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Old 25th Apr 2021, 1:23 pm   #1
hillsrob
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Default JVC HR3330 Lower Drum Issue

I bought a complete JVC HR3330 on Ebay primarily to obtain some cosmetic parts for my now working HR3300, i.e. a foot, a spring that goes inside the cassette housing and a front panel for the timer. (For some reason my HR3300 has the slightly later timer fitted to the HR3330s)

On receiving the HR3330, I decided to see if it might be salvageable as a complete machine. On powering up and pressing rewind the head drum proceeded to spin up with a bit of a clatter but immediately quietened down. It loaded a tape happily and showed something of a poorly synced picture with audio that was clearly running slow. I decided to replace all 7 belts before investigating further.

Note that at this point I don't have a scope to hand but I do have a used one on order from Ebay.

Having fitted the belts I managed to get the audio locked at what seemed by ear to be the right speed by adjustment of the 'CAPSTAN SAMPLING POSITION' pot.

At this point the drum servo was clearly unlocked but I was able to get a reasonably stable picture by adjusting the 'DRUM SAMPLING' pot. The drum however was still mechanically quite noisy. At first I thought that the bearings were shot however something made me think that the noise might be coming from the position sensor on the bottom of the lower drum.

I removed the drum flywheel and sure enough one of the embedded ferrite pieces was chipped as if it had impacted the pickup head. Perhaps that was the clatter I had heard at initial start up? I decided to set the flywheel slightly away from the head and it now seemed to spin quietly. Problem solved I thought.

The picture was now fairly stable but with a slight periodic pulling to the left about once a second or so. This was resolved by adjusting the 'DRUM DISCRIMINATOR' pot.

So I settled down to watch Thelma and Louise. About one hour into the movie I noticed that the drum had started to become noisy again. So maybe the chipped ferrite was a symptom of something more serious? Sure enough, even with the flywheel removed the drum shaft was quite noise when spun by hand. While running the machine upside down I suddenly lost the picture completely. The Avtex TV I was using as a monitor blanks out and displays 'no signal' if fed with an unrecognised video signal.

So it looks like this machine might be a breaker after all but my curiosity leads me to look further into what has really happened? Could the rotary windings in the lower drum assembly have moved too far apart to couple the head outputs? Watch this space.
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Old 25th Apr 2021, 1:52 pm   #2
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Default Re: JVC HR3330 Lower Drum Issue

I remember that sound a noisy drum could make, its quite distinctive. Sometimes they would quieten down on their own as I recall.

Drum motors were the main cause of drum servo issues that I remember although it took us a while to suss that one out in the very very early days.

A good test (scope needed) was to look at the ripple voltage across the motor. I can't just remember the figure we used now, possible around 200mv peak to peak. If it was high and electrically noisy then the motor was replaced.

Now all from memory and this was decades ago... I can remember adjusting the drum servos by strobing the head off the TV screen and setting the drum free speed. Then the servo gain was adjusted until the drum just started to kick and then backed off a little.

I think... it was ages ago.

The rotary transformer coupling has to be critical although using it upside down is a non valid state and there is bound to be some movement and increase of the gap. Lower drums 'losing goodness' as we called it was something of a mystery. They just suffered with low output for no obvious reason.

Those carriage springs (if the one I'm thinking of) make great mountings for T092 transistors to keep them in thermal contact with power device. I seem to remember the material being changed to something more durable as the years passed.
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Old 25th Apr 2021, 2:10 pm   #3
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Default Re: JVC HR3330 Lower Drum Issue

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Originally Posted by Mooly View Post
Those carriage springs (if the one I'm thinking of) make great mountings for T092 transistors to keep them in thermal contact with power device. I seem to remember the material being changed to something more durable as the years passed.
So that's where they all went.

