JVC VCR PSU problems
 

Hi,

I’m having problems with JVC 8700ek S-VHS player I recently got.

When plugging in from a cold start up ie being unplugged for 24 hours then plugging it back in all that seems to happen is the fluorescent display flickers and there is a very slight clicking coming from the PSU. Then after about 30 seconds to a minute it’ll power up and work completely fine.

Something is obviously not working correctly until it’s been heated up.

Do you think this could be PSU capacitors on their way out or some other component?

Thought I’d ask on here first for some suggestions as these late VCR’s aren’t very service friendly And isn’t easy to test any components in circuit with having to remove the whole board and loading mechanism>:(

Re: JVC VCR PSU problems
 

I would start by checking all the electrolytics in the primary and secondary side of the power supply with an ESR meter. Also look for dry or cracked solder joints. A wise man once said, the reliability of any electronic device is inversely proportional to the number of electrolytic capacitors it contains. :)

Fivos

Re: JVC VCR PSU problems
 

Agreed. In fact I personally would just change all the electrolytics in the power supply.

Re: JVC VCR PSU problems
 

Certainly suspect secondary side caps on power supply.

Re: JVC VCR PSU problems
 

I’ve currently just been leaving it plugged in on standby.

Not sure how hard it’ll be trying to get the whole thing removed from the chassis.

I’ll check them with my ESR meter:)

Capacitors look to be made by Samsung.

Re: JVC VCR PSU problems
 

Probably Sam but not Sung. Maybe Young or Wha. Those do tend to fail over time.

Re: JVC VCR PSU problems
 

C1502 27u 35v in psu primary was always the main one to go use a 33uf its next to the chopper transformer

Re: JVC VCR PSU problems
 

Noted.

It’s annoying that there doesn’t seem to be any sort of service manuals for these last of the line JVC’s

I’m guessing JVC obviously thought they would be scrapped in favour of a DVD player long before they ever started to need maintenance.

Does feel quite cheap compared to earlier players, however it plays most tapes very well.

Although I do find TBC can make some tapes look worse which I found quite disappointing :-/

Re: JVC VCR PSU problems
 

Not in any way a related model but I have an ITT Nokia S-VHS machine from the early 1990s which was left unused for a long time. It then exhibited this flickering of the fluorescent display and not much else until it had been left on for a while. It turned out to be a rechargeable button cell used for preserving some memory settings. Leaving it on for a while charged the cell enough for the machine to spring into life. If left for a week or so it would revert to the flickering display again. I'm guessing that the discharged cell put a load on a supply rail needed for other functions.

Re: JVC VCR PSU problems
 

When you replace the electrolytics, make sure you use Low ESR types 105 degree. Using cheaper 85 degree types will end in tears or at very least a power supply that won't work at all. Switch mode supplies such as this are very critical of capacitor types. Fitting the wrong type can cause damage to semiconductor devices....

Re: JVC VCR PSU problems
 

To add to this, I'd suggest Panasonic 105 degree or similar by, for example, Vishay or Rubycon. Steer clear of anything with an X in the name or something that sounds vaguely Chinese. Also I have had bad experiences with Multicomp, also marketed as RS Pro.

Re: JVC VCR PSU problems
 

I usually use 105c Panasonic capacitors or Chemicon.

I’ve noticed a lot of Nichicon’s tend to be undervalued when it comes to the UF capacitance whereas the Panasonic’s always tend to be a few UF’s over on my meter.