Ferguson Videostar 3V29 fault

[williamsunique]

Originally Posted by Simon_m74

Hi all,

Belt changed.
Switch cleaned.

Loads fine!

Thanks......but

Picture is not perfect.
Photo attached.

Slightly loosing colour in patches, 'pulses' of interference going down the screen.

I tried tracking and it has little effect.

Any ideas for this next fault ?

Have you cleaned the audio/control head? It could be you are missing control pulses.

Paul

[Welsh Anorak]

Could be.
Questions:
Does the picture come OK then lose quality rhythmically?
Is the sound OK?
Does the tracking contol have any effect?

Check no plugs have come out when you opened the lower PCB - easily done.

Glad things are getting closer...

[Simon_m74]

@Paul
Yes all heads cleaned.....but I did have to remove the audio/traking head assy to clean up a mech around it. So thinking about it, maybe its not aligned......

@Glyn,
Picture seems to have a rhythm to its interference, so I think its a `speed mis-match` between tape and head.
Sound - `seems` ok, maybe slightly muffled, but I`m not sure what I`m to expect from a VHS machine of this age.
Tracking control - no effect at all - I`ll clean that with some IPA / contact cleaner.
Plugs - I`m sure all are still connected - I did not disconnect anything from the main base PCB when I started this repair - I just disconncted what was needed to remove the deck - and also I removed one PCB to the left (to trace the solenoid signals).

Ideally I hope to get this working by Friday, as its for a friend who lives in Portsmouth, and I`m in Leicester. My friend us up on this weekend - but I wont see them again for a couple of months...and I want it out of my mancave to help get some space back for other projects (like fixing my laserdisc player - a post on that in due course!)

[Simon_m74]

ok
heads all cleaned
I set a star trek TNG tape going, while synced the same episode on my tv,
Only about half way through the episode (about 20 mins)m and the VHS is about 30 seconds behind already,
So confirmed - the tape is running slow.

Suggestions please.....

[Mooly]

I'm not sure that is a valid test tbh, to many unknowns. A duplicated tape may not be totally accurate, the tape may be stretched over the years and the synced episode may be at a different absolute speed for technical reasons.

Ultimately the capstan is servo locked to a crystal oscillator and any issues in speed would show in problems with the replayed picture as the rotating heads wander on and off track during their helical scan.

A good test would be a proper alignment tape and to look at the audio test tones for accurate replayed frequency.

[Simon_m74]

I think the tape is ok. It's an original, barely used.

I'm not sure if this is anything to do with the capstan motor is running backwards after dismantling it to clean it (it was ceased). I had to reverse the wiring to get it to run in the correct direction.

[toshiba tony]

Ceased or seized? Please clarify, I'm watching this post. Spent many infuriating times with the 3v29.

[Simon_m74]

Sorry for clarity.
It struggled to rotate on power before I cleaned it

[Simon_m74]

ok, I think I found the issue..
The head was seized too when I got it, so I dismantled it to clean it all up, and it ran smoothly....well until I checked again.
correct way up - if I spin by hand - seems to have a section of rotation with slight resistance, and soon stops.
If spun upside down - this resistance does not exist, and it spins very smooth for a long while.

I`ll investigate this.

But the major thing now:
I have dismantled the very noisy backwards running capstan motor.
I didnt take the armature away from the brushes first time, but I did this time.

Brushes are GONE, the brushes remainder metal stips are rubbing on the comutator, which is mostly worn away!

Does anyone know of a new replacement motor for this one?

[Simon_m74]

I found the brushes.
VERY worn out!
I have made some new ones made from a large brush from a hand-held Angle Grinder spare brush set I had.
Just waiting for some conductive glue to arrive, so that I can fix the new brushes in place.

[Mooly]

That sounds a pretty adventurous repair attempt, well done, I hope it is successful...

[Simon_m74]

Hello all!
So New brushes sorted.
I could not bond my newly made carbon brushes to the copper arms within the motor.
So I sourced a pre-bonded brush pair - from a Scalextric car motor!
These have been soldered on, and the motor is running much quieter AND also the correct way.

Deck all reassembled, but I`m still getting that interferance on the image.

Things done:
Video head : had some `resistance` on on position on its rotation. Corrected, Head was dismantled, and I found that I have missed out a VERY thin shim. That back in now, and the head is spinning fine.
ALL HEADS: Cleaned with IPA and cotton buds (Video was done with IPA on paper method)
Tracking potentiometer: Dismantled and cleaned with contact cleaner - didnt look too bad anyway.

The interfererance:
about once a second, I get a band (or 2) of interfererance that starts almost mid to bottom third of screen, then moves up quick and off the top of the screen, then the image is ok for another second.

