Sony Videocorder Model AV-3420CE

[af024]

I'm struggling away to locate service information for one of these Sony Videocorder AV-3420CE machines.

The machine I have is pretty much dead apart from the meter at the front and a solenoid 'clunk' inside. There is no motor action whatsoever. I've eliminated the absence of a tape by lacing one up to operate the microswitch.

If anyone does have some info I'd love to hear from you - all costs met ... naturally.

Thank you.

Here's hoping.

Regards,


Andy

[Studio263]

I had this fault on one of these, it was caused by the motor not working. Taking it apart, it was clear that what had happened is that the foam rubber blocks that they had stuck to the back of the brushes had shrunk and pulled the brushes out of contact with the commutator. Cutting away the offending foam was all that was required to restore normal results.

[af024]

Thanks.

That sounds like an excellent place to start.

Cheers,


Andy

[Studio263]

From memory, the motor was hidden somewhere like in the base of the head drum (like the later SL-C7UB etc). There was another smaller motor in there too that may have been used as a "brake" for the servo, this was initially confusing as with all the belts removed certain parts would "limp" round. This took days to work out!

[af024]

Well I found the end of the motor wires and disconnected one just in case the motor was pulling the supply down. No joy - no supply present. Whilst the wires were disconnected, I used a PP3 battery across the motor (just to see if it was suffering the brush problem you described) - it wasn't, the motor turned ok.

The motor I found seems to turn everything - capstan, reels and heads. Not sure how one motor can do the lot though, but there you go. Maybe it's just as you describe. The trouble is, I guess I now need the data. It's almost impossible tracing wires as everything is so tightly loomed and lacquered over etc.

Mmmmmm ....

[af024]

I think I may have confused things earlier.

The motor with no power on it is the one shown to the upper right in the photo (round black inner). I suspect that this motor only gets power to sync things up when the main motor is operating.

The main motor (the one directly coupled to the video heads) seems to have power (at least it does if I've identified the wires correctly - white and red). This isn't running. I guess this is the one that you were referring to Studio263.

I have no idea how to get into the thing however. I did start to try and attack it from the underside. I nearly wrecked a coil (not realising how the fine wires were terminated), but I got away with it. Eventually having removed the coil, plates, pulleys and spacers etc, I got to a round tin. No way to get it open/remove it. It looks like it's probably secured from the top somehow. The thing is, it looks like I've got to come in from the top (which concerns me greatly since I've got to shift out all the heads etc).

Is this the motor Studio263 and can you remember how you got into it?

Cheers,


Andy

[Studio263]

I'm sure I got to the motor parts through the bottom, I don't recall having to take the heads off.

Thinking about it again, there were two structures in there that were motor-like, I think I made your possible mistake too, powering it up made it spin so I thought it was OK. However, when it comes apart it is like there are two motors in there, one is a servo generator, the bigger one was the actual motor. If it was in front of me I'm sure it would all be clear, just like so many things...

[af024]

Yes I got as far as the servo coil and stripping further only got me to a gold-coloured casing with no sign of actual motor. I could see a circlip holding a bearing to the casing, but that was it. No way would the casing budge (ok, I didn't have a go at the circlip). I simply thought at this stage that it must be secured somehow from the top (doh!!). Thinking about it, I can't see how the circlip would hold the casing on so tight (there wasn't even any rotation possible). I wish I'd taken a photo of where I'd got to before I put it back together now (just in case it brought some memories back).

Geez, I hope I don't have to go for the heads!! I have visions of total disaster if I go there ...

Regards,

Andy

[af024]

Well I decided to take the plunge and remove the heads.

Sure enough the bolts underneath were those holding the underside cover on. As a point of note, the inner screws hold the brushes in place (and you’ve guessed it, there’s just a nut the other side, so if you undo them fully, the nuts will fall away and you’ll have to go for the entire strip down anyway).

It was still by no means easy as the brush assembly is retained and the armature comes away with the casing and permanent magnet. Goodness knows how they put the thing together since the red/white wires (for power) go through the casing and then get soldered onto the brush assembly. Just try to pull the casing away without ripping the wires off (then you’ve got the excitement of putting them back later).

