Sony SLV-780 Resurrecting The Beast

all cops and robbers or murders, or surreal movies or really terrible sitc om reruns, very few of which were any good in the first place. Plus I got t oo much time on my hands.

ving trouble finding out what they mean. It has L 07 11, L15 60, L 18 11, L 00 11.

and then is OK, but if plugged in with a tape in it, it is really uncoopera tive.

ete. Couple of other codes have to do with not being able to tell what mode it is in or something.

h for the mechanical state switch. However I am having trouble figuring out how to get it out to clean it. I already resoldered the connector to it on the board, no good. It worked a few times and then threw up an error code, not sure which, it seems to like to throw about 4 different ones at random .

ow, and that is where it does not sound like a mode switch. I've never hear d of a switch going thermal.

g time ago, I got 2 with this problem. The other is a 740 but inside they a re identical. The 740 is a sacrificial goat because it has other problems a nd some corrosion from being in a bad environment.

hey came out and working on bigscreens mostly, so when they were newer I ne ver worked on one.

Sony is notorious for using really bad lubricants that turn into mud. Many problems in VCRs (including broadcast machines) can be restored by cleaning out the krud and re lubing.

The first thing to do is replace any rubber drive bands, especially on loading/eject cycle and mode switch. Check the plastic pinion on the mode switch drive motor spindle is not cracked , due to temp changes and steel/plastic expansion probs

Not this time. Everything moves smoothly.

Though I do have a 920 around that I will not plug in because they are know n for tearing up the rack gear that moves the arm that pulls the tare aroun d the pinch roller. That needs to addressed eventually when it goes back in to service. but this 780 is a totally different deck, called an H mechanism . It is newer. And all the grease looks good.

I am convinced the problem is not mechanical.

ading/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. A nd there are no switches on the loading mech.

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 wit h the record prevent switch and the end sensors. There literally isn't anyt hing else. When there is no tape in the machine the record prevent switch i s not allowing record. The micro knows this because whenever there is a tap e 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 t ape 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 mod e switch it knows if the record prevent is really on or off on this tape. I f off it loads further and pulls the tape around the pinch roller and acros s the ACE head for the linear time counter. If on it proceeds that little b it more into play as most machines do.

It uses the same motor for everything except the capstan and reels. There a re 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 go t 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 condi tion" where the little marks on the gears go when you recomombobulate it. Y ou 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 ha ve been minutes. My spatial and 3D reasoning was better, and Icould see. No w 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 con nections from the mode switch all the way to the processor.

The processor may actually be bad, the thing works a few times and then act s up. If it is going thermal I can try some spray solvent to cool it off an d see if it starts working again. I would bet my left nut that it is no lon ger 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 bec ause they are notorious for tearing up that big long rack gear, and I bet t hat 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.

I got the manual for the 690 or something. The mech is the same but the board is not. I am pretty sure it is an electronic problem at this point. The IC that handles this is IC 501 on the print and IC 201 on the board.

Any ideas at all on where to get the print for this particular board, or possibly an equivalent model ? System control is all I need, everything else seems to be fine.

All the years repairing VCRs, perhaps 200 units or so, I think only 2 were electronics problems, 1 a CCD display driver chip problem, and another a large BGA chip problem that needed a push. Are there indexing marks/arrows etc in the mechanism , in case its jumped a tooth?

jumped a tooth? "

There are some. You have to figure it out though because in the manual ther e is no picture depicting "Setting condition" which shows you how to put it for reassembly. I got it pretty much figured out because I have a guinea p ig, another VCR that is nearly identical. The goat...

I took the goat apart and found that the mode switch is full of nice grease and it is not even dirty, and it was treated much worse than the deck I wa nt to fix. All the grease is good, and mind you this 780 works sometimes, i t's just that after it warms up and/or goes through a few cycles it does th is shit, and displays a bunch of different errors, most of which come back to either it cannot tell what state the mech is in or the unloading is inco mplete. I have tested the mode switch with an ohmmeter and it is either a d ead short or open depending on the position and which terminals you check. When it works it does not try to overrun the loading motor or anything of t he sort.

The fact that it works sometimes leads me to believe the mech is fine. I st arted to try to trace the mode switch connections back to the IC but the do uble sided (or more) PC board makes that impossible. In fact it is more tha n two layers because the traces from the mode switch go to vias and then on the other side is solid copper, a ground obviously. there must be at least one more layer in between.

