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-   -   JVC 3320 Transport Failure (https://www.vintage-radio.net/forum/showthread.php?t=162300)

peter_scott 20th Dec 2019 2:16 pm

JVC 3320 Transport Failure
 
1 Attachment(s)
Recently I made a YouTube of from a 405 line VHS tape and noticed ghosting. I didn't understand why this occurred but fortunately Nick (1100 man) came to my rescue in another thread:

"I found using a 3V29 to record and play 405 tapes, that the drop out compensator got in the way on playback. This caused a 'ghost' image about a third of the way across the screen. I seem to recall (I would need to look at the circuit again) that shorting out the delay line for the DOC cured the problem. 625 tapes really did need the DOC to be working though as the dropouts were very obvious.

Cheers
Nick
"

So rather than using my Panasonic NV-FS90 for playback I thought I'd dig out my previous machine from its hibernation in the attic for 20 years. It only required one belt replacement and after struggling to remember how to re-install the cassette carrier so that the eject button still worked I eventually got it to lace up. Unfortunately, although the mechanism looks to be locking in place and the drum rotates it only transported the tape a few inches before it decided to unlace again and stop.

Any thoughts anyone? It does have the tape breakage lamp lit ok and is happy to fast forward and rewind.

Peter

peter_scott 20th Dec 2019 2:51 pm

Re: JVC 3320 Transport Failure
 
Sorry, a little persistence persuaded it to play. I'll ask about the next problem after I've played a little more.

Peter

bobbyball 20th Dec 2019 3:44 pm

Re: JVC 3320 Transport Failure
 
If you are referring to the 3V29 and JVC equivalent being reluctant to play, the weak link in this machine and similar models (3V30, 8940, 3V31/2 and similar) is the loading mechanism and it's weedy belt. Also failing/dried up grease after many years of storage - all the usual things!

peter_scott 20th Dec 2019 4:08 pm

Re: JVC 3320 Transport Failure
 
4 Attachment(s)
Hi Robert,

The video I'm trying to revive is a JVC 3320 top loading piano key unit.

Here below are the screen image and unrelated frame and line respectively.

Thanks,

Peter

p.s. The fourth image is showing some improvement but the break-up rapidly scans down from top to bottom and is stationary if I pause it. The tracking control makes no difference.

bobbyball 20th Dec 2019 4:21 pm

Re: JVC 3320 Transport Failure
 
Ah, sorry, I never did get the hang of the JVC model numbering system, barking up the wrong tree as usual!

The JVC "mechanical" machines do suffer from grease and lubrication issues but I'm sure you know that anyway. Also intermittent problems due to the multi-contact slide switches operated by the record and other keys.

There certainly seems to be a lot of noise on that picture...

peter_scott 20th Dec 2019 4:26 pm

Re: JVC 3320 Transport Failure
 
Thanks Robert,

I am certainly suspicious of possible congealed grease issues and it does appear to be improving so perhaps I'll just let it run a bit longer and see what happens.

Peter

peter_scott 20th Dec 2019 9:48 pm

Re: JVC 3320 Transport Failure
 
My problem is what looks like a head switch point that scrolls up or down the picture when the tape is running but if I pause it the the "switch point" remains static along with the picture. This short video shows the noise bar scrolling and also static when the recorder is paused. The video starts with it paused.

Please ignore the blacked out parts. These are just aliasing effects that are not visible in real time.

What would cause this behaviour?

Sorry, I don't know how to prevent YouTube from passing on to other videos at the end of this one. Hit curly return symbol on the LH side to replay.

Peter

https://youtu.be/MHb03DJl0ok

1100 man 20th Dec 2019 11:02 pm

Re: JVC 3320 Transport Failure
 
Hi Peter,
It sounds as though the capstan servo is running out of lock. This will give the effect of a noise band or complete screen of noise scrolling up or down the picture. The tracking control will have no effect.

The most likely cause is missing control pulses from the audio/control head. Check that the head is clean and that the tape is passing over the correct part of the head and not being pulled up or down the head by the pinch roller.

I can't get the link to work, so can't see the effect.

I assume this is what I would know as a 3v22? Like Bobbyball, I never got to grips with the JVC numbers!

