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#1 2011-11-05 04:59:11

beedoola
Member
Registered: 2009-05-25
Posts: 58

What caps to change?

I replaced the can caps on my VT-22 cause they were old - I got the amp used in need of work. I sprayed the pots with some deoxit as well as the sockets. There is still a large amount of noise - something ain't right.

Looking inside, C209 is cracked, should probably replaced. I'm posting some pics..What other caps should probably be replaced?

http://i157.photobucket.com/albums/t54/Beedoola/IMG_1463.jpg
http://i157.photobucket.com/albums/t54/Beedoola/IMG_1466.jpg
http://i157.photobucket.com/albums/t54/Beedoola/IMG_1464.jpg

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#2 2011-11-05 06:53:13

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: What caps to change?

change those little yellow caps with the black line on one side.  (.01uf) Those things are incredibly unreliable.   I had a bunch of those fail in my magnavox vt-22.   they went bad one by one for a few months, and finally I changed them all out.   See a lot of V4s come in with the same problem.

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#3 2011-11-08 18:09:51

beedoola
Member
Registered: 2009-05-25
Posts: 58

Re: What caps to change?

I changed all the .01uf caps as well as C203, 204, 208, 209 and 9. Problem is still there : /

I haven't changed any of the electros - they seem like they're not stock but I don't know. What about that weird cap on the Pots PCB? Anything on there notorious for failing?

Tubes have been tested, all are ok, no cold solder joints from what I can gather - at least from my work any how.

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#4 2011-11-08 19:08:45

hangman
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From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: What caps to change?

describe the noise.  is it a hiss, or a hum?   is it crackling and popping?

if you run a cable out of the ext amp jack into a mixer or something is the noise there?

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#5 2011-11-08 23:58:53

beedoola
Member
Registered: 2009-05-25
Posts: 58

Re: What caps to change?

Ya the noise is a crackling and popping. Still present when using the ext. speaker jack.

The crackling fades as the amp gets warmer but is still present. The kind of rhythmic low crackling and popping..

Last edited by beedoola (2011-11-09 00:12:09)

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#6 2011-11-11 07:32:05

ROBO
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From: na
Registered: 2010-01-26
Posts: 134
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Re: What caps to change?

My v4b, as well as a few other peoples that iv talked to, seem to often have issues with crackeling popping especially when first turned on. I know in my situation it would be at its worst right after I went out of standby and seems to go away as i played, But the noise would still come thru everyonce in a while. If the noise is there when you go out of the "ext" jack then that means is it originating in the preamp half of the amp.
It is most likely an old dry cap, either a coupling cap or by-pass cap on the preamp.

hell at this point all the caps in the amp are at least 30 years old if orignal, it shouldnt really be of any suprise if they are ALL crusty and dry.
Good luck buddy, Its sounds like your on the right track.


Less talk, More rock

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#7 2011-11-11 17:48:00

beedoola
Member
Registered: 2009-05-25
Posts: 58

Re: What caps to change?

Hey Robo,

Thanks for that! And thanks to Hangman again for all the help!

There are some ceramic and other film caps that I did not replace as well as all the electros - which look newer but who knows. What about the caps on pots PCB? any of those show to be problematic.

and what about resistors? Any particular resistor prone to going out? I'll plan on changing most of the caps to see if that will help!

I'm pleased that I got the amp this far - it was noisy as hell when I first got it and this is my first "big" amp I've been repairing - yes, I'm taking all the proper safety precautions : )

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#8 2011-11-11 18:12:10

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: What caps to change?

here is something to try,  to help locate where the problem is coming from. 

turn the amp on,  hear the crackle,  turn it to standby,  remove v1.  turn it back on.  is the crackle still there?   if yes turn to standby,  put v1 back in,  remove v2.   turn amp on,  is crackle still there?   
if yes, turn amp to standby  put v2 back in remove v201 (6k11) 
.... and so on,  you get the idea
this will help us isolate which part of the circuit the noise is coming from.   

so go in this order v1,v2, v201 (6k11),v3(12dw7),  v202(6cg7),v203(12ax7)

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#9 2011-11-11 20:24:42

beedoola
Member
Registered: 2009-05-25
Posts: 58

Re: What caps to change?

Ok, sweet! Will do!

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#10 2011-11-12 17:40:34

beedoola
Member
Registered: 2009-05-25
Posts: 58

Re: What caps to change?

The noise dropped out on the V201 but was gone completely when pulling V3 (with V201 socketed)

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#11 2011-11-13 03:32:11

hangman
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From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: What caps to change?

any change when you pulled V203?  (12ax7 on same circuit board as v201)

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#12 2011-11-14 23:18:36

beedoola
Member
Registered: 2009-05-25
Posts: 58

Re: What caps to change?