If the lower drum is faulty I guess it's the end of the road. I will need a flywheel too but how the ferrite got chipped is a mystery. I just wonder if the shaft has moved up somehow but then I would expect to see a gap between the upper and lower drum? Looking at the diagram the lower drum seems to be fixed to the aluminium base assembly with 3 screw which in turn is screwed to the steel base with just 2 screws? I think I'll take another look with everything in situ before attempting surgery.
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Old 25th Apr 2021, 2:15 pm   #4
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Default Re: JVC HR3330 Lower Drum Issue

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Originally Posted by Mooly View Post

A good test (scope needed) was to look at the ripple voltage across the motor. I can't just remember the figure we used now, possible around 200mv peak to peak. If it was high and electrically noisy then the motor was replaced.
The manual mentions the ripple voltage at TP9 (DRUM INVERT) which should be <0.5V on a DC level of 6 to 8V.
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Old 25th Apr 2021, 6:06 pm   #5
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Default Re: JVC HR3330 Lower Drum Issue

Oh, is it in the manual, it's decades since I last worked on a Metal Mickey.

The 8900 series (Ferguson/Thorn) were just appearing when I started in the trade and I do remember the 'swinging chroma' effect of the faulty drum servo and our then best VCR tech (the one who went on the course at Gosport I think) spending days working on the problem, even to the point of changing time constants in the servo and using tants... we were desperate... when it was just the motors all along.

The other issue that comes to mind (and anyone from Thorn days might recall the nickname) was 'twisted chassis syndrome' where the FM (guide adjustment) once adjusted correctly would not stay put. If you just lifted a corner of the VCR it all went to pieces.

Happy days.
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Old 25th Apr 2021, 9:14 pm   #6
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Default Re: JVC HR3330 Lower Drum Issue

I delved a bit deeper today. I removed the upper drum, then the flywheel and the static slip ring and contacts. It was then easy to pull the shaft ,together with the top half of the rotary transformer, out through the top. Above the top bearing and below the bottom bearing were one washer each. The bearings looked and sounded quite dry. I was careful to apply just 2 drops of hair clipper oil to each turning the machine over to let gravity do it's work. I then re-assembled everything and started the machine up.

Still no recognisable video output at the TV but the drum was now much quieter but periodically breaking into a sort of motor boating rumble! So the bearings are definitely shot. I wonder if they could be replaced from bearing manufacturer part numbers but it would take some skill and eyesight that I no longer have.

My scope (A Tektronix TDS 1002) arrived today and I planned to set up the capstan and drum servos properly but alas I have the manual for the HR3300 and the servo and audio board on the HR3330 is quite different. I also have the manual for the HR3660 but that is different again with slow motion and freeze frame.

So the plan for now is to go through the electronic adjustments on the HR3300 and try to find a manual for the HR3330. Maybe a 3rd JVC will come along with a serviceable drum so that I can make 2 good ones out of three.
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Old 25th Apr 2021, 10:40 pm   #7
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Default Re: JVC HR3330 Lower Drum Issue

If you go to worldradiohistory.com and download the December 1980 issue of Practical Television, on page 94 it gives instructions for setting up the drum servo on the HR3330. There is also an alternative method of setting up the discriminator using a scope and a 100R resistor given on page 592 of the September 82 issue. This is part of a series on servicing VCRs written by Mike Phelan which begins in the September 81 issue. Well worth a read.
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Old 26th Apr 2021, 7:05 am   #8
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Default Re: JVC HR3330 Lower Drum Issue

I suspect bearing renewal would be very specialised and need a press of some sort. The tolerances and positioning are going to be very very critical.

As is often the case with CD players... if the adjustments seem/are super critical then that often points to a problem. A machine in good basic order is generally pretty tolerant and most adjustments fall into place.

These are getting very old now and I wonder if any small electrolytics are starting to show their hand. Any in the video signal stages could be restricting LF bandwidth and causing problems with corrupt frame sync pulses and so on which might cause issues with video muting on some monitors/TV's.

A scope check can be very revealing in such cases looking at the before and after quality of the signal on any such cap/s.
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Old 26th Apr 2021, 8:35 am   #9
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Default Re: JVC HR3330 Lower Drum Issue

Quote:
I suspect bearing renewal would be very specialised and need a press of some sort. The tolerances and positioning are going to be very very critical.
We used to service timelapse security VCR's in the '90's and head drum bearing replacement was a standard part of an annual 10,000 hour service. Consider that in the course of a year, the head drum was spinning 24hrs a day for 365 days - that's 8760 hours!

Not all the machines that came in had noisy bearings, but many did. It's a strange sound and sometimes it comes and goes, but it's pretty obvious as to what it is!

