Telpro C561
 

Hi Guys , it’s been a while since I’ve 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 , it’s 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 I’m 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.
I’ve also noticed the loptx has a hole in the overwind but I’m sure I have one of those somewhere
As I say it’s 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 )

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.

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

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

Re: Telpro C561
 

Hi!

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

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.

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

CHRIS

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.

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.

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.

Re: Telpro C561
 

Hi!

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

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.

Regards,

Phil.

Re: Telpro C561
 

Afternoon Phil!

Alas to say I don't have the Circuit Diagrams – all I have at the moment were grotty 1 bit Mauritron– type photocopies of the board layouts on a few ancient A3 sheets I got from my friend Mike Smith's dog–eared 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 – another Member Howard gave me the tips for plotting the Valve Base Footprint on Easy PC!

Chris Williams

Re: Telpro C561
 

Isn't one of the panels discussed in this thread the one you need?
https://www.vintage-radio.net/forum/...=tyne+if+panel
Rich

Re: Telpro C561
 

Hi!

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

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?

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
Chris

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.

Re: Telpro C561
 

Thanks Glyn
I had a feeling it was the same just needed a second opinion
Cheers
Chris

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

Re: Telpro C561
 

This is the new loptx fitted
And to show the old loptx with a hole in the overwind

Re: Telpro C561
 

I can just imagine the old one sizzling! Hope it's successful Chris.

Re: Telpro C561
 

I wouldn't connect the tripler just yet. It looks like the LOPT failed for its own reasons, but you never know! It's nice to find a reason the set was retired as then most other panels (except the msiing one, of course!) will probably be OK.

Re: Telpro C561
 

Hi!

Update on the replacement PSU board for the OP Chris Field – my design is now virtually all complete apart from the two +25V and the –35V smoothing caps – I've only to measure the original caps, make the PCB footprints and drop them in!

Final job is to email the OP a paper template to measure up against his chassis and then once confirmed the size is correct it can go for manufacturing!

Chris Williams

Re: Telpro C561
 

Hi!

Replacement PSU and AF Panel design for the OP Chris Field's Telpro C561 now complete and ready to send for manufacturing!

I'll post the Gerber files once I've had confirmation from the OP that it's the correct size!

I've laid it out using original Bradford components, so hopefully everything will fit OK!

Chris Williams

PS!

I made provision on this board for both revisions of the PCL82 Audio Circuit that Decca used in their Bradford chassis, as I am of the opinion that running the pentode anode of the PCL82 direct from the main 300 V h.t. line is far too much for this valve, so included provision for both the main h.t. feed resistor R82 (1k8 9W fusible), the main decoupler C84 (33uF 400V), and the additional screen-grid/triode anode decoupling components R83 (4k7, 1W) and C83 (4uF 400V).

Re: Telpro C561
 

Hi!

Circuit diagram to which the PCB has been designed now attached!

Chris Williams

Re: Telpro C561
 

Hi!

Panel manufacture now complete and on it's way to me!

Chris Williams

Re: Telpro C561
 

Keep keeping us updated Chris! Plenty of Deccas about but next to no Telpros.

Re: Telpro C561
 

Hi!

New PCB now arrived and ready for assembly, which I'll get started on this weekend!

My grateful thanks to Member "Davidh1041" who furnished me with a spare Decca Bradford PSU for the transformer, etc!

The PCB was designed and laid out using "Easy PC", but it should be possible to replicate this type of panel using the free "Design Spark" software as it is not necessary to use an "autorouter" – the AR in D.S. is absolute rubbish!

I have already provided the TTFs for the "Radio Constructor" style lettering used on the silkscreen printing elsewhere on this forum, by the way!

Once assembly is complete I'll test it and get it posted to the OP later next week!

Chris Williams

PS!

Gerber Files and a ready–made PCB available from me on application via PM!

Re: Telpro C561
 

Wow Chris! That PCB looks fantastic. How are you getting along with it?

Re: Telpro C561
 

Hi Taz , still waiting to hear from Chris about the power supply board ,
Last I heard he was fitting parts that was back in June , I don’t like to ask in case the dreaded COVID has been a problem

Chris

Re: Telpro C561
 

Ah, okay. He's probably inundated with all sorts! We'll just have to wait.