Suggestion please as I really want to get this finished.
As I said, its for a friend who lives in Portsmouth.
They were up in Leicester a few weeks ago, but I missed that - due to the machine not fixed.
They are up again, this Saturday - Nov 4th.
I wont see again till Mid December if at all this year!
I need this out of the way as its taking space up I need back!
I have lots of stuff in the queue to repair, that I dont have space to do so till this is completed.

[Mooly]

So hard to diagnose at a distance... it must be 25yrs since I last prodded and poked a VHS deck.

I would begin by looking at the FM on a scope and also look at the control track pulse, again on the scope and make sure it all looks OK, sufficient amplitude and so on.

Make sure the tape path alignment is OK. You can get it 95% spot on visually by looking at reflection changes in the bottom edge of the tape as it begins to contact the lip of the lower drum.

Use a torch and turn the input and exit guides until you can just detect obvious curl on the lower edge of the tape, back the guides off at that point and then turn again but this time look for the subtlest reflection change to show that contact has just been made. The scope will let you finalise that point but you can get it 95% correct without. Keep altering the tracking to keep the FM at maximum while doing this.

Then look at the control track.

Also is the back tension OK?

There is much you can do with fingers as a diagnostic tool (for tape path suspicions) but its not easy to explain...

[Simon_m74]

the only thing I can answer now while I`m at work and the VHS is at home is about the back tension belt.
It was VERY frayed. So I remade it with the only thing I could find about the house.
I removed the `leather` (or what ever it is) and bonded on some lint free felt.
Its not perfect, but it does seem to work.

I think that the tape guide alignment is ok - but I`ll double check that tonight.

It could be the control track actually as I know that the audio head assy was moved.
How I got it back was only roughly done, by listening to audio and tweaking the head assy`s position till it sounded the best.

[Mooly]

Back tension is critical and not something you can easily guess at. Ideally you need a back tension cassette/gauge.

Carrying on from what I posted above... if the audio head has been disturbed (other than just sliding it along its elongated baseplate slots) then you need to do an alignment check of that as well. By disturbed I mean the azimuth and height screws.

Sliding the head forward and back affects the 'X' distance and that in turn affects compatibility and lip sync but its the easiest of the adjustments to get basically correct.

If those other screws have been disturbed then the head may not be vertical and that will affect the run of the tape causing it move up or down the head depending on the angle.

Faced with scenario I used to remove the head completely and play a tape and set the entry and exit guides visually (using reflections which in practice give incredibly fine control).

With the tape running running correctly on the lower drum the audio/control head is fitted and the three alignment screws adjusted visually so that the tape runs equally over the audio part at the top and the control track part at the bottom without the tape being to high or low. If the head is not vertical it will pull the tape or up down which you will notice on the exit guide and also the capstan/pinch roller.

If you can rig up some kind of 'parallel plate' (like an L shape) even if just a careful cardboard cutout affair it will get you close to a vertical control head. The deck baseplate is used as the reference point. Another method (maybe not recommended) is to rub a light wax onto the head and look where the tape removes it. The tape must never be used again (bin job) and the capstan and roller need cleaning afterwards.

Now set the azimuth by listening to a known good prerecorded tape.

You now go back over all the alignment again and tweak it all. Set the 'X' distance somewhere close to the middle of the movement range and finalise the setting by having the tracking centred and moving the X distance to get maximum FM.

The back tension is a major concern though. Maybe slacken the adjustment right off and then increase only a little. I can't remember the figures now but it was something like 20 grams from memory. To much and you will wear the heads and drum in no time.

[Simon_m74]

Hi all!
Sorted - thanks to all your help!

Finally - it was the tracking control head.
At first I was focusing on audio (easier to sort than video) and got that `good` - without taking consideration of the video as I knew at that time - the video head had a rotaional issue - as mentioned on previous post.

Tracking all sorted now - adjusted the screws and video and audio is fine!

rewinding is a bit shakey due to back tension, but the owner wa happy with everything, so they have had it back.

Time, and more impotantly - SPACE , to work on more projects!

Thanks again all.

[Mooly]

Good to hear you have it all working.

[Simon_m74]

LOL A friend bought an identical one in case I needed it for spares...
but now I don't, they want me to repair that one!

After getting the first one out of the way - here I go again!!!!

[Nickthedentist]

Well done! They're basic machines but built like battleships with a very well-known fault history. Every student house in the early 1990s seemed to have an ex-rental one, so they bring back fond memories for me. The manual is amazing too.

I found one of these put out for the bin men last year. Haven't had a chance to look at it yet.

I know what you mean about space. I've had the chassis of a big 1950s German radio on the bench for much longer than I intended...

[Simon_m74]

During its repair - another friend `secretly` bought me another one for spare parts to see if would help.
They didn't realise that I had fixed this one and returned it.

They now want me to fix this one so we can sell it on Ebay!
typical - I was happy to get it out of the way, and now within 2 days I have another!!!!!

Less faults on this one though it seems.