I don't recall that we needed any special tools to do it. Once the upper drum with the rotating transformer is out of the way, the bearings are just press fitted into the lower drum housing, one at the top, one at the bottom. A gentle tap will get them out. I don't recall there was any effect on alignment, but we would have done a full alignment anyway.

The bearings were readily available from bearing suppliers by part number on the bearing and most machines of whatever make, used the same bearing. I seem to recall we only used to stock two different types.

I've never done it on a 3V22 type machine, but I'm sure it will be the same idea. I've never got my head around the JVC model numbers- I've only ever used the Ferguson 3Vxx numbers!

I get the impression that this machine is a more advanced version of the 3V22, but not quite a 3V16 with trick play functions?

I've got a couple of 3V22's, but would like a 3V16 as that was my first VHS machine when I was a teenager. The servo arrangements are totally different to the 3V22 and much more stable. I do rather like these early machines.

All the best
Nick
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Old 26th Apr 2021, 9:14 am   #10
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Default Re: JVC HR3330 Lower Drum Issue

Quote:
Originally Posted by Mooly View Post
These are getting very old now and I wonder if any small electrolytics are starting to show their hand. Any in the video signal stages could be restricting LF bandwidth and causing problems with corrupt frame sync pulses and so on which might cause issues with video muting on some monitors/TV's.
There's also a capacitor in the drum servo circuit (C33 I think) that goes low in value and causes problems with hunting. It's a tantalum one.

Quote:
Originally Posted by 1100 man View Post
I've never done it on a 3V22 type machine, but I'm sure it will be the same idea. I've never got my head around the JVC model numbers- I've only ever used the Ferguson 3Vxx numbers!

I get the impression that this machine is a more advanced version of the 3V22, but not quite a 3V16 with trick play functions?
The Ferguson equivalent is the 3V00 I believe.
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Old 26th Apr 2021, 10:41 am   #11
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Default Re: JVC HR3330 Lower Drum Issue

I remember the old TTR (Thorn Television Rentals) number, 8902, 8904 was the one with proper freeze frame and 60/40micron heads... its all such a long long time ago.
Ferguson variants were more for 'retail' than rental and JVC versions were considered the more upmarket brand for those customers wanting to buy.

Replacing bearings is something we never even considered with normal service/repair/refurb and any such issues either saw a new lower drum fitted or the machine written off. The relay pulley bearing (that one that transfers drive from top to bottom of the deck) could become noisy as a I recall.

The clip on timer modules were great, someone put one in their car.
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Old 26th Apr 2021, 10:52 am   #12
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Default Re: JVC HR3330 Lower Drum Issue

Quote:
Originally Posted by birksholt View Post
If you go to worldradiohistory.com and download the December 1980 issue of Practical Television, on page 94 it gives instructions for setting up the drum servo on the HR3330. There is also an alternative method of setting up the discriminator using a scope and a 100R resistor given on page 592 of the September 82 issue. This is part of a series on servicing VCRs written by Mike Phelan which begins in the September 81 issue. Well worth a read.
Thanks for that birksholt. I've already downloaded a few copies of Television from that site. What a convenience to have these publications available to zoom into in every detail. I have a feeling that something went wrong while I had the machine running upside down with the main board open. The wiring is under quite a bit of stress at the point. Checking that the servos are working properly would be a good starting point. Before that I'm going to go through the motions on the HR3300 partly to get the hang of my new scope.
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Old 26th Apr 2021, 11:02 am   #13
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Default Re: JVC HR3330 Lower Drum Issue

I'm surprised that no-one has scolded me for using clipper oil on the bearing. Most of the original JVC parts are no longer available. You know when you are onto a loser when Google tells you that there aren't many matches for your search.
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Old 26th Apr 2021, 11:33 am   #14
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Default Re: JVC HR3330 Lower Drum Issue

My recollection of noisy drum bearings was that lubricating them wasn't very effective. Perhaps I should have used something a bit more viscous than the Electrolube clear mechanical lubricant (which came in a spray can).

