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  1. dorke

    Miniature Speaker to Laptop Audio Jack

    1. Is the Laptop actually producing sound?can you verify that with another "audio system"? 2. You should use a stereo 3.5mm on the Laptop output,can you show what you are using photo and diagram. 3. Note that he audio amp you are using is actually differential input .
  2. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    That is probably O.K . What is written on Z601,Z602? When you short the probes of your DMM (lowest resistance range)what do you get? Could you please post a photo of the DMM or a brand and model number. Another set of tests diodes D615,D617,D619,D621 -in diode test mode. What do we get?
  3. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Z601 should read 0.22 ohm center to edge ,and 0.44 edge to edge. Could you please check Z602 for comparison.
  4. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    The tests of Q631/Q633 are inconclusive. They don't appear to be "obvious bads" . I would take out Q631/Q633(carefully and mark which goes where), test them out of circuit. What do we get? The bridge output is no longer shorted. About testing Q627/629. Better test them after Q631/Q633 are...
  5. dorke

    Is It A Transformer 220vac-110vac ?

    It will never be a truly safe device,but you can improve it a little: 1. Shorten the bare wires in the solder joints to minimum(now it looks like 2-3mm). 2. Re-solder without excessive solder(prevent does "humps"). 3. Use RTV non-conductive sealant around and on the solder joints to glue and...
  6. dorke

    Is It A Transformer 220vac-110vac ?

    Well just move wire G1 and connect it together with N. It should solve the problem. like so:
  7. dorke

    Is It A Transformer 220vac-110vac ?

    The explanation is somewhat strange. It looks to me like it isn't wired properly ! Please verify this diagram I made. With the N going directly from in to out not feeding the transformer it can't work.
  8. dorke

    Is It A Transformer 220vac-110vac ?

    Like Dave said it is an auto-transformer. It will work but the build quality is horrible,it doesn't look like a safe device.
  9. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    In general,it is not normal for the transistors readings to be un-stable. When testing in-circuit they can be ,usually due to capacitors charging/discharging. It is not clear which are Q631 readings and which are Q633 ones. When you write "then rising to 1" it is ambiguous. Do you mean...
  10. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Now it is time to re-check(in circuit) transistors Q631/Q633 , and check Q627/Q629 as well. Verify that the resistance between +/- DC of the bridge is high(much higher than the 005 that was there before). What do we get?
  11. dorke

    EBay stores

    I'm buying on Ebay as well. You can get the very same "trash", whether you buy from an "Electronic specialized" store or an "I sell everything" one. What matters is the % positive feedback they get. The biggest worry I have is with counterfeit devices,the higher the price the bigger the risk.
  12. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Sounds like a good price for a good product , and it comes with a 1.6mm chisel tip as well.
  13. dorke

    Cheapest way to get data from multiple(100s) of sensors?

    As bob said and, I would add the layout is the simplest possible.
  14. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    The 937 (and 936) are lower quality Chinese replicas of the Hakko models (obsolete by now,they were replaced by the 888). It will do the job,I guess...tip quality is unknown but you could get a Hakko tip if it isn't good enough. How much will it cost including shipping? The CSI is a total...
  15. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Iceman, you are welcome. "Nice looking and on paper specs." won't last long or do a good job! The price difference (about 55-65%) is very likely well justified. Can you please post a direct link to it.
  16. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    If you are going to invest in a station that is going to last for a long time, I would try one of the following: The Weller WES51 for 92$ here (need to inquire about the pencil that comes with it). The Hakko FX888D should be a good buy for 97$ here How is your soldering class progressing?
  17. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Q631 & Q633 are probably fine(no dead shorts on them), the readings show "bad values", but that is due to the faulty Q635 & Q637 e.g. Q633(C-E)=75[Q635(B-C)] + 2.2 + 5.6 =83 . We should re-measure them after Q635 & Q637 are pulled out . About the soldering iron, Agree you don't have the...
  18. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Please show us a photo of the soldering iron you already have(tip included) ,it may be good enough for this repair. You will need a good 40w iron with "pointed" chisel type tip , and good thin soldering wire 0.025" diameter(like Kester 44 ) as well. Soldering stations may be expensive and not...
  19. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    It looks like the Left Channel power amplifier of your receiver is blown. You have 2 burned "bandits" Q635 and Q637 . Their C-E junctions are shorted (1 ohm) as expected ,creating a short on the bridge rectifier. There could be some more bad devices on the Left Channel. We shall do some more...
  20. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    O.K were lucky here, the transformer is o.k:) I think the bridge-rectifier is probably fine as well. I assume you are testing the bridge-rectifier "in-circuit",Is that so ? The "DC-DC" reading of 005, is almost a dead short load on the output of the rectifier. In that case that short on the...
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