Pioneer XC-L7 AEK fuses??

Maybe it's a stupid question, but after the sucesfully back to life of my SA-3000 (thanks to everyone who helped!!) picked my wife's XC-L7 that was faulty and in a forgetted box in the storage room, (this seems like a aerospace ship compared with the SA-3000 internals)

Opened and making measures arround the power supply (by somewhere I should begin), I founded that there is not the +15v (unregistered) I don't know what means, and there is a small yellow fuse that seems is broken, because the 15v arrives to fuse but not after that.



Solved myself the doubt there, I removed the fuse, checked and it's broken, also, 3 more were broken, one in the power transformer. I have replaced for testing purposes with a thin filament. After that I geve a try to see what happens, the unit powers up, but nothing else, the VFD display is barely legible, so unplugged to check voltages on the +-12v tracking generator board.

I have:

V+B = 29,6v
V-B= -29,6v
V+fan: 0v
V+12: 0v
V-12: 0v
XPOW: 0v
UN-: -14,9v
UN+: 14,7v
CD+5: 0,2V
XCDPOW: 0V
E+5.6: 5.4v

Also from the power transformer, seems that the FLAC1 and FLAC2 are very low on voltages, I think this ones supply the VFD screen, where is expected -22v

I have removed Q53 and is burned, tested another in place and burned again instantly...

https://www.dropbox.com/s/tr44lw9byy8n0mj/pioneer_xc-l7_rrv1946_sm.jpg?dl=0

Any help will be apreciated!

Some update! 25views and 0 comments! woow, this seems difficult!

I am shocked. dismayed. :tears: and angered :nono:

25 people looked at the post and said "UH OH!!!", MTF's gonna LOVE this!!! I'd better avoid this disaster in progress.

I can't be completely sure, but your "fuses" are resistors. Replacing them with

I have replaced for testing purposes with a thin filament

Click to expand...

is akin to tuning up for maximum smoke.

I have removed Q53 and is burned, tested another in place and burned again instantly...

Click to expand...

You are well on your way to tuning up for maximum smoke. resistors of 3500 ohms, 750 ohms, 500 ohms and 315 ohms, all replaced with low resistance shunts.

You have probably induced far more damage that was originally present - and if you blew up any specialized chips, all this is good for is soldering practice before you throw it out.

Get your ohmmeter and test the resistance of each and every one of those four parts. Did you write down what came from where? IF NOT, you have to start identifying just what you DID.

WHERE did each of the four come from? I am NOT going to invest the time to figure THAT out from the schematic diagram, keying on their unique values.

Q53 was FINALLY found in the schematic, a 2sb1566. WHAT did you replace it with and HOW did you get both the number of the replacement and where did you get it?

This is going to be the calibration standard for blindly bulling ahead.

HAD you asked, with that level of technology and interconnection used, simply disconnecting each connector and reconnecting it to get better contact for ALL connections MAY have cured the problem. It HAS happened many times before, but that results in a very short thread that is easily overlooked.

I have run out of time. Literally.

Thanks for your answer!

I thought too that they where resistors, but a close look on the service manual, sais that they are fuses, so replaced with a thin filament to test. There are five of these on this board:

IC2 (marked as 3500) is a 3.5A 125V fuse
RED marked, IC3 (marked as 3500) is a 3.5A 125V fuse
RED marked, IC32 ( marked as 750) is a 750mA 125v Fuse
RED marked, IC61 (marked as 315) is a 315mA 125v Fuse
RED marked, IC51 (marked as 500) is a 500mA 125 Fuse

They are on the 12v tracking generator (the first pair IC2 and IC3 in the power transformer). I replaced the fuses with the filament and for the Q53 (marked in yellow) and used the other one 2sb1566 that was on the Q73 (CD5v generator) (orange one)

They both blow without any heat, only a noise, and both now have continuity between the Base and Collector.

I found some Zeners that have continuity on both sides, removed one leg from the board, and the same, I supposed thery are defective:

D23 MTZJ33A (500mW 33v)
D24 MTZJ6.2B (500mW 6.2v)
D51 MTZJ18B (500mW 18v)
D61 MTZJ18B (500mW 18v)

Is there any difference on the A or B types?? standard zeners will do?

How can I check the correct work of the 4558DD?

Also tested all the other diodes on board, no more were faulty.

please, do not talk all at one time!!

q53 burned because there was too much of a load.

test q52 and if it is damaged, then the 4558 is suspect.

a and b are manufacturer's numbers and need to be checked via the part's data sheets.

yes, conventional zeners, as long as they are through hole devices, these will work:
512-1N5257B Fairchild 33 V, 0.5W zener
512-1N5234B Fairchild 6.2V, 0.5W Zener
512-1N5248B Fairchild 18 V, 0.5W Zener
512-1N5248B Fairchild 18 V, 0.5W Zener

re: talking all at one time, patience... I am running out of time and MUST do other things, it's not like I am paid to do this. And other issues make demands upon my remaining time.

Others will speak when they are familiar with the problem, and you have brought to us a very UNcommon problem. Perhaps if I do not answer for a few days others will try to fill the gap, but almost certainly not in just one or two days.

Thanks Mark, sorry, was only joking, your help is much appreciated!

I sourced some Q53 to replace the burned ones.
Removed the Q52, appears good, but "if for the flies" will replace both Q53, the Q52 and the 4558dd they are pretty cheap.

But one must find the extreme load (short?) that is killing Q53.

Do a resistance check to ground at Q53's collector (it's output).

Q53 Collector to ground resistance is 7,04K
Q62 Collector to ground is 18,01K

Don't know if these are relevant because I have the 2 zeners in this small board, all transistors and the 4558 removed. There are only the resistors, condensers and the 5.6 voltage regulator (IC31)

When the replacements arrive, will mount all and check for that before power on

Quick update:

Replaced the zeners, the 4558DD and the 2x 2SB1566 (Q53&Q73). Now powers up and sounds, al voltages are present and OK.

The problem now is that the CD drive won't spin. Entered the service mode to force spin it but no way, also the tracking didn't work. Checked the voltages to the spindle motor and there is 0v.

Seems that something prevent it to spin and move the tracking. Laser seems to power and the lense moves slightly, but not UP-Down as I have seen on other devices, it's like a lateral vibration.

Can be focus problem?

Can this unit be played in the united states and if so does it need a converter or does it have a 120/220 selector on it?