Recent content by 1rebmem

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    Operation and effectiveness of the protection circuit on the Sansui 3000A

    The Sansui 3000A dates to 1967/1968 time frame so its design was unusual. The protection circuit is very uncommon I believe. The 3000A has + and - 40v rails and a .3 ohm resistor is fitted in the 3000uF main filters ground line to sense rail supply excessive current flow and then feed a voltage...
  2. 1

    Filter capacitor replacement for vintage gears (controversy)

    I'll share my electrolytic capacitor experience from my working years (retired 4 yrs ago) in nuclear power plants. I calibrated and repaired various equipment that monitored and controlled reactor pressure, level, temperature etc and various neutron monitoring equipment. Thats a very brief...
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    SX 750 restore

    The drawing in the opening post isn't correct. The original power switch contact should be in series with the gate resistor. I have done the triac mod on three SX-750 receivers so far. I mount the triac along side the power transformer using one sheet metal screw. I attach a small solder...
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    SX 9000 - I'm impressed!

    Dan, I replaced the transistors per this thread: https://audiokarma.org/forums/index.php?threads/top-ten-worst-transistors-noisy-failure-prone-whatever-and-replacements.731653/ Jef
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    SX-950 - FM distortion after running awhile, starts out clean

    Paging @markthefixer ............
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    Pioneer SX-727 Power Supply Unit issue

    That suggests to me the circuit is flowing excess current to ground (to terminal #1), from the base of Q1 going through Q2 and through D6. Check D6 as pete suggested. The 3.7v to ground on the base on Q1 is essentially reading the voltage drop from the base of Q1 to the anode of D6..... Check...
  7. 1

    Pioneer SX-850 Bias Problem

    As to the 28v supply reading 12v, the problem could be with the power supply OR the Equalizer Amp AWF-011. If not too hard, de-solder and lift pin #6 on AWF-011 then check if the 28v goes back normal when unloaded. Or you could do a similar lift at the power supply board. That 28v is derived...
  8. 1

    SX-434 blue Sanyo caps in tuner?

    As much as we strive to troubleshoot logically, it can give us tunnel vision and bite us........
  9. 1

    Pioneer SX-850 Bias Problem

    A few things...... - Q9 collector should have about 45 volts instead of the +.47v you show above. Double check that. - You show Q7 collector voltage at -1.03 (which may be ok) but Q11 base should be the same, not -.13 as you show. Check on that. Same issue with Q8 and Q12. Q8 collector should...
  10. 1

    Pioneer SX-850 Bias Problem

    The 28v only feeds the "Equalizer Amp" which is your phono amp or pre-amp. So you have two issues to chase down. Without knowing your skill level, can you take voltage readings per the schematic on the power amp transistors Q5 and Q7 (Q6 + Q8)?
  11. 1

    SX-434 blue Sanyo caps in tuner?

    Hey CT Jim....I did do a post yesterday but seconds later I deleted it when the included schematic link was dead. I also didn't want to needlessly dilute your thread. I am just finishing up a full restore on a SX-838. I replaced all E-cap's on the tuner board, which is almost the same as...
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    SX-1010 question

    I don't usually chime in on these questions but I feel compelled for some unknown reason. I am 63 yrs old so similar in age. I had a SX-1080 (120WPC) that I gave to my son about 8 yrs ago. I just didn't care for the sound compared to my SX-750 that I have owned since 1979. I restored both. But...
  13. 1

    SX-1010 Intermittent Protection Relay - resolved

    Good to hear that the voltage fluctuations were due to components on the EQ board. I find it very interesting that the removed components checked good even though it fixed your problem. Something inside a cap or transistor was breaking down or leaking in a cyclic manner with no easy way to...
  14. 1

    SX-1010 Intermittent Protection Relay - resolved

    In regards to the fluctuating voltages, it could be caused by the power supply itself OR the loads on those supplies. My suggestion is to desolder the -24 volt pin from the power supply board and see if it still wobbles, for example. Or maybe you could desolder and lift a component lead on the...
  15. 1

    Pioneer SX-9000 Replace with LED's or original bulbs?

    I did mail it out to you yesterday.
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