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  1. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. david winter

    Top Crap transistors list and "not-always-crap" types

    Hi, I have been using the "Top Crap" tansistor list for a while, and wanted to know if there's a place on AK where that list is stored. If so, it would be interesting (if not already done) to update it with more classic transistor references which are not as crap as those already in the list...
  9. david winter

    SPEC 4 variants (AWM-146-0 / AWH 066-B)

    Hi, I recently scored a nice Pioneer bundle: SPEC3 + SPEC4 along with a PL1000 and CT-F1250. I started going through the SPEC4 and noticed some differences in the board revisions, which brings a first question: is there a place where all revisions can be found to compare ? I downloaded two...
  10. david winter

    Olson stereo amps & docs ?

    Hi, It looks like there's little technical information about Olson tube amplifiers. I'm trying to go through an unidentified model equiped with a 5AR4 rectifyer, four EL84 PP and 5 12AX7 (all testing good). There's some residual audible ripple after recaping the power supply whatever the...
  11. david winter

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

    Hi, I need to replace the broken start switch of a Dynacord IST 104. The original model is a Dialistat 2-pole type (DPDT), same as the one pictured below but with a larger metal holder allowing screwing it to a metal plate, itself attached to the metal body of the turntable. The blue plastic...
  12. david winter

    Luxman M-2000 can't adjust bias

    Hi, I'm trying to find out why the bias on both channels can't be adjusted. The amp was recaped, I cleaned the relays which work fine (the first clicks within one second after powering up, followed by the second relay (which turns the VU lights on) 3 seconds after). The voltages going to both...
  13. david winter

    Luxman M-2000 fuse lamps: adapting 6.3V models for 10V operation

    Hi, This amp uses longer fuse lamps of 45mm. As 41mm ones also fit, I wanted to know if someone used the common 6.3V fuse lamp. This one shows a 270 ohms resistor on the bottom side of the pcb, so I wondered if replacing it with a 430 ohms (or so) would do the trick. Or whether there is a 10V...
  14. david winter

    50Hz pulley for Garrard AT6, AT60 etc

    Hi, I got a Garrard AT-6 record changer equiped with a 60Hz pulley. I need to find a 50Hz pulley and wanted to know if there is a specific model or other Garrard turntable models that could help me find it. Thanks !
  15. david winter

    Luxman L-31 power switch replacement model

    Hi, Is there a model of power switch which fits the Luxman L-31 ? As I don't have the amp with me right now, I can't even try to see what can directly replace it. Thanks !
  16. david winter

    Technics SL-7 (revised version): what diode type is D306 ?

    Hi, All the service manuals I can find are the normal version where the arm motor drive is made using discrete transistors. My version uses a BA6109 IC instead to which a green/yellow "ball" diode like those in amplifier bias circuits, referenced D306. It tests at 1.967V so I presume it's a...
  17. david winter

    C-70: mistake around zeners near T211/T212 ?

    Hello, I am repairing a nice C-70 pre. Between T211 ant T212 (symetrical sub-power), are two 27V zener diodes (D126 / D127). The glue used to stick the two 220/35 capacitors corroded both zeners and one had a broken leg. No reference is visible on them, so I took the schematic and realized that...
  18. david winter

    HITONE H250: burnt mains transformer / specs

    Hello, I have a nice HITONE H250 amplifier (7591 output tubes) with a burnt mains transformer. It seems very close to the H225 model which has 7868 outputs. The H225 schematics indicates the following voltages: B+ = 300Vac (420Vdc after the diode bridge) H1 = 12Vac (to heat the first 12AX7 in...
  19. david winter

    Source for 2SC2240 GR/BL & 2SA970

    Hi, My source for original Thoshiba 2SC2240 (GR, BL) and 2SA970 can't provide them at the moment. Anyone can point me to a reliable source ? I have one Sansui to finish which needs at least 16 2SC2240 (8 GR and 8 BL) but I could need a bit more for a few other amps depending on how many can be...
  20. david winter

    Sansui QR-6500 restoration - What means the red dot on some 2SC871F ?

    Hi, I recently acquired a nice Sansui QR-6500 receiver. There are a number of 2SC871 transistors inside (along with some 2SC458) which I intend to replace due to known failures. However, several have a red painted dot on the top, which I think is a factory selection. Does it mean that they had...
  21. david winter

    Armrest remake for Thorens BPT12S & TP14 arms ?

    Hi, Anybody has tried to remake the fragile Y armrest for Thorens BTP12S and TP14 arms ? Thanks.
  22. david winter

    Melody H88 (KT88 PP) - Cathode resistors power ?

    Hi, As I can't find a schematic for this 2 x 50W model, I wanted to know the power of the 100 ohm cathode resistors. There are two per tube connected in parallel. They measure 24mm x 8mm and seem to be 7W, but not definitely sure. Thanks !
  23. david winter

    Garrard 4HF idler rebuild (almost like 301 / 401 idler)

    Hello, Anyone knows a quality service to rebuild an idler for a Garrard 4HF in the European Union ? It's almost same as the 301 / 401 idlers except for the thickness (as far as I recall), so not a "female" type to insert around an axis, but the opposite (has two thin axis going into small...
  24. david winter

    Recaped Scott 255S - Schematic variants & DC output

    Hi, I've done this amplifier more than once and have rarely seen to identical specimens. The one that I fully recaped has a constant 50mV dc on both channel outputs even after replacing the differential transistors by matched pairs. I wonder how to minimize this dc offset. Some differences I...
  25. david winter

    Technics SE-A5 with random fault (supposedly bias)

    Hi, I'm stuck on this amp. The input board has been recaped. I also changed two small electrolytics on the power stage board. Right channel works fine, and bias adjusts without trouble. Left channel will intermittently work well with stable bias once adjusted. However, when the problem happens...
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