Ferguson videostar 3v32 drum speed problem.

[Snarf81]

Hi all,
I've finally managed to get hold of a Ferguson videostar 3v32, but I've noticed that the drum is not running at the correct speed. You can hear it speeding up and slowing down. If I gently use my finger as a brake on the top of the drum then it slows down enough to get a picture but as soon as I take my finger off it starts to speed up again. I've swapped the main bottom board for a known working one but it's still the same.

Any advice on this would be gratefully appreciated.

Thanks
Richard.

[Snarf81]

Well.......

The oddest thing has just happened with this VCR.
After leaving a tape playing for a little while, it has cured itself!!

I don't know what happened or what was wrong but it's working like a charm now.

Could this be closed please?

Cheers
Richard.

[vhs doctor]

Maybe you have faulty capacitors or the drum bearings run more freely now

[Snarf81]

I did notice that when the drum was over speed there was a sort of rattling noise coming from the drum. All seems ok now though.

[Snarf81]

The silly thing is playing up again, darn. Watching a video when the drum just sped up very fast again.
Could the drum motor be at fault, or is there a more common problem with this model?

The drum motor speeds up then gradually slows down until there's a picture, but the picture isn't stable, and whilst it's acting up, the pause function doesn't work, it advances in slow motion. When the drum speed is running at the correct speed the pause function is fine.

Thanks
Richard.

[toshiba tony]

Sounds like the FG pulses are disappearing intermittently. I don't know if this results on the deck shutting down as on the 3V00\3V16.

[Snarf81]

Thanks for the reply, Tony.

Do you happen to know which board in the VCR controls this? I have a scrap ITT version which I can swap a board over with.

Thanks again
Richard.

[dj_fivos_sak]

That definitely sounds like the drum servo circuit is misadjusted. See my screenshots taken from the JVC HR-7655 service manual.

Fivos

[Snarf81]

Hi Fivos,
Many thanks for the reply.
Those adjustment pots are on the main board underneath the VCR. I swapped the board for a known working one but the problem is still there.

Cheers
Richard.

[dj_fivos_sak]

Hmm. Then maybe the frequency generator pick-up head/hall sensor next to the drum motor has failed? If I recall correctly, the drum motor has magnetic signals encoded onto the edge of it and as the motor spins, the hall sensor signals the servo circuit so it knows how fast the drum is spinning and when to switch between the video head A and video head B.

[Snarf81]

Hmmm, you may be correct! I'll try swapping the pick-up head over and if that fails, I'll swap the bottom of the drum motor over and see if that does anything. I'll get around to that hopefully tomorrow or Friday and I shall report back.
Cheers
Richard.

[tony brady]

you may want to check the bottom of the drum motor is in the correct position first. undo the allen key and see if you can push it up, then re-tighten. I've seen them too low and in one case it had fallen off.

cheers
Tony

[Snarf81]

Thanks Tony, I'll check that.
I've misplaced my Allen keys, but they're somewhere amongst the junk, so when I've found them I'll do what you suggest.

Thanks again
Richard.

[davyrocket2]

if you have a indentical machine try and see if its easy to remove the complete drum assembly .I think the problem is 2 fold ,1 is bearings failing hence the noise ,2 could be capacitors failing in the drum servo circuits ,lastly if this solves the problem then changing the heads over is fairly straight forwards job

[Snarf81]

I've checked that the bottom of the drum motor is pushed onto the shaft as much as it can go and cleaned the pickup head but still no joy.

[Vauxfan2k]

In my experience with these machines, especially one of my 3v36's the alignment of the ace stack and it being spotlessly clean affected the drum speed, almost as if it was playing a long play tape in short play mode ( even though it was a short play tape)

Try cleaning the ace head first with alcohol. Then get a small Phillip's.(non magnetic) out if that doesnt work, and make very very small.adjustments in each direction, keeping count of the number of turns (to revert back to)

Should solve your problem.

[Snarf81]

Hi Vaux,
Thank you for the suggestion.
I don't think alignment and cleanliness of the ACE head is the issue here. It's spotless and the alignment is bang on, as when it was behaving I made a test recording and it played back beautifully on my other vhs vcrs without tracking adjustments. Also I played back a genuine JVC alignment tape with the tracking at centre click and all was perfect. I'm thinking it's definitely an electrical fault somewhere, but where I don't know as I don't have a scope or any other test equipment to check anything.
It'll probably get sent off to be looked over professionally.

Thanks again for the suggestion though

Ps) Have you found a spare working audio board for a 3V36 amongst your spares yet that you'd like to sell?

Cheers,
Richard.

[Vauxfan2k]

In my case it was 100% the ace stack that caused the fault. I've come across it on other machines whilst trying to eradicate crackling audio on stereo sound that if adjusted wrongly or the wires to the connector on the top of the stack arent right that it makes the tape play at the wrong speed, including speeding up of the head drum.

With regards to the sound board, I have 4 3v36 machines. I took the time to grade them all based on physical condition and playback quality, but they were then put in storage. I wouldnt be inclined to split a working machine for parts (given I have so many spares) but I may sell one of them complete. Again this is dependent on me finding them in my storage unit.

[Snarf81]

Okie dokie, I shall check the wires are connected properly to the ACE assembly and see if anything happens with the drum motor speed as at present it spins so fast that if a propeller was attached it'd probably take off and fly out the window!

No worries about the 3v36 then. I don't particularly want another machine just for the audio board.

Thanks again
Richard.

[toshiba tony]

Surely pulses from the ACE head would result in a capstan servo issue. Otherwise how would you get a still pause picture with the tape stationary. I think a scope is needed for this one. I used to use the scope more more than my meter for VCR's. The original poster says he replaced the bottom board but that didn't cure it. I don't recall that exact model, we were multi dealers including Philips (1700 and V2000) enough said! Open circuit FG head?
Not unheard of, but I think the time has come for a scope. He would find it in minutes, an o\c feedback loop, there is still a multitude of things it could be but a scope would narrow it down and eliminate what it isn't.