The print depicts IC 501 and on the board is IC 201. That is where the diff erence starts. The board.

I probably posted prematurely, I was going to somehow check the end sensors because they are involved in the loading process. But last night I decided to putz around with it and find the place where the mode switch actually g ets to the IC. I'll need to test it on the actual deck I am fixing because the goat is all apart, and I found out that little plastic things break whe n you remove the mode switch. So I am treading lightly because I know most of theparts are unobtainium. And if it is the IC, not only do I not have th e proper equipment to change it, I don't have it to get the replacement out of the goat, and plus it has the same problem,or at least it was found in the same state, tape stuck etc.

I might have to just say fukit and fix the 920, now that one IS dried greas e. I have not worked on one but I am familiar enough to know the the grease on the one tape arm dries up and it strips the rack gear. Yes, one of thos e. So I intend to address that before even plugging it in. I got LPS2 which is so good it will do it without disassembly, but I would rather do it rig ht, get all that goop out. The grease in the 740 (the goat for the 780) is in such good shape maybe I should use that.

Printed circuit boards are always composed of layer pairs. So there must be at least *two* layers in between.

Wonderful.

I remember the days when I could look at the PC and actually draw a schematic of the circuit. Usually I could just "see" the circuit in my mind but some were a bit more complex so I had to draw it out.

It actually got easier when they started designing the more modern, rather than hand drawn. I could count the foils "from the big one" and add and subtract as needed.

It actually got easier than following the old point to point circuits which I used to do well. But now I am a bit lost. I find the old Tektronix type ceramic bindings a bit easier to follow, but not much. I guess I am just losing it.

I actually could follow a two sided board until everything got too small. I had good spatial reasoning and could turn the board, or me, to see the other side and lock my eyes to the point where I wanted to see.

We've noticed.

Hardy har har. Got any ideas on this VCR?

Yeah. A dumpster comes to mind.

board is not. I am pretty sure it is an electronic problem at this point. The IC that handles this is IC 501 on the print and IC 201 on the board.

r possibly an equivalent model ? System control is all I need, everything e lse seems to be fine.

You were lucky. I'm still throwing out all sorts of worthless electronic p arts from VCR days. Capstan drive ICs, reel end sensors, smps specific par ts, system control parts etc. But we were doing a minimum of 50 per week i ncluding those from two pawn shops and several other dealers who only did b elts, idler tires and head cleanings.

he board is not. I am pretty sure it is an electronic problem at this point . The IC that handles this is IC 501 on the print and IC 201 on the board.

or possibly an equivalent model ? System control is all I need, everything else seems to be fine.

parts from VCR days. Capstan drive ICs, reel end sensors, smps specific p arts, system control parts etc. But we were doing a minimum of 50 per week including those from two pawn shops and several other dealers who only did belts, idler tires and head cleanings.

Tried to send you a message, but it was rejected. Send me a note at dansabrservices AT yahoo DOT com

I have many reasons to not toss this. Namely old tapes. It is about like new save for this one issue.

If you are the type who just throws shit out you are part of the problem. You can at least give it away on Craigslist or Freecycle, and on the latter someone might trade you something for it.

Our landfills are filling up at an alarming rate, and tons of money going to China et al to build everything for us.

parts from VCR days. "

I have seen motor drive ICs go bad, after all they are a power output. End and reel sensors as well. Never a microprocessor. I suspect something in th e system control circuit, but the IC last, after all other relevant things are checked.

I have only seen one SMPS transformer bad. It was putting out too much volt age and would not achieve regulation. I figure its resonance was high, indu ctance low possibly due to a cracked core. I had that once in a TV which pr oduced too much HV and a narrow raster. the pulses on the collector of the HOT/LOPT transistor.

The last time I saw alot of bad non-power ICs was in Sylvania Alpha tuners and the old Magnavox "digital" tuners which were not PLL, just voltage synt hesis.

I thought you said you had one just like it?

Not hardly. I have a 5000 sq ft shop full of "Shit with wires." Only the truly deserving get a one way trip to the dumpster.

Don't you find watching old tapes on a modern TV painful?

I've gone down that route, and the picture quality stinks, even with very good equipment. Unless the screen is small, and even then.....