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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 21st Jul 2019, 9:56 am   #21
dazzlevision
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Default Re: KB KV014 - VC4 chassis

The VC1 chassis (alone) had provision for connecting a "baby alarm" unit.

This was a small piece of SRBP board, upon which was mounted:

3.5mm jack socket
BS415 mains isolation grade capacitors
a ferrite "pot core" transformer
a single transistor amplifier.

It fixed to the inside of the back cover, which was pre-punched for it.

The unit connected to the audio amp stage in the set via a small tag strip mounted on the chassis.

You connected a microphone (placed in the baby's location) to the jack socket and you would hear through the set's speaker, if it started crying.
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Old 21st Jul 2019, 10:05 am   #22
dazzlevision
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Default Re: KB KV014 - VC4 chassis

All sets prior to the arrival of the VC4 range would have "twin panel" CRTs, such as the A47-13W, with a clear thick moulded plastic implosion protection cover over the CRT's faceplate, secured by an optical quality clear gel/adhesive.

The VC4 sets had CRTs with integral implosion protection provided by the riband (e.g. A47-26W/R), which also had a mounting lug at each corner, to allow the CRT to be fixed to the cabinet. A much neater arrangement, which also provided direct viewing, for a clearer and brighter picture.

At least one regunned CRT manufacturer offered a kit to replace a twin panel CRT with a rimband type, which included a soft black plastic extrusion to fill up the significant gap between the CRT's periphery and the cabinet.
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Old 21st Jul 2019, 11:21 am   #23
FERNSEH
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Default Re: KB KV014 - VC4 chassis

Quote:
Originally Posted by dazzlevision View Post
At least one regunned CRT manufacturer offered a kit to replace a twin panel CRT with a rimband type, which included a soft black plastic extrusion to fill up the significant gap between the CRT's periphery and the cabinet.
To replace the twin panel CRT Mullard produced the "Inckit" which consisted of an A47-26W rimband CRT and all the necessary tube installation parts.

DFWB.
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Old 3rd May 2020, 8:32 pm   #24
1100 man
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Default Re: KB KV014 - VC4 chassis

Thanks to the mods for reopening this thread!

While waiting for some Kapton tape to arrive in order to continue with the LOPT repair on the Sobell, I thought it was high time I got this set back on the bench and did some more to it.

It's been so long ago that I can't even remember where I got to with it.

Powering it up on 405 produced a raster but no audible line whistle! So unless my hearing has now fallen below 10Khz, the line frequency is way too high.

Feeding in a signal on Ch1 produced a mess on the screen with no sound. The fine tuning control, which usually has a pretty large range on other types of tuner, had no effect.

Having already removed and sorted the fine tuning arrangements on the UHF tuner, I decided to do the same on the VHF one.

It is the sweetest little tuner I've ever seen! It's tiny and uses tiny valves as well! It's a Philips unit and I've not come across one before. One nice feature is that the fine tuning control operates a little plastic wheel on each 'biscuit', thus the fine tuning can be preset on each channel. Very clever!

Another nice touch is when switching to 625, it doesn't matter what channel the VHF is on- you don't have to rotate it to a UHF position.

In 625, HT is supplied to the UHF tuner and removed from the RF & mixer stage in the VHF one. Again rather a neat way of doing it.

One of the other things I need to do before the wires drop off, is to secure the EHT rectifier valve holder.

Steve, (Colourstar) who kindly gave me the set, had fitted a new LOPT to replace the one that had been previously robbed. However, I assume the mounting plate for the EHT rectifier went with the old transformer.

I can see the marks on the end of the LOPT screening metalwork where the mounting plate has been screwed on.

Does anyone have a picture of what this plate should look like and in fact if it's made of metal or plastic? If I can see a picture, I can make up something suitable. I've trawled the internet and the Forum for pictures of the chassis but can't find one that shows the end of the LOPT housing.

I would be most grateful if someone could come up with a picture!

All the best
Nick
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Old 4th May 2020, 11:35 am   #25
dazzlevision
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Default Re: KB KV014 - VC4 chassis

The EHT rectifier valve base plate looks like this....made of metal.
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Old 4th May 2020, 6:26 pm   #26
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Default Re: KB KV014 - VC4 chassis

If the fine tuner does not operate [it is a Philips tuner] you will see there is a cam that sides a tiny plastic core into a very low value ceramic capacitor.
The minuscule plastic rod breaks leaving the sleeve stuck in the ceramic tube giving an off tune symptom.
They are a real fiddle to replace even if you know the 'knack'. The problem is getting a tuning core as we called them. I used the last one I had a few months ago in a KB Featherlight VC11 that uses the same tuner. It was a very common fault due to the tuner being used in a huge range of makes and models.
If it is broken you may be able to preset the core or with a great deal of care, make a new one.
This is the fine tuner core from thr earlier Tg155 series with the larger tuner. The core is around twice the size of the one in the later tuner and is slightly different in appearance. John.
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Old 4th May 2020, 7:51 pm   #27
1100 man
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Default Re: KB KV014 - VC4 chassis

Hi Dazzlevision, Many thanks for the great pictures- that's exactly what I needed! I have a scrap radio chassis that will yield some suitably plated metal, so I should now be able to make one.

Actually, I found your thread on your restoration of a KB VC11 portable. This seems to be much the same electrically as the VC3, 4 etc and you seemed to face many of the same issues as me!

It's a great thread and well worth a read: https://www.vintage-radio.net/forum/...ad.php?t=94115

Lots of details about the VHF tuner, raster distortion due to warped scan coils and striations on the picture, which is how I found the thread in the first place.

Hi John,
Thanks for the info on the tuner. The fine tune slug you picture is why DV's tuner didn't work. I stripped mine down last night and cleaned & lubricated it. My slug seems fine, luckily.
It's a really nice little tuner and well designed. My main problem was the plastic fine tune shaft binding up on the plastic spacer due to very slight deformation. This meant when the fine tune knob was turned, it tended to also rotate the channel change knob!

Anyway, it all works a treat now but the main reason for no picture on CH1 was that the Aurora was set to CH2!! You'd think I would know that wouldn't you?

I obtained a pretty good picture but with the raster distortion mentioned in DV's thread. There are magnets glued into the scan coils, but not adjustable. The plastic has also deformed quite a bit but has not crumbled to dust like the Sobell ones! They do look like they are manufactured by the same firm though- Plessey maybe? I might modify them to those magnets on metal stalks that you can bend to where you want them.

Apart from that, the EHT regulation is not as good as I would expect and the picture changes size with brightness. Not hugely, but it's got a stabilised timebase, so I'm sure it should be better than it is. I'll check the components in the width circuits and feedback resistors.

The other issue was noticeable striations. A blank screen looked a bit like a tabby cat's tail- bands of light & dark, worse on the left but visible over the whole screen. My first port of call will be the brightness decoupling caps. If it's not those, I'm not sure where to look as there is no linearity coil to damp!

Will have a play a bit later and see what I can achieve! Oh, and I had the set on for about half an hour after which time, the LOPT was stone cold! That's a new one for me: I bet it won't last!! The overwind is a crinkly plastic affair rather than the pitch covered thing in DV's picture. I'm sure Colourstar said he fitted a new one but I can't rightly remember!

All the best
Nick
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