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New video head = sharper picture?


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Old 21-02-2011, 12:06
Soundbox
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I have two identical models of Panasonic VCR. One well used and one clean and much less used. The used one has just had a new video head fiited ready to give to a family member.

Checking them back to back (looking at the same frame on a tape) I see the model with the new head has improved resolution (I can see two distinct freckles where on the one without the new head the two freckles are merged).

I know worn heads give distinct on screen symptoms, but is subtle resolution loss a known issue? If so, is there a 'wear vs resolution drop' scale?

Not seen this mentioned before so I thought I would ask.
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Old 21-02-2011, 12:09
AidanLunn
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I have two identical models of Panasonic VCR. One well used and one clean and much less used. The used one has just had a new video head fiited ready to give to a family member.

Checking them back to back (looking at the same frame on a tape) I see the model with the new head has improved resolution (I can see two distinct freckles where on the one without the new head the two freckles are merged).

I know worn heads give distinct on screen symptoms, but is subtle resolution loss a known issue? If so, is there a 'wear vs resolution drop' scale?

Not seen this mentioned before so I thought I would ask.
Do the VCRs have picture sharpness controls, as this may contribute?

The video sharpness control I believe adjusts the bandwidth between the video heads and the various processing circuitry.
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Old 21-02-2011, 13:50
Nigel Goodwin
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New heads certainly improve the picture, although been an FM signal you wouldn't really expect it to.

I suspect that the higher signal levels from the new head give a better signal to noise ratio, and the electronics compensates with the higher signal to noise ratio of worn heads by rolling the HF off.
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Old 21-02-2011, 22:46
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Settings were the same for both units - I checked that carefully.

Nigel, that sounds right - I can see the logic there. Signal to noise is one area I did not consider.

Thank you.
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Old 23-02-2011, 19:56
spiney2
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As said above, it's fm modulation for the luminance, but the "colour under" is am, which might make a difference!

Since all home videotape is very low resolution, a "watchable" picture depends entirely on a differentiator circuit to sharpen edges - why the picture looks so noisy - and the exact parameters of this vary between different machines.

Also, you're supposed to set up and balance the heads after changing the drum ...........
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Old 24-02-2011, 09:13
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Thanks. Yes, I had the head aligned after fitting (on a oscilloscope) and as a genuine Panasonic head was fitted the new one needed just a tweak of the guides and head switching point.

It is interesting to note how different decks (models of VCR)deal with the same frame of videotape. Some have more contrast and brightness and some go for stronger colour. The last decks >2003 are pretty poor really (too much contrast and squashed brightness). They have obvious video ringing too. This came about around the time after the removal of the modular power supply board/section - yet the Home Cinema mags of the time gave the machines glowing reviews.

Best ones are from the late 80's - 90's.
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Old 24-02-2011, 09:16
Nigel Goodwin
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Also, you're supposed to set up and balance the heads after changing the drum ...........
Only in a very, very tiny number of machines - most of which were Betamax. In the vast majority of cases it's just a question of dropping the drum assembly in place and adjusting the mechanical tracking.

I've still got the eccentricity gauge for setting Sony Betamax heads up
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Old 24-02-2011, 09:57
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I don't think I would dare take on a Betamax head swap. It is a shame that no modern component racks seem designed to take Beta machines though as I love their colour and bold look on screen.
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Old 24-02-2011, 16:44
AidanLunn
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Only in a very, very tiny number of machines - most of which were Betamax. In the vast majority of cases it's just a question of dropping the drum assembly in place and adjusting the mechanical tracking.

I've still got the eccentricity gauge for setting Sony Betamax heads up
I hear these are damn complex things!
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Old 24-02-2011, 20:45
Nigel Goodwin
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I hear these are damn complex things!
It was certainly a LOT easier putting heads in Ferguson/JVC VHS machines!
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Old 25-02-2011, 12:11
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When I use my Beta machine for recording TV it looks better on-screen than VHS but I feel a bit odd using 30 year old gear to record modern TV shows.

