ┬┐burnt amp? ... I check for dead parts, replace them, and it can be repaired in less than an hour.
Now those complaints such as: "weeellllll, it *does* work, sort of .... BUT ...... "
That BUT may be a can of worms, often work well in the bench so "nothing to repair" ... and later rise their ugly head again, so ..... can be big time wasters.

freecrowder

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Re: Peavey 212 VTX classic
« Reply #4 on: March 20, 2014, 09:49:45 PM »
OK so I am not a player so help me understand.  I have repaired this amp.  I replaced both speakers with 16 ohm units in parallel for 8 ohms.  I think it had scorpians for 4ohm.  I do not have a footswitch to test with.  so is the saturation control even active w/o the footswitch.  Because I have doubled the load does that mean it will overload sooner because the output stage is running out of voltage.  I really am starting to think that there is nothing wrong just an overloaded output.
One oyher thing I come from the hifi world where everything is linear and undistortred.  There are2inpuys on this amp hi and low gain.  It says there is a clean and distorted channel activated by footswitch is that just signal path or the physical input.

Enzo

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Re: Peavey 212 VTX classic
« Reply #5 on: March 21, 2014, 03:29:45 PM »
8 ohms is not a heavier load than 4 ohms, just the reverse.  An amp works only half as hard into 8 ohms compared to 4 ohms.

There are two input jacks, high and low gain, and they are wired together and go to the same place, the input to your amp.   The way they are wired makes the low gain one 6 decibels less loud.    It is what we call a "pad."

This tube output stage will not be overloaded by the difference between 4 and 8 ohms, it really does not care.   None of the differences in tone and dynamics are a threat in any way. 

Channel switching has nothing to do with the two input jacks.   Once the signal has entered the amp it branches into two paths, the clean and the dirty.  The footswitch determines which path is in use.

nashvillebill

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Re: Peavey 212 VTX classic
« Reply #6 on: March 21, 2014, 03:46:43 PM »
Listen to Enzo, he is the Peavey guru.

Without a footswitch, the dirty channel is stuck ON all the time, which means of course the Saturation control--which controls the amount of distortion--is active all of the time.

I strongly advise you to download the manual for this amp and read it:  http://assets.peavey.com/literature/manuals/80343008.pdf


g1

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Re: Peavey 212 VTX classic
« Reply #7 on: March 21, 2014, 07:18:44 PM »
  So the crackling is there at any volume level if the saturation is up, but there is no crackling when the saturation pot is turned all the way down, no matter the volume level?
  If this is the case, then a dirty/oxidized  saturation control is a good bet.

Jack1962

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Re: Peavey 212 VTX classic
« Reply #8 on: July 03, 2014, 06:35:17 AM »
I agree with G1 sounds like a bad saturation pot , however increasing the impedance to 8 ohms does effect a few things , you basically cut the output power in half , the tone should be a bit better though . and it will also effect the life span of your output transformer.

Roly

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Re: Peavey 212 VTX classic
« Reply #9 on: July 03, 2014, 12:35:34 PM »
it will also effect the life span of your output transformer.

The only thing that will meaningfully "effect the life span of your output transformer" is driving the amp without a load connected when the primary can flash over internally and die instantly.
If you say theory and practice don't agree you haven't applied enough theory.

 

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