Marantz 2220B intermittent voltages in power supply

[Donguri]

A power supply is behaving a bit erratic in my Marantz 2220B.
I think I can recall putting this unit aside a couple of years ago after it developed a sizzling "bacon" kind of sound in both speakers which would indicate a problem in the power supply, perhaps some transistor.
However, after trying it now it doesn't display that problem at all, instead another problem emerged where it sometimes doesn't produce/delivers power to the preamp board at J812.
Sometimes it works and produces 34V at J812 and sometimes after using the unit the sound stops and there is 0V at that pin.
When it sounds it sounds great.
Before diving into the PS board and pulling parts I would like some thoughts on where to troubleshoot.
The voltages at the two transistors H805 & H806 differs quite a bit to the Service manual, is this acceptable?

H806
B: 14.25V (SM 14.7V)
C: 43V (SM 35.7V)
E: 13.68V. (SM 13.68)

H805
B: 44V (SM 35.7V)
C: 46V (SM 41.2V)
E: 33V (SM 35V adjustable)

At H804 diode? there is about 24V

The capacitors seem to hold up measured with my Peak tester.
Any thoughts?

 

[AE Bob]

By all means do not just throw parts at the power supply. Troubleshoot the issue, and figure out what is causing it. The supply is not that complicated. You don't need any more than a multimeter to troubleshoot it. Just throwing parts at it can lead you down a deep rabbit hole. Heck, it could be nothing more than a bad connection on F801 fuse holder.

 

[Donguri]

By all means do not just throw parts at the power supply.

Hello and Thank you for your input.
It is my intention to troubleshoot this before changing any parts, just not fully sure how to go about it.
I´ve checked voltages, capacitors and a quick check on some of the resistors (in place).
Problem is that I haven't been able to replicate the problem where the power disappears, been trying to tap the board to see if it is an bad connection, I will check the area around F801.
BTW the voltages measured on the transistors are when it is delivering power to the preamp.

 

[dankik]

I put your measured voltages onto the schematic for a better view.

• When the voltage at J812 goes to 0v, what are the voltages on H805 EBC?
• Where on H804 did you measure 24V, there are 3 leads. If it's the center lead it should be close to 42v, otherwise it's ACV.

 

[Donguri]

I put your measured voltages onto the schematic for a better view.

Thanks, Appreciate that! Should've done that myself..

When the voltage at J812 goes to 0v, what are the voltages on H805 EBC?

Having difficulties to reproduce the 0V symptom, it has happened a couple of times, seemingly random, will give it more try tonight when I get home.

Where on H804 did you measure 24V, there are 3 leads. If it's the center lead it should be close to 42v, otherwise it's ACV.

Ah, didn't realize it had 3 leads, thanks for pointing that out, will check that also and report back.

 

[AE Bob]

When the voltage at 812 goes to 0, measure the voltage on the base of H805. If it has voltage on it (likely over the 44 volts listed), it indicates that H805 is defective. H805 is a TO220 style transistor, and they go intermittent FREQUENTLY. I think I might just replace that one part, and see if the issue ever comes back.

 

[Donguri]

Been playing the unit for 4 hours tonight and did not display the problem...

If it's the center lead it should be close to 42v

The center lead of H804 measured 45.8V, maybe it is higher because of a higher line input? Here in Sweden it is around 240V.
Are the voltages I measured on H805 and H806 a sign of some problems or can I leave it as it is?

If it has voltage on it (likely over the 44 volts listed), it indicates that H805 is defective. H805 is a TO220 style transistor, and they go intermittent FREQUENTLY

Thank you, I'll be on the lookout whenever the unit decides to display the problem again.
Do you know if a MJE15032G would be OK as substitute for the 2SD330 D.E in this situation? Have some on hand.

F801 fuse holder

The solder side looked Ok.
But did discover some bad/cold solder joints on the R808 Trimpot which will be addressed later, don't think so but could this be the cause?

 

[Donguri]

Seems like the TIP41C is a common replacement for the H805, but have none of those at hand.