Marantz SR 7000 wont power up

Javenroth

Member
2013-01-16 2:14 pm
Hi folks,

I have problems with my Marantz SR7000. I really need your help to fix this.

I have this marantz for years now and has been setup for 5.1 home theater system in my living room. It was working nicely until last december.
I disconnected the power source before I went for vacation for about 3 weeks. And when I returned, the unit wont turned on while stanby led is on (red light comes out).

I opened the case and checked the unit and there is no sign of burn or damage. So, I clean the unit and use the hair dryer to get rid of humidity that may have created a problem.

After cleaning and drying, the problem still exist, the remote controller still wont make the power relay to click. I understand that the click of the relay will allow power to main transformer.

Further, I observe one capacitor (470uF/35V) is swelling. It was CB66 in the -30V rail (Vkk). The schematic shows -30V, but measurement with multimeter shows -60V. (I am confused by capacitor CB63 placed in series to 22.3V AC supply from transformer).

The service manual suggest to check this Vkk and FL. The FL, which is 5.1VAC from the transformer is OK. But Vkk is -60V ! And this has drive me crazy, since it supplied from 22.3 VAC through 100uF Capacitor.

I have checked all the capacitor and managed to do this:
1. Replace all suspected caps with new one.
2. Replace 6V regulator IC, 7806 to get 5V supply
3. Replace QB52 transistor, I was suspected this is the culprit. But it is not.
4. Pull out the power relay and check it. It is still good.
5. Replaced 8.2V zener diode at FL rails.

And still not working.

Additional info,
1. This power supply board PB54 is intended to provide 5V, Vkk and Fl to front panel. The Vkk is supplying pulldown voltage (?) VEE to FL driver IC which is mpd16311.
2. This board also provide 5V to "mother board" at the bottom of casing. Whenever I disconect the supply to motherboard, the power relay is vibrating.

Attached is the schematic. Any help or opinion is appreciated.

Regards,

Javen

0th04WZ
 
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On the standby power supply, what if anything is missing, voltage wise?
Have you got power to the standby/power relay?
Does it pull in?
Have you got 5v standby on pin4 of JB54?
Have you any AC coming out of the standby transformer?
Have you permanent AC feeding the standby transformer?

Don't loose sight of what you are doing and it will be a very basic fault.

Unfortunately you have replaced random parts and if unlucky may have caused other issues.
 

Javenroth

Member
2013-01-16 2:14 pm
Hi JonSnell, thanks a lot for replying.

Here are my answers.

On the standby power supply, what if anything is missing, voltage wise?

Answer:
If understand the question correctly, with all outgoing cables disconnected, everything is cool. Relay does not pull in, the supply voltage 5V is there. Vkk at -60V, and FL at about 5Vac. But if i connect the cables to front panel (the controller board) the relay vibrates.



Have you got power to the standby/power relay?

Answer :
No. That is why it does not pull in. The relay rating is 24VDC. There is no 24Vdc at relay.

Does it pull in? Answer : No.

Have you got 5v standby on pin4 of JB54? Answer : Yes

Have you any AC coming out of the standby transformer?

Answer : Yes, all secondary coils give me correct ac voltage.

Have you permanent AC feeding the standby transformer?

Answer: This standby transformer is fed from phisical switch at front panel. So, Yes if I push the switch to stand by position.

Don't loose sight of what you are doing and it will be a very basic fault.

Unfortunately you have replaced random parts and if unlucky may have caused other issues.

Trust me, I did replace them very carefully. But I will re check again.

Javen.

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Javenroth

Member
2013-01-16 2:14 pm
"(I am confused by capacitor CB63 placed in series to 22.3V AC supply from transformer)."
It is a simple voltage doubler. 22v3 AC becomes at least 44v6. If no load it will climb higher that that.
The 8v2 zener clamps the heaters to within 8volts of the cathodes.

Thanks for the expanation. So it is probably correct that it climbed to about -60V without load. But, why it is still -60V when it is connected to the load? Do I have faulty circuit in the load (display FL driver IC mpd 16311, is the only thing fed by this Vkk).

Rgds,

Javen.
 

BSST

Member
2018-07-07 2:21 am
Don't kiss your amp goodbye just yet! You may still get responses from previous post authors.

A good place to start would be JonSnell's questions in post #3 since they explore the state of the power supplies, some which should be active in standby mode.

Make some preliminary checks of the supplies first. But I'm going to make an optimistic leap and presume presence of about 25VDC at QB51 emitter, and that nearby parts are OK. If so, you should be able to short QB52 collector to ground and thereby energize the relay. Maybe that will provide further troubleshooting insight. Let us know what you discover.

Good luck!
 

rayma

Member
2011-04-29 8:37 pm
Please signal trace the problem, rather than replace parts at random.
That could possibly cause additional problems which would be even harder to repair.

Seems that either the control circuit that enables the 24V for the relay coil might be the problem,
or there is another problem that properly inhibits the operation of the relay coil enable circuit.
I do suspect that is the actual situation. The uCOM directly controls the relay coil driver circuit.

If a protection circuit is inhibiting operation, one should initially assume there is a problem
that is being detected, rather than the protection circuit itself being at fault, until proven otherwise.
 
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