I always found the servo's to be a bit basic on the 3v22, colour being displaced sideways to the luminance or moving relative to it seemed a common effect.

I had a 3v16 once as my first VHS machine. This has much better servo's as it has trick play capabilities and I found it much more stable than the 3v22.

I do have a great fondness for these early VHS machines. From what I remember, you should be able to record and play 405 material with no problems as I'm sure there is no drop out compensator.

Cheers
Nick

peter_scott 20th Dec 2019 11:19 pm

Re: JVC 3320 Transport Failure
 
Thanks Nick,

That's given me something to go on. (Yes, I think it is the same as 3v22.)

Peter :)

peter_scott 21st Dec 2019 3:57 pm

Re: JVC 3320 Transport Failure
 
Well, the control pulses are showing correctly at 25Hz so the capstan is running at the correct speed but the pulses from the head drum Hall effect sensor are running at 22.8Hz and so the video frame rate is too slow.

Unfortunately I don't have a schematic for the control board. Can anyone help me out with one?

I'm assuming that JVC 3320 = 3V22.

Peter :'(

FERNSEH 21st Dec 2019 9:06 pm

Re: JVC 3320 Transport Failure
 
Hi Peter, I'm certain there is Ferguson 3V00/3V22 full service manual in the shop somewhere. Because I have a 3V22 in my collection there's no way such a manual will have been thrown out.
Will take look tomorrow or Monday at the latest. I think the manual is upstairs above the shop.

DFWB.

peter_scott 21st Dec 2019 9:09 pm

Re: JVC 3320 Transport Failure
 
David,

That would be great if I can just get a copy of the drum control loop circuitry. There's no urgency for this.

Peter :)

davyrocket2 22nd Dec 2019 11:57 am

Re: JVC 3320 Transport Failure
 
Peter head drum hall effect I.C, devices are only found on direct drive motors ,the signal that you should be looking for is ,flip flop pulses sent from the north south of the drum flywheels magnets a very common fault on these machines is pulse failure due to the flywheel slipping on the shaft a gap approx of the thickness of your fingernail is all thats required .I think the fault on your machine will be sorted out in the correct setting up adjustment of the drum servo circuit as regard the other fault get clear and normal playback of 625 lines before altering for playing 405 line recordings regards David

peter_scott 22nd Dec 2019 5:13 pm

Re: JVC 3320 Transport Failure
 
Hi Davy,

Thanks for your thoughts.

I did remove the drum flywheel and it had the two magnets securely in place. I also ensured that when I refitted it that it was as far up and close to the sensor as it would go.

Although I started the thread explaining that my more modern VHS machine gave ghosting, the reason for the thread was so that I could revive my old JVC that has lived in my attic for more than 20 years so that I could play 405 tapes without ghosting.

All my testing on the JVC has been on a commercially recorded VHS 625 line tape. That said I did try a 405 line tape but of course it just displayed the same fault because the drum was still triggering the sensor at 22.8 Hz.

The sensor signal looks correct apart from the frequency and it is allowing generation of head switching pulses.

The JVC was put into storage in working order and I can't see any mechanical fault. I did replace the drum motor belt although it didn't need it and made no difference. The motor and drum rotate freely and removing the back tension makes no difference.

I think the most likely cause is a faulty capacitor in the drum servo loop. I don't think the servo IC is likely to have deteriorated with age but stranger things have happened.

Peter

FERNSEH 23rd Dec 2019 5:01 pm

Re: JVC 3320 Transport Failure
 
Hi Peter,
had a rummage around upstairs and found the service manual for the Ferguson 3V16, so that one is available if you want to borrow it. Somewhere in this shop there is the manual for the Ferguson 3292 and the 3V00.

DFWB.

peter_scott 23rd Dec 2019 5:33 pm

Re: JVC 3320 Transport Failure
 
Hi David,

Would it be possible for you to scan the 3v16 schematic with the drum servo control circuitry on it and email it to me?

Peter

FERNSEH 23rd Dec 2019 6:24 pm

Re: JVC 3320 Transport Failure
 
Hi Peter,
I'll do that when I return home.

DFWB.