Anyway, the difference between models of VHS machine is so great it has to be seen to be believed. The quality of Hi-Fi sound also.
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Old 25-02-2011, 15:05
AidanLunn
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When I use my Beta machine for recording TV it looks better on-screen than VHS but I feel a bit odd using 30 year old gear to record modern TV shows.

Anyway, the difference between models of VHS machine is so great it has to be seen to be believed. The quality of Hi-Fi sound also.
LOL, do you still use gramophones? What Beta model is it? It wouldn't surprise me if it was a Sanyo deck as they were bomb-proof.

I've certainly heard earlier HiFi VHS machines and they definitely are better than later rubbish. Those pre-NICAM ones from JVC/Ferguson are the best, in my opinion. Even their mono audio track seems clearer than 90s/00s rubbish.
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Old 25-02-2011, 15:07
spiney2
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Only in a very, very tiny number of machines - most of which were Betamax. In the vast majority of cases it's just a question of dropping the drum assembly in place and adjusting the mechanical tracking.

I've still got the eccentricity gauge for setting Sony Betamax heads up
In theory, you were supposed to align the transformer for best impedence match (min noise). I suppose nobody bothered ..........
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Old 25-02-2011, 15:50
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Yes, I use (wind up) Gramophones, usually with soft tone needles (Columbia or Golden Pyramid). I service my own machines and my favourite soundbox is the HMV No.4 which has a clean and easy tone.

Yes, my machines are Sanyo Betacords and a later Sanyo VTC-M40 for Hi-Fi work. I could not take on a Sony with all their issues and problems...

Concerning VHS Hi-Fi, my favourites are the Panasonic NV-F70 and NV-75 series (late 80's to early 90's). These are NICAM, but have a clear and full soundtrack. The Panasonic NV-HS1000 from 1994 has great sound too, with almost no head switching buzz. I think some extra circuitry was fitted in that model.
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Old 25-02-2011, 17:33
Nigel Goodwin
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In theory, you were supposed to align the transformer for best impedence match (min noise). I suppose nobody bothered ..........
You don't touch the transformer, on either Beta or VHS, and there's no adjustments for it either.

The requirements for changing heads are fully explained in the service manuals, including any special tools required, and all adjustments.
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Old 25-02-2011, 18:20
AidanLunn
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Yes, my machines are Sanyo Betacords and a later Sanyo VTC-M40 for Hi-Fi work. I could not take on a Sony with all their issues and problems.
I've always wanted an M40 to get beta HiFi (I'll start using Betamax regularly if I get a BetaHiFi ) But for the moment, I'm stuck with a VTC5150 for transferring Betamax recordings.
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Old 25-02-2011, 18:26
bobmeades
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Yes Nigel, those Sony Beta heads were a pain to change the Sanyo beta were a lot easier (5000 etc), though the pic quality was never as good as a good Sony EG a C9. It never stops to amaze me, when you have the lid off an early VCR & one of the last production models - piles of electronics & circuit boards - crammed on to a few surface mounting chips in the later ones - the deck side did not change very much though!
Bob
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Old 25-02-2011, 18:39
AidanLunn
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Yes Nigel, those Sony Beta heads were a pain to change the Sanyo beta were a lot easier (5000 etc), though the pic quality was never as good as a good Sony EG a C9. It never stops to amaze me, when you have the lid off an early VCR & one of the last production models - piles of electronics & circuit boards - crammed on to a few surface mounting chips in the later ones - the deck side did not change very much though!
Bob
Except Philips and Grundig decks - some of the models from them had a Betamax-style lacing mechanism. "C-wrap" = "Crap wrap" Also, earlier VHS machines definetly did have more parts than later ones - impedance rollers were dropped from later deck machines, and the loading motor was often laid out differently between models.
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Old 25-02-2011, 19:29
bobmeades
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Except Philips and Grundig decks - some of the models from them had a Betamax-style lacing mechanism. "C-wrap" = "Crap wrap" Also, earlier VHS machines definetly did have more parts than later ones - impedance rollers were dropped from later deck machines, and the loading motor was often laid out differently between models.
Oh yes, I now remember those Dire later Philips VHS decks! get your broken bits of plastic here.
I do remember the little earners of the earlier machines, the lamp that blew & killed the whole deck, also those early piano key machines, that after a little wear, the picture reminded one of the tide going in & out!
Oh happy days.........
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Old 25-02-2011, 23:59
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I've always wanted an M40 to get beta HiFi (I'll start using Betamax regularly if I get a BetaHiFi ) But for the moment, I'm stuck with a VTC5150 for transferring Betamax recordings.
Don't feel stuck! I often choose to use a standard deck as the Beta Hi-Fi models are really wasted on 'normal' tapes and indeed the mono Sanyo's like the VTC-M20 have a characteristic that I like very much - the picture is slightly smooth and comes over very well. There are many more mono tapes than stereo out there, but then again trying my VTC-M40 on a modern digital source reveals how good beta can be. That model has different picture processing.
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Old 26-02-2011, 00:19
AidanLunn
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Oh yes, I now remember those Dire later Philips VHS decks! get your broken bits of plastic here.
Quite.

