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#1 2013-01-18 14:59:51

bassofase
Member
Registered: 2010-12-13
Posts: 16

When to do a recap...

Got my V4B working again after a rebuild.
Its hums a bit....
When I look at the High voltage I see a triangle shape DC...
(Don't know the correct word for)
Its a bout 25-35 V. Is this normal? Or should I replace my caps?

Thanks for your input!

Dirk Sander, (Bass Of ASE)

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#2 2013-01-18 18:40:50

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

Re: When to do a recap...

Are you sure it is around 30 volts?  Is that peak, peak to peak or an rms reading?   If using a scope Double check your scope settings,   You should have some AC ripple there,  but it should be more like 7-10 volts peak to peak max at idle

To be frank,  if they are the original caps,  you need to replace them.  Don't wait or them to explode... That is a nasty mess to clean up.  Most techs would charge you a premium for cleaning that toxic goo up.

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#3 2013-01-19 12:33:15

bassofase
Member
Registered: 2010-12-13
Posts: 16

Re: When to do a recap...

The AC ripple its a bout 30v AC peak to peak.
I have some good cap's I cant use to replace them. But they are a little bit more uF. (Really good quality) They where quite expensive.

Could it be that old tube are pulling more current from the power supply? I only tested the amp with old original tube's.

Dirk Sander

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#4 2013-01-19 21:00:20

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

Re: When to do a recap...

I personally don't like to up the values too much on the reservoir caps.   How much are we talking?

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#5 2013-01-23 18:58:30

bassofase
Member
Registered: 2010-12-13
Posts: 16

Re: When to do a recap...

I have two 220uf/400V. There are from L.M.T.

Original the total value is about 55uf.

The new one's wil make it 110uF total. I saw this value in lots of amps.

Also I had this value in een old "Roost slave 200" amp from the UK. That amp used 6. el34 and sound really good!.

Thanks,
Dirk

Last edited by bassofase (2013-01-23 19:01:35)

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#6 2013-01-23 20:47:53

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

Re: When to do a recap...

It really depends on what you want the amp to sound like.   With higher cap values I find the v4 to sound much more stiff... Doesn't breathe like it does with the original values.   

Some amps behave differently with larger cap values.   I have a 100uf cap as the reservoir cap in my ampeg g12 (only 22 watts).  But the 7591 power tubes are so reactive in that amp to begin with.  Plus that is also a cathode biased amp which also gives it a more colored sound to my ears.

Give the caps a shot... Maybe you will like them,  but don't jump to the conclusion that bigger reservoir cap means less noise /better tone.

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