FERNSEH 23rd Dec 2019 9:58 pm

Re: JVC 3320 Transport Failure
 
1 Attachment(s)
The circuit diagram of the servo board.

I've sent you a PM.

DFWB.

peter_scott 24th Dec 2019 1:03 am

Re: JVC 3320 Transport Failure
 
1 Attachment(s)
Hi David,

Thanks for scanning the 3V16 circuit. Unfortunately I don't think it's the same as that in my JVC3320 (3V22).

Although the 3V16 diagram appears to show a 24 pin IC as part of the drum control loop and my control board also uses a 24 pin IC in this role I don't think it's the same IC from looking at the pins used and their signals. My 24 pin IC is a Panasonic chip AN318. My board doesn't have the 40 pin IC that's on the 3V16 diagram.

Peter

peter_scott 24th Dec 2019 9:10 am

Re: JVC 3320 Transport Failure
 
The pulse from the control head looks good and the signal from the drum sensor on pin 28 of AN318 also looks good apart from being 22.8 Hz instead of 25 Hz.The two monostables Det 1 and Det 2 look to have good output signals and the DET Flip Flop has a nice regular square wave output but things start to look irregular at the output of the MM monostable that is fed from the square wave.

1100 man 24th Dec 2019 10:19 am

Re: JVC 3320 Transport Failure
 
Hi Peter,
I don't think there is any similarity between the 3v16 & 3v22 servo circuits. The 3v16 set up even has an extra pcb which needs a deeper rear cover to accommodate it.

Looking back over some past threads about 3v22's, drum servo problems, with similar faults to the one you describe, seem to be a common issue. The drum motor itself seems to be a common cause. It's a brushed DC motor and I assume the commutator/ brushes degrade to the point where it can't go fast enough. Might be worth checking before assuming it's an electronic fault!

In my experience, storing vcr's or almost anything for that matter in lofts, seems to almost guarantee they will be ruined! Extreme temperature turns the rubber to goo and dries out all the electrolytics. Then you get damp and mould in the winter!

Sadly I don't think I've got a manual- only a 3v16 one.

Good luck with it
All the best
Nick

peter_scott 24th Dec 2019 10:42 am

Re: JVC 3320 Transport Failure
 
Hi Nick,

I'm very much in tune with your thoughts. I had suspected the drum motor. I couldn't easily access the connections on it directly but I think I accessed the supply on the control board and it was something in the range 6 to 7 volts (I'll need to check it again.) I just didn't want to admit to myself that the motor was faulty but I'll go and solder a couple of wires onto it and check the voltage just now.

Thanks,

Peter

peter_scott 24th Dec 2019 11:13 am

Re: JVC 3320 Transport Failure
 
1 Attachment(s)
Hi Nick,

Here's what the drum motor terminals look like. The lower trace is just to point to zero volts on the scope and the upper one is at 2 volt/ div.

What do you think?

Peter

peter_scott 24th Dec 2019 11:46 am

Re: JVC 3320 Transport Failure
 
There is a capacitor or two around the drum motor drive in the 3V16 but I've yet to discover if they exist in my circuit.

peter_scott 24th Dec 2019 12:23 pm

Re: JVC 3320 Transport Failure
 
I've now changed both of the capacitors but unfortunately without any improvement.

Peter :(

peter_scott 24th Dec 2019 4:40 pm

Re: JVC 3320 Transport Failure
 
Well I think the drum motor is OK. With the odd glitch I've got it running at about the right speed with drum pulses at 25 Hz.

The breakthrough came with a tweak to the sample pulse amplitude. It's still not totally stable but appears to be a question of getting the tape path working correctly on the reference edge and without wiggling light reflections off the capstan and take-up areas and tape tension. All easier said than done. :-/

Red to black 24th Dec 2019 6:19 pm

Re: JVC 3320 Transport Failure
 
Yes the servos could be a PITA to set up on these, I probably have a service manual (paper) for this machine, I won't be able to dig it out before Christmas now though.

peter_scott 24th Dec 2019 6:40 pm

Re: JVC 3320 Transport Failure
 
Thanks Red to Black, There absolutely no urgency for this but I'd certainly like to see the schematic of the control board and maybe a bit about the path set-up.

