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KR9940 in the house

Thanks for your kind offer. Let's see how the weekend goes. I'm hoping the snow will melt so I can get the last leaves picked up.
 
Putting together a parts list and remembered you mentioned replacing the original bias pots. Do you happen to have a part number handy and did it require any modification to fit?

Cheers
 
thanks Guy. I'll check this out. I did get the receiver working and just monitoring it to see if it will blow up again. So far, I've fixed/blown up the amp section twice. Each time taking out more bits. I really hate blowing up new parts.

My digikey order shows

https://www.digikey.com/short/p1cn74

these are 1/2 watt parts. you may want to verify this is correct.
 
rickl said:
here is a pic of the cleaned up receiver. big difference from the pic above.

View attachment 1615057
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Nice.My older brother had this back in the 70s.Never had the demodulater box.He gave it me in the mid 80s in need of repair.Had it repaired and used for about ten years until it failed.The tech said it couldn't be repaired so I told just keep it.The night visual of that receiver is one that I'll always remember fondly.My first real stereo.
 
Appreciate it, yeah the list just says 200ohm (b) with nothin about the wattage, will look into it.

Hopefully it doesnt blow again, if it does I have two more minor things I noticed that may be potential clues.

1) I seen in the SM in the Main Amp Section parts list a part "F19-0135-05 Heat-proof sheet" and then noticed in a pic from some polish hifi site that there is a black piece of paper under the main amp board, perhaps that is the sheet. Mine didn't have the paper in there but I found out mine had been serviced once before. Maybe R45-48 can get hot enough to melt those wires?

2) The silver shield inbetween the two heat sinks, yours is on backwards, i imagine it doesnt effect anything but i'm just mentioning that incase it was like that originally and is a clue that someone before you had taken apart the HS.

The schematic is slowly starting to sink in for me so hopefully I can be more help here soon. ;)
 

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rickl said:
Finally got channel A biased. Q8 emitter resister seemed to drift once warm.

Works great until I installed the bottom.

Then this
View attachment 1671999
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Just a little tip on biasing these I found..on the rear heatsink if you remove the top and bottom screw on both sides leaving the center screws only you can open up that heatsink by swiveling the top towards the back of the amp making access to those resistors much easier
 
superdog said:
Nice.My older brother had this back in the 70s.Never had the demodulater box.He gave it me in the mid 80s in need of repair.Had it repaired and used for about ten years until it failed.The tech said it couldn't be repaired so I told just keep it.The night visual of that receiver is one that I'll always remember fondly.My first real stereo.
Click to expand...
if you stil need a demodulator box I have 3 or four of them
 
Than
keven7 said:
if you stil need a demodulator box I have 3 or four of them
Click to expand...
Thanks for the offer.I gave that unit away 25 years ago.I did find another on shopgoodwill for nostalgias sake.It was working but then did the same thing my previous one did.It would play out of the headphones but not the speakers.I think I'm done with it.
 
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