Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Please login or register.

Login with username, password and session length
Advanced search  

News:

SSGuitar has moved to PHP 7.1, enjoy the speed!

collapse
Pages: [1] 2   Go Down

Author Topic: Peavey VTX Classic 212 65w Need Help???  (Read 2214 times)

Bquick

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 12
    • View Profile
Peavey VTX Classic 212 65w Need Help???
« on: December 21, 2017, 11:20:10 AM »

After many years of sitting around I finally powered up my Peavey VXT Classic.  I acquired it along with a 1966 KAY Truetone Guitar for the amazing price of $25.00.  Anyway after God knows how many years of not being used I fired up the amp and she sounded Great!!!  I do not have the foot pedal so I used the dirty channel but really kept it as clean as I could.  Just at the point if I rolled my volume down on my guitar she would be fairly clean & and if I cranked the guitar up to 11 the amp would break up.  I was really impressed with the tone and it had a mile of headroom.

Well that didn't last very long.  Maybe a couple of hours over several days.  Two days ago I noticed that the amp started to sound like it had some type of effect on the lows like a octave shift or something that lasted about as long as took me to walk over to the amp and really give it a listen.  Then it developed a static-Distortion my guitar was still audible but it had a hell of a lot of noise along with it.  I plugged the guitar in to the return and it does the same thing.

So I spent most of yesterday reading the old inter web and came to several conclusions: I downloaded the Schematic.  I ordered 2  100 uF 350V Axial Electrolytic-Illinois Capacitors, Several Audio driver transistors (MJE  15030) for Q7 & Q8, 2n3904 transistors for Q4 & Q5, and a new set of tubes.  After looking at the board it looks original and for an amp that was made in the early 80's I thought that was good.  The large Caps on the power side have slight splits in the cover of the cap.  Other than that it looked okay. 

I really don't have a lot of experience with electronics other than a couple of soildering jobs with cold joints and an upgrade I did on my Epiphone Les Pual.  Upgrade included: SD Humbuckers, CTS pots, Orange Drop Caps, Switch Craft switch, and 50's style wiring.

My question does anyone know of a procedure I can do with your help that would or could possibly pinpoint the problem????

Like I stated earlier.  I don't have a lot of experience but I'm no dummy!!! LOL...   I have a Fluke 26III True RMS Multimeter  & Fluke 12 Meter & quality Wells soldering gun.  So I'm pretty dangerous with all that equipment......   LOL   

Please Help if you have knowledge and Patience????
« Last Edit: December 22, 2017, 08:25:22 PM by Bquick »
Logged

blackcorvo

  • Elite SSGuitarist
  • *****
  • Chip Points: 4
  • Posts: 111
    • View Profile
    • My Youtube Page
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #1 on: December 22, 2017, 01:33:20 PM »


The large Caps on the power side have slight splits in the cover of the cap.  Other than that it looked okay. 


if by "splits" you mean something that looks like this:
https://upload.wikimedia.org/wikipedia/commons/6/6d/Electrolytic_capacitor_pressure_release_valve_blown.jpg

Then congratulations, we found ONE issue! Those capacitors are definitely blown.
Now, we need to figure out what CAUSED them to blow, IF that's the case.

Pictures help greatly, if you could snap a couple and post 'em here. Both sides of the board, if possible.
Logged

Bquick

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 12
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #2 on: December 22, 2017, 08:09:51 PM »

Not sure why???  I'm following direction but I can't get the pics I just took, saved, added as an attachment, to post...

FYI  Both boards are still in the chassis.  I thought it may be a good idea to keep them in until I receive the parts I ordered and if any testing or probing needed to be done...
Logged

Bquick

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 12
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #3 on: December 22, 2017, 08:41:54 PM »

Well I keep getting an error message when I try and post the PIC's?????   But after looking at the picture of the capacitor with the split ends.  No the large caps on this board are okay on the ends but the cover or wrapper has a split running long ways.  Not sure what your opinion is but after almost 40 years couldn't it go bad because of age?  Or because I see the split some other component caused that to happen?  If you send me your Email address I'll send you pics thru email...

