JVC VCRs

[Longbow]

Re: JVC VCRs

This reply has nothing to do with the fact that I am completely familiar with the units you have been working on. One of them - lucky you - has an automatic azimuth adjusting video drum. HA, one of JVC's dumber ideas. Each time the tape in put in, the drum assembly hunts around for its proper azimuth. The tiny motors wear out long before the rest of the unit. But I digress.

Beginning at the beginning is standard procedure for problem solving. Check your secondary supply voltages and look at them on a scope to be sure they are not full of high frequency switching noise. If they are OK, you won't be wasting your time dreaming about capacitor replacement. Most likely suspects on a partially working supply are 1) 5 volt line incorrect due weak filters. 2) +-30 line (if used) has suffered damage to a diode or filter due to voltage spike. A problem in one of the secondaries will affect all of the secondaries.

Once the supply is working normally, does a tape load and eject? Does it power up and stay on? Does the tuner work? Simple stuff first.

[hasefroch]

Re: JVC VCRs

Hope you are still willing to get in working order this VHS.

IMHO, R_J was right on the money in this: "check and possibly clean the mode switch (tells the electronics what the mechanism is doing and what part of the loading sequence it is in)"

If the mode switch sends incorrect data, the system assumes mechanism locked, cassette in bad position, or a combo of them. Then shutdowns the power to prevent the motors forcing the mechanism (usually 5 to ten seconds, sometimes a motor can be hear "trying" to move the mechanism until power off)

I attached one of your pictures with the mode switch circled. This switch has a gear that needs to be in a specific position respect to the chassis mount. Usually there are marks of alignment, but this is specific for every VCR.

I attached the only service manual that could find, and this algnment is not mentioned. Still, the same manual goes for the HR-S4500U and the HR-S7500U; perhaps helps to find a "donor".

Before disassemble the mode switch, google "vcr mode switch" to get a better idea of how it works (I used to repair VCRs everyday ... until some 15 years ago). In any case, give me a shout before. These switch aren't supposed to be taken apart for cleaning; that means being careful before trying, and if possible practice in other mode switch from another dead VCR.

Hope this help, please excuse my bad english.

[mrmazda]

Re: JVC VCRs

I've all but given up since after R&R'd the main assemblies to change PS section caps, the front panel never lights up at all as it always would before I started. I might try again after some time spent catching up on my round tuit shortage, but I'm not hopeful since that regression.