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ITT CVC 8

 
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ITT CVC 8

Post by freya » Wed Nov 04, 2015 1:05 pm

Just been given a couple of these, the owner had them stacked in his bedroom along with many more that were of the plastic variety. All the more recent sets have already been skipped....... but couldn't let these get recycled !
One is missing its front panel controls, the other is complete.
The complete one has its plug fuse missing and the 315mA on the switch board. Replacing these has brought life to the set with heaters and sound but the PL509 is glowing and no EHT.
Are there any stock faults on these please before I start delving in. Boost capacitor ?

 
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Re: ITT CVC 8

Post by slidertogrid » Wed Nov 04, 2015 2:26 pm

Hi Stephen
I think if the boost capacitor had gone short the PY500A would be glowing. I would check to see if there is any line drive.
It's a long time since I worked on one of these, but if there are any of those clear plastic cellophane capacitors in the oscillator I would replace those first.
The PL509 could be faulty I suppose, it's worth trying another. You could also try disconnecting the tripler in case the load is excessive.
The line transformers were quite reliable on these sets but I remember replacing a few when the sets got old, It seemed that a faulty tripler was more likely to kill the transformer when the sets had a lot of years behind them.
I really liked these hybrid ITTs. They had a very long service life and outlasted many of their peers like the Decca 30 and Pye 697.
The 22" in particular was very kind to its tube and many were well into their teens with the original Mullard A56 120x.
They were more reliable than many of the next generation of solid state colour sets
I can count the common faults for the CVC5/9 on the fingers of one hand, now try that with a Ferguson ICC5 or a G11 ! :cch
Rich

 
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Re: ITT CVC 8

Post by freya » Wed Nov 04, 2015 3:55 pm

Turns out the PCF802 oscillator valve was duff, replacing has restored EHT. In doing so the EHT cap has been highlighted (in corona :bba )
Its fairly rusty with deep tracking into the cap shrouds :cch what to do here then !

Set 2 looks much better inside, hardly any dirt or dust, but for some reason all the valves have been removed, like the control panel. also spotted a diode D54 circuit board reference that has been removed. This set with valves fitted shows no sign of life except tube heaters. Valves not lit.

 
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Re: ITT CVC 8

Post by slidertogrid » Wed Nov 04, 2015 6:17 pm

The heater chain is fed from a tapping on the primary mains transformer, the fact that you have tube heaters means the transformer has power so it should be easy to find the break. The first valve in the chain is the PL509 then PY500 PCF802 PCL805 PCL86 .
D53 and 54 are the HT rectifiers a BY133 should do as a replacement.
The arcing anode cap on the other set will need replacing if it has been tracking. I good clean of the anode connector on the tube should remove any conductive tracks. In really stubborn cases a little smear of silicone grease around the cavity connector usually does the trick, It was my ex service managers pet hate but sometimes needs must!
Groan..... now I fancy getting myself a hybrid ITT! :aaj
:bba
Rich.

 
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Re: ITT CVC 8

Post by freya » Wed Nov 04, 2015 6:29 pm

Hi Rich,

Its been on for an hour or so now, the corona now is very minimal so humidity must have played a part to some extent.
I will get some pictures soon, but can only do stills from video at the moment as its my only source of 625 with modulator :)

Set 2:
Will need to find a control panel for it, if something like that exists in a pile somewhere. I should be able to make something up for test purposes I guess.

 
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Re: ITT CVC 8

Post by crustytv » Wed Nov 25, 2015 1:30 pm

slidertogrid wrote:I can count the common faults for the CVC5/9 on the fingers of one hand, now try that with a Ferguson ICC5 or a G11 ! :cch
Rich

Perhaps you were lucky or looking back with rose tinted spectacles :qq1

I'm continuing to add more stock fault articles to the main site and today added 18 pages for the CVC5 http://www.radios-tv.co.uk/?page_id=17065

 
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Joined: Sun Sep 04, 2011 9:27 am
Location: Falmouth, Cornwall

Re: ITT CVC 8

Post by freya » Wed Nov 25, 2015 3:17 pm

I hadn't seen those Chris, thanks very much.
Will get back on the set now I have the positor and a pattern generator.


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