Roender's FC-100 prototype and builder's thread - Page 63

Rudi_Ratlos · 04:09 PM

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!

lucylu · 29th December 2012, 09:08 AM

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

Rudi_Ratlos · 29th December 2012, 10:01 AM

John, did you measure the DC-offset? How big is it?

Rudi

lucylu · 29th December 2012, 10:24 AM

Hello Rudi No not yet but will advise you i have not forgot,,taken my time
cheers john

Sheldon · 12:03 PM

Quote:

Originally Posted by lucylu

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

Rudi_Ratlos · 31st December 2012, 10:28 AM

... and another FC-100, of one of the GERMAN DIYers, working at first go.
The case is still temporary.

Best regards - Rudi

zsaudio · 31st December 2012, 10:33 AM

Where does that nice r-core come from?

Telstar · 31st December 2012, 12:03 PM

That one looks like Chinese. In eu you can find from selectronic in France.

franzm · 12:45 PM

Quote:

Originally Posted by Rudi_Ratlos

... 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.

jprco · 31st December 2012, 11:00 PM

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

31st December 2012, 12:03 PM	#628
Telstar diyAudio Member Join Date: Dec 2007 Location: Italy	That one looks like Chinese. In eu you can find from selectronic in France. __________________ "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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29th December 2012, 10:01 AM	#623
Rudi_Ratlos diyAudio Member Join Date: Jun 2009 Location: Hamburg / Germany	John, did you measure the DC-offset? How big is it? Rudi

29th December 2012, 10:24 AM	#624
lucylu diyAudio Member Join Date: Jun 2008 Location: England	Hello Rudi No not yet but will advise you i have not forgot,,taken my time cheers john

31st December 2012, 10:33 AM	#627
zsaudio diyAudio Member Join Date: Jun 2005 Location: Hungary	Where does that nice r-core come from?

31st December 2012, 11:00 PM	#630
jprco diyAudio Member Join Date: Jan 2009	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