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ampaddict

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About ampaddict

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    Perth
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    Australia
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    Brad

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  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. Item: Pioneer PR-101 or PR-100 10.5" silver reels and PP-220 adaptors Price Range: Negotiable Item Condition: New or Used Extra Info: 2 matching pairs of silver reels (1 + 2) plus adaptors ****FOUND**** had to sell a kidney! To suit Pioneer RT-909 etc. Must be matching pair or can buy separately to get 1 + 2 and must be silver. No warping and no blemishes on presentation side. Not asking for much am I 🙂 Now, where's that hen's tooth ...
  3. 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 ...
  4. ... 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!
  5. 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!
  6. am I correct to measure the bias across the pairs of emitter resistors (R837/R835) (R836/R838)? What's the target voltage please?
  7. 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
  8. 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?
  9. 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.
  10. 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.
  11. 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.
  12. 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
  13. Indeed, thanks mate. Would top off my SA-9800, TX-9800 and CT-F1250 flouroscans nicely. Also need a rack which is even harder to source! Challenge commenced ...
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