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Messages - tubeAMP

#1
Amplifier Discussion / Re: Amp malfunction
January 10, 2014, 01:38:16 PM
100W is a lot of power.  it should produce a lot of volume.  lot = lot :duh
not rocket science.  I would take it-back to the shop with the guitar that you play with it.  both you and the tech should listen at the same time and displace any suspicion  :grr
#2
Amplifier Discussion / Re: Peavey 212 Classic VT Series
January 09, 2014, 08:01:43 AM
it is getting to where I am working on more solid state than tube type apparatus.  its all good :loco
BTW I do have a variety around the house.  some people decorate with vases and lamps.  I decorate with radios and amplifiers from the early 30s to mid 60s :duh
#3
Amplifier Discussion / Re: Peavey 212 Classic VT Series
January 08, 2014, 04:27:45 PM
this is what I am working on lately.  attached is 8- transistor radio.  had an open IF transformer T4.  repaired it with a strand from 24AWG stranded CAT6 patch cable.  screaming loud now :dbtu:
#4
the two wav files of guitar accompaniment sound the same to me
the AMT 12AX7WS diagram looks like a tube diagram
where is the ss diagram of this device ?
is it FET, bipolar, what ?
secret  :loco
#5
Amplifier Discussion / Re: Kustom "Frankenstein"
December 16, 2013, 02:51:21 PM
grease ?  was it in a restaurant kitchen ?  that would make it greasy
have yo checked the speaker connections ?  normally closed contacts ?
#6
there you have it.  not an issue :duh
#7
Amplifier Discussion / Re: Peavey 212 Classic VT Series
December 16, 2013, 08:28:07 AM
yes we do :loco
the thickness of the board to its length ratio is flimsy.  pots mounting is delicate.  connectors are tight fitting.  there is no way not to stress the board when touching it.  this is what was partially responsible for finding the trouble area.  the board flex when moving it.  closer inspection revealed the trouble.  in this case a failed capacitor :duh
checking the amp this morning it cranks.  looking good sounding good.  I am much more familiar with it now :dbtu:
#8
Amplifier Discussion / Re: Peavey 212 Classic VT Series
December 15, 2013, 01:53:02 PM
the old beast was looking kinda dusty.  cleaned it up with some cleaner, brushes and a sponge.  vacuumed it out.  brushed-in a coating of ArmorAll into the Tolex then polished with a towel.  looking like a brand new 70s combo now.  sounding great.  in a godda da vida baby.  actually more like Howlin Wolf and Elmore James tunes 8)
#9
for you engineers out there if the power supply stress is such a big concern why no choke between rectifier and filter capacitors ?
I figured that these diodes are rock solid handling much higher current than vacuum tube rectifiers :duh
#10
Amplifier Discussion / Re: Peavey 212 Classic VT Series
December 15, 2013, 06:17:33 AM
all the parts that I have are high voltage for tube radios and tube amplifiers.  these low voltage solid state pieces are tiny and delicate.  looks like it was an electronic component failure after all.  capacitor replacement is noticeably larger but functional. 
PCB is kinda flimsy.  makes crinkling noises when flexed.  I wanted to re-seat the connectors but not coming off easily.  crinkle-crinkle
thanks for the input guys.  looks like we are on our way
#11
Amplifier Discussion / Re: Peavey 212 Classic VT Series
December 14, 2013, 05:32:31 PM
thought that I would check it before chassis going back into cab.  failed :grr
good thing that I can recreate the trouble by moving TREBLE and MID pots.  PCB flexes too but is isolated to this area.  checking continuity between resistors and capacitors looking for opens.  nada.  thought maybe a voltage change might indicate intermittent... poking C28 while amp is ON is creating the trouble.  reheat solder joints.  no improvement.  found a 600v .03uF in my stash for a replacement.  big and fat but fits.  Ragu, its in there.  is working good senior.  maybe problem solved.  C28 must have been going open.  everything mo bedda :dbtu:
tomorrow a new day will make some more checks before reassembly.  while testing the amp without C28 in the circuit the trouble is recreated exactly.  so I am pretty sure that was it but wont hurt to check it-out once more
#12
Amplifier Discussion / Re: Peavey 212 Classic VT Series
December 14, 2013, 02:35:57 PM
Thanks Enzo.  I think that I was getting it more or less in my second analysis.  close anyway.  looks like the ICs are held-up with voltage until the FS kills the power source with Q2 ground.  not used to these logic circuits.  hurts my brain.  I did see the simple ground (CT not chassis) circuit at FS-G for REVERB and PHASE.  sounds better when someone else says it as well.  keeps me focused.  confidence mo bedda :dbtu:
it is pretty cool design using transistors and IC switching :duh
thanks for taking the time with the walk through
happy trails to you
#13
Amplifier Discussion / Re: Peavey 212 Classic VT Series
December 14, 2013, 12:22:47 PM
you guys must have done this before.  I dont want to say that its working so it doesnt quit when I go check it again.  but its been working for at least an hour now with all controls functional.  there I said it knock on wood :trouble
took it down to the PCB for a solder touch-up and pot cleaning.  probably didnt get enough cleaner in there because I didnt take all the connections off to be able to turn the board up-side-down.  they are working well enough turning smoother after lubing the shafts and some in the pot openings.  the solder job is the main attraction and is doing well.
so now Im a candidate for more knowledge 8|
this means that I get to learn the flow of operation through the AUTOMIX jack to at least the tone stack hopefully :dbtu:

muchas gracias
#14
Amplifier Discussion / Re: Peavey 212 Classic VT Series
December 13, 2013, 02:52:43 PM
I am going to get to it this weekend.  it is good to have feedback for best focus :tu:
#15
Amplifier Discussion / Re: Peavey 212 Classic VT Series
December 13, 2013, 12:22:16 PM
just sitting at my desk killin tyme looking over this schematic waiting for the next request to go on.  lots of tyme to put to good use 8|