As you described earlier Studio263, the brushes WERE being pulled back away from the commutator by shrinking foam. I dug all the remains out and cleaned up with nail varnish remover, bent the spring carriers out a bit and restuffed with some new foam (but this time with some felt backing affixed, so that in years to come, when the foam goes the same way, the brushes won’t be pulled back again, well that’s my hope anyway). I decided to put the foam back since there was some significant sideways movement without. I didn’t want the brushes going twist about round the commutator during high torque.

As predicted, the re-build was an absolute pain and somehow I managed to end up with shorter red/white wires (presumably I left more inside the casing). At least there are no horrible signs of internal clicking!

Having reassembled, the first pass of my only tape only produced some snowy pictures (of a TV set!). Having realised that I’d had to disturb the video heads, I did a little tweak on the guides and hey presto – better pictures!

The tape is squeaky and will only motor for the first 2 mins or so, the belts are a bit slack and things don’t sync up very well, but at least I’ve got some action now.

I’d like to try a new recording using modern tape, but I don’t have a spare spool and I have no idea about the pin-outs of the multi camera connector (the only way to get video and audio into it, it seems). If anyone can help me with either, I’d be very grateful. Someone with a spare connector would certainly get top marks!

So thanks for your tip with the foam. Just goes to show that not only 8-track cartridges suffer from the problem.

Pictures attached.

Regards,


Andy

[af024]

More photos ...

[ppppenguin]

Originally Posted by af024

....I have no idea about the pin-outs of the multi camera connector (the only way to get video and audio into it, it seems). If anyone can help me with either, I’d be very grateful. Someone with a spare connector would certainly get top marks!

Assuming you are talking about the 10(?) pin circular connector I may have a lead with the connector on one end and BNCs/phonos or something similar on the other. Possibly just a male connector. PM me to remind me to take a look in the morning. Yours for the cost of the postage and maybe a couple of beer tokens. If it's the 8(?) pin rectangular connector I may have those too.

A photo of the connector panel would help to refresh the old memory. ISTR there were other connectors but time can play tricks.

[arjoll]

Originally Posted by af024

The tape is squeaky and will only motor for the first 2 mins or so

Are you noticing the heads clogging after playback? If so the tape may have sticky shed - squeaky tape and a gradual slow down (and loss of high frequencies on audio tape) are common symptoms. Its rare on Japanese tape (never seen it on Maxell, for example) though so might not be your problem.

This is from audio tape experience - it might not be applicable to video tape but there's no reason for it to be less prone to sticky shed than audio tape!

[af024]

Thanks Jeff and arjoll.

Yes it's a round connector - something like 10 pins, yes, sounds like you've identified the beasty. I'll put a photo up soon. Thanks Jeff.

arjoll, yes I think that the tape is sticky. It's badged as Sony, so in view of what you've said about Japanese tape it's would seem odd. I've certainly come across sticky tape for Philips N1500 and N1700 machines (but they weren't Japanese). Head cloggs, mech slow down and even stalls.

Cheers,


Andy

[af024]

AV in-out/camera connector picture ...

Cheers,


Andy

[Station X]

I think the one on the right is called a "Hirose". In fact it has what looks like HRS written on it. Plugs to suit them were/are available from Farnell.

They're a Br to solder up though!

[af024]

Yes I bet they are a pain to solder AND I don't have the pin-outs either. I'm hoping Jeff comes up trumps. I didn't know it was called a Hirose - thanks for that.

As for the set featured on the tape ... I don't know. When I first saw it amongst the snow I thought it was a KB Vanguard (something I've been after for a while), but as the snow cleared I could see that it was a lot more modern than that.

Just a spare reel needed now ...

Do you think I could wind some modern VHS tape onto a reel and use that ok?

Cheers,

Andy

[ppppenguin]

Originally Posted by af024

Yes I bet they are a pain to solder AND I don't have the pin-outs either. I'm hoping Jeff comes up trumps. I didn't know it was called a Hirose - thanks for that.

Not too bad to solder. I've done it.

[Station X]

You've probably got better eyesight than me though Jeffrey. I wired up a couple of hiroses a few years back, ten pins on about a 1/4" daimeter circle, and had to use a magnifier. That's why I like valve stuff. Easy to see. Surface mount etc. is too much of a pain or should that be strain for me nowadays.