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Old 10th January 2010, 10:31 AM   #531
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Thanks
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Old 1st February 2010, 06:52 PM   #532
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Quote:
Originally Posted by audio1st View Post
If it is OK you can unscrew and remove the 1u5F cap, cut the wires near the board and remove the 100k resistor near the input.
Hi Barry

The amp is working OK, and hasn't blown a fuse. I haven't removed these parts, do they need to be removed?

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Old 3rd February 2010, 03:02 PM   #533
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Hi Richard

Not necessarily..

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Old 14th February 2010, 11:31 AM   #534
dodo is offline dodo  Poland
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Hi I have question to some EE
How importnat is the transistor matching in the cap multiplier circuit , f.e. in Pedja discrete regulator
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Old 14th February 2010, 06:03 PM   #535
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To be honest Dodo - I don't know! I have only ever bought those transistors in ones and twos so have never had the chance to match them.

However, I've built four of those modules now and they all appear to work very well without any problems!
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Old 15th February 2010, 08:40 AM   #536
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Hi I have question to some EE
How importnat is the transistor matching in the cap multiplier circuit , f.e. in Pedja discrete regulator
Hi Dodo

I built a pair of these last year, and from what I can remember the transistors don't need to be matched. I think its preferable to purchase them with a '-16' e.g BD139-16 as it of guarantees a certain power output within a range.

Transistors sold without the -16 extension could have a wider tolerance.

I maybe wrong, but I'm sure someone will correct me if I am.

I hope this helps
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Old 15th February 2010, 10:34 AM   #537
AndrewT is offline AndrewT  Scotland
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no need to match or select, just solder them in.

The 16 indicates the gain range (hFE at the specified test current and temperature).
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Old 15th February 2010, 11:04 AM   #538
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See...it didn't take long
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Old 5th April 2010, 02:24 AM   #539
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This is my GC LM 3886 with PSU. Dioda I used RHRP3060 dan 4 transformer 0-24VAC..
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Dioda:
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Old 20th April 2010, 03:39 AM   #540
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Quote:
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Hi Dodo ... I built a pair of these last year, and from what I can remember the transistors don't need to be matched. ... I hope this helps
Tripmaster is right on here! (So is AndrewT.)

Trying to "match" the power supply regulation transistors is like chasing that last 1% in engineering design. Too much work for too little reward.

Better point: How about dual "pilot light" LEDs instead of the single LED1 = This would do a better job of more closely "balancing" or "matching" the +/- rail voltages.

If you really want to make the two +/- rails "match", you might consider a variable pot substitute at R13 (= 2k linear variable trim pot) ... which would let you more closely match the minus (-) side rail with the plus (+) side ... find a really good volt meter for this. Best to "trim" under load = amp(s) all running and connected to speakers, input source quiet but connected. When you get to a 3 decimal point match, seal it and ignore it for at least 1 year, then trim it again ... I would bet no future trimming is necessary.

(Don't try matching the Zener Diodes ... )

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