Bought another JVC HR-D470U..

[redk9258]

I looked at the faulty display hoping to find a high ESR cap or something obvious. I checked about 4 caps for ESR and they were OK. There is another PCB that 2 ribbon cables attach to. It also has 7 plugs going to it. It's a small PCB that also has the memory backup cap. Only the memory cap checked bad.
I had another same model VCR that has a very nice display but has no picture.
I swapped the front display PCB and it was nice and bright but still missing the same segments as the original display. I went ahead and swapped the small PCB and guess what. It all works now! Still need a memory backup cap but the whole thing works!
I hate troubleshooting like this but I was stuck. Now I need to go over the original PCB with a fine tooth comb. Ill bet it will be obvious when I find the problem.

[redk9258]

Originally Posted by redk9258

I looked at the faulty display hoping to find a high ESR cap or something obvious. I checked about 4 caps for ESR and they were OK. There is another PCB that 2 ribbon cables attach to. It also has 7 plugs going to it. It's a small PCB that also has the memory backup cap. Only the memory cap checked bad.
I had another same model VCR that has a very nice display but has no picture.
I swapped the front display PCB and it was nice and bright but still missing the same segments as the original display. I went ahead and swapped the small PCB and guess what. It all works now! Still need a memory backup cap but the whole thing works!
I hate troubleshooting like this but I was stuck. Now I need to go over the original PCB with a fine tooth comb. Ill bet it will be obvious when I find the problem.

I wanted to add some closure to this thread because I hate when someone fixes something and does come back and tell how.
I have the original PCB in with the diode modification. The diode was fine but one on one end the solder connection wasn't good. After putting it back in, the display was still missing parts. I put it aside until the other day. I looked over the PCB and it has several transistors. Most are digital switching transistors that my meter will not test. There is one 2SD638 - Q301 that tested bad. It was shorted emitter to collector and showed something other than a diode drop base to collector and base to emitter. I replaced it with a 2SD1996 because I was able to get some from DigiKey. It is a similar transistor in a similar package. Anyway.. It works! This VCR that would not power up is fixed! It is sporting all of it's original parts (PCB / display). I wish I new more about that diode modification. I wonder if this unit took a power surge hit or something that took out this transistor and caused the cap in the power supply to short, which took out the fusible resistor just a little upstream. Anyway, I watched a couple of movies and it's been running for a few days now. The bad transistor is the one in the upper left corner.