No, pulling v203 didn't. The noise stomps totally when pulling v3. Could any of the caps on the pots board be to blame?

Also, if a solder joint is cold, could that contribute. Does the 50/50 can and 47uf axial run in between v3 and v3? Looking at "E" on the schematic .

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#13 2011-11-14 23:35:26

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: What caps to change?

a cold solder joint on those filter caps could certainly cause some crackling/popping.   
I would check there for sure.   
Also since only 1/2 of V3 is in the circuit before the ext amp out,  I would  check out all the circuitry between pin 4 of the 6K11, and the ext amp out.

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#14 2013-09-13 18:16:37

beedoola
Member
Registered: 2009-05-25
Posts: 58

Re: What caps to change?

I'm bumping this cause I'm working on my NMV V4 and wanted to know what caps to check out. I've already done a cap job on it and some other caps look like they're been replaced.

C205 - tropical fish cap is cracked and maybe bulging so I may replace that one. Any others you would suggest?

http://i157.photobucket.com/albums/t54/Beedoola/59063ABE-C056-416E-8146-F212B0F7E5D6-9181-0000024B2F7A518A_zps89b334ac.jpg
http://i157.photobucket.com/albums/t54/Beedoola/D963AFE8-365A-4589-BB69-8620244D77AF-9181-0000024B3A0D60FF_zpse7695bd8.jpg

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#15 2013-09-13 19:03:29

Liquids
Member
From: CT
Registered: 2010-08-01
Posts: 491

Re: What caps to change?

I am just throwing in my 2 cents...not saying this is "what to do"

I think it just makes sense to replace every single cap.
They're all past their lifespan.  Leaking DC, especially in the wrong place, ain't good. 
Fenders/Marshall/Vox etc type amps keep a certain amount of 'mojo value' if they're the right amp and have "all original parts."  Ampegs...well, they are players amps and most valueable when convincingly stable and fresh out of the shop, so to speak. 
For now.

Keep your old caps.  No harm in saving them in case one is concerned that the old ones might become more valuable and someone wants it all original someday.

It's just a waste of time, to me, to figure out this vs. that cap.  Caps aren't cheap but they're not expensive...and it takes more time to figure out which ones are dead or dying than to just 'blind' replace them all in one fell swoop.  If you play it, you'll not have to worry about it blowing up because one or more caps exceeded their realtime life expectancy (since they've already exceeded their anticipated life expenctancy in years, if not hours).

Again, just offering my 2 cents to the mix.


Matthew

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#16 2013-09-13 19:22:30

beedoola
Member
Registered: 2009-05-25
Posts: 58

Re: What caps to change?

Thanks. I'm actually getting ready to sell it, so I want it performing at tip top shape. I think the people that would/do buy V4s aren't looking for collector/show room condition amps but functional/kickass amps.

I just want to make sure its tip top before I list it.

I just installed a new reverb pan as the V4 was missing it when I got it - thankfully nothing was/is wrong with the reverb circuit.

I do get a little bit of crackling when first turning the amp Off Stand By. It goes away but I'm wondering what it could be - happens even when the Master volume is off. I just pulled all the tubes and clean the tube sockets.

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#17 2013-09-13 20:28:55

Liquids
Member
From: CT
Registered: 2010-08-01
Posts: 491

Re: What caps to change?

I think that is fairly normal.  I get a kind of old-school tv-set turning on or off, "ffwwammmth!" kind of sound when I power on or off standby...that may be different than what you describe though.

I wonder if it has anything to do with the amount of current drawn more than anything...has anyone ever tried an "in-rush current limiter" so that when one flips the standby, current doesn't spike? 

Not sure that would change things in terms of the sound but it might not be bad?

Be sure to change the "7W resistor" on the board that feeds the screens.  10W available, hard to fit on the board in a pretty way...may mount it on the non-component side...but if you're sending it off, replace at least that resistor...may as well replace and/or increase the screen resistors while you're at it, and possibly those plate resistors too.  Whatever you can so that the buyer doesn't come back to you, or feel they got screwed...one never knows what components might blow, crack, or be abused by the user due to stressing the components electronically or physically, when we're talking old components


Matthew

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#18 2013-09-13 21:05:42

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: What caps to change?

Although I don't disagree with liquids that replacing every cap isn't a bad idea.  I see no point in replacing all the coupling caps.   I doubt that any of them are leaking dc.  They are metalized film caps,  not oil or electrolytics.  Replacing every single one is overkill.   Frankly I would replace the blue one and any electrolytics and then leave the rest be.   Those yellow molded ones while not being well known for their sound are reliable.  I rarely see them fail.

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