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  1. markthefixer

    SX-3900 Intermittent Left Display

    the pin 11 which is Q11, MJE15032G, is showing E: 1.53v C: 1.53v B: 2.21v. collector voltage is too low a transformer secondary ac voltage runs through a 2 diode and 2 e-cap doubler that feeds 10v to Q11 collector. I have almost no access to my reference material, I suggest new 1n4004 diodes...
  2. markthefixer

    SA-7500II Phono preamp problem

    heat in/made by the phono board kills it. research phono heat on this forum follow the heat paths through the duff components
  3. markthefixer

    Pioneer SX-980 constant hum

    cap1, do them both check both the ccs jfets, they are used as hum eliminators.
  4. markthefixer

    1250 AWR-106 Board Issue

    which means pin 15 at -87v or so is OK. That tells me little about the internal voltages. Post eb&c voltages for Q5, Q6 & Q7 if you don't fix it tonight. TAKE EACH READING AT THE WIRE LEAD OF THE TRANSISTOR. that bypasses bad traces and solder joints.
  5. markthefixer

    2sc710 on awb-023

    That's the FM local oscillator. BC548 LOTS of variants at mouser, down to $0.10 ea 512-BC548BTA 512-BC548CTA 637-BC548A most assuredly the FM tuning will have to be readjusted, but if you are very careful it will stay in-band.
  6. markthefixer

    SX-3700 Tuner Alignment questions

    you tried to start a real time chat exclusive to just me. I am still in the hospital, flat on my back in bed, also have no service data. the manual is correct, and clear to me, but voluminous typing to 'splain it is beyond me now. one of those steps minimizes (nulls) the (unwanted) 19 kHz...
  7. markthefixer

    1250 AWR-106 Board Issue

    remember, it worked until you intervened. there are several analysis / explanation threads done by me for the regulator board. you have not posted either a schematic NOR present voltage readings. here's a posted schematic...
  8. markthefixer

    Pioneer SX-1080 left channel issue

    you can trade the other channel's dual transistor, when borrowing it disconnect that other channel's output transistors.
  9. markthefixer

    SX-1250 Tuner board.. oops

    also the encapsulated filter is well known as a signal black hole.
  10. markthefixer

    Pioneer SX-1080 left channel issue

    YES IT DOES. it makes noise with the pre-power jacks disconnected. note, the pair of ksa992's replace Q1, a 2sa979 which has two transistors internally, and five external leads. Q2(offset) changes at the same time, to a ksc1845. Q8(protection) also changes at the same time, to a ksc1845. these...
  11. markthefixer

    1250 AWR-106 Board Issue

    your PC board repair is right at the -65v regulator transistors. the pin 13 -65v rail is showing -17.13 volts, yes? the pin 14 -25v rail is showing -17.2 volts, yes? you jumped R4 to Q6 base. That whole repair area needs a tighter repair, it looks like you are relying on the green solder mask...
  12. markthefixer

    Pioneer SX-1080 left channel issue

    suggestion: there were multiple tests called for, with MULTIPLE, EXCLUSIVE results - which you glossed over with muddy result reporting. it is a MAJOR game changer to have the defect occurring with the pre-power jumpers removed. DOES IT???
  13. markthefixer

    Adventures with my SX-3800

    heatsinks VERY sensitive to airflow & orientation, MUST mimic normal operation to set.
  14. markthefixer

    Pioneer SX-1080 left channel issue

    swap Q1 & Q2 jfets, see if it moves to the other channel ask here about where to get jfet replacements.
  15. markthefixer

    Pioneer SX-1080 left channel issue

    left channel only, no balance or volume control of junk. turn off tone controls, filters finally disconnect pre/power jumpers. check flat Amp Q3 for actual part number on it's case manual says 2sa726, replace with different lead patterned KSA992. Do other channel Q4 as well.
  16. markthefixer

    Pioneer SX-3800 Won't Turn On

    just summing up trimpots and initial settings of NSA amps offset voltage adjust, middle of range then the output voltage is adjusted to 0.000 Vdc IDLE CURRENT adjust, STARTS at zero ohms of a maximum of one hundred ohms, with minimum idle current occurring at zero ohms.. NSA trim of idle...
  17. markthefixer

    Pioneer SX-3800 Won't Turn On

    post the volts base to emitter at each empty output socket. REMEMBER:red dmm probe to base, black dmm probe to emitter AT THE SAME TIME most likely the initial trimmer settings now... if less than 1 volt, turn the second idle trim opposite itself.
  18. markthefixer

    Pioneer SX-3800 Won't Turn On

    no... zeb the second idle current target pot at full CCW is max resistance which gives minimum voltage to the nsa diode string, which feed the bases of the NSA transistors! there's some bad stuff in there as it was sorted out! bad = DAMAGING stuff! explaining it needs more supporting...
  19. markthefixer

    Pioneer SX-838 - Protection Mystery

    pin 12 is 7.7vac yet q6 base is NOT pulled negative, check the diode etc connected to pin 12 to get -5v or so at that e-cap. I don't have scat to be more specific. q7 base won't go higher until relay current (collector to emitter) lifts q7 emitter to about 9v through the q7 emitter to ground...
  20. markthefixer

    SX-780 help?

    order the 200, leave the other original 200 alone.
  21. markthefixer

    Pioneer SX-850 HG "switchable" ? to 110v ?

    ac voltage not high enough at protect's AC sensing input
  22. markthefixer

    Pioneer CT-F1000 head assembly

    YES I cant PROVE that right now...
  23. markthefixer

    Replacing *this* tantalum cap (see image)

    higher capacitance = lower rumble. impedance of next stage greatly influences frequency range of this stage. i'm not "back"...
  24. markthefixer

    Replacing *this* tantalum cap (see image)

    it's an output cap, no NEED for UKL, but no Hurt either. 22 vs 10 cuts TT rumble output
  25. markthefixer

    Pioneer SA-9100, possible design error in Filter AMP AWK-021? With my recommendtion.

    I vote for a drafting error (R5, R6) during development that was inadequately corrected. Pioneer was just learning to draw adequate schematics and manuals, and the sa-9100 is a pretty poorly documented model.
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