I'm at:  BrantQuick@gmail.com
Logged

phatt

  • Legendary
  • ******
  • Chip Points: 221
  • Posts: 1928
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #4 on: December 23, 2017, 02:11:48 AM »

This reminds me of a chap who replaced the radiator in his car (at substantial cost) only to find out he only needed to replace the cap (minimal cost) :duh
The idea is to find the fault,,THEN you replace parts otherwise you may just add more confusion making it even harder to find the initial fault. 8|

First check all the voltages are within spec.
Having just checked a schematic (Which is below) the PSU board is separate so should be easy to check but check power pins on the opamps are getting power.

This thing has a fancy output section, SS driven power valves so I'm out of my depth with that circuit idea but others here will know more.

Re posting pics,, keep in mind,,Max file size is 5120KB.
some hi res shots need to be resized.
Or;
I'm not sure but new members may have to make several postings before you can up load pics,, Joe or others here will know why :tu:
Phil
Logged

phatt

  • Legendary
  • ******
  • Chip Points: 221
  • Posts: 1928
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #5 on: December 23, 2017, 02:25:08 AM »

Oh yeah,,,Regards split cap wrappers; they are a type of shrink wrap plastic and if subjected to heat over a long time the plastic will eventually split. The cap may still be working fine.
Phil.
Logged

blackcorvo

  • Elite SSGuitarist
  • *****
  • Chip Points: 4
  • Posts: 111
    • View Profile
    • My Youtube Page
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #6 on: December 23, 2017, 06:48:02 AM »

Bquick, post your pics on IMGUR and paste the links to them here.
I didn't notice you were talking about the plastic covers on the caps having splits, my mistake! If it's just that, then yes, they are probably okay.
I'd still like to take a good look at the board myself.
Logged

Bquick

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 12
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #7 on: December 24, 2017, 08:21:28 AM »

https://imgur.com/a/Ou4mB

I hope this works.   
Logged

Bquick

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 12
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #8 on: December 24, 2017, 08:32:47 AM »

Yea!!!!  Thanks blackcorvo that looks like it worked.  As far as the parts I've ordered I think I've spent less than $20.00.  I think just having the peace of mind knowing that parts that are close to forty years old are new know.  I'll feel a lot better when I go to a GIG and plug the Amp in...  LOL

Correction:  The (2) new JJ 6L6 tubes cost $35.00 plus the $20.00 for transistors and Caps.

Let me know what I can do to (or how to) check components???  like checking voltage at specific points on the board.  AC or DC ???  or resistance = Ohms   Continuity = Beep.....   

See I know a little...   AC/DC  I love that band!!!!!    Just kidding around.....

I hope someone can give some help and guide me thru the technical stuff????
« Last Edit: December 24, 2017, 09:23:03 AM by Bquick »
Logged

Bquick

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 12
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #9 on: December 24, 2017, 08:33:44 AM »

                                                       Merry Christmas
Logged

galaxiex

  • Legendary
  • ******
  • Chip Points: 42
  • Posts: 502
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #10 on: December 24, 2017, 09:40:23 AM »

Pics...
« Last Edit: December 24, 2017, 09:44:15 AM by galaxiex »
Logged
Fear leads to Anger, Anger leads to Hate, Hate leads to Suffering.

phatt

  • Legendary
  • ******
  • Chip Points: 221
  • Posts: 1928
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #11 on: December 24, 2017, 09:27:23 PM »

Well if one of the DC supply voltages has blown then it won't work.
So obviously all the DC voltages need to be checked.
The PSU board should be obvious if you follow the schematic.

The in coming transformer wires are all the ACV so set DMM to ACV.
Then switch DMM to DCV and check all the DCV.

Make sure those voltages are present at the pins on the opamps and also the HT at the Valve sockets. The Red,Yellow and Black wires that run to the power valves will be the high voltage. you can check those by probing directly into the back of the white sockets (safer)

BUT Before you go pulling stuff apart.
Pull the power Valves and reinsert them,
Reason;
You mentioned the Amp has been sitting for a long time and valve sockets corrode and just by reinserting scrapes the corrosion and amp comes back to life.

I had a messa rig come to me with horrible noise issues,, had me scratching my head for a while but it was just dirty pins on the valve sockets.
If you live in a humid climate or near the sea you are prone to corrosion.

