I have six bits of stereo stuff on the bench...all with varying degrees of problems.
Pioneer SX3700 receiver, circa 1981. This is a transitional receiver. It has an analog tuner with a "quartz lock" mechanism that will fine tune the stations for you. It has a fluorescent power meter and frequency display in addition to the analog dial. Works fine except for poor reception on FM frequencies lower than 102MHz and a scratchy volume knob. Needs an alignment and a shot of tuner cleaner.
Technics SA370S all in one stereo thingy, again, from 1981
Numerous issues. Blown output stage repaired, has intermittent readouts on the dB meter and the shortwave/AM section is silent. Tape deck still works though. Got lucky getting the needed STK module.
Technics SA-404. Blown STK 8040 modules....rails on the output, protection circuit was fortunately not out to lunch and the speakers were saved. Using the more robust 8050 module for repairs. This is another transitional unit from the early 80s. It has a fully digital tuner but a funny meter on the front panel that has been calibrated to the AM/FM dial.
Pioneer SA something from 1981:
This cool 60W or so amp is dead. The fluorescent meter lights up but no click of life comes from the relay. I picked it up from a repair shop that went under and got bought out and turned into a comic book shop. Got it and a dead Onkyo amp for the amazing price of $5.
Its a cool looking amp...the usual silver faced with FL meters; just the way I like em! It will be a perfect companion to my SX3700 "Fluoroscan" receiver in the shop.
The repair shop did the expensive part for me! It has a new set of output and driver transistors! All the solid state stuff seems fine but one burnt resistor was left by the shop.
This resistor feeds the +24V supply that feeds the relay and the protection circuit among other things. Im gonna have to get crafty to figure out what it was without a schematic.
I know or can measure the following:
The voltage on the main PSU VCC rail
The power dissipation capability of the burned resistor (1/4W)
and I know the voltage that the circuit wants due to the relay saying 24V.
Time to get cracking with Ohm's Law.
Precision probably isn't paramount here. As long as I don't put too much voltage to the circuit it should be fine. 2-3V off and it should still work.
Technics SU-V5
This is a sweet amp. 60W/ch at an amazing 0.0005% THD. Amazing cosmetics and those awesome VFD meters I like so much. Its not the prettiest thing they ever made (that would be the nearly unobtainable SU-8099) but it sure is nice....when it works. 29 years have not been kind to the electrolytics in the signal path. Turning the volume WAY up will cause the sound to suddenly come back to life for anywhere from 5 minutes to 5 days. The volume pot itself is not scratchy.
Technics SU-V3
This is the little bro to the V5 above. Less preamp features (doesnt have MC/MM option in the phono amp) and 40W instead of 60W but the rest is still there. It powers up but there is no sound from the relay. I suspect a shorted output transistor or a bad electrolytic cap in the protection circuit.
Well time to get crackin! Pics coming later!
Pioneer SX3700 receiver, circa 1981. This is a transitional receiver. It has an analog tuner with a "quartz lock" mechanism that will fine tune the stations for you. It has a fluorescent power meter and frequency display in addition to the analog dial. Works fine except for poor reception on FM frequencies lower than 102MHz and a scratchy volume knob. Needs an alignment and a shot of tuner cleaner.
Technics SA370S all in one stereo thingy, again, from 1981
Numerous issues. Blown output stage repaired, has intermittent readouts on the dB meter and the shortwave/AM section is silent. Tape deck still works though. Got lucky getting the needed STK module.
Technics SA-404. Blown STK 8040 modules....rails on the output, protection circuit was fortunately not out to lunch and the speakers were saved. Using the more robust 8050 module for repairs. This is another transitional unit from the early 80s. It has a fully digital tuner but a funny meter on the front panel that has been calibrated to the AM/FM dial.
Pioneer SA something from 1981:
This cool 60W or so amp is dead. The fluorescent meter lights up but no click of life comes from the relay. I picked it up from a repair shop that went under and got bought out and turned into a comic book shop. Got it and a dead Onkyo amp for the amazing price of $5.
Its a cool looking amp...the usual silver faced with FL meters; just the way I like em! It will be a perfect companion to my SX3700 "Fluoroscan" receiver in the shop.
The repair shop did the expensive part for me! It has a new set of output and driver transistors! All the solid state stuff seems fine but one burnt resistor was left by the shop.
This resistor feeds the +24V supply that feeds the relay and the protection circuit among other things. Im gonna have to get crafty to figure out what it was without a schematic.
I know or can measure the following:
The voltage on the main PSU VCC rail
The power dissipation capability of the burned resistor (1/4W)
and I know the voltage that the circuit wants due to the relay saying 24V.
Time to get cracking with Ohm's Law.
Precision probably isn't paramount here. As long as I don't put too much voltage to the circuit it should be fine. 2-3V off and it should still work.Technics SU-V5
This is a sweet amp. 60W/ch at an amazing 0.0005% THD. Amazing cosmetics and those awesome VFD meters I like so much. Its not the prettiest thing they ever made (that would be the nearly unobtainable SU-8099) but it sure is nice....when it works. 29 years have not been kind to the electrolytics in the signal path. Turning the volume WAY up will cause the sound to suddenly come back to life for anywhere from 5 minutes to 5 days. The volume pot itself is not scratchy.
Technics SU-V3
This is the little bro to the V5 above. Less preamp features (doesnt have MC/MM option in the phono amp) and 40W instead of 60W but the rest is still there. It powers up but there is no sound from the relay. I suspect a shorted output transistor or a bad electrolytic cap in the protection circuit.
Well time to get crackin! Pics coming later!
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