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The teleman 16th Feb 2021 3:22 pm

Telpro C561
3 Attachment(s)
Hi Guys , itís been a while since Iíve posted anything on here due to other commitments , This set a Telpro C561is a set I acquired recently from a good friend .
On inspection the set was missing a power board ( please see my wanted add )
But the rest of the set looks in pretty good condition ,
The crt reads 100% on all 3 guns and the rest of the panels look remarkably clean
These sets are basically the same circuit as a Decca Bradford but the layout is totally different and the panels are NOT interchangeable with the Decca
I remember servicing these back in the day some gave better results than others , itís only now I wish I had kept the service manual for it
The set is going to be a challenge to say the least as it looks like Iím going to have to make a power board the only thing I would need is a photo of the under side of a power supply panel if any has one I would love to see a photo.
Iíve also noticed the loptx has a hole in the overwind but Iím sure I have one of those somewhere
As I say itís going to be a challenge , if anyone has anything to offer in the way of help please feel free
Many Thanks for looking
Chris (The Teleman )

its ur aerial 20th Feb 2021 8:32 pm

Re: Telpro C561
I worked for Telefusion (TAM as it was) back in 1979, but this Telpro cabinet, doesn't look familiar:shrug: Am I getting old and loosing it:dunce: or was their more than one version ?
Ken G6HZG.

Chris55000 20th Feb 2021 11:52 pm

Re: Telpro C561
Evening Chris!

A Bradford 22" LOPT is the one you want for this – I seem to remember it was a Mullard AT2055 if my memory serves me correctly!

If you can't get a genuine Bradford or Weyrad transformer, PM me if you're stuck and I'll go through my newly acquired stash of CTV service manuals and list all those that are the most compatible with the circuit!

You could probably get one from a GEC (2040 s/s) or ITT hybrid (CVC5) (or even!) a Pye hybrid one to work if you amended the fifth–harmonic tuning capacitors – all British hybrid CTVs used identical specification line scan coils, so if you were able to mount it on the chassis ok, any s/s British hybrid LOPT for 25kV tripler operation will do at a pinch, although you might have to experiment with the auxiliary pulse feeds if you're really unlucky to get the pulse polarities and amplitudes right!

Unfortunately I don't have any old line transformers myself as I migrated over to T & M when the analogue TV transmitters closed down — Aurora's were much more than I could afford at the time so I never got into CTV restoration myself!

Chris Williams

toshiba tony 21st Feb 2021 4:17 am

Re: Telpro C561
Ah, the Telpro, saw a few, making a psu eh? Not impossible I would imagine, and an audio stage! And beam limiter.

Not an impossible task, was line and frame shift carried out on the same board too. HT rectifier was, can't remember re the LT bridge, a couple of years ago I may have had one, certainly a challenge but I modded a Sony 20in set that required a psu, not the dreaded KV1810 but the KV2000, went for years, used a two chip Bush PSU. But good luck with yours, will watch your posts.
Tony Walker

Chris55000 22nd Feb 2021 11:01 am

Re: Telpro C561

A full new set of Telpro C561 Circuit Diagrams has just been started - I found some (very bad!) photocopies of the Telpro PCBs amongst the vast wads of paper munuals in my collection at home and half an old Bradford Manual (no circuits in it, only the last few components lists!)

These are being drawn in Abacom's sPlan 7 and PDF sheets will be posted in this thread as soon as they're complete! Chris's PCB design will get under way as soon as I get the parcel of Bradford Panels on their way to me - this will be done in Easy-PC and I'll include the File Viewer for them!

Chris Williams

Hybrid tellies 22nd Feb 2021 10:28 pm

Re: Telpro C561
Just a note about the Decca Bradford 30 25Kv PSU panel.

On this panel you will find the main HT rectifier diode and 3.9 ohm surge resistor, the two LT rectifier diodes plus two smoothing caps, the negative LT line diode with its smoothing cap, the preset brightness control, the PCL82 audio/output circuit, the screen feed to the PL508 frame output valve, the line and frame shift controls, the pincushion correction circuit and the the two fuses both 500mA anti surge one for the HT line and the other for the LT supply.

I suspect this will be the same as that of the Telpro sets but with a different layout.

The teleman 25th Feb 2021 8:23 pm

Re: Telpro C561
The TELPRO seems to have considerably less on the power board than the Decca30
it has the audio output pre set brightness and LT supplies and that is about it
the line and frame shift are done on the relative panels
the set looks well built but from what i remember about them ( very little )
is the quality was very hit and miss some sets performed brilliantly others looked awful but you could never get them to improve even from new
i remember only ever seeing one 26inch set and it was awful
the majority at the time were 20 or 22inch
i hope this one performs well when its restored


peterpixel 26th Feb 2021 10:36 am

Re: Telpro C561
An uncle of mine was a rep for Telefunken for many years and I remember him refering to the Telefunken 632 as using the 'Decca' chassis.I inherited his service manuals and after a search came across the 632.For what it's worth at first glance the decoder board and crt base board are similar if not identical with the Telpro pictures but the psu layout is different although the component designations seem the same.The functions carried out on that board,ie audio output and frame circuitry etc tally and seem to agree with the comments made by Simon and Chris.It may be that different versions were produced for different manufacturers.Telefunken produced technical information known as 'Teltec' and describes a change of psu which was interchangeable.I hope this info may be useful.Peter.

