canuckaudiog
On a quest for high fidelity
Oh, don't forget to clean and retension the tube sockets as well.
Sansui 1000a trouble
- Thread starter jcon109
- Start date
jcon109
Active Member
John
Thanks for the Connie link That is a beautiful airplane.
My first thought was a preamp tube, had one let loose a few years ago and acted like this. I re cleaned all the tube sockets and pots up front, not sure how to clean the switches they look sealed.
Turned it back on and took the handle end of a screw drive and tap lightly around on tubes and front and popped and made static then all the sudden it became rock solid with no noise. Not sure if it is fixed or what??
Thanks for the Connie link That is a beautiful airplane.
My first thought was a preamp tube, had one let loose a few years ago and acted like this. I re cleaned all the tube sockets and pots up front, not sure how to clean the switches they look sealed.
Turned it back on and took the handle end of a screw drive and tap lightly around on tubes and front and popped and made static then all the sudden it became rock solid with no noise. Not sure if it is fixed or what??
canuckaudiog
On a quest for high fidelity
My thought is the pin wasn't making perfect contact with the socket and you moved it into place.
Great thread! Learned a lot reading all the responses.
Sometimes if the socket is worn, the tension on the pins and contacts are poor. In the past I've actually pushed the pins on the tube itself a little inward or outward to make them a bit tighter with the socket. By contracting or expanding the pin mounting circle, you may be able to get them to have more consistent contact.
Sometimes if the socket is worn, the tension on the pins and contacts are poor. In the past I've actually pushed the pins on the tube itself a little inward or outward to make them a bit tighter with the socket. By contracting or expanding the pin mounting circle, you may be able to get them to have more consistent contact.
canuckaudiog
On a quest for high fidelity
I am like you, I really enjoyed restoring my 500a. It was a lot of fun, and you learn so much from it. I recently picked up an AU-70 and am going through the same thing again. It's amazing how much quicker the recap process went this time, although unfortunately there is a hum on one channel and that's a whole different ball of wax.
But yeah, it's a lot of fun to pick out the parts, order them in, fine tune it, recap it.. and then ultimately, enjoy it after.
Trnsfmr
Well-Known Member
I restored a 1000A a couple years ago that was missing one of the diodes. It simply was not there with no signs of burnt leads or anything. I think it was the one on the lower half of the doubler. Amazingly, you could turn it on, and it worked!! It would make audio.
The HV was about half what it should have been. I replaced the missing diode and thoroughly rebuilt the rest of the PS. and the restoration came out good.
I would never have a 1000A without putting a rather large fan on it. I never found out what operating temperature it would stabilize at, as I could not believe how hot the transformers got. They seemed to be fine, measured exactly the same. While I had it, I would always run it with a fan or fans blowing on the output section.
And my mains voltage was not particularly high, 118vac or so.
Very nice sound, though.
The HV was about half what it should have been. I replaced the missing diode and thoroughly rebuilt the rest of the PS. and the restoration came out good.
I would never have a 1000A without putting a rather large fan on it. I never found out what operating temperature it would stabilize at, as I could not believe how hot the transformers got. They seemed to be fine, measured exactly the same. While I had it, I would always run it with a fan or fans blowing on the output section.
And my mains voltage was not particularly high, 118vac or so.
Very nice sound, though.
Take the temps with a laser or infrared thermometer. Normally a transformer can get as hot as 190* with no problems. Obviously the cooler the better. But they can get as hot a a dishwasher load of water (150* hot enough to cause 2nd degree burns) under normal operation. 120*water from a water heater is HOT on the skin.
The problem with the SANSUI is the placement of the tubes. All 3 transformers are affected to some extent but the center transformer is hot consisently across it's width due to tube placement. the outers will be cooler but still warm to slightly hot on the outer ends. Tung-Sol 7591a re-issues will help with this as the bottles are the size of the originals vs. the oversized bottles of the EH's.
I've placed HVAC Aluminum DUCT tape (silvered face) on the sides facing the tube to reflect some of the heat away from the transformers. Also the POWER RESISTORS on mine have been moved to the front fascia panel behind the dial cord. If these are in the original mounting expect the temps on the power and center output transformers to be 10-20* higher.
The transformer temps on my 1000A are: (after 1 hour of operation both sets of tubes). Temps are FARENHEIT.
EH7591A's
POWER: End side 135 tube side 143
Center output : 145 across transformer
outer output : 140 tube side, 135 end side
TUNG-SOL 7591A Re-ISSUE's
POWER: End side 135 tube side 138
Center output : 140 across transformer
outer output : 136 tube side, 133 end side
Tube choice has some bearing on transformer heating.
This is with NO FAN and cover off. Obviously temps will be slightly higher with the cover on. With the way mine is set up I see no need for fans directly on it. I do have a 12" fan in my room that moves the air around in the room. But it's not directed at the 1000A.
The problem with the SANSUI is the placement of the tubes. All 3 transformers are affected to some extent but the center transformer is hot consisently across it's width due to tube placement. the outers will be cooler but still warm to slightly hot on the outer ends. Tung-Sol 7591a re-issues will help with this as the bottles are the size of the originals vs. the oversized bottles of the EH's.
I've placed HVAC Aluminum DUCT tape (silvered face) on the sides facing the tube to reflect some of the heat away from the transformers. Also the POWER RESISTORS on mine have been moved to the front fascia panel behind the dial cord. If these are in the original mounting expect the temps on the power and center output transformers to be 10-20* higher.
The transformer temps on my 1000A are: (after 1 hour of operation both sets of tubes). Temps are FARENHEIT.
EH7591A's
POWER: End side 135 tube side 143
Center output : 145 across transformer
outer output : 140 tube side, 135 end side
TUNG-SOL 7591A Re-ISSUE's
POWER: End side 135 tube side 138
Center output : 140 across transformer
outer output : 136 tube side, 133 end side
Tube choice has some bearing on transformer heating.
This is with NO FAN and cover off. Obviously temps will be slightly higher with the cover on. With the way mine is set up I see no need for fans directly on it. I do have a 12" fan in my room that moves the air around in the room. But it's not directed at the 1000A.