Adcom 585 problems 1 side hot other cold?

ben62670 · 21st November 2008, 04:42 AM

Well I did a large amount of work to this amp, and the boards have been cleaned, and all the caps replaced(thanks Chris). The DC offset is well within spec, and the bias is set to 24mv. Every thing is good except one heat sink is pretty hot, and the other is very cool. Also the 680r on the soft start board is very hot. You can not leave your finger on it. You can barely touch it! Both channels play, but I am not running it know out of concern.
Thanks
Ben

K-amps · 23rd November 2008, 08:05 PM

24mV bias on both channels confirmed?

ben62670 · 24th November 2008, 05:03 AM

Yes sir.

K-amps · 24th November 2008, 10:15 AM

Check for HF oscillations on the hot side.

check for open emitter resistors / outputs on cold side...

ben62670 · 24th November 2008, 07:47 PM

The emitter resistors are the small value resistors on the outputs on the trannies?

K-amps · 24th November 2008, 08:07 PM

Yup... the white handsome ones....

What the heck check the all the resistors on the OP boards...

ben62670 · 24th November 2008, 11:06 PM

Yeah I will. I checked everything on the inputs. Did the ultrasound simple green clean. Replaced all the caps, OpAmp, input resistors, diodes, and a couple other parts

I learned the hard way to not skip over anything that I can test.
Thanks
Ben

sajti · 25th November 2008, 09:12 AM

To check the HF oscillation, put one resistor, some 10ohms across the output terminals. If this resistor will be hot, you have oscillation on that channel.

Sajti

ben62670 · 25th November 2008, 09:57 PM

Quote:

Originally posted by sajti
To check the HF oscillation, put one resistor, some 10ohms across the output terminals. If this resistor will be hot, you have oscillation on that channel.

Sajti

What gets me is it plays fine. I should be able to hear an oscillation correct?

K-amps · 25th November 2008, 10:01 PM

Mostly all you hear is pssst or pffft if it is audible.... usually it is ultra-sonic (maybe your dog can hear it if you have one).. but not you or I.

Music would play ok.... that is not a sign that you lack oscillations...

21st November 2008, 04:42 AM	#1
ben62670 diyAudio Member Join Date: Dec 2006	Adcom 585 problems 1 side hot other cold? Well I did a large amount of work to this amp, and the boards have been cleaned, and all the caps replaced(thanks Chris). The DC offset is well within spec, and the bias is set to 24mv. Every thing is good except one heat sink is pretty hot, and the other is very cool. Also the 680r on the soft start board is very hot. You can not leave your finger on it. You can barely touch it! Both channels play, but I am not running it know out of concern. Thanks Ben

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23rd November 2008, 08:05 PM	#2
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	24mV bias on both channels confirmed?

24th November 2008, 05:03 AM	#3
ben62670 diyAudio Member Join Date: Dec 2006	Yes sir.

24th November 2008, 10:15 AM	#4
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	Check for HF oscillations on the hot side. check for open emitter resistors / outputs on cold side...

24th November 2008, 07:47 PM	#5
ben62670 diyAudio Member Join Date: Dec 2006	The emitter resistors are the small value resistors on the outputs on the trannies?

24th November 2008, 08:07 PM	#6
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	Yup... the white handsome ones.... What the heck check the all the resistors on the OP boards...

24th November 2008, 11:06 PM	#7
ben62670 diyAudio Member Join Date: Dec 2006	Yeah I will. I checked everything on the inputs. Did the ultrasound simple green clean. Replaced all the caps, OpAmp, input resistors, diodes, and a couple other parts I learned the hard way to not skip over anything that I can test. Thanks Ben

25th November 2008, 09:12 AM	#8
sajti diyAudio Member Join Date: Apr 2003 Location: Vác, Hungary	To check the HF oscillation, put one resistor, some 10ohms across the output terminals. If this resistor will be hot, you have oscillation on that channel. Sajti

25th November 2008, 10:01 PM	#10
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	Mostly all you hear is pssst or pffft if it is audible.... usually it is ultra-sonic (maybe your dog can hear it if you have one).. but not you or I. Music would play ok.... that is not a sign that you lack oscillations...

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