Panasonic AG1980P power supply problems

They used to offer kits for these. They included the Mosfet/Transistor, dr iver, ref IC, a bunch of zeners, and all the capacitors in the primary and secondary. It's normally high ESR caps in the primary that wipe these out. As long as they're plugged in and warm they're happy, but if they lose po wer and go cold, they'll blow the mosfet as soon as power is restored.

Email my brother and see if he has any supplies left for these. I know he got rid of a lot of stuff but you never know. If you find one somewhere, m ake sure you recap it before plugging it it.

Lenny, Once you recap these and replace the mosfet, please check the 18V zener to ground on the 15V line. Very likely that it will be shorted. Chuck

Chuck In looking at the schematic I don't see an 18V line. At the output there is a plug. It has outputs of 4.0V, 6.0V, and 14.60V, but nothing marked 18V. Actually, the only zener I see on the board is D1018 and it is off the emit ter of Q1006. Could that be the one you're referring to? Also I heard that some parts stores were selling repair kits for these but that was a while a go. Do you know who might still have these available or at least where I co uld still get the Mosfet? Thanks, Lenny

Looks like the schematic is available on line.

I would DL the schematic and rip one of the four apart and try to fix it. Then decide about the other 3.

mark

Lenny Though I worked on many of these units, I confused this P Supply with a different Pana supply that had crowbar protection on the 15V line. I would guess that IC1001 is bad and I don't know of any kit that is available. Chuck

Chuck, John Del had a novel idea. He said if the mosfet was good and even i f the caps had bad esr I might be able to get the supplies to start if i he ated them up. I used a heat gun on this one supply and then connected it to the VCR and to my utter amazement the unit came on. I dumped power a few t imes and each time it started up, so that was a really good tip. The caps a ll check good but I suppose that I should replace them anyway. Do you have a good source for good, (Nichecon or equiv) 105 degree caps? Thanks, Lenny

is a plug. It has outputs of 4.0V, 6.0V, and 14.60V, "

He was probably referring to the 14 or whatever line that usually has an 19 VZD for protection. Might even be 12.

THAT line is what you test. Silly techs I met checked the 5V, which is not that good an indicator because it is on the feedback loop. As the output go es down in that supply all the others go up. The 12 or whatever volt line i s a first thing indicator. BEFORE it blows up. If it is over 14V then you n eed the 5V caps.

Some more complex feedback systems have been used, as well as MOSFETs inste ad of bipolars, but the 5V as far as I can see FEEDS the opto, which is the main control mechanism. It supplies the drive to the chopper to regulate. When the load increases or the line voltage drops the frequency drops and m ore current is applied to the primary of the transformer thus increasing ou tput to compensate. The opposite happens when the load decreases or the lin e voltage increases.

You CAN see the action of this system by connecting hot and cold grounds to gether, using an isolation transformer that is variable and find some sort of dummy load(s). People go "EGAD" when I sat connect hot and cold grounds together but you can do it. You NEED an isolation transformer, and do not c onnect it to anything else. I have done it many times. But I can go with th e scope to both hot and cold sides and actually see just how the feedback w orks. I found it is much simpler than it seems.

One of the MAIN things about those supplies frying out on the absence of se condary filters is on the drain or collector of the output. In the old days it was 4.7uF/250V. I have also seen 10uF. If that cap opens it destroys th e chopper. It is not hard to find, follow the cord through the rectifiers a nd to the primary of the transformer. Look at the "C" or "D" terminal of th e chopper and you'll find a lytic. That is critical, no matter what else is going on with it.

Nuff for now. Give me more detail and I will give you more detail. I can't give detail when I didn't get any.

Were you able to switch back to petrol to keep it going?

Sounds like he needs surge protection or a UPS.

Some early generators will interact with switch mode power supplies causing them to surge.

On Wednesday, April 10, 2019 at 2:18:36 PM UTC-4, snipped-for-privacy@gmail.com wr ote:

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if the caps had bad esr I might be able to get the supplies to start if i heated them up. I used a heat gun on this one supply and then connected it to the VCR and to my utter amazement the unit came on. I dumped power a few times and each time it started up, so that was a really good tip. The caps all check good but I suppose that I should replace them anyway.

They'll read much better when hot so it's best to check them when cold. In any case, checking ESR in circuit isn't foolproof. Today we run into low ESR smd low value caps bypassing high value electros and fooling the ESR me ter.

Since these supplies run 24/7/365 and are stuffed into an enclosed and tigh tly spaced can, they're well beyond any reasonable expectation of hours. C hange every electo in the can and you should be good for another 10 years.

Mouser Electronics. They also carry Panasonic 105C caps which I prefer.

John's idea does work on this supply. The one I was thinking of would have had the shorted 18V zener so it wouldn't start. Good luck with the other supplies. As JUR6006 says, the 5V line caps are definitely bad. With an ESR meter, you'll probably find others. Good luck. Chuck