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My Pioneer amplifier (>15 years old) cannot power-on anymore. When pressing the On-Button, you always hear a relay toggling in an endless loop.

So, I got the datasheet (containing the schematics) and started to search and measure:

  • The voltage from the both green points to GND at the left side is nearly 0
  • Also the relay (blue circle) is the one that makes the toggling sound (on-off-on-off-....)
  • Since there is something wrong with the power supply, but the voltages at the points are nearly 0, I assume it is the transformer (red circle) that is broken.

enter image description here

What do you think? Is there any way to confirm 100% that it is the transformer? Reason, why I want to avoid trial and error is that the transformer is really expensive (80 $). So if I order a new one, I just want to be sure. Any help appreciated!

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    \$\begingroup\$ It seems you have measured a lot of stuff while avoiding the transformer itself. I'd check that there is AC line voltage on the input and see that you're getting the expected AC voltage out of it. \$\endgroup\$
    – jwh20
    Commented Nov 22, 2020 at 18:02
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    \$\begingroup\$ That transformer would appear to be fine since it powers the relay; it's the other one that powers the amp. Check the fuses first, then measure the big transformer. \$\endgroup\$
    – user16324
    Commented Nov 22, 2020 at 18:05
  • \$\begingroup\$ Have you checked basics like V801 and V803 are 120 and 240V AC respectively when you switch on? You are switching to DC to measure the green ones? Is there a signal into ACRY to hold Q811 and Q812 on so the relay stays energised? \$\endgroup\$
    – Guy Inchbald
    Commented Nov 22, 2020 at 18:58
  • \$\begingroup\$ 1. jwh20: Ou, mea culpa, I think I did a wrong measurement: Input is ~230V AC and output is ~14 V AC. I could not get the datasheet from the transformer, but at least there is something coming out of it. 2. BrianDrummond: I updated the schematics with only the placed fuces. They are correct (and also the transformer). 3. @GuyInchbald: V801 is not placed and the voltage is 230V AC. I also measured AC voltage on the output of the transformer and the green points. However, I assumed that the output voltage potential between the output pints of the transformer. ACRY stays at ~1.9V AC \$\endgroup\$
    – Ernte1893
    Commented Nov 22, 2020 at 21:20

1 Answer 1

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I did not realize the AC/DC converter inbetween. Therefore, the measured voltages showed that the transformer works correct.

Please see attached the schematic diagram with the correspondent (correct) DC and AC voltages. As it turns out, they are all correct. I check if it is the relay. However, this would be then another thread

enter image description here

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  • \$\begingroup\$ @SamGibson: Well, it is (a) actually. Since I cannot mark comments as an answer, I summed it up in a separate comment. I asked in the original comment, how can I confirm that the transformer is broken. This was done. It does not answer my complete problem, but I decided to close this thread and rather open a new one. Because otherwise (if I would update my original question), the useful comments would not fit anymore to the question. \$\endgroup\$
    – Ernte1893
    Commented Nov 22, 2020 at 22:51
  • \$\begingroup\$ Thanks for updating the answer. I've deleted my previous comments to reduce clutter, as it is now clear that this is an answer which can close the question, and not an update. \$\endgroup\$
    – SamGibson ♦
    Commented Nov 22, 2020 at 23:54

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