I`ve got 1969 Sansui 5000A tuner amplifier and it worked for a day. Then both channels became very weak and distorted, both at the same time. Sound became choppy and at full volume it`s just a distortion. I`d expect 1969 amplifier in need of recapping but both channels became like this at the same time make me think that problem lies in power supply since it`s shared by the both channels. Ideas?
Are you able to measure DC voltages? Certainly take the hood off and see of there's something burned/burning and what the power supply voltages are now. Post the results here - it could be something as simple as a shorted diode.
Thanks for a quick reply. Yes I can measure voltages.there nothing burned, no black residue, no smell.
output transistors collector to ground shows 79 volt and half that on the next transistor, exactly what it should be i think. Will get to power supply directly next. While it was playing yesterday output was feels like underpowered. Hard to explain but didn`t sounded right. Both channels. For a moment I thought power supply not providing enough juice. not terrible bad but certainly not as expected.
output transistors collector to ground shows 79 volt and half that on the next transistor, exactly what it should be i think. Will get to power supply directly next. While it was playing yesterday output was feels like underpowered. Hard to explain but didn`t sounded right. Both channels. For a moment I thought power supply not providing enough juice. not terrible bad but certainly not as expected.
You're very fortunate that something more serious hasn't happened, after 50 years all of the original electrolytic capacitors will have deteriorated and a complete failure of one of them could result in an exploding capacitor or damage to power transformer, rectifiers or components/semiconductors in the amplifier. I would not even turn it on again until all of the electrolytics have been replaced. (not just power supply)
I moved it to solid state..I’d replace all of them. Thank you.Its just I want to find a failure first. Amp spent most of those 50 years in its box. Not powered up capacitors shouldn’t deteriorate at the same rate.
Get two 2200uF/100VDC electrolytics for the main supplies, and one 2200uF/50VDC for the aux supply.
Replacing those three will probably get it working well enough to check out the rest of the circuit.
Then check the two 25VDC voltage regulators for proper outputs, and also the two electrolytic output
coupling capacitors, which probably should just be replaced. This is a single supply circuit, so the amplifier
outputs sit at half the supply voltage, before the output coupling capacitors. Use only 100V parts there too.
Replacing those three will probably get it working well enough to check out the rest of the circuit.
Then check the two 25VDC voltage regulators for proper outputs, and also the two electrolytic output
coupling capacitors, which probably should just be replaced. This is a single supply circuit, so the amplifier
outputs sit at half the supply voltage, before the output coupling capacitors. Use only 100V parts there too.
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Nichicon from Digikey or Mouser, but your capacitors may have axial leads rather than pcb mounting
like most new ones are. See what kind of case the ones in the receiver have.
If you intend to complete restoring the receiver, you may want to order all the rest of the electrolytics
at the same time as these to save the extra shipping cost. They shouldn't cost very much.
Post some photos of the circuits.
like most new ones are. See what kind of case the ones in the receiver have.
If you intend to complete restoring the receiver, you may want to order all the rest of the electrolytics
at the same time as these to save the extra shipping cost. They shouldn't cost very much.
Post some photos of the circuits.
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I discharged all big capacitors. When shorted Two capacitors I pointing too has charge on them. Lower two has nothing.