Pioneer CLD-99 VWR1200 power supply board

[elara]

Hello to all, please your help.

I am only a hobbyist of electronics and I have only basic knowledge but a lot of enthusiasm :-). I pulled out the VWR1200-D power board from the equipment and I could see that the F1 fuse was blown and the Q1 transistor was shorted. I replaced the transistor with exactly the same one and the fuse (foolishly) with the only fuse I had, a 5 amp one and the equipment ran for 10 minutes and then failed again. Now the power board has the same Q1 transistor shorted but besides the filter coil at the input of the primary badly overheated.

I have the service manual but I cannot find the model of the L1 coil to replace it. (really I cant find any spec´s for the electronic elements in the manual for power board)

Any idea about the possible source of the problem?

Will there be a friend who can share with me the specs for the electronic elements of the VWR1200-D power card, SYPS Board in manual?

The L1 coil has printed 4D-123 51M and D4 Zener seems to indicate the 272 number.

Any idea what there are meanning?

Please your valuable help.

Greetings to all.

[MIPS]

Not to be rude here but fuses exist for a reason.....
By the sounds of it there's an upstream or feedback issue causing the transistor to drive too hard and the fuse was protecting the circuit. By swapping a far higher rated fuse (a 2A is the spec I believe) and trying again sure it did work briefly but since nothing else in the circuit was rated for 5A it fried out anything that couldn't handle it.
Capacitors, transistors and the other common electronics staples are easy to replace sure but the inductor isn't something I expect to find on a shelf somewhere.

[Electronic M]

Is that inductor the line filter between the input of the full bridge rectifier and the power cord?...if it is you could probably get away with one from another piece of gear.

Before installing transistor number 3 you should make sure the switch mode oscillator is running/supplying the transistor with square wave, and check capacitors... something is blowing that transistor and until you find it it'll keep blowing .

[elara]

Hello, thanks. Yes, L1 is in line between Input power cord and the rectifier bridge. I am uploading a part of schematic image here. I marked in red circles L1 and Q1 transistor.
Now I have a 2 Amp fuse and Q1 transistor for replace. I already check the rectifier bridge and it seems to be ok. On the other hand, next week I will have an ESR tester for check all the capacitors, but I dont have any idea about the L1 specifications for buying a replacement.

Thanks for any clue.

[Electronic M]

L1 is a line RF noise filter choke as I suspected. Any differential noise* on the power line from the switch mode transistors or the wall outlet will cancel it's self out.

* Common mode noise is not as prevalent.

If that was a working LD player you could replace that with 2 jumpers and it would still work (though there could be more noise in the picture and sound with it gone).

Almost every modern switch mode power supply has one of those, and one from just about any other device that has one will work as a replacement...if you have a junk power supply from something else with a dual line choke like that that will physically fit it should be a usable replacement.

[Notimetolooz]

Switching power supplies are not easy to troubleshoot. The power levels are high and the safety margins are thin. Because they use feedback circuit methods it is difficult to isolate the problem.
If you want to be successful with electronics you cannot just use parts you happen to have on hand at the moment, there are too many variations and you know too little.
Modern electronics are harder to find the right parts for because things are seldom documented well because few people will have them repaired. The repair costs are too high. Most people will simply buy a new unit.

Please do not open many threads on one unit. It is rude.