Panasonic PV-8662 VCR, no power.

I could be wrong but hard to imagine. If that were the case there would be a seperate power source to the uP to allow it to do that. If you pull the plug from the psu to the rest of it does it work? Perhaps it shutting down because of excess load, another fault further in the system.

JD

Given that the main switchmode transistor was shorted, it may have taken a fusable resistor with it. It's R23 on

--- sam | Sci.Electronics.Repair FAQ Mirror:

Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is ignored unless my full name is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Yeah I was gonna ask if power was getting to where it should but thought that would be too obvious :)

In addition to the possibility of a bad fusible resistor, as Sam mentioned, I would also look at any control transistor near the main switcher (often designated Q2) and of course look for a shorted 18 volt zener and bad caps on the secondary side, and let's not forget a shorted recifier on the secondary will do this also.

But then you probably already knew most of this, yes?

Mark Z.

VCR repair? Just wondering what the average charge for repair is. when I see

can

see

components

power

uP

mentioned,

Hi Mark, Sam, and Jonathan,

Yes, I know all the weak points of these switching power supplies except for the problem with this one. lol. This set is only a couple of years old and unlike in the olden days (maybe more than a few years ago), these power supplies are part of the main board. It's not a separate module. To service it requires removal of the mechanism and main pc board. One of the nice features about this set is that it has "commercial advance." Somehow it knows where the commercials are and skips them during playback.

I did replace Q1001, 2SC4533, with an SK replacement. Though it is stamped with the same number, I'm wondering if somehow it may not be up to specs. There is a secondary transistor, 2SD2259, Q1002, which tests good. Looking through the archives, somebody mentioned to replace it anyway even though it tests good. I've checked all the other passive components and the ones that looked questionable, I removed from the pc board just to make sure they were good.

Here are the voltages I've measured:

Q1001: coll. 144V, base 0V, emitter 0V Q1002: coll. 0.4V, base 0V, emitter 0V

I rang the switching transformer with Bob Parker's flyback tester. It tested good. I'm not sure whether that tester was designed for a transformer like that but it was an easy test.

Thanks for your replies.

I believe you said it wasn't starting up. According to your measurements, there is no drive to Q1001. If the supply is at all similar to the generic in:

then there are only a small number of components that can cause that.

--- sam | Sci.Electronics.Repair FAQ Mirror:

Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is ignored unless my full name is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

The

some

(often

caps

for

and

service

stamped

specs.

Looking

though it

that

were

tested

like

generic in:

excessive

is

And the answer is....

I purchased another switching regulator transistor, 2SC4533, at a different parts store. This time, NOT an SK replacement. The set now works fine. That will be the last time I ever buy an SK part. By the way, the SK transistor junctions check good on a DVM test. Maybe I'll build a quick, home made curve tracer and see what's up with this SK device.

Thanks to all that helped.