Help!! ITT CVC32/2

[yampy187]

Hi all.

I have just managed to get my hands on one of the above sets. it has a frame fault though, just a white line across the screen. it hadn't been used for a number of years. its in fantastic condition and i would like to get it going. any ideas?

Also, are these sets actually any good or have i just bought a lemon?

any help would be much appreciated.

Jan

[neil29]

Hi Jan, Would you like the service info for the set?.


Cheers,Neil.

[yampy187]

Hi Neil. Yes please!! That would be a great help.

Thank you

Jan

[neil29]

Ok then I'll take the info with me to the NVCF and hand it to you there if that's ok.


Cheers,Neil.

[yampy187]

Hi Neil. Unfortunately I won't be attending the nvcf.

Thanks, jan

[Studio263]

First check the scan coil plug where it goes onto the little "convergence" board on the yoke, cracked solder joints are very common here.

After that it's the usual drill, check the supplies to the frame output stage and then work back from there. I think this version has diagnostic LEDs fitted, so a good start would be to make sure that they are all lit.

Unfortunately the LOPTs were rubbish in these sets so you'll have to keep your fingers crossed that yours doesn't "go". You can improve it's chances by reducing the HT a little (use the width control to compensate) and making sure that the tripler is in good condition - if you doubt it then put a new one in. Tripler failure in these would often damage the overwind of the LOPT, causing it to fail a short while later. An expensive annoyance then, a disaster now!

[Welsh Anorak]

Hi
As far as I remember the frame output used TIP transistors in a slightly odd configuration. Also make sure the service switch is OK.

Apropos of Tim's very valid comment about tripler failure cooking the LOPT, I remember some Grundig sets had a small fuse in series with the tripler. This might be an idea whenever a LOPT/tripler combination is encountered. A very low value 32mm fuse, suitably sleeved, would do the trick I'm sure.
Just a thought.
Glyn.

[thermionic]

Hi . I concur with the previous comments, especially dry joints on the scan coil connector on the little PCB. The frame output transistors are a TIP 31 & TIP 33 if I remember correctly. Check both of these as I seem to remember one of these used to go open circuit . Also check for dry joints and soldering to the chassis which act as ground returns.
It's been a few years since I have seen these but used to repair them in reasonable numbers. Unlike John (HKShort), I did not keep any fault notes on sets I repaired - unfortunately!

Good luck. SimonT.

[yampy187]

Hi all, thanks for the replies.

It turns out its a CVC32/1 so could a moderator edit the title please

I have re-soldered all the joints mentioned. No joy! i will check the frame output transistors next. if one turns out to be faulty, are these transistors still obtainable?

Thanks again,

Jan

[thermionic]

Hi Jan.

A quick Google proves a few suppliers still list these. If you still have the originals fitted, the TIP 33 is the larger package of the 2. I think I used to replace the output transistors as a pair. I seem to remember using a couple of BD239's , but I may be incorrect here. If I still have the manual, I'll dig it out & have a look.

Of course, the transistors may be fine, it may be a supply rail fault.


SimonT.

[Welsh Anorak]

Hi
There's one big and one small transistor - I think from memory they worked in a class A-B circuit. There shouldn't be a problem getting them. Remove them to check them - I agree that the TIP33 (big one) used to go open-circuit, hence best to test them out of circuit. I think the print and the earthing strip used to give problems in this area - the trusty Weller gun was handy here to cure intermittent jitter.
There's not too much in that area - I might have a manual somewhere if you run into trouble.
Glyn

[yampy187]

Hi Glyn,

Both the transistors appear to be bd807's and there seems to be no voltage reading from any of the pins on either of them?? A fault further down the line somewhere? There doesn't appear to be many components in the circuit. I have checked the resistors and substituted a sick looking cap in the vicinity. also ive re-soldered anything suspicious looking. Still nothing though?

I really haven't a clue what to look at next.

Thanks again everyone,

Jan

[Hybrid tellies]

These are good sets and well worth effort of clearing the fault. If you have no voltages then either the frame output transistors have gone short circuit or more likely there is a problem with the power feed from the line output stage. You definitely need a circuit diagram to proceed further.

[yampy187]

Hi Simon. thanks for the reply,

Would it be anything to do with the big green cap on the back of the LOP transistor that decided to split open and throw its guts up? Which caused the set to start tripping. I think it's an 8 microfarad 2Kv type. The writing has worn badly so I can't really tell.

Thanks,

Jan

[MALC SCOTT]

This will be the line o/p tuning cap. Its value will be in nf. The line output transistor may well have died as well. A circuit diagram would be a great help.

[yampy187]

Hi Malc. Thanks for the reply. There was still a white line across the screen when I switched it off so I think the line output transistor just about survived!! I currently don't have a diagram, or any replacement caps for that matter I will get a replacement 8nf 2kv cap this afternoon. I am assuming its value has to be critical?

Thanks again,

Jan

[MALC SCOTT]

Cap must be correct value/voltage. The lack of voltage around the frame o/p suggests that the supply is missing.
I have now located a cct, there are two supplies feeding the frame cct. 35v and 12v. The 35v is fed via D26/R101 from the loptx. Check R101 4.7 ohm fusible, if o/c replace and D26. The 12v is fed from T14 collector, fed from the loptx via R100A and D27, check these also, Malc.

[yampy187]

Hi Malc. Thank you for that info. I will have a probe around and let you know how I get on.

Thanks again, jan

[yampy187]

Hi Malc.

I have replaced the EHT tuning cap with an identical type. The line is still on the screen so i imagine the LOP transistor survived. The 12v supply is there on D27 up at 13.5v. R101 is ok and D26 is O/C which is a BYX55-600. so i guess that's the problem

I will get a replacement Diode ordered and report back.

Thanks again,

Jan

[yampy187]

Hi all.

I have replaced D26. still no joy there is 37v at D26.

i think its a case of what to look at next

thanks again,

jan