(Same problems with much later makes and models and noisy capstan motors, lubrication with oil or even grease never lasted)
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Old 26th Apr 2021, 11:42 am   #15
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Default Re: JVC HR3330 Lower Drum Issue

The bearings are usually sealed with grease inside. There should be a number embossed on at least one of the sealing covers. The number will be something like 6202 and they should not cost more than £5 each for good quality types. If there are no numbers on these bearings, then once out measure the external dimensions and shaft hole dia, then check for replacement bearing types in the bearing manufacturers data. As already mentioned the bearings are a push fit and as long as the replacements are the same dimensions there won't be any issues with parts positioning.

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Old 26th Apr 2021, 6:51 pm   #16
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Default Re: JVC HR3330 Lower Drum Issue

Hair clipper oil worked like a charm for lubricating the bearings of my Panasonic NV-7500's lower drum but I had to adjust the head switching position after reassembling the drum since the two PG magnets were mounted on the surface of the rotor and of course you can't put it back together with the PG magnets facing in the exact same position they were before, so slight adjustment of the PG shifter controls was needed. I have an HR-3330E service manual on pdf. Let me know if you want it and I will post a link here.

Fivos
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Old 26th Apr 2021, 9:04 pm   #17
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Default Re: JVC HR3330 Lower Drum Issue

Quote:
Originally Posted by dj_fivos_sak View Post
Hair clipper oil worked like a charm for lubricating the bearings of my Panasonic NV-7500's lower drum but I had to adjust the head switching position after reassembling the drum since the two PG magnets were mounted on the surface of the rotor and of course you can't put it back together with the PG magnets facing in the exact same position they were before, so slight adjustment of the PG shifter controls was needed. I have an HR-3330E service manual on pdf. Let me know if you want it and I will post a link here.

Fivos
Yes please Fivos. That's very kind of you. I tried to find it online but no luck.
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Old 26th Apr 2021, 9:12 pm   #18
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Default Re: JVC HR3330 Lower Drum Issue

Quote:
Originally Posted by G6ONEDave View Post
The bearings are usually sealed with grease inside. There should be a number embossed on at least one of the sealing covers. The number will be something like 6202 and they should not cost more than £5 each for good quality types. If there are no numbers on these bearings, then once out measure the external dimensions and shaft hole dia, then check for replacement bearing types in the bearing manufacturers data. As already mentioned the bearings are a push fit and as long as the replacements are the same dimensions there won't be any issues with parts positioning.

Dave
I'm very tempted to give this a try. I already found your example bearing 6202 for sale online. Thanks again for the information G6ONEDave.
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Old 26th Apr 2021, 9:29 pm   #19
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Default Re: JVC HR3330 Lower Drum Issue

Quote:
Originally Posted by hillsrob View Post
Quote:
Originally Posted by dj_fivos_sak View Post
Hair clipper oil worked like a charm for lubricating the bearings of my Panasonic NV-7500's lower drum but I had to adjust the head switching position after reassembling the drum since the two PG magnets were mounted on the surface of the rotor and of course you can't put it back together with the PG magnets facing in the exact same position they were before, so slight adjustment of the PG shifter controls was needed. I have an HR-3330E service manual on pdf. Let me know if you want it and I will post a link here.

Fivos
Yes please Fivos. That's very kind of you. I tried to find it online but no luck.
Found it on my Google Drive. Here's the link:
https://drive.google.com/file/d/10kG...ew?usp=sharing
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Old 27th Apr 2021, 9:21 am   #20
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Default Re: JVC HR3330 Lower Drum Issue

Quote:
Originally Posted by dj_fivos_sak View Post
Quote:
Originally Posted by hillsrob View Post
Quote:
Originally Posted by dj_fivos_sak View Post
Hair clipper oil worked like a charm for lubricating the bearings of my Panasonic NV-7500's lower drum but I had to adjust the head switching position after reassembling the drum since the two PG magnets were mounted on the surface of the rotor and of course you can't put it back together with the PG magnets facing in the exact same position they were before, so slight adjustment of the PG shifter controls was needed. I have an HR-3330E service manual on pdf. Let me know if you want it and I will post a link here.

Fivos
Yes please Fivos. That's very kind of you. I tried to find it online but no luck.
Found it on my Google Drive. Here's the link:
https://drive.google.com/file/d/10kG...ew?usp=sharing
Many thanks Fivos. You might just have saved and old HR3330 from the scrap heap.
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