Blue Screen on Play JVC VCR HR-S4700U

[Dan Schafer]

Hi All
Been looking at an old JVC model HR-S4700U VHS VCR. The machine loads & ejects & responds to transport buttons when pressed. In play mode I can only get a blank, blue screen. The search mode in fast-forward gives a good image and the re-wind search gives an image with slow vertical rolling. The pause/still button also produces an image but not as clear. The sound is OK. Just looking for any quick suggestions that I can check on the machine before I toss it. I cleaned the heads & tape path with no improvement. Thanks in advance.

[zenithfan1]

What did you clean it with? Those cleaning tapes don't do a good job on a really dirty head, it's best to use a Q-tip and 90% rubbing alcohol. It sounds to me like the heads are still dirty.

[holmesuser01]

I also think the heads are still dirty.

[Barry777]

If the machine is out of mechanical alignment, the VCR blanks the picture rather than show it with poor quality. Those can be somewhat challenging to align, since you can't even see the picture until you're fairly close to optimum. You might try adjusting the 2 guide posts a little at a time, and seeing if the picture pops in. Or, you might have bad play heads if the machine has seen heavy use. As a last resort, you might try a dry type head cleaner, which actually laps off the top layer of the heads - but no more than 10 or 20 seconds using this type of cleaner.

[JCFitz]

If none of the suggestions work you may have a unit with a bad drum motor ic mounted where else on the drum motor as part of it. It loses one of the feedback pulses needed for proper servo alignment. Was a common problem on JVC vcrs of the 90s. The drum motor has to be replaced to fix it.

[Ed in Tx]

Originally Posted by JCFitz

If none of the suggestions work you may have a unit with a bad drum motor ic mounted where else on the drum motor as part of it. It loses one of the feedback pulses needed for proper servo alignment. Was a common problem on JVC vcrs of the 90s. The drum motor has to be replaced to fix it.

Actually on a lot of those JVCs you can simply replace the 3.3 uFd/35V (as I recall) SMD electrolytic capacitor that fails on the drum stator board. You can usually get to it from the bottom but sometimes you have to lift out the cylinder assy. I've fixed many like that. It loses the PG pulse when that cap fails which is how the servo knows where the head cylinder is, causing the head-switching to be anywhere rather than being locked to the position of the cylinder and heads, and you get the blue screen just like no video or clogged heads.

[Ed in Tx]

Here's a picture I found showing the bottom of the cylinder assy, which I have circled and pointed to the culprit SMD capacitor...




I'd almost bet money replacing that will fix it.

[Barry777]

I can vouch for Ed on this, as his suggestion fixed one of mine!

[Dan Schafer]

Thanks Ed in Texas.....great photo! Very helpful! I will give it a try & let you know.
Dan

[robertc2]

Had one of these VCR's with the video problem in a box in the basement for years, and was about to toss it, then I came upon this thread. Thanks all and especially Ed in TX. That surface mount capacitor was the problem. Blue screen is gone and the picture looks quite good once again.

[Ed in Tx]

Cool! Another one saved from the scrap heap!