sony st- jx430

[budm]

Re: sony st- jx430

Do not worry about that resistor on the board, you need to concentrate on why you are only getting 80vac at the end of the power cord which does not make sense to me at all, it also expalin why you are only getting 10VAC (if the input is 120, then the output will be about 15VAC) output on the secondary side of the transformer. Do you have other power cord from old stuff to use in place of the old cord, you can solder the other cord to those two points that I marked with 120VAC.

[mmoore5553]

Re: sony st- jx430

I am at work right - working hard lmao.

As soon as I get home I will unsolder the AC line from the board and test to make sure i am getting the right voltage. I will measure across your two points as last night i think I was just measuring across the black/ white wire and black wire.

[budm]

Re: sony st- jx430

Those two points I marked as 120VAC are connected to the end of the power cord.

[mmoore5553]

Re: sony st- jx430

Sorry all I have been sick with the flu but i finally am able to work on this again. I changed the cord out and now i have 120 volts across those two and now in the back across the two red wire posts i have 20 volts. I also have 120 volts at the back plugs. It still in stuck in standby. I am going to check transistors now. I looked over the board and did not see any burnt caps or anything. Not sure where to go next.

[budm]

Re: sony st- jx430

So did you hear both relays (on on the small board, one on the main board) click?
Also check the DC voltage on that largest electrolytic cap which is the main filter cap, and the voltage on the components mounted on the heat sinks. P/N of those two on the heat sinks?

[mmoore5553]

Re: sony st- jx430

Okay I am learning slowly but now i know there are around 4 voltages to look for in a receiver the 3v , 5v ,10v, and sometimes 15 - 20v. I am slow but learning . Now I did not know this but i sound like a muppet when i recorded the click. It sounds like only one but not sure. I almost recorded it again and said HI ho this is kermit the frog.

Memo.zip contains the recording. You can use winzip, winrar , or just windows to open the file.

TIA everyone.

[mmoore5553]

Re: sony st- jx430

The parts are ic501 la5666 on the bottom of that chip 6b1 and then q505 t880 and on the bottom gr 5j . I felt the IC and transitor on the heatsink and they did not feel that hot at all. One i felt nothing and other slight warm. Looking at the bottom i do not see any burn marks that are too bad.

[budm]

Re: sony st- jx430

At this point you will need to trace out the board to see how it is connected together, I am not sure what the relay on the main board is for. We already know that the relay on the small board is for the switched outlet on the rear panel.

[mmoore5553]

Re: sony st- jx430

Well i finally fixed this one as I turned out to be ic501. Not sure why though as it was reading fine but no voltages was going too it at all. I decied to replace the two chips ic501 and q505 and out of standby.

Thanks budm for the tip on changing the power cord. I would never have though the cord would have went bad.

[budm]

Re: sony st- jx430

Glad to hear you found the problem, sure like to know what is really wrong with that power cord.

[mmoore5553]

Re: sony st- jx430

So do transitors sometimes read good but still not function ? I thought it was odd meter said it was fine but changing it brought it back from the dead... Now i am wondering if on the other stereo if I should just replace even though meter says good.

Also i am tempted to buy a Panasonic tc-p42s30 -- comes on for 15 minutes and then dies ...you let it sit and then plug in later comes back on. You think for 50 bucks a good buy ?

[budm]

Re: sony st- jx430

You cannot rely 100% on testing the transistor using Diode mode on the DMM.

[mmoore5553]

Re: sony st- jx430

Is there another method i should be testing ? Or another tool I can buy hahha

[budm]

Re: sony st- jx430

I use curve tracer which not for hobbyist.
http://www.ebay.com/itm/TEKTRONIX-TY...item43c174bc7c
I got mine cheap from my work place when they up grade the old equipment.