Testing power transformer

[tech2014]

Hi guys. I have a CD player that is dead and I am thinking it might be the power transformer. It is only outputing voltage on 1 secondary winding and missing voltage to engage a relay. The numbers on the side of transformer T901 are 8200-66040-003-0. On schematic is says NPT-1391D

I want to find a data sheet. Here is a screenshot of the schematic.
I am getting voltage out of secondary pins 14 and 15, but the rest are 0v

[budm]

Re: Testing power transformer

It is odd to have taht many widings go out. What do you get at 14-15? dc v @ c913?
Resistance readings on:
8-9?
10-11?
12-13?

[tech2014]

Re: Testing power transformer

It is odd to have taht many widings go out. What do you get at 14-15? dc v @ c913?
Resistance readings on:
8-9?
10-11?
12-13?

I get 10v DC at C913. Resistance is 1.1ohm from pins 8-9, 0.6 ohms for 10-11 and 0.6 ohms for 12-13. I get 5v on pins 14 and 15. Resistance for pins 14-15 is 1.7 ohms.

[budm]

Re: Testing power transformer

That is strange with no open windings, so 0VAC on all those windings.
5v on pins 14 and 15, that 5VAC? If it is, that is not right either since 5VAC will only gives 5VAC * 1.414 = 7.707 - 2Vf drops of the rectifiers = 5.87VDC on C913, you are getting 10VDC, there must be error on measurement or the meter is bad.

[tech2014]

Re: Testing power transformer

oops my bad I had it on DC for the transformer, duh lol. Will check again when I get back home. Thanks Bud.

[budm]

Re: Testing power transformer

I have a feeling the transformer is OK.
For the relay to come on, there should be about 2VDC at the P901B 'POWER' pin.
AC/AC on P901B, that should be the filament voltage for the fluorescent display.
-VP is also for the fluorescent display.
5.6V is the stby power supply.

[tech2014]

Re: Testing power transformer

I get 0v at the power pin on P901B. I get 4.5v on the POFF pin.

[tech2014]

Re: Testing power transformer

I have a feeling the transformer is OK.
For the relay to come on, there should be about 2VDC at the P901B 'POWER' pin.
AC/AC on P901B, that should be the filament voltage for the fluorescent display.
-VP is also for the fluorescent display.
5.6V is the stby power supply.

I get my 5.6v. the -VP is about -1.5v, should be -27. I did find that d909 was shorted, have to wait for part.

[budm]

Re: Testing power transformer

I get 0v at the power pin on P901B. I get 4.5v on the POFF pin.

The main board is not sending the ON signal.

[tech2014]

Re: Testing power transformer

nope. The processor pin 31 POFF is an input, not an output.

[budm]

Re: Testing power transformer

I am talking about the POWER pin which is the receiving pin which receives the POWER ON signal from the main board which turns on Q904 which turns on the relay, look at the diagram again.

[tech2014]

Re: Testing power transformer

ok I got the AC voltages on the transformer secondary. Pin 8/9 are 2.2v,pin 10 is 17V, pin 13 is 17 and 6.5v on pins 14/15. I am only get 1.6v at the input of Q901, the 12v regulator. I don't hear any clicks so I know the relays are not getting the voltages to activate them. I removed the relay to test out of circuit and it works fine.

[budm]

Re: Testing power transformer

OK transformer is OK.
"I am only get 1.6v at the input of Q901, the 12v regulator. I don't hear any clicks so I know the relays are not getting the voltages to activate them. I removed the relay to test out of circuit and it works fine." As I indicated in post 9 and 11, the relay will not be on until you get the DC Voltage from the main board to the POWER pin.
"I get 0v at the power pin on P901B" You are getting 0V on POWER pin!

[tech2014]

Re: Testing power transformer

Q901 is the 12v regulator. The input voltage is 1.6, out is 2V, no emitter or base on Q901.

[budm]

Re: Testing power transformer

I update post 13, I got the Q number mix up with the Q for driving the relay.

[tech2014]

Re: Testing power transformer

Thats what I figured. So the fault is on the main board, the one with the processor on it?

[budm]

Re: Testing power transformer

Yes, as I said in post 9. It can be the firmware corruption, fail circuit some where on the main board.

[tech2014]

Re: Testing power transformer

ok thanks will take a look. will update later?

[tech2014]

Re: Testing power transformer

wow it took a lot to get to the bottom board which has the micro on the bottom side
Pin 41 the power amp is reading 0v.