What I don't understand is if Philips wanted to do such a deck, why didn't they just re-badge the Grundig decks that had such mechanisms? I've heard from others that they were reliable and fairly easy to service.
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Old 26-02-2011, 00:21
AidanLunn
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Don't feel stuck! I often choose to use a standard deck as the Beta Hi-Fi models are really wasted on 'normal' tapes and indeed the mono Sanyo's like the VTC-M20 have a characteristic that I like very much - the picture is slightly smooth and comes over very well. There are many more mono tapes than stereo out there, but then again trying my VTC-M40 on a modern digital source reveals how good beta can be. That model has different picture processing.
My main problem is the fact that it's a top-loader, and it's not really ideal for my room, due to the amount of space. I'd much prefer a front-loading deck but they always seem to sell for a bomb on eBay, particularly the ones where the button panel goes yellow and starts peeling off.

The only other issue is that the replacement idlers for these never last long at all, or at least the ones that Colin McCormick supplies (no offence to Mr McCormick if he is reading).

Oh, and mine seems to be suffering from a dry joint problem around the heads, which is taking forever to get round to.
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Old 26-02-2011, 07:25
bobmeades
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Quite.

What I don't understand is if Philips wanted to do such a deck, why didn't they just re-badge the Grundig decks that had such mechanisms? I've heard from others that they were reliable and fairly easy to service.
I think Philips did eventually use other manufacturers VHS decks with their Philips electronics........I well remember a Pre-VHS machine, the Philips 1700. 2 hours of good quality Luminance in huge co-ax cassettes, but due to a design fault - if the Chrome was intensive with one colour (EG a darkroom RED scene) then vertical pattens were the rule of the day, but it was all we had before VHS & Beta. The bearing on the head drum used to get dry, so once a year, a bitof lube was needed - a bit like servicing a car.
Bob
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Old 26-02-2011, 09:08
Nigel Goodwin
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Quite.

What I don't understand is if Philips wanted to do such a deck, why didn't they just re-badge the Grundig decks that had such mechanisms? I've heard from others that they were reliable and fairly easy to service.
I don't think Grundig usually made VHS mechs?, they normally bought their mechs from Panasonic (the Panasonic G Mech).

The appalling Philips VCR's used the Charlie mech - but I don't think Philips ever made a decent VCR (or anything much else!).
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Old 26-02-2011, 12:02
webbie
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I remember the old Philips 1700 in the local bang and olufsen shop - buttons that disappeared into the unit when pressed and a little analogue clock on the front. And very expensive.
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