Yamaha RX-V1067 Av Receiver protection mode due to PS2, but why?

[kensmart]

Hi All Need help with a Yamaha RX-V1067 Av Receiver. Region Australia. (A)
The unit is going into protection mode due to PS2 being low at 79 instead of the required 81 to 153, as shown below.

Service manual here.
https://elektrotanya.com/yamaha_rx-v1067_htr-8063_rx-a1000.pdf/download.html

Before going too far I replaced the green caps on Power (1) PCB [page 118] C201 and C203 from memory, this had no effect and the caps I removed tested OK. Standby voltage = 5.469 measured at Page 139 M6 W2001. (start simple you might get lucky)

Explanation of fault:
[Page 62]
P1-2. PS1/PS2
Power supply voltage protection detection
The voltage at 2 pin (PS1_PRT)/1 pin (PS2_PRT) of IC902 are displayed.
Voltage detects
PS1: +3.3s, ACBL, ACM1, ACM2, +5, DCDC, -3.3V, +3.3HDR (U model)
PS2: +/-12A +/-12RY, +5A, +44V, +5DK
Normal value
PS1: 84 to 141 (Normal), 132 to 190 (PURE DIRECT)
PS2: 81 to 153 (Reference voltage: 3.3 V=255)
* If PS1 or PS2 becomes out of the normal value range, the protection function works to turn off the power.

Reported Numbers PS1= 118 (cool and normal) PS2= 79 (low)

Placing the unit in self-diagnostic mode [Page29] allows for the testing of voltages.
Looking at the cct [page 142] [I5]and board layout [page 124] I have confirmed the following voltages. At Function (3)_CB805 [I4]  [page 136]
-12 = -12.0
+12 = 12.0
5A = 5.0
So that looks OK, I did replace IC351 and IC352 being KIA7812API and KIA7912API with 7812 and 7912 regulators as I had everything apart and was beginning this journey with the usual suspects. This had no impact as the originals were most likely OK as PS2 still reports 79.

I then ran some wire wrap wire up from Main (3)_CB131 [Page 138]  to check the following as I couldn't find them accessible higher up when the unit is back together and operational, in self-diagnostic.
RYB+ = 12.14
RYB- = -12.09
PS1_PRT = 1.46 got the wrong pin wanted PS2_PRT but this confirms the level reported in the self-diagnostic mode for PS1 @ 118.

Then checked Video (3)_CB352 for the following:
 +44V = 47  (is this too high? the unit reports low voltage?)
PS2_PRT = 1.066 this confirms the level reported in self-diagnostic mode for PS2 @ 79 or 80.
At this point I have confirmed all PS2 voltages as correct except for +5DK, I can’t find this anywhere and there is only one reference to it in the manual on page 62 as shown above. Does DK represent a different region?

I then moved on to checking the PS2_PRT circuit, as well as much as I can.
Looking at the cct [page 142] the sense resistors are all in the H column of the diagram. Located the resisters on Video (2) board layout [page 124/5].
R3519 = 47K
R3520 = 47K
R3517 = 15K
R3516 = 47K
R3518 = 47K
All correct.
On the Video (3) board I checked.
R3609 = 120K also correct.

Where to now? Is there another power supply +5DK? That I can’t find? If so where the **** is it?
Should I lower the value of  R3609 to raise the PS2_PRT voltage from 1.066 up to around 1.4 to keep the protection cct happy?

Your thoughts are most welcome, I know there are a few Yamaha techs on the forum, what am I missing?

[kensmart]

Hi, All the Yamaha people must still be on holidays or isolating for COVID.
As an update, I found the +5DK power supply seems to be associated with the Ipod dock.
Page 134 E2 SM regulator.

I reassembled the unit to test that voltage level as it is accessible at the dock port pin 1? the unit came on with a PS1-2 error 185H / 119.
So now PS2 is in the normal range and PS1 is high. I double-checked my re-assembly as I had at least 5 boards out of the unit.

I had left off connector CB351 from the transformer to Video(2) PCB (power supply) connected it up and repowered the unit and it came on no errors.

PS1-2 now sits at 114 / 119 which is bang on perfect  so I will hook it back up and do a soak test and see how it holds up.