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Old 26th May 2012, 07:50 AM   #961
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by danielwritesbac View Post
Elvee told me that the reverse voltage spec isn't used since there's no reverse voltage employed at those locations. At D4/5, the 35v and 45v diodes are fine.

At D7, you could use BAT86 if you wanted a stronger part, but BAT85 will also do fine.
A word about D6/D7: if the BATxx is not available, a possibility is to replace both diodes by fast 1A ones like BYD33, BYV26, UF4004, etc.
This combination will be equivalent to 1N4148+BAT85 (Do not use schottkies!!!)
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Old 26th May 2012, 08:39 AM   #962
abetir is offline abetir  Philippines
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Originally Posted by terranigma View Post
In Philippines, you could find a plenty variety of good transistors out there.
That is correct after I have sampled the sonic quality of this amp, I may have to settle for D1047s.... But I think I am in trouble...right now. I did Elvees and using the latest mods for the CFP, but after powering, D669s were getting too hot in a matter of seconds...

I am not so sure though if I did rightfully the mod for the omission of the offset trimmer. It was stated "apply 10k between point A and B". I decided to use a low +/-24vdc (pre-amp supply) just for a test. Near the 331pf (red cap) was the 470 ohms input resistor and in the image it was missing but I have corrected that now. I did a comparison with the component lay-out provided and it looks though that I did it correctly excepting the phase-splitter trannie as you can notice in the picture they were facing the other way because I used 2N5551. The TO-220 devices were MBR1045...but now I just can't seem to find what was amiss...

...guess I will be needing your help guys..
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File Type: jpg IMG_0039.jpg (561.8 KB, 287 views)
File Type: jpg 10Kb_bias.jpg (560.3 KB, 266 views)
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Old 26th May 2012, 11:54 AM   #963
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Quote:
Originally Posted by abeteer View Post
. . .D669s were getting too hot in a matter of seconds. . .
At Q5, Q6? There's a high chance of fake Hitachi. You can review this photo to find out <link

Do I see light gray colored drivers (Q9, Q11)? BD140 types max out at 40+40vdc rails.

The drivers do need a heatsink.

P.S.
There are some toshiba pairs that Elvee tested as working well for vas and driver--2sc5171, 2sa1930 and 2sc3421, 2sa1358
P.P.S.
With your 24+24vdc supply, did you also adapt R21, D8, D9?
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Last edited by danielwritesbac; 26th May 2012 at 11:57 AM.
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Old 26th May 2012, 12:27 PM   #964
abetir is offline abetir  Philippines
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R21=33k
D8, D9 = 12v 1w zeners

BD140 (gray) & D669a are fakes...but I am not so sure though, they look like made in the Philippines... In my place and in my experience, fake ones will work ok but of course they won't last. I've been utilizing them just for testing purposes only and when everything works fine I replaced them with the genuine ones. Genuine 2SC3421 is available here (expensive though costs 3x the local one). I have not installed the driver heatsink yet it was a quick test and the PSU was only around 0.5 ampere. Was the parts orientation correct?
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Old 26th May 2012, 12:34 PM   #965
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Quote:
Originally Posted by Elvee View Post
A word about D6/D7: if the BATxx is not available, a possibility is to replace both diodes by fast 1A ones like BYD33, BYV26, UF4004, etc. This combination will be equivalent to 1N4148+BAT85 (Do not use schottkies!!!)
Can MR types be used for this?
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Old 26th May 2012, 12:41 PM   #966
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Quote:
Originally Posted by abeteer View Post
R21=33k D8, D9 = 12v 1w zeners
BD140 (gray) & D669a are fakes...but I am not so sure though, they look like made in the Philippines... In my place and in my experience, fake ones will work ok but of course they won't last. I've been utilizing them just for testing purposes only and when everything works fine I replaced them with the genuine ones. Genuine 2SC3421 is available here (expensive though costs 3x the local one). I have not installed the driver heatsink yet it was a quick test and the PSU was only around 0.5 ampere. Was the parts orientation correct?
I can't quite see the parts orientation. You'll just have to trace. Either that or go buy the trimmer.

You might want to check your gray drivers to see if the leads are especially/unusually flexible because of soft copper inside the leads. Those might be the very rare (and desirable) Philips BD140, such as in this photo. <link
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Old 26th May 2012, 01:01 PM   #967
abetir is offline abetir  Philippines
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Very similar (from the link) the number was imprinted in black ink too, not the usual embedded pattern. The leads had this white powder coated flat finish and yes they are soft, easily bends when poked around...but they come cheap here so I figure they are imitation.
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Old 26th May 2012, 02:33 PM   #968
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Quote:
Originally Posted by abeteer View Post
Very similar (from the link) the number was imprinted in black ink too, not the usual embedded pattern. The leads had this white powder coated flat finish and yes they are soft, easily bends when poked around...but they come cheap here so I figure they are imitation.
Early genuine Philips BD ones marked with ink and having soft legs (pure copper?) just like you mentioned. They have to used with heatsink bars on circuit.

If your heat observation related Q5/Q6 is really excessive, (I mean above 100 °C) you may be straight about for a possible issue. I used metal bodied genuine transistors as Q5/Q6 on my builds and I didn't notice any excessive heat dissipation from them with healthy builds. You have to be sure about they are genuine and you have to accept that plastic package transistors can't dissipate heat that much already.

Did you measure dc-offset and quiescence current? Circuit must waste 150-200mA without any load. Offset trimmer is not a critical part of circuit, you can omit it if you haven't any concern about precise offset. It has nothing to do with hundreds of milivolts of offset.

I attached an image with correct values with Elvee's latest experiments on CFP edition's compensation values.
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Last edited by terranigma; 26th May 2012 at 02:46 PM.
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Old 26th May 2012, 03:10 PM   #969
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abeeter, it looks like some transistor's orientation in CFP row is problematic. I marked them with red circle. You may refer to post #809 for actual layout.
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Last edited by terranigma; 26th May 2012 at 03:25 PM.
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Old 26th May 2012, 03:19 PM   #970
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Quote:
Originally Posted by abeteer View Post
Very similar (from the link) the number was imprinted in black ink too, not the usual embedded pattern. The leads had this white powder coated flat finish and yes they are soft, easily bends when poked around...but they come cheap here so I figure they are imitation.
They're $10 apiece here and were discontinued in 1988. Maybe your vendor is unaware that the stock houses have eventually begun to run out.
Anyway, if you have the gray Philips BD139, they're COB 6pf and the specs work for Q5, Q6 (a LOT better than fake hitachi exploding in about 10 minutes).

EDIT: The rating on the Philips BD139 says its going to need a heatsink, such as an inexpensive small to220 clip heatsink or the circle from the bottom of the beer can--anyway, about that much metal. They do also need thermal paste.
With the plastic case devices you'll need to get the heat out of them since they do all suffer from internal heat pooling because of their plastic cover.
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Last edited by danielwritesbac; 26th May 2012 at 03:38 PM.
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