Any luck on getting the 5.1v fixed?  The schematic in my preceding post shows some related voltages to check.   It is unlikely to work correctly with only 4.25V, though something might operate, or operate erratically...

Also, it's possible that something is dragging the 5.1v down to 4.25v somewhere else, like maybe the processor board. Speaking of which, did you check both electrolytics? The startup capacitor 4C10 doesn't have to explode in order to fail. 

The Main relay will normally pull in and click when the system is plugged in.  It is energized so as to turn the main power to the amplifier OFF, not on. As the relay coil circuit is active when the system is OFF, this could also drag down the auxiliary voltage, it should be around 12v before transistor TR12 and 8v after.

Good luck!

No, unfortunately no grogress - i am not the expert in reading ciscuits :-(

When you say, did you check both electrolytics, which one do you mean? 

No, unfortunately no progress - i am not the expert in reading ciscuits :-(

When you say, did you check both electrolytics, which one do you mean? 

On the microproccesor board, Board 4, inside of the metal can are two electrolytics.

One appears to have a tendency to explode, capacitor 4C1.   The one that didn't explode is a 33uf axial designated 4C10,  4C10 is responsible for "startup reset", without which the CPU won't start. It is located right next to 4IC3, and on the systems I have worked on they have all degraded seriously without exploding or showing any visible degradation.  In particular, on my system that would not start, 4C10 measured a few Picofarads, which is very far from the rated 33 Microfarads, and this was preventing the CPU from starting. 

So I highly recommend removing and testing 4C10.

But you also have pretty low standby voltage. at 4.3v, when it should be at 5.1v.  

On Board 2,  connector P14 terminal 2 should measure around 12v and terminal 4 about 8v.  Terminals !,3 and 5 should be at 5.1v, all referenced to chassis ground on P14, terminal 9.

Looking at the pictures, Keri seems to have already swapped out 4C1 (the backside of the PCB shows the position as empty), which presumably was the exploded one.
So maybe a good idea to swap out 4C10 too ?

I just checked the two big 10000yF capacitors with my new MESR-100.

both seem to be not good (even if the capacity seems ok).

rhey show 3,97 ohm and 4,11ohm.

should I replace them?

best regards 

69er

Hi 69er

I would hold off on the two big caps for now, they are not used during Standby.

You say the relay opens upon attaching power to the unit. This is the normal Standby state of the relay 2RL1.  The microprocessor system must de-energize this relay to turn the system ON. At this point, the two large 10,000uf capacitors come into play.

In particular, p-14 pins 1,2,3,4,5 and 9 seem most relevant to Standby. 

You say pin p-14-4 is at 18v.  I believe it should be at 8v.

You did not say what p-14-2 is at.  It should be around 13v according to the schematic, I could check on my system later.

You said that p-14-6 is at 12v.  According to the schematic, it should be around 40v.   This comes from the main power winding of the transformer, tthrough a 15 ohm Fusible resistor 2R18, rectified by diode 2D10 and filtered by capacitor 2C10.   As resistor 2R18 is designed to blow open like a fuse, it is a likely failure point for this circuit.

This apparently powers the infrared remote control on display board 9, so I'm not sure how much it would affect Standby.  Of course, something like this "could" drag down voltage from elsewhere, like maybe the 5v Standby. If 2R18 is indeed open-circuited, the most likely cause is a short circuit in capacitors 9C15 or 9C20 on display board 9.

I would first check resistor 2R18. It should read 15 ohms or possibly less if in circuit but not more.

If 2R18 is found to be "open" it must be replaced with a similar 15 ohm Fusible resistor. If it is replaced with a regular 15 ohm  resistor, causing damage elsewhere is more likely.

You might also try unplugging connector P11 on display board 9  to see if this has an effect on Standby voltage. If  I am right, about 5.1v Standby voltage being dragged down, I would start here.

Also, What is voltage on 2P14-2 and 2P14-4?  18V seems wrong for 2P14-4  2P14-9 should be 0v.

Good luck!

Hi Keri,

i think you read my measurement wrongly or i did not make it clear.

On P-14 i have following voltages 

P-14-1 : 4,18v dc

P-14-2: 8,85 V dc

P-14-3: 4,18v dc

P-14-4: 6,12v dc

P-14-5: 4,18v dc

I will check everything else you wrote - thank you very much for your help!

Best regards

69er

I know more:

2r18 has 22ohm

when disconnected the display 11

p14-1  4,97v

p14-2   13,11v

p14-3.   4,97v

p14-4.   8,2v

p-14-5.   4,97v

p14-6.   0v

p14-7.    2,47v

p-14-8.   4,9v

p-14-9.   0v

best regards

69ee

P14-6 is 43v