Yamaha RXV-620RDS

[cowasaki]

Just got hold of a Yamaha RXV-720RDS AV amplifier.  When it is switched on it powers down after a second.

Going into diagnostics mode on switching it on it reports: "PS PRT :021 B" which appears to be an incorrect voltage in the power supply with "21" and "B" supposed to be giving an idea as to what.

In the manual it states:

PS PRT display
(When the power is turned on without this abnormality corrected, the protection function activates about 1 second later to shut off the power relay. Display may not light if there is an abnormality with the power supply for the display.)
Cause: There is an abnormality in the power supply section (voltage). Supplementary information: As the power from the following sources is detected, it is possible to determine where an abnormality exists.
Main (5): Transformer secondary winding CB373 (AC voltage)
Power (3): Regulated power supplies ±12, ±5V, +5D

Besides the above possible causes, the cause may be a disconnected connector or around the CPU.
PS PRT and DC PRT displays include the abnormal A/D value in % (voltage value obtained by considering 5V as 100%). Concerning this value, refer to DIAG menu No.11 AD DATA CHECK described on page 26.

then on page 26

DC/PS (Detection of the protection function) [Remote control code: 7A—0B (CD SKIP –)]
DC: Protection value for DC detection (Normal value: 1~13) 0.05V~ 0.65V (reference voltage) When the value is out of the normal value range, the protection function works to turn off the power.
PS: Protection value for power voltage (Normal value: 23~37) 1.15V~ 1.85V (reference voltage) When the value is out of the normal value range, the protection function works to turn off the power



But it doesn't give any supplementary information. Has anyone worked on one of these?

The "normal value" is shown as "23" is the "21" from the error the reason ie the voltage is too low by about 8-9% of minimum?


Manual: https://elektrotanya.com/yamaha_rx-v620_htr-5460_rx-v620rds.pdf/download.html#dl

[cowasaki]

OK based on the above I took it apart and followed rule #1.......  Checked the voltages which all appeared to be ok as 12, -12, 5, -5, 1.85 then looked at the circuit diagram and the 1.85 should have been 5v !!  Replaced a 7805 and it is now working perfectly

That was the simplest repair I've had in a while

[rexjred]

replaced it on the power supply PCB? 

[PKTKS]

That YAMAHA error codes  sometimes they do a pretty good
job helping to spot the fault location.

But other times they just trigger a fault without
any code that really helps.

Depends  very much of failed device.

Some transistors went bad causing that in locations
far from the PSUs. Nevertheless the fault helps

Paul

[cowasaki]

replaced it on the power supply PCB?

Yes. From memory I think there were two but one had blown. It’s been working daily since then.