Edison 12, can anyone help?

SoundRight · 17th January 2012, 03:12 PM

Hi, I recently resurrected my Edison 12 power amp which had been in storage for nigh on 15 years and had new matched valves before being put away. But it had always had a problem on switch off..a chirrup through one speaker.

I have found a friendly and valve experienced qualified engineer who has established that one channel, on switch off, goes unstable in the RF range...immediate switch on causes the amp to oscillate.

Not taking anything from him but to speed up diagnosis..any one got any ideas? I have supplied him the schematic copied from another Edison 12 thread so he has that but it is quite apparent that many of the values are different....

Anyway..any advice!?

DF96 · 17th January 2012, 03:16 PM

Why not supply us with the circuit too?

flatheadmurre · 17th January 2012, 03:53 PM

Schematic.

http://www.erikasson.se/schemor/edison12.gif

M Gregg · 04:22 PM

If the diagram in post 3# is correct,

And the fault is in one channel...

Check the bias voltage (output tubes) across the cathode resistors on the good and bad channel
Post the values that you get..

Its important that when you take these measurements (make sure a load or speaker is connected or you will damge the OP Tx)..(Also dont start swapping tubes about etc or the results are of no use)

Regards
M. Gregg

flatheadmurre · 17th January 2012, 04:40 PM

I have a vague memory of a cheap multicap involved in some trouble in Edison 12.

The quality of the caps are probably not the best since it was designed as a fairly priced kit.

Is the amp factory buillt or a kit ?

SoundRight · 17th January 2012, 04:40 PM

Hi,

Thanks Flatheadmurre (and M Gregg)...I was just logging on to post the circuit!

Any useful tips I will pass on to the engineer who has it..this is an area in which I have no qualification...

I posted on the off chance that someone may have had the same problem and solved it...so thank you all for any input!

M Gregg · 17th January 2012, 04:44 PM

OK,

First of all is the fault in both channels..IE is it a stereo amp or monoblock?

SoundRight · 17th January 2012, 04:45 PM

..I don't have it here but as I recall it was "factory" built by a company in Brighton if the screen printing on the back panel is anything to go by! They have long gone...

It also has screened on the circuit board.."Edison 12 by Erik Anderson" or something similar...

flatheadmurre · 17th January 2012, 04:47 PM

The link i posted is the sight of the engineer of edison.

He´s a nice man and will answer any questions we can not solve here.

flatheadmurre · 17th January 2012, 04:48 PM

It´s a stereo amp.

17th January 2012, 03:12 PM	#1
SoundRight diyAudio Member Join Date: Jul 2010	Edison 12, can anyone help? Hi, I recently resurrected my Edison 12 power amp which had been in storage for nigh on 15 years and had new matched valves before being put away. But it had always had a problem on switch off..a chirrup through one speaker. I have found a friendly and valve experienced qualified engineer who has established that one channel, on switch off, goes unstable in the RF range...immediate switch on causes the amp to oscillate. Not taking anything from him but to speed up diagnosis..any one got any ideas? I have supplied him the schematic copied from another Edison 12 thread so he has that but it is quite apparent that many of the values are different.... Anyway..any advice!?

17th January 2012, 04:10 PM	#4
M Gregg diyAudio Member Join Date: Jun 2010 Location: UK	If the diagram in post 3# is correct, And the fault is in one channel... Check the bias voltage (output tubes) across the cathode resistors on the good and bad channel Post the values that you get.. Its important that when you take these measurements (make sure a load or speaker is connected or you will damge the OP Tx)..(Also dont start swapping tubes about etc or the results are of no use) Regards M. Gregg __________________ What is the sound of one hand clapping? Last edited by M Gregg; 17th January 2012 at 04:22 PM.

17th January 2012, 04:44 PM	#7
M Gregg diyAudio Member Join Date: Jun 2010 Location: UK	OK, First of all is the fault in both channels..IE is it a stereo amp or monoblock? __________________ What is the sound of one hand clapping?

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17th January 2012, 03:16 PM	#2
DF96 diyAudio Member Join Date: May 2007	Why not supply us with the circuit too?

17th January 2012, 03:53 PM	#3
flatheadmurre diyAudio Member Join Date: Mar 2011 Location: Jarna	Schematic. http://www.erikasson.se/schemor/edison12.gif

17th January 2012, 04:40 PM	#5
flatheadmurre diyAudio Member Join Date: Mar 2011 Location: Jarna	I have a vague memory of a cheap multicap involved in some trouble in Edison 12. The quality of the caps are probably not the best since it was designed as a fairly priced kit. Is the amp factory buillt or a kit ?

17th January 2012, 04:45 PM	#8
SoundRight diyAudio Member Join Date: Jul 2010	..I don't have it here but as I recall it was "factory" built by a company in Brighton if the screen printing on the back panel is anything to go by! They have long gone... It also has screened on the circuit board.."Edison 12 by Erik Anderson" or something similar...

17th January 2012, 04:47 PM	#9
flatheadmurre diyAudio Member Join Date: Mar 2011 Location: Jarna	The link i posted is the sight of the engineer of edison. He´s a nice man and will answer any questions we can not solve here.

17th January 2012, 04:48 PM	#10
flatheadmurre diyAudio Member Join Date: Mar 2011 Location: Jarna	It´s a stereo amp.

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