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Old 21st May 2013, 12:23 PM   #471
shaan is offline shaan  India
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Very very beautiful job John. Enjoy your Peeceebee.
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Old 22nd May 2013, 04:35 AM   #472
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Concerning elcos, a friend of mine who is in repair business for a long time, just reminded me that until elcos are fully formed various kinds of strange behavior are possible, including offset drift and even bias drift. No matter how good or expensive elcos are used, when new they will leak a little until fully formed. Especially critical are ones in NFB loop, 2200uF in this case.

Therefore, allow amp some time to achieve this equilibrium.
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Old 22nd May 2013, 07:25 AM   #473
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Quote:
Originally Posted by JOHN BALI View Post
Maybe just my feeling
They are tested & I will drill the heat sink, prepare PSU, etc,... anything that need to do

Now it time to share what I made

Thank you Shaan, Lazy Cat, PMI, Naf & everyone that support me
see you soon

I want to give it a name: VSV PeeCeeBee
PeeCeeBee size 50 mm * 84 mm a bit smaller than your ID card
I will slowly build PeeCeeBee design of Mr. Jhon
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Old 22nd May 2013, 09:51 AM   #474
AndrewT is offline AndrewT  Scotland
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Originally Posted by ivanlukic View Post
............... No matter how good or expensive elcos are used, when new they will leak a little until fully formed..........
When stored, or unused, not just when new, they will leak a lot, like 10000times more leakage than when fully re-formed.

Re-forming of test samples is a standard adopted by ALL manufacturers immediately before starting the measuring of parameters.
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Old 22nd May 2013, 12:51 PM   #475
PMI is offline PMI  United States
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Originally Posted by ivanlukic View Post
...Especially critical are ones in NFB loop, 2200uF in this case... Therefore, allow amp some time to achieve this equilibrium.
That would argue against just letting the board warm up, setting the offset, and then removing/replacing the trim pot with a permanent resistor.
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Old 22nd May 2013, 01:00 PM   #476
AndrewT is offline AndrewT  Scotland
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Or re-form all critical electrolytics BEFORE you solder them into your assembly.

Timing caps, audio coupling caps, biasing caps, DC blocking caps, HV caps, etc.
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Old 22nd May 2013, 01:29 PM   #477
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That would argue against just letting the board warm up, setting the offset, and then removing/replacing the trim pot with a permanent resistor.
Yes, I think when board is made in such way to include trim pots, they should remain there. Also, after several years of work there will probably be some drift in resistors and other components, so it is nice to have an easy method of compensating offset. In this case I prefer the board that you designed because it has trim pot!
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Old 22nd May 2013, 01:37 PM   #478
PMI is offline PMI  United States
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Originally Posted by AndrewT View Post
Or re-form all critical electrolytics BEFORE you solder them into your assembly.

Timing caps, audio coupling caps, biasing caps, DC blocking caps, HV caps, etc.
That is probably the best approach. However, the rail caps and the input cap won't change the setup, I think. The 2200 uFd cap just might.

I am aware of electrolytic caps' characteristics changing, and settling over time. I do NOT have any previous experience comparing two boards on separate channels that were built a few days apart.

I assume it will be difficult to compare test results in this thread, since we are all using different components...

In other words, any suggestions you may have will probably be helpful here.

Last edited by PMI; 22nd May 2013 at 01:40 PM.
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Old 22nd May 2013, 01:44 PM   #479
PMI is offline PMI  United States
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Originally Posted by ivanlukic View Post
Yes, I think when board is made in such way to include trim pots, they should remain there. Also, after several years of work there will probably be some drift in resistors and other components, so it is nice to have an easy method of compensating offset. In this case I prefer the board that you designed because it has trim pot!
Thank you, kind of you to say that! I am looking forward to some feedback when someone has built and listened to it!
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Old 22nd May 2013, 01:57 PM   #480
banat is offline banat  Serbia
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Originally Posted by AndrewT View Post
Or re-form all critical electrolytics BEFORE you solder them into your assembly.

Timing caps, audio coupling caps, biasing caps, DC blocking caps, HV caps, etc.
Andrew T

You are right 100 % ,
BTW , from many years of my experience Elko`s with lower ratings voltage is more critical than same Elkos with higher voltage for same reforming issue , but also for final operative life to , so I suggest that both 2200uF GNFB Elkos to have 16VDC ratings as optimum value , 105 C rated is not bad choice to .

Best Regards to All !

( Repair Man )
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