Safety;
Regards checking voltages,, First establish where the Mains wires run and cover them with plastic if they look like you could touch them.  Be careful not to short any terminals.
I use an alligator clip on the neg probe this allows you to probe freely and keep your left hand behind your back.
Don't rush things.
Phil.
Logged

Bquick

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 12
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #12 on: December 26, 2017, 12:30:38 PM »

Cool deal Phatt Phil!!!  I'm away from the house for the Holidays but will be back home in a couple of days.  I really want to say Thank you for taking the time to give me a hand.  I cant say thanks enough!!!   That goes to everyone that is willing to give me a hand.  Thanks also  galaxiex for getting the Pic's posted on this thread.  It's really a cool thing when others with much more experience and wisdom are willing to share valuable information..  It must be the holiday magic everyone is experiencing.  LOL

I'll post my results and/or questions as soon as I get home. 
Logged

Bquick

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 12
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #13 on: December 27, 2017, 06:11:06 PM »

Okay I used some deoxit  on the terminals of the Tube or Valve.  I worked the tube in and out of the socket and NO difference is the sound.   It still sounds like s*#t= crap !!!  So I put two brand new tubes in the Amps and same thing    I sat and watched about 30 YouTube videos on reading schematics today and really none turned the light bulb on???  for me...     I know that the transformer takes AC power and turns it into DC.  Power = Voltage.  How do I verify that the amp is getting the -15 and the +15 volts that I see on the schematic?  I think I should attach the black lead to ground or the chassis and what terminals or pins do I need to touch? on the tube socket?  to find the tubes are getting the proper power?????????

If you think you can help me please let me know???  IF YOU THINK THIS IS A LOST Cause  THEN PLEASE LET ME KNOW. 

As far as the terminology goes No I really don't know as much as you...  If anyone really wants to help and see what I know and what I don't know you can call me at 321-234-9745.  If I do not answer that's because I drive a tour bus and sometimes it's tuff.  Just like the music world today.  If your really in to music you'll know what I'm talking about.  I work just about all year long.  Artist include:  Jackson Brown, Joan Baez, W. Nelson, TRHCP, Neal young, and many, many, more....  I can't really bother other tour members because we all have a job to do.  SO LEAVE A MESSAGE AND WE CAN FIX THIS GOD DAMN AMP!!!   I'm NOT A ROBOOT AND WOULD REALLY LIKE TO LEARN!!!!  MAYBE I COULD HELP YOU I??????
Logged

Katoda

  • SSGuitar Regular
  • ***
  • Chip Points: 4
  • Posts: 41
    • View Profile
Re: Peavey VTX Classic 212 65w Need Help???
« Reply #14 on: December 28, 2017, 04:04:31 AM »

Ok, so for checking the DC voltages:
If you look at the schematic, you will see that each op amp has +15 and -15V connections, which connect to the pins specified on the schematic (like U1 has them on pins 4 and 8). Keep in mind that U1A and U1B are the same chip, just different sections. When you locate the op-amp power supply pins, you connect the black probe of your voltmeter to ground (or chassis) and check those pins with the other probe. The voltmeter must be set to DCV, with the range set accordingly.
You check the power supply board and tubes the same way. Basically, if it says there should be DC voltage on the schematic, you should locate that point on the layout and measure it. If it differs from whats written on the schematic a lot, you might have found the problem.

Wow, seems like a cool job you have there. Are you trying to make us jealous?   :)

Logged
Pages: [1] 2   Go Up
 

* User Controls
 
 
Welcome, Guest. Please login or register.
Did you miss your activation email?
* Recent Posts
Peavey Filter Caps by phatt
[December 13, 2018, 04:50:35 AM]


HH IC100L schematic anyone? by maxkriz
[December 12, 2018, 05:22:35 AM]


Fried Ampeg SVT-200T by Used.Benz.Parts
[December 07, 2018, 02:57:06 PM]


Simple SS Power Amp Build - +/- 40V Push/Pull by Jazz P Bass
[December 05, 2018, 01:19:15 AM]


British Maine solid state amps by FanofJapan
[December 04, 2018, 03:11:47 PM]

* Sponsors