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willnotwish / pioneer-repair

My attempts to repair a Pioneer AV receiver
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Investigate the power-on behaviour of the POWER PACK ASSY (board E) #2

Closed willnotwish closed 2 years ago

willnotwish commented 2 years ago

Having reassembled the whole unit, I now find that is refusing to start at all, with the relay on the standby SMPS board clicking repeatedly every second or so, and my dim lamp tester flashing brightly at the same frequency. Previously, it was powering up for a few seconds before shutting down as a result of XPROTECT going low. Now it appears to be drawing too much current, thus forcing the SMPS to shut down.

I think it would be wise to power the main transformer directly from my isolated variable supply, in order to test whether there is a short on the POWER PACK ASSY (board E) or not. It may be the case that the power pack is fine, but that my dim bulb tester is causing the problem because the transformer inrush current is too high, causing the input voltage to drop and the standby SMPS not to power up cleanly. I have seen this before when dealing with the Samsung TV's SMPS.

It may well be the case that bypassing the lamp allows the SMPS to start, but I feel it would be sensible to check board E for faults first. I have suspected all along that one or more of the Pioneer amplifier modules are faulty.

Originally posted by @willnotwish in https://github.com/willnotwish/pioneer-repair/issues/1#issuecomment-1193194759

willnotwish commented 2 years ago

I disconnected all other auxiliary supplies and left just these red, white and black thick wires to the POWER PACK ASSY E: power-pack-supply-designations

The power to board E is fine. With 240V applied I measured a symmetrical unregulated DC voltage of ±45V.

Note that the dim-bulb tester lamp is quite dim with 240V applied. Board E draws current even at no load; the main heat sink warms up slightly. This implies that the Pioneer amp modules are not misbehaving when idle.

willnotwish commented 2 years ago

There is another low current two-wire cable linking TRANS 2 ASSY V to the POWER PACK ASSY E. Its designation is JH4701 at V. I will reconnect it and observer the power-on behaviour.

Turns out that it makes no difference. I measured 5.4V AC with 240V mains connected.

willnotwish commented 2 years ago

There is another power connector CN4901, this time from board W TRANS 3 ASSY, used to power the digital circuitry via board S REGULATOR ASSY.

I found that plugging this in made no difference. However I still don't know why the unit will not start when powered via the IEC connector.

willnotwish commented 2 years ago

With the XPROTECT et al cable from the POWER PACK ASSY plugged in to TRANS 3 ASSY W, XPROTECT was measured at -0.7V. However, with the cable disconnected, XPROTECT was 4.76V.

This implies that there is something happening on board W which is causing XPROTECT to be pulled low and the power light to flash, as observed in https://github.com/willnotwish/pioneer-repair/issues/1#issuecomment-1193194759.

willnotwish commented 2 years ago

Closing this now as the POWER PACK ASSY seems to behaving itself as far as start up is concerned.