Best wishes for a Christmas without thoughts of VCRs.

Peter.

Techman 26th Dec 2019 1:44 am

Re: JVC 3320 Transport Failure
 
2 Attachment(s)
Just been looking through my old manuals - these may be the ones you want, although one isn't very clear as the originals have been laminated, so the scanner struggled.

Techman 26th Dec 2019 1:56 am

Re: JVC 3320 Transport Failure
 
1 Attachment(s)
I've just had another go with the not so good one pressing hard down on the lid and with it showing the other end that was partially missing before, so perhaps you can work with the two. I think it's a bit clearer than the previous one.

peter_scott 26th Dec 2019 10:59 am

Re: JVC 3320 Transport Failure
 
That looks like my circuitry all right Techman and I can read them just fine. Thank you very much for this Christmas present. Very much appreciated!

Peter :):thumbsup:

peter_scott 26th Dec 2019 5:01 pm

Re: JVC 3320 Transport Failure
 
Hi Techman, Can you tell me which model your schematic is from? It is using the AN318 chip but unfortunately it is configured in quite a different way to my JVC3320.

I'm now unsure whether I have an electrical fault or a mechanical one. The drum speed is varying above and below its correct speed.

In this video the first part shows the period of the drum sensor at 5 mS/div so for the correct speed the leading edge should be at 40 mS but you can see that it varies earlier and later than this. The second part of the video shows the drum motor drive voltage. (The drum speed is of course damped by the inertia of the flywheel.)

https://youtu.be/QS1oARbcTzo

Peter

peter_scott 27th Dec 2019 12:31 pm

Re: JVC 3320 Transport Failure
 
2 Attachment(s)
Although Techman's schematic is rather different to mine it was very helpful in trying to identify the parts of my circuit. I eventually tracked it down to the limiter in the drum discriminator circuit with some help from:

https://www.americanradiohistory.com...e-Beeching.pdf

It was a leaky 10uF on the output of the limiter.

Thanks to everyone who offered help but especially to Techman.

So returning to my original problem of ghosting on a "modern" VCR I can play a 405 tape without the ghost.

Peter

Techman 15th Jan 2020 3:14 am

Re: JVC 3320 Transport Failure
 
Hi Peter. Sorry, I completely forgot about this thread, so just catching up. Great to see that you got the fault sorted in the end. The circuit I posted was from the portable version of the early piano key top loader, which I thought would be the same. If 'Red to black' happens to see this and has his copy to hand and is able to post it, then it would still be interesting to see the differences and for completion of the thread for future reference.

peter_scott 15th Jan 2020 9:36 am

Re: JVC 3320 Transport Failure
 
I am really surprised at the number of significantly different circuit versions there are for what externally look like the same VCR.

Peter

dj_fivos_sak 16th Jan 2020 1:31 pm

Re: JVC 3320 Transport Failure
 
Hi. A bit off-topic question so I apologize. What are the differences between the HR-3320 (3V22) and the HR-3330 (3V00)? I have an HR-3330TR which is multi-system (PAL, SECAM, NTSC 4.43). Was the 3320 released in the UK only with the EK model suffix?

mark2collection 16th Jan 2020 1:52 pm

Re: JVC 3320 Transport Failure
 
Quote:

Originally Posted by peter_scott (Post 1207884)
I am really surprised at the number of significantly different circuit versions there are for what externally look like the same VCR.

Peter

You're not kidding, I have the Baird version (looks standard enough) and an Akai version, where (from memory) the sys-con plus audio board are green and double sided! This being the only time I've seen double sided technology in a piano key machine.

Really must do something with these two, either enjoy them or, move them on. The Akai machine must be quite scarce(?) Cannot remember the model, begins 'VS' I think, the number 9300 rings a bell.

The Akai on occasions, unlaces whilst playing. The grease has turned to soft wax.

Mark

peter_scott 16th Jan 2020 5:06 pm

Re: JVC 3320 Transport Failure
 
Well, I can tell you that the 3330 uses an HA11711 chip in the drum servo control circuit whereas the 3320 uses AN318 an no doubt a million other differences.

Peter


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