Just got a Sansui 5000. Heatsink very hot. Found out the bias in this thing was running at 450ma! Ouch. Lucky It dont have blown outputs. Was able to turn pot all the way own and get 26ma but something is obviously wrong with this driver board. Heard there is diodes that go bad and there is a mod but cant seem to find how to actually do the mod. Anyone familiar with this mod?
You mean this problem ?
Sansui 5000 w/ 1040 driver boards - potential for problems? | Audiokarma Home Audio Stereo Discussion Forums
And this type of "cure " --notice I don't think its a correct cure in the sense a redesign should have taken place but a "money saving " one-
When spare parts are no longer available... Sansui 5000 Receiver repair - DIY Audio Projects - StereoNET
Fit the diodes CLOSE to the output devices.
Sansui 5000 w/ 1040 driver boards - potential for problems? | Audiokarma Home Audio Stereo Discussion Forums
And this type of "cure " --notice I don't think its a correct cure in the sense a redesign should have taken place but a "money saving " one-
When spare parts are no longer available... Sansui 5000 Receiver repair - DIY Audio Projects - StereoNET
Fit the diodes CLOSE to the output devices.
Thanks for reply. I still dont see a how to anywhere even though they talk about it. They give a link to one but its a dead link. I was thinking the diodes replace the ones on top of driver transistors but you are saying put those close to output. Mabye I'm confused about the mod. Do you happen to know which diodes to replace and where to mount.
The output transistors circuit had a design fault that was well known to the manufacturers causing overheating , instead of adding extra heat-sinking they tried to overcome it by fitting diodes .
Their problem was that they fitted them on the opposite side of the board therefore not completely curing the fault , it was recommended that they be fitted near the hot output devices for better control.
Its not surprising that various versions of your amplifier were built.
My old Sansui I use for my TV has hot output devices but I don't use it for recreational hi-fi only for the TV so it doesn't get run near or at its limit.
Their problem was that they fitted them on the opposite side of the board therefore not completely curing the fault , it was recommended that they be fitted near the hot output devices for better control.
Its not surprising that various versions of your amplifier were built.
My old Sansui I use for my TV has hot output devices but I don't use it for recreational hi-fi only for the TV so it doesn't get run near or at its limit.
From what I remember they were standard 1N4148 diodes but I don't remember the connections I will check into it again.
Thanks I would appreciate that. I know there is a upgrade board F6013 but those are pretty much unobtanium unless you buy a whole receiver. I also love the way this one sounds. I had a 5000A with the upgraded board awhile back and dont remember it sounding as good as this one. very tube like for a receiver.
Try -
Sansui 5000A Driver Circuit Board F-6013
Canadian company --cost --$55 (USD)
The diode replacement was a temporary fix that wasn't 100 % reliable and was why they kept on upgrading versions of the basic 5000.
Or again in Canada -
Sansui 5000 5000A 5000x F-6013 amplifier Boards, Pair, reproduction Photo #2446419 - Canuck Audio Mart
Sansui 5000A Driver Circuit Board F-6013
Canadian company --cost --$55 (USD)
The diode replacement was a temporary fix that wasn't 100 % reliable and was why they kept on upgrading versions of the basic 5000.
Or again in Canada -
Sansui 5000 5000A 5000x F-6013 amplifier Boards, Pair, reproduction Photo #2446419 - Canuck Audio Mart
Thanks for links. The original one is out of stock and a just a little wary of the clone boards-sound quality might suffer. It is the diodes heatsinked atop the old round transistors on the driver boards that goes bad correct? Was thinking of replacing those changing heatsink compound on outputs, under bias to mabye 20 instead of 23 and put small fan on it if necessary.
If you are going ahead with the diode fix then yes put them as close as possible to the output devices , if you look at the updated card notice it has a BJT actually attached to one of the output devices so they realised that was the fault.
Yes small fans are cheap and will help ,make sure it blows on BOTH output devices .
Yes small fans are cheap and will help ,make sure it blows on BOTH output devices .
I replaced the diodes and bias current dropped significantly on the board mentioned. I ended up not using a fan because got to thinking if component failed anyway and caught on fire the fan might accelerate it. Lowered bias factory current from 23 to 20. I wouldn't think it would significantly affect quality. I may end up buying the clone boards but just think they are pricey considering this isnt a 500 receiver.