I am restoring a Sansui 1000A tube receiver. There seems to be a few versions. Some have a voltage selector switch and also the dual power resistors 68k & 600 ohms ones are either mounted near the output tubes or underneath the chassis. Someone removed the under chassis ones and added a sandcast one above. Prior to installing the last 20uf x4 can everything was fine except missing sound from the right channel. After installing the can, and using the variac (35V) I notice the can was producing a metal ringing noise from the can perimeter. I believe initially the metal twist tabs were being grounded to chassis. It blew the fuse and took one of the 6AN8?. It cracked the glass after voltage was removed. So, I have to figure the wiring from the power resistors to one of the 20uf lugs. Anybody know what went wrong?
Hi!
I have had several of these and when they are brought back to life they are an excellent sounding receiver. One other thing that needs to be looked at besides the electrolytics is the coupling caps for the 7591 tubes; they are almost always leaky and pass DC. In fact all those coupling caps that are grey in color and say "Japan" "oil" or whatever else on them are all leaky; change them out. It will save you a lot of headaches later on.
By the way, the output transformers in these receivers are excellent!
I have had several of these and when they are brought back to life they are an excellent sounding receiver. One other thing that needs to be looked at besides the electrolytics is the coupling caps for the 7591 tubes; they are almost always leaky and pass DC. In fact all those coupling caps that are grey in color and say "Japan" "oil" or whatever else on them are all leaky; change them out. It will save you a lot of headaches later on.
By the way, the output transformers in these receivers are excellent!
Hello
Thank you for the kind reply. I always replace all electrolytic and coupling caps as I did with the Sansui 1000A with the exception of 2 electroyltic cap (.005). I retraced my work and found 1 cap was soldered to a wrong lug (.05). However the two power resistors connections were done by some else whi left out 1 lead. There should be a total of 6 leads from the 6K and 608 resistors. But, it still worked minus one channel out. Since I have a second receiver I will install themas they should, 2 under the chassis and one above next to the output tube. Strange though that there are a few variations to this receiver. One being some have the voltage switch 120/240 and other do not. Could a simple missing wiring of one couple cap cause a fuse to blow and take out a 6AN8 tube to crack?
Anthony
Thank you for the kind reply. I always replace all electrolytic and coupling caps as I did with the Sansui 1000A with the exception of 2 electroyltic cap (.005). I retraced my work and found 1 cap was soldered to a wrong lug (.05). However the two power resistors connections were done by some else whi left out 1 lead. There should be a total of 6 leads from the 6K and 608 resistors. But, it still worked minus one channel out. Since I have a second receiver I will install themas they should, 2 under the chassis and one above next to the output tube. Strange though that there are a few variations to this receiver. One being some have the voltage switch 120/240 and other do not. Could a simple missing wiring of one couple cap cause a fuse to blow and take out a 6AN8 tube to crack?
Anthony
Dan is spot on about leaking coupling capacitors. To keep the OEM voicing intact, install Soviet surplus K40 paper in oil (PIO) parts. Top notch "oilers", like "Vitamin Q" and K40, are hermetically sealed. They don't leak.
Dan is also correct about the O/P "iron" Hashimoto is still winding.
Hmmm.
A leaking coupling cap. frequently causes an O/P tube to red plate and (perhaps) fail.
Dan is also correct about the O/P "iron" Hashimoto is still winding.
Hmmm.
A leaking coupling cap. frequently causes an O/P tube to red plate and (perhaps) fail.- Status
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