VHS won't play, sounds like tape will load then power shuts off.
This is similar or identical to another post, but here is an answer...
Hi, I have a solution you can try.
I had exaclty the same problem. When I tried to play a tape it would load (However, I recall I had to push hard to get the tape to be accepted, which is part of the problem) but would shut off after about 12 seconds, then when I powered back up the tape would eject. Finally I took the unit completely apart and attempted to use it with the covers off. Lo and behold, I found I could play a DVD on the unit without the unit powering off, but only if the room lights were on! If I tried to play a tape it would shut down the unit. So that led me to diagnosing the infrared loading and reel sensor circuits.
Background on that is there is an infrared LED that shines up through a plastic light pipe lens. The light from that LED (you can't see it) should shine on two photodiodes that are on either side of the tap mechanism, plus down through a gear with holes in it on to the reel sensor. When there is no tape inserted the two photodiodes will be illuminated and have about 0.2 volts across them. When a tape is installed the light will be blocked and the voltage goes up to above 2.5 volts across the diodes. You have to check this with the room lights dim as the diodes will respond to that light. When you block the light on either side of the plastic light pipe with your finger (with the unit disassembled) you should see the load motor engage, and it will back off when you take your finder away. For some reason in my unit the light from the LED was insufficient to turn on one of the diodes, and also to pulse the reel sensor when the gear turned. That could be due to component aging, or even if the light pipe started to cloud due to age, I don't know. However I was able to get the thing working...
In short I got the unit working by adding 3 resistors.
To do this you'll have to remove all the covers and remove the main PCB from the bottom chassis, unplug the power supply from the PCB, and the two ribbons going to the DVD unit. But you won't have to take off the VCR assembly, which is a pain. You just need some basic soldering skills, and remember where all those screws go...
First, I adjusted the voltage across the right-hand side load sensor diode to get the diode to switch on and off. I recall that I added 1meg across the diode. So the voltage then went from about 0.5v up to 2.8v from light to dark condition.
Second, I increased the current to the IR LED. I added a 330ohm resistor across the feeder to the LED. I recall that was R511 and was originally 220ohms. That was not quite sufficient to get the reel sensor working reliably. I didn't want to stress the LED by putting too much more current through it so looked for another idea.
Third I added 56k across the reel sensor diode to bring the voltage across it down so it would switch on and off as the reel sensor gear turned.
I now have a tape playing continuously in the unit and it seems ok for the time being. Hope that might work for you too.
on Oct 06, 2016