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  1. david winter

    Sansui Serial Number Database Update

    AU-999 021080376 Details (as never moded until restoring and improving it): - 2SA640 on all preamp boards - CDC8002/9002 / XA495 on driver boards - Subsonic filter present (version with 2 signal wires) - Crowbar circuit present at speaker outputs
  2. david winter

    Blue "ladder" slide for input selector (PM-65AV, PM-80 etc)

    Hello, I need to replace the blue "ladder" slide which links the front panel rotary input switch to the linear input switch on the input board. The thin flat metal strip has broken and I can't manage to solder something on it. I don't know the right term for this part, and can't find a...
  3. david winter

    MAC1900 - Acceptable AC chassis leak

    Thanks for your answers. I'll finally opt for the simplest solution: replace the mains cable with an earhed one (and remove the 2M resistor).
  4. david winter

    Denon PMA-701 : 2SC1735 & 2SC1775 subs

    Hello, I'm going through a nice Denon PMA-701 amp. Seems a bit cheap in manufacture, but worth restoring. The tone control uses a number of 2SC1775 and 2SC1000. Haven't replaced any yet. The output stage also has a pair of 2SC1775 which I plan to replace by 2SC1845 unless there is a better...
  5. david winter

    MAC1900 - Acceptable AC chassis leak

    The audio problem is fixed. The real problem is that I don't know if there's an earth problem where the MAC 1900 is being used. If there's an earth issue at the AC plug but not at the antenna amplifier (which isn't connected to the same AC line). You just send the AC leak to the antenna...
  6. david winter

    MAC1900 - Acceptable AC chassis leak

    Hi, I'm working on a MAC 1900 for someone who apparently had troubles with a blown external antenna amplifier system. The MAC 1900 works in 230Vac mode. The person called an tech to replace his antenna stuff, and the tech measured a 108Vac leak from the FM antenna plugs and the earth, which is...
  7. david winter

    Mission DAD-7000 (= Philips CD-104): radial motor no longer moves

    Hi, I'm trying to figure out why the radial motor of a Mission DAD-7000 (Philips CD-104) no longer moves. The CD loads and stops spining after 2 around seconds. Before this happened, the player was almost working despite one silent channel (the other just turned bad with white noise in play...
  8. david winter

    QR-6500 / QRX-6500 : stuck with a different version of the F-1322 FM decoder

    Thanks a million times for taking the time to picture your boad. That's really helpful :) The green wire is barely visible on the far right of my picture, just between the white and black wires. Looks almost black. Time to put everything back in place, and check the regulated psu.
  9. david winter

    QR-6500 / QRX-6500 : stuck with a different version of the F-1322 FM decoder

    Thanks, that would be great ! :thumbsup: If you look at my initial pictures, you will see a jumper on the solder side (red arrow). All I need to know is where it goes as it was put back incorrectly. Its end near the border is correct, but the other isn't.
  10. david winter

    QR-6500 / QRX-6500 : stuck with a different version of the F-1322 FM decoder

    Your board has the same mods than mine. All other photos found around the web didn't match. Do you still have the receiver ? There are holes on the chassis edges which, with proper lighting, allow seeing the underside of the board partially. Thanks for your photos!
  11. david winter

    QR-6500 / QRX-6500 : stuck with a different version of the F-1322 FM decoder

    The board has several differences: - R461 replaced by 1µF / 25V (in series with the 47K as explained above) - R468 replaced by 100µF / 25V (C493). This is visible on Rev. C schematic below. - TR415 is confusing because its reference should have been put closer to it instead of next to a NPN. I...
  12. david winter

    QR-6500 / QRX-6500 : stuck with a different version of the F-1322 FM decoder

    Thanks for posting this. It's version D, which differs from my board which has a few differences, including a 330K resistor between pins 4G and Gnd. This 330K is in series with the 47K (in place of D409) going to the base of TR416 (2SC711) and the - of a 0.1µF electrolytic, which + goes nowhere...
  13. david winter

