Cant get my blue ray working because of amp. Anyone ?

[alexk0il]

Also power leads/connectors
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I might be able to unclip the unswitched connector, pull it out and desolder the wires, but how do i detach the main lead cable/connector?

[snowman_al]

Yes that is not the easiest to work on.

''I will try to reconnect all de-soldered wires back to confirm that the problem has gone''. -- That's the plan!

''I will try to find the way to attach the earth wire when I am done'', -- Please fit the earth lead before you plug it in again.
''the Asian/Latin american power board might be different and not have the connectivity to the ground. I will simply attach a proper lead to one of other Gnd terminals (Green wire on the LED PCB board on my photos).'' -- I would not.
-- The Very Best place to fit the earth lead to is the back of the GND terminal (it shows in your second lot of pictures). That way the case and chassis are always protected. (Using a point that includes a PWB track or thinner wire could result in it acting like a fuse in a fault condition and that would leave the case and chassis being Not Protected.)
There are a couple of useful things to read here about Earth Safety. http://sound.whsites.net/psu-wiring.htm sections 2.2 and 7. And http://sound.whsites.net/earthing.htm

TBC.

[snowman_al]

Question is do you need to take it apart any more?

Right now you just want to prove it works OK, so put it back together as much as is necessary.
To make it safe to test, without replacing the mains lead right away, add an external earth wire from the plug to the GND terminal on the case. Just make sure it is a good connection.

Then when you know it is working fit a 3 core mains lead. I expect removing the mains transformer will get you more room to do that?

To get the aerial connections off you need to unsolder the 2 wires from the case and then the 3 terminal lugs from underneath.


Again are there any caps you cannot get to without taking it all apart?

[alexk0il]

Hi Alan,

Finally got the job done, though I killed the FM receiver in the process and got a really nasty burn on one of my fingers from the soldering iron:

• grounding problem - fixed
• power supply capacitors - recapped
• bias - adjusted

We couldn't see it on a half disassembled amp because it only appeared when the heat sink panels were properly screwed to the chassis. It took me a while to find that it was related to the heat-sinks, but once I found it the rest was easy. The amp has a special jumper board attached to the heat sink, to switch between 220V and 240V. The person that screwed this jumper board was an imbecile, the 220V side was pressed so hard to the grounded heat-sink panels that the jumper board was bent. The 240V had a nice 3-5mm of clearance as it should. This would not be a problem, unfortunately two other factors kicked in:

1. The jumper was set at 220V instead of 240V, which contributed to overheating
2. Both bias regulating potentiometers were set exactly in the middle of their range, i.e. not regulated. The readings at test points gave 150mV/190mV for L/R channels instead of the required 8mV; another factor co contribute to the overheating

My guess, after years of running at extreme temperatures the insulation of the jumper board gave up. There were only ~3-5 Ohms resistance left between that wire and the Ground at that point. Not nice!

To fix it, I moved the jumper to 240V, plus squeezed a peace cut from my old driving license between the 220V point and the heat dissipating panel. I also readjusted the bias to 8mV, so no more overheating. See the attached image.
20180613_214126.jpg

The sound coming from this amp is now amazing - full, vivid, rich, detailed, dynamic, the humming and noise completely eliminated, and it is still getting better and better every day. It's headphones output is also so much better than of my Beresford BM, which I thought to be the pinnacle of the sound clarity and details, that I completely stopped listening to my headphones through the BM, only thorough the amp now.

Anyway, thank you for your guidance and help. I would have never made it without your support, and who knows, I could have been electrocuted due to the ground issue if I tried to work on the amp before fixing it. The beers are on me if you get to Marlow/Maidenhead area.

[snowman_al]

Well done Alex. Not a problem to help and I'm glad it is working safely. I wondered if it was in the skip by now ;-)

I can now see what the problem is from your latest picture...
You are correct, whoever assembled the voltage selector tag strip was a complete (expletive) twonk.

You MUST turn it trough 90 degrees and use the two vacant holes in the tag to mount it. You will have the correct clearance (loads) between the high voltage connections and the heat sink. And get your licence back!

Go and do it now ehy! Alan

[alexk0il]

Hi Alan,

Thanks for the tip, I see what you mean by 90 degrees, makes perfect sense.

Unfortunately I can't do it. The screws got "welded" or corroded into the mount and I don't have either a good clearance (can;t take the back panel off, remember ) and can't apply enough pressure to unscrew them without stripping the head off. I will check periodically if it is ok, may be will add insulating pads at 240V side as well. Or may be I will get a wrench that can work at 90 degrees, though I am still not sure if unscrewing it is still feasible. That little screw on the left (it is actually twice shorter than on the right) does not want to move.

Cheers
Alex

[snowman_al]

Maybe one of these ?

https://www.eurocarparts.com/ecp/p/t...xoC9BsQAvD_BwE

Alan

[alexk0il]

I will try, though it might not work. Im trying not to think about WD40, another option is to cold weld a nut to the screw and to use a nut socket with your tool.

Anyway, I'm on a a very long business trip, it'll probably take me more than a month to "get my license back" as you put it.