Picked up another VCR for the collection, this one to expand the mid to late 80s section to join the recent TVs of the same era.
This was a bargain and just a £10, cosmetically in good condition, flap intact but missing the LCD remote (*). Described as non-functional due to a tape stuck inside, I couldn't resist such a bargain.
It arrived yesterday morning and as luck would have it a mate, who's a retired TV engineer, used to service this exact model, so off with the lid to see what was causing this stuck tape. First things first, power up and checked FF, that worked, next RW, that works too, tried play, that does not work. OK, finally, let's try to eject. The tape unload process functioned exactly as expected, but as the tape is pushed towards the opening for manual removal, it did not come far enough to be able to grab, off with the lid.
After much observation, checking and operating the unload by hand, it was deemed to be performing as expected, however, clearly something was jamming the left-hand side. It was agreed nothing was wrong with the carriage, the tape for some reason was jammed, so more positive forced was applied, and the tape came out, it now became apparent what the problem was. We could clearly see the window of the cassette had been pushed in on one corner. Looking back at the top part of the carriage top plate showed there was a pronounce bow on the left side, someone or something had bent it downwards, this in turn causes a tang to push down too hard jamming the cassette on the left side. Simple solution, remove the plate and straighten. Now the tape will load and unload.
So, the other transport function work, now to see if play works, a big NO! The head does not spin.
It was then noticed on the right-hand side of the large PCB (right where there are top holes in the case) what appeared to be liquid damage. There were also a few dry looking solder pads and some of the mask was flaking in places, you can clear see the where I've marked the outline of the liquid spread.
Checking TP802 confirmed the 5V rail was present, however when checking TP801, the 12V rail is missing. A few of the CP fuses were checked and the main glass ones on the PSU, all were ok. My mate then said he fully expected the STK5481 to have failed, it was a source of problems back in the day. Also, where the potential liquid damage is located is right above that regulator.
A check of my STK stock was the usual result, plenty of STK's but not that particular one. Needless to say, a couple are on their way to the Crusty workshop.
(*) I managed to find both the original remote and the manufacturer's service manual, so they are on their way too.
Some more photos, I need to remove the notorious black grease, it's not set hard yet but apparently it does.
To be continued....
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It was then noticed on the right-hand side of the large PCB (right where there are top holes in the case) what appeared to be liquid damage. There were also a few dry looking solder pads and some of the mask was flaking in places, you can clear see the where I've marked the outline of the liquid spread.
I am having flashbacks some forty years ago to the Sharp VC-482H I was brought which a dog pi**ed in. Yes, really. I got it working again though (heavily-corroded 64-pin shrink-DIP IC), even though Mum was less than impressed with me cleaning the PCB in the bath!
The remote looks identical to the one my JVC HRD-750EK used for programming: I thought it was the best system ever for remotely setting the VCR's timers.
Also beware of that brown/black glue that Jap manufacturers were fond of using. It can become conductive. I had a Sharp video that had several odd faults, the main one being lack of servo control which pointed to the mechacon control chip. Quite by chance I found that touching the chip would produce strange effects so I decided to clean the brown goo off and investigate further. I didn't need to....once the gunk had gone, it worked perfectly. I've had all sorts of odd problems caused by that stuff.
- Hydroscopic glue is still present in a lot of newer electronic equipment.
As I'm getting nowhere fast on the Sharp TV, and as the STK5481 arrived at lunchtime, I decided to install it and see if that resolves my missing 12V rail and thus my head spin fault. I also spotted a poorly cap so while at it replaced that too.
Well, I have the 12V rail back, that's a win and the head does spin, another win, but the tape fails to play. It appears to lace, but after a few seconds it stops and the VCR shuts down. At least the service manual has arrived, so I can start to give that a read and see if I can figure what's what.
It's just not my week for success, I guess.
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Most common cause was a slipping loading belt or very rarely a dirty mode switch. Select play and hit pause as soon as the guides hit the V blocks. If the machine stays laced then it's a takeup/reel drive or takeup sensor issue, if the guides return to the unlaced position belt or mode switch.
John.
tape counter won't be working either if it's a reel sensor problem, can't say for sure without getting out the service manual but some take up spools had a reflective plate underneath the use to get dusty.Most common cause was a slipping loading belt or very rarely a dirty mode switch. Select play and hit pause as soon as the guides hit the V blocks. If the machine stays laced then it's a takeup/reel drive or takeup sensor issue, if the guides return to the unlaced position belt or mode switch.
Manual suggests the take up sensor may be a slotted castallation on the bottom of the take up reel.
