Marantz CD63 Power Supply Problem-Help Please!

[KevinLee]

Hello,

I have a Marantz CD63 with a weird power supply problem.

There are two 12v regulators right after the filter caps and bridge. One positive 12v and one negative 12 volt.

My problem is that I am only getting +3 volts out of the positive regulator. I have tried a new regulator with the same results. I am getting -12 volts out of the negative regulator.

When I disconnect the + regulator and measure the voltage coming out of the bridge, I get +18 volts and -18volts. I believe this to be good.

In the schematic it shows the transformer as having 18 volts AC out into the bridge. I only measure about 12 volts. Is this a problem.

The regulators in question are Q801 and Q802, page P-116-2/2 of manual.


Any ideas.

Thanks

KevinLee

[jewilson]

If you pull the output lead of the regulator and it's +12 vdc
you have a shorted component on the board. The only other problem could be a missing ground on the comman pin of the regulator.

[KevinLee]

Hello Jewilson,

I disconnected the output side of the regulator from the pcb and measured again. I got 10 volts.

Weird. I will check further tomorrow and report my findings.

Thanks

KevinLee

[TaylorG]

This sounds like a similar problem I had once. After some searching, I found a shorted ceramic cap ( the only one I've ever seen fail).

[ALW]

Not much to go wrong, really - checking the rectifiers and caps should get you there.

With the reg removed check it on a PSU to make sure it is producing 12V, then whilst it's out check D801, 802 and C801, 802 and 803.

The only other thing it can be is a joint, track or transformer problem - take a good look around.

Andy.

[KevinLee]

Hello All,

I have removed the output leg of the 12v+ regulator and measured the voltage, I got +10 volts. It should be +12v.

I tried a second +12v reg and got the same results.

I measured the voltage going into the reg and it is +18 volts. On the negative reg it is -18 volts. This seems ok.

I replaced all 4 diodes in the bridge, checked soldering and circuit traces, the ground to the +reg is good.

Does having the output leg of the +reg removed from circuit mean that my problem is between the transformer and the +reg? I do not know what else could be causing this problem.

The filter caps after the bridge are currently removed as is the 470uf cap after the +12v reg.

Any ideas would be appreciated.

Thanks

Kevin Lee

[jewilson]

If the input to the +12 regulator is at +18V check the ground trace, or use a jumper. Take the jumper and connect it to you common regulator pin and a good ground. It should measure 12 vdc on the output lead.

You can remove the regulator for the PCB and just connect it with jumpers also.

[KevinLee]

Hello Jim W,

I soldered a jumper between the common groung pins on the + & - regulators. I still get only 10 volts out on the +reg.

When the +reg is fully inserted and soldered into the circuit, the transformer seems to heat up a lot on the secondary side. I also only get audio out of one channel and my display is dim.

Could this have something to do with only getting 12 volts ac out of the transformer instead of 18 volts ac as per the schematic?

Thanks

Kevin Lee

[KevinLee]

Hello,

Is it possible my transformer is bad?

How would I determine this for sure?

Thanks

KevinLee

[li_gangyi]

Most probably only the secondary side AFTER the regulator is bad...maybe you would want to check your results with another multimeter?? A shorted smoothing cap after the regulator seems to be the problem...as to the IC only outputting 10V...maybe the Ground pin is not connected well?? Might want to try using the negative side to confirm...or use an external PSU and try pumping it into the regulator to make sure you did not get a defunct part...where did you get the regulators from??