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Everything posted by ampaddict

  1. Thanks folks and sorry for the delay. Great call on the US parts suppliers Mike. I use RS and E14 but Mouser seem to have a greater range of the vintage replacement parts. Will update once the rebuild begins ...
  2. That's better. Multi-turn trimpots reinstalled. Bias good. It sounds amazing and I'm assuming will only get better once the caps bed in ...
  3. ... hangs his head in shame but happy all that work wasn't for nothing! So used to measuring across a pair of resistors, I didn't think to change my approach. It sounds bright and detailed with the WIMA and Nichicon FG series and all new trans. Thanks everyone!
  4. Thanks Pete. I was measuring across the pairs of resistors and getting 26V but when I measure across one of the resistors, I can adjust the bias to spec. Seems I was simply measuring it incorrectly!
  5. am I correct to measure the bias across the pairs of emitter resistors (R837/R835) (R836/R838)? What's the target voltage please?
  6. Problem is same on both channels. Amp works but is slightly distorted on both channels, very noticeable when applying base. Resistance in circuit as follows: R837 0.5ohms R835 0.5ohms but seemed to fluctuate up to 1ohm before settling on 0.5 - could be just a dirty connection R836 0.5ohms R838 0.5ohms To confirm, do the VR's adjust DC offset or BIAS voltage and where exactly to measure? Just the speaker posts as MBZ pointed out? If DC offset, am I aiming for a reading as close to zero as possible? On other Sansui's like AU-2900, I've measured bias voltage across the pair of emitter resistors to get a low, mV reading and used the VRs to bring it to spec. I assume the 2900 is not a cap-coupled amp like the 101? Thanks for your patience and help
  7. Good advice. I had replaced them with multi-turn trimpots but reverted to the original as part of the troubleshooting. So on this amp, the only points to measure bias is the speaker terminals?
  8. Thanks for that. I'm just used to measuring across the emitter resistors. Had no idea it would cause them to fail on this particular amp. The service manual mentions nothing about adjusting the VRs. I will check the 4 emitter resistors. I do have a dummy load so once I've replaced the resistors, I'll connect the dummy loads and measure DC at the speaker terminals, using the VRs to adjust.
  9. Hi and Happy New Year folks. I've attempted my first AU-101 rebuild and have hit a wall. So confident I'd get it right first time too! Have replaced all electrolytic caps , small signal transistors and power transistors on the main amp board and getting 26V (not 10mV!) across the emitter resistors. I have even reinstalled the original transistors 1 at a time to see if if any of them was the issue. Tested all resistors for open circuit. Just can't get any bias voltage close to spec and the VR's make not difference. Such a high DC voltage. Have taken extreme care to watch pinouts on trans and even used a semiconductor component analyser to ensure BCE correctly identified. Have also done a recap and transistor replacement on the tone board. All caps like for like bar 1uF on the tone board replaced with WIMA MKS2 film caps - these don't appear to be polarised? Also, upgraded the main filter cap to 2200uF and the 2 output caps to 3300uF but even switching these back to the original Elna caps made no difference to the bias issue. The amp was working perfectly, only a little warm sounding, until I got my hands on it. I should not have recapped and replaced trans at the same time and should have taken a single component>test approach. Lesson learned. I'm sure I'm missing something blatantly obvious but can't put my finger on it. It does perhaps point to a power amp problem but where to look?? Any help would be greatly appreciated.
  10. certainly wouldn't hurt as I'm sure they are all under spec. The motor control board is going to be tricky to remove as it's plastic welded to the motor chassis.
  11. Has anyone had any experience with this DD fully automatic TT? I have one with runaway speed issue that the strobe speed adjust is unable to reign in. The speed gradually builds to very fast then slows again and continues this fluctuation. The auto mechanism of the unit works fine, it just runs at a very inconsistent speed. Have cleaned the strobe speed pots to no avail. It looks like there are motor speed adjustments via 2 VR's on the motor control board. However, I'm not convinced it would simply be an adjustment of a VR, given the inconsistency. My next step would be to remove the motor and check all components on the control board. Perhaps some caps are out of spec, open res or noisy trans??? It's a nice TT so worth repairing I think. Any advice greatly appreciated. Cheers, Brad
  12. thanks all. Was wondering why I couldn't log in - thought I was in the dog house 🙂
  13. Hi folks, I'm restoring a beautiful Luxman L-308 integrated amp which is working but sounding a little too warm for my liking. Looking for any experience on what the correct bias voltage should be across the emitter resistors please. After warm up, I'm getting around 16mV bias and around 0.3mV DC offset on the power amps. I have only been able to locate a schematic but no service manual, so a little stuck. Any pointers gratefully appreciated. Cheers,
  14. Geez, lucky I was present when mine popped and I cut the power within a couple of seconds. I dodged a fiery bullet!
  15. Thanks Chris. I managed to get one from DaDa Electronics in Melbourne but handy to have the Quad UK contact too. It's a common point of failure when the devices are left idle too long. Thankfully, it's a 20 buck fix. Cheers, Brad
  16. Hi folks, Moved post to correct thread, sorry. My Quad 34 emitted a puff of smoke and on inspection looks like the suppression cap is blown as per photo. What's that smell! Trying to locate a replacement for RIFA 0.047uF 100ohmx2 PMR209MB 40/085/56. Original part # NPMR20A. Element 14 and RS have a Kemet 47000pF, 250V but resistance is listed as 47ohms. https://au.rs-online.com/web/p/rc-network-capacitors/0209213/ Should I run with this and add a 47ohm resistor in series or 150ohm in parallel or neither? Struggling to find data on original part. Any experience/help appreciated. Thanks, Brad
  17. Good call! I definitely want to keep one for myself too. I'll probably go all out and replace / upgrade all components. Would be worth too much to sell then 😛 Cheers
  18. Cheers Bruce. I have already amassed a rack of amps that I need to tidy and breath life into again so it's sink or swim for me! Hey, at least I get to listen to great sounds while I'm chocking on flux fumes 🙂
  19. Thanks Pete. Would you recommend swapping the old ceramics with WIMA MKS too?
  20. thanks guys! I'd ordered FG series for <10uF from RS but will jump online and source now. Looks like RS don't stock Wima but Element 14 do, great!
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