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Old 20th August 2013, 08:57 AM   #131
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Your final checkout number are diffrent then mine.
Forgive me for saying that but did you checked that you recieve 350V from the PT. (mybe they switched the pins ).
If i run PSUD with 400V and not 350V i get your number.
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Old 20th August 2013, 10:39 AM   #132
zxx222 is offline zxx222  Europe
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Ran, thank you for a tip, it makes sense. I am posting picture of my PT wiring - it seems to be right 350-0-350. But I must obviously check it - they might have soldered secondaries to wrong pins in factory

It should not be the case as PT seemed to be factory tested, but you never know - I will measure and post values of all secondaries along with mains voltage.

It will be lol if they mixed stuff up
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Old 20th August 2013, 01:24 PM   #133
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Quote:
Originally Posted by zxx222 View Post
I ordered set of 2.2 and 4.5 uF 450V electrolytic caps -
For those values I would use film caps, they are affordable and reasonably sized. A basic film cap (like a Solen) will outperform a boutique electrolytic and they are available in 600V rating.

You can get your B+ lower by lowering the first cap value. Pick up a few values less than 1uf like .22uf, 33uf etc and try them. Vanilla no-name film caps work great for these tests.

The lowest that you can get will be about 90% of your transformer secondary (pseudo L-C supply with a tiny first cap)

Do you have different primary taps on the 9612 like 220V and 230V?

It does seem odd that your B+ is so different than Rans with exactly the same PS components.....
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Old 20th August 2013, 07:37 PM   #134
zxx222 is offline zxx222  Europe
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I am confused - Pt secondries are ok, these are my voltages at no load:
Mains 230V actual is 232V.
The only primary for pt is 230 V (2x 0-115V in series)
Both 6.3v 4a secondaries are 6.33V
5v 6a secondary is 5.07V
700V secondary is 712V
800V secondary is 814V
I connected to board 350-0-350 and do not understand why I get such high B+. It seems that now I must crank up bias to 70mA to see how much B+ drops with current capacitor value as boywonder suggested. I will post my findings after that.
Regarding type of caps - I use dirt cheap electrolytics in series for start up, but I have purchased audyn MKP Q6 8.2 F 600v for C4 based on values that Ran was posting, however in my case it seems to be useless. I will use film cap after I will tune B+ to desired value.
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Old 22nd August 2013, 06:58 PM   #135
zxx222 is offline zxx222  Europe
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I am stupid - I was biasing power tubes not 70 mA, but 7 mA. I was rather surprised that tse was playing music more silent than sse and then checked multimeter scale.

Now my B+ is 324 V, bias 70 mA, so I guess it is safe to put 8.2 uF C4 film cap for 400B+.
Thank you boywonder and Ran for help. Will run it breadboarded for some time for break-in, enjoying HD Acis and Galatea performed by Dunedin Consort
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Old 22nd August 2013, 08:12 PM   #136
zxx222 is offline zxx222  Europe
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It probably was not the best idea to use cheap electrolytics in series for C4 - after couple of hours playing I noticed strange smell and bias of power tubes went down to 44mA from 71 mA, B+ also drifted down from 325 to 270 Volts.
One of caps that were in series started leaking and oak board below them was soaked with electrolyte. So I guess I have to finally put film cap there before making any furhter listening tests.
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Old 22nd August 2013, 09:22 PM   #137
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Quote:
Originally Posted by zxx222 View Post
It probably was not the best idea to use cheap electrolytics in series for C4 - after couple of hours playing I noticed strange smell and bias of power tubes went down to 44mA from 71 mA, B+ also drifted down from 325 to 270 Volts.
One of caps that were in series started leaking and oak board below them was soaked with electrolyte. So I guess I have to finally put film cap there before making any furhter listening tests.

What was the voltage rating of that cap?

When you run HV caps in series you need equal value resistors across each cap (like 220K or so) or the differing ESR of the caps will result in one taking more voltage drop than the other. The resistors are a simple voltage divider forcing the node between them to be half way between B+ and ground. I suppose you could pick unequal resistor values of your caps have different voltage ratings.
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Old 23rd August 2013, 07:15 AM   #138
zxx222 is offline zxx222  Europe
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It makes sense - I did not put any resistors across capacitors, both of them were 450V rated, but different capacities - that probably had negative effect too. I will take it into acount for future projects. I have 8.2 uF film cap with 600V rating that was dedicated for that position, I will simply put it instead of those leaking electrolytics - anyway I was planning to use them only for initial tests to dial-in B+.
I see that what I get with 2.7 uF cap is close to simulated result of PSUD I, so it is safe to asume that with 8.2 uF I will have close to 400V B+.
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Old 23rd August 2013, 07:28 PM   #139
zxx222 is offline zxx222  Europe
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Indeed, with 8.2 uf C4 my B+ is 398/402 volts with power tubes biased at 64 mA. Connected additional 30 uF film cap in parallel to C5 and will let amp to burn in for some time.
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