Welsh Anorak 26th Feb 2021 2:37 pm

Re: Telpro C561
I only ever saw the Telefunken that had a 'proper' Decca 30 chassis in there. It had the seven sloping selectors on the front. We always heaved a sighh of relief when it was one of these and not the dreaded 711chassis!
The Telpro/Tristar was a good idea from a servicing point of view and meant changing the 3.3 ohm surge limiter, the PCL82 or the HT rectifier didn't result in yelps of pain, though LOPTs and tripler were just as much of a pain to replace. However I always found the pictures to be poor compared to the Bradford - the IF response seemed degraded. Also the customer controls were flimsy and didn't stand up to much use.

toshiba tony 27th Feb 2021 9:42 am

Re: Telpro C561
Yes, the Telpro sliders were dreadful. Plus I always thought the set didn't come near a Decca 30. Plus the backs always came away, am I biased. Probably, we did both Korting hybrids and the Telpro, Kortings sold better.

Chris55000 27th Feb 2021 11:44 am

Re: Telpro C561

My friend Mike Smith got a huge pile of the Telpro sets in his area when he was working at Telebank – he said he'd at least 50 or 60 to look after, all with a coin box on the back for the rentals!

My board will incorporate additional thermistors in the H.T. line and heater chain for additional surge–limiting – Television Magazine's service notes said these sets had a tendency to blown h.t. and mains fuses and the PCL82 heater going pop at intervals!

I've now got the parcel of Bradford 30 parts, and all I need is for Chris Field (OP) to furnish me with the Telpro S.M. information I've asked him for – he sent me a nice email confirming he has a copy of the Original Telpro Manual!

Chris Williams

SWB 18 27th Feb 2021 12:15 pm

Re: Telpro C561
Hello Chris,

I posted the photocopy of the manual to Chris (OP) on Monday, so you should have it soon.

The original board layouts are A3 in the manual, but I also enclosed a couple of reduced copies, having more contrast, to help you when you come to produce the replica board.

The original circuit diagram is printed on thicker paper than normal and so proved awkward to get flat to copy, but has good overlaps and should be easier to work from than your old photocopies.



Chris55000 27th Feb 2021 3:56 pm

Re: Telpro C561
Afternoon Phil!

Alas to say I don't have the Circuit Diagrams Ė all I have at the moment were grotty 1 bit MauritronĖ type photocopies of the board layouts on a few ancient A3 sheets I got from my friend Mike Smith's dogĖeared Telpro Manual, dumped years ago, hence my project to draw out new ones!

Chris Field has received your bookwork and has confirmed same to me Ė another Member Howard gave me the tips for plotting the Valve Base Footprint on Easy PC!

Chris Williams

slidertogrid 8th Mar 2021 9:06 pm

Re: Telpro C561
Isn't one of the panels discussed in this thread the one you need?

Chris55000 8th Mar 2021 9:31 pm

Re: Telpro C561

Yes, the Telpro panel is a single valve audio stage with the h.t. (300V) and l.t. (25V) rectifiers plus the negative voltage for the preset brightness control – from the pics Chris posted, he doesn't need an I.F. panel!

My design to make the OP an exact plug–in replacement for the one shown missing in his photos isn't far off completion now, and I have all the parts needed to build it, including the audio o/p transformer and the correct Pressac PCB–mounted male connector plugs!

Chris Williams

slidertogrid 8th Mar 2021 10:31 pm

Re: Telpro C561
I think the panels in the thread I set a link to are Telpro audio and line panels.
I found the thread when I was searching for a picture of the Tyne IF panel that I thought I may have posted a picture of. I think that's why the link has "IF panel" in the wording. but if you click on it it will take you to the thread discussing the Telpro panels.

Not that it matters now if Chris is making one of course.

When I searched for ' Tyne' Or 'Tyne IF panel' I expected just a couple of results but I got loads, maybe I just don't know how to set a search correctly?

The teleman 26th Mar 2021 12:24 pm

Re: Telpro C561
The latest update on this poor little Telpro set
As I may have mentioned I noticed the loptx has a burn in the overwind
Now the only replacement I can find in my stash of very few transformers
is for a Decca 1910
Now my question here is would this be a suitable replacement as it looks identical to the transformer fitted in the Telpro, the 1910 transformer is a weyrad type I know the 17/1830 transformer is different just wondering if this was too

Many Thanks

Welsh Anorak 26th Mar 2021 2:38 pm

Re: Telpro C561
As far as I remember all the Bradford (and therefore Telpro) transformers are identical. Even the small screen ones were the same, the difference being in the tripler/doubler.

The teleman 27th Mar 2021 10:45 am

Re: Telpro C561
Thanks Glyn
I had a feeling it was the same just needed a second opinion

The teleman 27th Mar 2021 3:33 pm

Re: Telpro C561
Well today I replaced the line output transformer as the original had a burn hole in the overwind, while I was at it I also replaced the boost capacitor as a precaution as I’ve had these fail in spectacular style .
Everything els in the set looks ok except maybe the main smoothing this will be replaced all in anticipation of the power supply currently being made by CHRIS 55000

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