Yet another broken VCR
 

If you know me, you know I can't resist a mid 80's Panasonic VCR if it's cheap. I bought a 1986 Panasonic PV-1360 today for $5. I expected it to work, but I couldn't have been more wrong. This VCR has the worst power supply I have ever seen on a mid 80's Panasonic. I got home, plugged it in, and it is dead as a doornail. I opened it up, saw a blown fuse, so I did what any insane person like myself would do, I jumped it. When I plugged it in after that, sparks and flames shot out of the power supply, and almost caught the carpet on fire. The source of the sparks was a transformer/coil right underneath the fuse holder. I don't know if that is the shorted part, or if some other part failed and caused a chain reaction.

That is a line filter dual choke. The two power cord wires go through it's two windings....Which have just enough inductance and are 180 deg out of phase so that frequencies above 60Hz are attenuated.

It will feed a diode bridge, that then feeds a XXXuF 160-450V cap, that then feeds a switching transistor, that then feeds that bigger high freq transformer that then gets rectified and regulated to PS B+/- rails....

First make sure you did not short or open that choke. Then check the bridge and cap for shorts....Beyond that and cap changing I'm not all that good at SWMPS (switch mode power supply) repair.

There is an error in your post: most sane electronic techs, don't jumper a blown fuse...They pop in one 150% of the amperage of the original and see what happens...Unless they don't particularly care what becomes of their gear. :D

Thanks for the info. If you look at my post, I said "I did what any INsane person such as myself..."

You're welcome. IC now...Lol.

And what really boggles me about this whole thing, is that this VCR is in excellent condition. The top cover has no burned spots at all from the SMPS. And the entire inside is very clean. I wonder why such a low hours machine would tear up like this?

On e thing comes to mind. A lightning surge on power line will cook a switch mode supply faster than you can say"Bobs your uncle". All the best, Tom.J

I used to fix those all the time. A few electrolytic caps, usually the smaller value in the primary and some in the secondary, maybe a new driver transistor, possibly replace a shorted zener that is there for overvoltage protection to the rest of the deck electronics. If it took a lightning or power surge then likely the driver transistor, fuse and the protection zener on the secondary side.

btw.. fuses are there for a reason! NEVER jump a fuse and just plug it in straight to the wall. If you must, use a 25 or 40W light bulb in series with the AC. Upon first power on after repairing the power supply I would always plug it in with a 40W bulb in series to make sure I got it all fixed.

If you do not have an isolation transformer, don't work on the power supply plugged in. Primary side is hot to AC.

Dig through an old MCM, Consolidated, or MAT Electronics catalog and you'll find rebuild kits for those SMPS (VEPSXXXXXX) power supplies - the MOSFET or Switching transistor, all the support semis (diodes, zeners, small signal transistors and optoisolator), and a few electros.

Get the kit, or assemble one yourself and you have a greater than 80% of fixing it...

Later models had the modular unit power supplies that were consumable - just buy a new one for under 20 bux. MAT and MCM had them, but they are probably long gone. I have some NOS ones for RCA VCRs, but I dunno the VEPS number.

I always use the lamp trick. I have a 40,60,100 and a 200watt lamp for my hot lamp tester. The wattage depending on the size of the load.
The line choke doesn't look too healthy anymore. :sigh:

Rather than take this useful thread on Matsushita machines in a direction away from player power supply issues, a new one will be started.

Many people were fond with the mid-80s Panasonic-made VCRs, but if you just stare at the photos carefully for one hour, you will immediately notice they were built more cheaply than other brands, and not designed for longest-lasting. Even Funai VCRs that once bought all chassis mechanism from Shintom to save on costs looked more-expensive quality than the Panasonics.

For any untested VCR, including the ones never plugged in to test, Panasonic is one of the last brands I'll consider buying.

Im so sorry Tud :(

I hope you have a good working unit now :) (This one seems like its been not treated well :()

It was until you set it on fire! :banana:

I jumped the fuse a few months ago on a little tire inflator I had in the garage, learned my lesson. Guess I'll stick to the old light bulb trick.

Got some bad news for you. I e-mailed Studio Sound Electronics of your problem, and he told me it's not repairable and you have to trash it.

"Yep, there are a lot of people out there who apparently don't understand the concept of a fuse. What could have been a fairly simple repair now likely means the VCR is not repairable, or at the minimum involves a major rebuild, which is probably not worth the effort or expense.

These people should be deserving of a Darwin Award: http://www.darwinawards.com/

What happens is that the line-filter inductor right after the fuse draws several amps of current because the chopper transistor was previously shorted. This amount of current immediately smokes the inductor and in most cases sets the inductor case ablaze. This in turn burns the circuit board, which often renders it unrepairable. The amount of damage is proportional to how long the power cord remained plugged into the wall. If the power cord is yanked pretty quickly (within one to two seconds maximum), only the inductor, all of the capacitors and multiple transistors and diodes, along with perhaps one or two resistors would need replacing. If the power cord isn't pulled immediately, the power supply is usually ablaze by that point, causing it to be damaged beyond repair in addition to collateral damage to other parts of the VCR."

Studio Sound Electronics