Re: Telpro C561
 

Hi!

Not the dreaded, just a combination of eye–trouble, mislaid bits and a duffy iron!

Update on this with a small confession – I've mislaid some of the small parts, which I'm slowly in the process of finding, (as I've put things away everywhere!) and I'm also having a bit of bother with my soldering iron station, and I'm in the process of waiting for a Black Jack BK2000 one I won last week, hopefully that will get my iron up and running again!

Hopefully more progress soon, sorry for the delay Chris!

Chris Williams

PS!

I'm signed off work due to eye–trouble so I've not got access to the top–notch soldering/desoldering tools at my work's fleapit that would build this really quickly!

Re: Telpro C561
 

Hi!

PCB now completed and handed to the OP Chris Field @ RetrotechUK this morning – my job is done & I'll hand back to the OP to carry on his tale from here!

Chris Williams

PS!!!!

Now got my Duratool ZD915 new desolder gun and the Black Jack BK2000 soldering station that enabled me to catch up on Chris Field's PCB at long last!

Re: Telpro C561
 

Hi!

Design update I forgot to mention earlier – when I got the new PCB back from manufacturing I found the only preset potentiometer footprint in my Easy–PC was one of those little tiny "halfpenny size" ones, so I'll modify my PCB to use a standard Piher one – doing that only means turning one resistor round and moving some silkscreen text, and I'll add another 10 mil to the pad hole diameters so the little Erie PCB resistors go in more easily!

Chris Williams

Re: Telpro C561
 

Update on the Telpro 561
As Chris Williams was designing and making the power supply panel for this set it had been put to one side for a while
On Sunday at the retro tech meeting Chris delivered the remanufactured pcb to me and wow what a fantastic job he has done this it a totally professional job
I would like to take this opportunity to say a massive THANK YOU to Chris for all his time and efforts in re making this power supply .👍

I had the opportunity to fit the pcb today and it worked perfectly, the rest of the set needs attention to make it perfect but the power supply is absolutely spot on .

Re: Telpro C561
 

Not much to do now!
That board is so much better than the original offering and will last far better.
Imagine if this was possible in the Seventies and he re-manufactured Pye CDA panels. Everyone would have beaten a path to his door.

Re: Telpro C561
 

Hi!

I'm currently two–thirds of the way thro' a BRC2000 h.t. regulator board that's currently proving a bit tricky in places!

Don't all come rushing up at once for Pye Hybrid CDA or 697 vertical PCBs yet please, I'll not be able to keep up. . .!

✏️ ���� ✏️ ���� ✏️ ����

Chris Williams

PS!

PL802 valves still reasonably priced and plentiful. . . .!

Re: Telpro C561
 

I know the one you're doing - it was a little bit awkward!
A Pye vertical PCB would be a challenge....

Re: Telpro C561
 

Hi!

Not impossible tho' Glyn, as long as I had the remains of an old one to get the dimensions and the edge–connector contacts correctly sized!

I have had a request for a G6 s/s I.F. panel, but I would need to borrow an old one to design the outline correctly and get the spacings of the coil pins!

(I think it's only panels with really awkward shaped internal cutouts may be a problem perhaps!)

Chris Williams

Chris

Re: Telpro C561
 

That Sound PCB board does look impressive. I can appreciate the work that you put into this.

Re: Telpro C561
 

While running this set & sorting out other faults I noticed the audio would go off and not come back thinking this was probably due to a valve fault I replaced the PCL82 and the audio was back only to go off a few moments later , while voltage checking around the PCL82 the audio came back on when I placed my meter probe on the pentode grid section , on close examination of the PCB I discovered a small section of print missing at the junction of R81 & C82 a small wire link restored normal sound , now this is not down to a fault in Chris Williams design as the print is actually there on the design so must be due to a production error but it’s no big deal and soon sorted .

Re: Telpro C561
 

This is a great save! There can’t be many Telpros out there now in working order. Well done, both of you!

I only came across a couple when I was in the trade, but my personal opinion is that the Telpro is of a better mechanical design than the Decca...

.....takes cover......😬😬