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Thread: A take on my hands down on an overhaul on my Pittbull Classic.....

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  1. #1
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    Default A take on my hands down on an overhaul on my Pittbull Classic.....

    The anxiety comes wild when at one point I decided to put my hands on an overhaul on my VHT pittbull classic....
    Ordered few "big caps" spent few hundreds on hunting down the old exact Mallory or Sprague caps....

    Took out the boards, unwire few wires, clean up the underside of the two long boards, tend to change all da "big caps", power supply caps, an omron 24VDC relay, change the omron power sockets and da old amphenol 9 pin tubes sockets, renew few resistors, renew the diodes 1N4003 & 1N4004, change opto coupler, change screen resistors, change and place new mounting for a voltage regulator....

    Gathering all materials and soon to commence any discussion be great help me walk thru my take on refurbishment on my VHT Classic

  2. #2

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    Quote Originally Posted by HopkinWFG View Post
    The anxiety comes wild when at one point I decided to put my hands on an overhaul on my VHT pittbull classic....
    Ordered few "big caps" spent few hundreds on hunting down the old exact Mallory or Sprague caps....

    Took out the boards, unwire few wires, clean up the underside of the two long boards, tend to change all da "big caps", power supply caps, an omron 24VDC relay, change the omron power sockets and da old amphenol 9 pin tubes sockets, renew few resistors, renew the diodes 1N4003 & 1N4004, change opto coupler, change screen resistors, change and place new mounting for a voltage regulator....

    Gathering all materials and soon to commence any discussion be great help me walk thru my take on refurbishment on my VHT Classic
    Looking forward to it!

    I think you'll be pleased with the relative ease of your refurbishment. For a PCB amp (which I prefer), VHTs I've found are fairly easy to break down. At least, that's been my experience with my D60 and 50/CL. Make sure your take plenty of pictures of things so you don't lose your way when you're reassembling everything!

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    Quote Originally Posted by metalhobo View Post
    Looking forward to it!

    I think you'll be pleased with the relative ease of your refurbishment. For a PCB amp (which I prefer), VHTs I've found are fairly easy to break down. At least, that's been my experience with my D60 and 50/CL. Make sure your take plenty of pictures of things so you don't lose your way when you're reassembling everything!

    Hi metalhobo..... Thanks for your encouragement..... Its my first time taking out the VHT board... I didn't wanna do a post here but again due to fellows who own a VHT classic and who has electrical and electronic background.... I can stage a few small information here.....

    How do you normally take out your D60 board ? The Classic has an interlock on the board by the power sockets and input jacks for the speakers and loops.... I guess the right approach is to painstakingly desolder all the points at the power tube sockets and slowly tilt the board abit and it should be out...

    But I did a mistake by pressing down hard on the sockets till it all went free off from the chassis below and from there I quickly slide it out...

    I guess the board and copper tracks survived that grave mistake I made lol

    The preamp board was also interlocked by the control pots and a V1 preamp tube with base shield... Guess the right approach was to desolder that preamp tube with base shield and the board will be free ....

    I literally snip off that metal base shield off from the preamp socket and the board was out...

    The board beneath was hell dirty with lots of dirt and the old solder flux was removed by pure isopropyl alcohol... I got the hang of the terrible alcohol smell at one point and hope my lungs are not at risk lol....

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    Have posted this elsewhere but am still waiting for the caps to arrive and others ie resistors,diodes and voltage regulator... am looking to get good quality ones but so far the voltage regulators i got and diodes 1N4003 1N4007 are all made in china..... i wonder if anyone could link me up on japanese or amercian made ?

    I have gotten da "big caps" most of it NOS but am not too sure if they will be as good supposedly to be stored in shelves for 20 over years ..... will post pics of the old caps and ratings and brand as they were all glued with the ratings hidden from sight....
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    Last edited by HopkinWFG; 06-20-2016 at 12:42 PM.

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    Quote Originally Posted by HopkinWFG View Post
    Have posted this elsewhere but am still waiting for the caps to arrive and others ie resistors,diodes and voltage regulator... am looking to get good quality ones but so far the voltage regulators i got and diodes 1N4003 1N4007 are all made in china..... i wonder if anyone could link me up on japanese or amercian made ?

    I have gotten da "big caps" most of it NOS but am not too sure if they will be as good supposedly to be stored in shelves for 20 over years ..... will post pics of the old caps and ratings and brand as they were all glued with the ratings hidden from sight....
    Hi I have the same amp, 1992 model. I want to do a cap job on mine. What are the values of the caps you pulled out?

    Mine are the same hidden from view.

    Thanks

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    Quote Originally Posted by Brad.Cagle View Post
    Hi I have the same amp, 1992 model. I want to do a cap job on mine. What are the values of the caps you pulled out?

    Mine are the same hidden from view.

    Thanks

    Hi Brad.cagle... sorry have not really logged on for long its been dead quiet here but hope all VHT/Fryette still lives here haha...

    I did get back the boards inside and wiring done fired up was pretty much happy... but i still cant solve the popping issue when switching between clean to either green or red channel of the classic...

    The problem solved with the intermittent shutdown on volume but with all tubes and leds still fuctioning well.. volume recover when i switch off and back again on the mains... and this amp has got no loud pops anymore when i switch on the standby and off on the mains.. i also notice the amp now runs more quiet...

    I will be blissed if someone can help and walk me thru on how to solve the channel pop issues...

    Again thru my experiences soldering out the big cap without taking out the boards will be hard... reason is if you have a soldering iron of 30 watts or 40 watts and even 80watts working on the solder points without accessing them from the underside of the board the solder will hardly melt...maybe because of these big caps it generally acts like a big heat sink and heat will be fast enough to dissipates thru the body of the caps rather than heat passing thru the underside of the solder points...

    Those "big caps" i still have the values noted down are as follow below...

    C107 Sprague atom 50UF 0-100VDC 85 degree C
    C108 sprague atom 50UF 0-100VDC 85 degree C
    C115 Mallory 60MFD (60 micro farad) 350VDC @85c
    C114 Mallory 60MFD 350VDC @85c
    C117 Sprague 220UF 350VDC @85c
    C116 Sprague 220UF 350VDC @85c
    C49 Mallory 20UF 450VDC @85c
    C5 Mallory 20UF 450VDC @85c
    C106 Sprague 30UF 500VDC @65c
    C19 Sprague 30UF 500VDC @65c
    C101 Mallory 30UF 500VDC @65c

    Dont forget RTV silicone before placing back new caps

    Maybe if you would also wanna share what causes you to decides on a cap change ? And what makes good after the cap changed ?

    Maybe we can also side track by measuring the voltages of these new caps to see if we are generally on the right values ?

    Hear from you soon.

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