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Old 27th December 2012, 04:06 PM   #621
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John is on the right way now, and I think that it won't take long until he posts: "Simply beautiful sound".

Best regards - Rudi

P.S.: I love your pictures!
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Last edited by Rudi_Ratlos; 27th December 2012 at 04:09 PM.
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Old 29th December 2012, 09:08 AM   #622
lucylu is offline lucylu  England
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Default The other side

Hi After sorting out one side with Rudi s guidance i started on the other side.
No problems works perfectly 36mv with 5 active tt diodes.

The problem i had with r28 smoke stopped when i changed the input short from 2 wires to ground(alum plate) to using a croco clip as in pic .. next music

regards john
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Old 29th December 2012, 10:01 AM   #623
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John, did you measure the DC-offset? How big is it?

Rudi
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Old 29th December 2012, 10:24 AM   #624
lucylu is offline lucylu  England
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Hello Rudi No not yet but will advise you i have not forgot,,taken my time
cheers john
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Old 29th December 2012, 11:56 AM   #625
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by lucylu View Post
Hi After sorting out one side with Rudi s guidance i started on the other side.
No problems works perfectly 36mv with 5 active tt diodes.

The problem i had with r28 smoke stopped when i changed the input short from 2 wires to ground(alum plate) to using a croco clip as in pic .. next music

regards john
You don't want a DC connection between circuit common and earth/heatsink. It should be connected AC only, via a cap. Something around 1uf will do.

Sheldon

Last edited by Sheldon; 29th December 2012 at 12:03 PM.
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Old 31st December 2012, 10:28 AM   #626
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... and another FC-100, of one of the GERMAN DIYers, working at first go.
The case is still temporary.

Best regards - Rudi
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Old 31st December 2012, 10:33 AM   #627
zsaudio is offline zsaudio  Europe
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Where does that nice r-core come from?
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Old 31st December 2012, 12:03 PM   #628
Telstar is offline Telstar  Italy
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That one looks like Chinese. In eu you can find from selectronic in France.
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"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
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Old 31st December 2012, 12:40 PM   #629
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Originally Posted by Rudi_Ratlos View Post
... and another FC-100, of one of the GERMAN DIYers, working at first go.
The case is still temporary.
Wow! Horizontal cooling fins. Cool. I mean hot.

Last edited by franzm; 31st December 2012 at 12:45 PM.
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Old 31st December 2012, 11:00 PM   #630
jprco is offline jprco  Canada
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Hi Rudi, follow up Post #610.
I wish I could say the New Year started on a happy note, but I'm starting to think this amp only works in Germany ( joking of course).
I measured the Vf's as best I could. The "hot" channel values varied from 430-450mV with the bypass on a 447mV one. The bias is steady at 36-38 mV, the DC offset is low at 1 mV but and the heat sink is hot at 60+C.
However the "cool" channel values were higher (470-490mV) with the bypass on a 470mV one BUT one diode measured low at 386mV. So I bypassed it since I don't know what I'm doing and now the bias on this channel starts at 25-30 and just keeps increasing 35-40-45-50 no sign of leveling off even while tuning back the trim pot, so power off. If I don't bypass that one but another, all is okay bias at 38 mV offset <3 mV and heat sink stays cooler at 45C!!!
This amp seems very touchy. Any ideas?
Happy New Year to all.
Jean
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