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Forum 141

ITT/KB SV-049

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Nuvistor
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We had the ITT agency so we would have sold a few of these sets but I don’t remember much about them, so they would have been reliable. BW sales were few compared with the colour sets in the 70’s for the shop I worked at.

Callins were like Hunts paper capacitors, suspect and very often faulty. The Mixed dielectric caps  in the set are worth testing.

Frank

 
Posted : 18/10/2018 8:27 pm
Cathovisor
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Posted by: PYE625

As a matter of interest, it looks like there are several mixed dielectric capacitors dotted about plus one or two black Callins electrolytics. For instance, C82 in the PCL805 cathode circuit is a Callins 100uf...… Hmm I wonder....

Doubt that has anything to do with the lack of frame hold, but it'll certainly muck up the linearity...

That set just looks so... modern inside. And a PCB too! But I do like it

 
Posted : 18/10/2018 8:35 pm
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PYE625
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Any attempt to increase the scan further than that shown in the above photo results in loss of frame lock. 

 

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 18/10/2018 8:47 pm
Focus Diode
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Some good advice here from John Walekey over at the UKVRRR. See post #40.

Looking great so far.

https://www.vintage-radio.net/forum/showthread.php?t=149566&page=2

 
Posted : 19/10/2018 10:50 am
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Lloyd
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That's weird how capacitors that measure absolutely fine for capacitance and leakage just simply don't work!

That ITT/KB looks like it's going to produce an excellent picture once the frame is sorted.

Regards,

Lloyd

 
Posted : 19/10/2018 11:20 am
Nuvistor
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Posted by: Cathovisor
That set just looks so... modern inside. And a PCB too! But I do like it ? 

It does and I like the look of it.

We started selling the ITT range due to disappointment with the offering of Pye 697 chassis and the RBM range. We wanted a range of large screen CTV’s, Hitachi and Toshiba were only small screen up to 20 inch sets at that time. The ITT range were reliable sets for us.

 

Frank

 
Posted : 19/10/2018 1:41 pm
PYE625
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The Callins 100uf electrolytic in the cathode of the PCL805 proved ok. However, C77,78 and 81 in the frame stage are not. The values have increased and they are slightly leaky at only 320vdc. I can assume that the remainder of the mixed dielectric capacitors are likely to be in a similar condition. I have ordered replacements of the suitable values and voltages.

After substituting C78 and C81 (0.022UF 1000V) a dramatic improvement was seen. The ones I have are only rated at 400v, but were sufficient to temporarily prove the point.

itt 17
itt 16

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 19/10/2018 4:01 pm
Cathovisor
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Mixed dielectric - the worst of both worlds! Treat as paper IMO. 

 
Posted : 19/10/2018 4:03 pm
PYE625
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I couldn't agree more Mike. The above result speaks for itself. 

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 19/10/2018 4:06 pm
Cathovisor
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I wasn't aware those grey Plessey caps were mixed dielectric to be honest; one day I may have to go through my stock of NOS and excise them if I have any. 

 
Posted : 19/10/2018 4:09 pm
PYE625
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I am assuming they are mixed dielectric, but if not, they are not good quality. The two removed ones behave like paper capacitors in as much as they take a longer time for a DC voltage to reduce through them, but never quite make zero vdc leakage. Whereas a new polyester film capacitor is at zero almost immediately.

IMG 4848 3 50

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 19/10/2018 4:32 pm
Cathovisor
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Cut one open, perhaps? Increased capacity is often seen when paper caps go 'leaky'.

 
Posted : 19/10/2018 4:40 pm
Nuvistor
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Apart from the colour they look very similar to TCC Duomold capacitors, Duo, mixed dielectric?

 

Frank

 
Posted : 19/10/2018 5:01 pm
Focus Diode
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Excellent result! I would still replace the Callins capacitor though as it's bound to give trouble sooner or later.

 
Posted : 19/10/2018 5:15 pm
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PYE625
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I think it can be safely said without doubt they are mixed dielectric. It is clear to see the polythene on one side and thin paper on the other side of the foil.

itt 20
itt 19
itt 18

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 19/10/2018 5:39 pm
Cathovisor
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We have evidence. Nice one, Andrew.

 
Posted : 19/10/2018 7:07 pm
PYE625
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Why on earth they could not have made them with polythene on BOTH sides is beyond me. 

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 19/10/2018 7:37 pm
Cathovisor
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Posted by: PYE625

Why on earth they could not have made them with polythene on BOTH sides is beyond me. 

One of three reasons: characteristics, available technology, price.

However... what a splendid little telly. 

 
Posted : 19/10/2018 7:47 pm
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PYE625
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It certainly is Mike, and I'm very pleased with it.

For one thing, I can't fault the convergence or greyscale.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 19/10/2018 8:43 pm
Nuvistor
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Excellent picture, I wonder if the capacitors were made by TCC or was Plessey and TCC now part of the same companies?

Back in Suffolk, childminding duties for the next 10 days or so, post when I can. Had the family with me in Wigan for a week, just driven them home to Suffolk.

 

 

Frank

 
Posted : 19/10/2018 10:51 pm
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