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[email protected] jurb6006@gmail.com is offline
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Default Sony SLV-780 Resurrecting The Beast

"The first thing to do is replace any rubber drive bands, especially on loading/eject cycle and mode switch."

There is only one belt from the capstan motor to the idler assembly and it is a toothed belt. There is also a tensioner and it isn't even stretched. And there are no switches on the loading mech.

"Check the plastic pinion on the mode switch drive motor spindle

is not cracked , due to temp changes and steel/plastic expansion probs"

Looks good, there are no cracks.

This thing is something, the way it detects a tape I have determined is with the record prevent switch and the end sensors. There literally isn't anything else. When there is no tape in the machine the record prevent switch is not allowing record. The micro knows this because whenever there is a tape in it art least one end sensor is covered. If neither is covered and it is not allowed to record it knows there is no tape in it. When you push a tape in the linkage allows the switch to go to allow record and it runs the motor and draws it in. At that point, determined by the position of the mode switch it knows if the record prevent is really on or off on this tape. If off it loads further and pulls the tape around the pinch roller and across the ACE head for the linear time counter. If on it proceeds that little bit more into play as most machines do.

It uses the same motor for everything except the capstan and reels. There are no switches on the loading mech. Pretty nifty how they do that eh ? This is an H deck and the first one of its kind I have ever worked on. And I got some bits and pieces of manuals, and of the one that seems to be complete as well as the one for the deck only, neither one shows the "setting condition" where the little marks on the gears go when you recomombobulate it. You have to figure it out for yourself I guess. I got it mostly figured out, at the expense of some time. Took a few hours, in the old days it would have been minutes. My spatial and 3D reasoning was better, and Icould see. Now Ihave to do everything with almost no depth perception. Sometime Ithink I am tinning a wire ad I fid outI and burning my hand or something.

I have determined that the problem is not in the deck itself, it is in the mode switch connection to the board, or an end sensor, or something on the board in the system control.

A couple of the error code mean it can't figure out what position it is in, which means mode switch or end sensor(s). Once I rule out the end sensor(s), if one of them is not the problem, then I guess I have to follow the connections from the mode switch all the way to the processor.

The processor may actually be bad, the thing works a few times and then acts up. If it is going thermal I can try some spray solvent to cool it off and see if it starts working again. I would bet my left nut that it is no longer available, so if that is the case i will try some sort of heat sinking, like with that thermally conductive glue used on other surface mount chips.. Though I haven't seen it yet, it is a good bet that it is surface mount.

If it doesn't work I will have to dig up that old 920 and see if I can make that work. I won't even plug it in until the lube on the arm is redone because they are notorious for tearing up that big long rack gear, and I bet that is pure unobtainium.

the micro should be the same in many models, I might be able to scare up a used one, but I don't have the proper tools to change it.

Six of one, half a dozen of the other. Damned if you do.