    QR-6500 / QRX-6500 : stuck with a different version of the F-1322 FM decoder

    I forgot to mention that the right side of the strap (red arrow) is correctly soldered. It goes to the + of a 1µF electrolytic, itself in series with a 100K resistor. The problem is with the other side which was put to the wrong place as per picture: cathode of D491 / + 100µF/25V / emitter of...
  14. david winter

    Sansui 7000 FM problem

    Hi there, I'm working on a QR-6500 which has the same F-1322 board but with a few changes (like two resistors in place of two diodes). One additional 1uF cap as well as one additional 330K resistor don't show in the SM. There's a strap on the solder side with one end put at the wrong place, and...
  15. david winter

    QR-6500 / QRX-6500 : stuck with a different version of the F-1322 FM decoder

    Hello, I am close to finish restoring a QR-6500 (serial is 211091683 if this can help with differences / mods). I need to verify the position of a strap (see picture below) on the solder side of the F-1322 decoder board. The service manual seems to have the right schematic (at least something...
  16. david winter

    Sansui 771: incorrect polarities for C17 / C18 on F-1504 preamp board and schematic ?

    Hi, I have been wondering what caused some low background noise on a 771 which I almost completely restored. Two electrolytics on the F-1504 preamp board (C17 and C18) apparently have incorrect polarities both on the schematic and the pcb silkscreen. They had -5V accross them. The 2SC1313 were...
  17. david winter

    Sansui Serial Number Database Update

    771 serial 814060007
  18. david winter

    Heathkit AA-40 - strange voltages at 6AN8A plates

    Channel A has the original 500K pot with shielded AC switch, and it is log, unless it got replaced by a log type despite the same visual aspect. At first I browsed the manual to see whether the type of pot was mentioned, but it wasn't. What if someone wanted to feed it with a source without...
  19. david winter

    Heathkit AA-40 - strange voltages at 6AN8A plates

    Indeed ! I took two other NOS 6AN8A and could never get the same voltage. I even got 125V on one side and 55V on the other. For the sake of those voltages I ended up with a pair getting 75V / 82V so pretty close IMO :) I also found why I had a quite different gain between both channels: someone...
  20. david winter

    Heathkit AA-40 - strange voltages at 6AN8A plates

    I was just wondering if the paper wasn't wrong since the tubes had the correct voltages at their screens and cathodes, but didn't make the calculations. Still, I can't understand the 50V at the other 6AN8A plate but I will swap the tubes to make sure. They both tested NOS (I use a Metrix U61).
  21. david winter

    Heathkit AA-40 - strange voltages at 6AN8A plates

    I did another test with another (Fluke) DMM: same problem with and without the 20µF cap. With the cap in place I have 88V (Channel A) and 48.5V (channel B) and the plates. Both voltages constantly vary of +/- 100mV. I double checked (again) all resistor values and wiring around the 6AN8A but...
  22. david winter

    Heathkit AA-40 - strange voltages at 6AN8A plates

    Thanks for your suggestions. I've been working on tube amps for almost two decades without such trouble, but I'll do the test anyway (eventually using a smaller decoupling cap). I'll also use another DMM (Metrix or Fluke) to compare, although I never had that issue with my usual DMM before. I...
  23. david winter

    Heathkit AA-40 - strange voltages at 6AN8A plates

    I thought about that but the 10K is new and both 330K measure 338K so close enough IMO. For the sake of closer values I replaced the 820K and both 330K which tested good. The screen voltage of the 6AN8A is 40V, and still have the same trouble at the pentode plates. Voltage before the 330K is 400V.
  24. david winter

    Heathkit AA-40 - strange voltages at 6AN8A plates

    Hi, I have been working on a Heathkit AA-40 amp for which I did the following works: - Set to 230V mode (powered at 240Vac). - Surgistor replaced with CL-90 varistor - Tubes: two NOS Sylvania 6AN8A + four good EL34 - All electrolytics and coupling caps replaced - Most resistors replaced (out of...
  25. david winter

    Broken Dialistat switch: compatible models or "plastic solder" glue to fix ?

    Thanks ! With some luck I found an old ebay listing for the 2PDT switch and the seller still has some. I thought about sticking the parts together but that was done in the past already and I prefer using a new part.
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