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Old 15th September 2011, 12:13 AM   #11
Ronj is online now Ronj  Singapore
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Mission complete with out any causalities so far...
I changed'm all!!! All power supply caps I increased by 1000F or so... so used 4700F and 3300F instead of 3300F and 2200F respectively...

I used Panasonic caps for all power supply filtering... All small electrolytics I used Nichicon... And all caps 3.3F and below, I used Panasonic Metalized Polypropylene including for what seemed to be two sets of signal coupling caps at 3.3F...

Here is the picture of the board after change...


Oh yeah it still works! Took 2-3hours for the high-end to come out though... I don't know why... I was never a believer in electronic component break-in...

To deal with the "sticky situation" of those diodes... I have used some silicon selant for the time being,,, I know it is not supposed to be used... so still waiting for someone to help me find the right glue...

Cheers...

Last edited by Ronj; 15th September 2011 at 12:17 AM.
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Old 15th September 2011, 12:14 AM   #12
Ronj is online now Ronj  Singapore
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Old 15th September 2011, 01:45 AM   #13
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Hi RonJ
Those thermal sensing diodes will be for the bias control and the main requirement is close contact with the heatsink. Clamp the diodes to the sink while any adhesive sets to make certain. Funny that they became detached - why?

So long as the leads remain electrically isolated from the sink, any high temp. adhesive will work (i.e. not 5 min. epoxies). It is surprising that a metal flag type was not just screwed to the sink - this was common practice with thermistor/diode sensors in the same period. There is no glue requirement there, perhaps just a dab of heat conductive paste.
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Old 15th September 2011, 02:17 AM   #14
Ronj is online now Ronj  Singapore
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Quote:
Originally Posted by Ian Finch View Post
Hi RonJ
Clamp the diodes to the sink while any adhesive sets to make certain. Funny that they became detached - why?
They were never clamed to the heat-sink at least no traces of any clamping... They were covered with something that look like soldering flux... and they were stuck on to the heat sink with that... then I saw two the diodes were no longer in contact with the heat-sink... thats how I noticed it...May be I will clean then throughly and re-attach using some epoxy which can take 100DegC or so...
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Old 15th September 2011, 03:02 AM   #15
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... They were covered with something that look like soldering flux... and they were stuck on to the heat sink with that... then I saw two the diodes were no longer in contact with the heat-sink...
Well, that explains it (they used the dreaded brown glue)- lucky that the amplifier did not go into thermal runaway when the diodes became detached.
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Old 15th September 2011, 03:23 AM   #16
Ronj is online now Ronj  Singapore
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thermal runaway... hmmm whats the worst case? fried power transistors? So i need to glue them again... then paste some heatsink compound on top? I dont know these epoxies how good of a heat conductor are they...
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Old 15th September 2011, 03:40 AM   #17
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If the amplifier was still working, don't be concerned. Just use normal epoxy and clamp whilst setting. Nothing more - since you can't improve thermal contact with a covering of anything.
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Old 4th October 2011, 09:29 AM   #18
Ronj is online now Ronj  Singapore
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Just an update! Amp has nicely settled in now. It sounds excellent. Everything works as before... All caps have been replaced. Every cap below 10F have been replaced with a polypropylene equivalent. I am using this amp everyday now... Trying to fix a Sansui S-40 to be used with this amp...

Read more about it here...
Sansui S-40 3-way vintage speakers
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Old 1st September 2012, 05:57 PM   #19
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Default Sweet amplifier

I am in love with this amplifier.....lovely one!

regards,

Carlos
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Old 1st September 2012, 06:11 PM   #20
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Originally Posted by destroyer X View Post
I am in love with this amplifier.....lovely one!

regards,

Carlos
Me too ...!!
I recapped totally a Nikko TRM 600 three months ago
And I'm thinking of eliminating all the knobs ....
well , that would be a new amplifier .
Because it has a separation between pre and amplifier stages , in the
end I much preferred to use a separated and specialized preamplifier.
The preamplifier is the real bottleneck of the project , though it does its
duty decently ( you wouldn't believe it after seeing the schematics : transistor>coupling cap;transistor>coupling cap;etc ) Also , after having substituted the supply caps from
6m8 to 10 mF , I had encountered another big bottleneck which was the wiring to the speaker selector , then the switches , then the 'surge' protection
and eventually the binding posts . I removed them and put big wires and binding posts ( the wires, I used them for my mid-tweeter )
Indeed , many clever people say ' do not mess with old amps and don't touch or change anything' ....

Last edited by picowallspeaker; 1st September 2012 at 06:15 PM.
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