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1977 Aphelion TV :Telefunken 712 Chassis

 
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1977 Aphelion TV :Telefunken 712 Chassis

Post by crustytv » Tue Jul 05, 2016 4:05 pm

Just added a uniquely designed German British TV to the early colour collection, it joins the other German set the SABA. This TV employs the Telefunken 712 Chassis and uses a 20AX CRT the an A66 500X In-line tube. If anyone knows the sets model identity I would love to know.

http://www.radios-tv.co.uk/1977-telefunken-palcolor/

Edited: After much investigation the sets identity was established and the title of this thread amended accordingly.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Sat Jul 16, 2016 2:03 pm

The workshop has a BRC 2000 ( Fergy 3700) and a Philips G6 stacked on top, room needs to be made.

I can't lift or move the G6 on my own nor the Telefunken so today I enlisted the help of my next door neighbour. The G6 was relocated to the TV display room, then the Telefunken which was residing in the lounge was relocated to the workshop so work can commence on its repair.

You can see from the photo ( below) how the Telefunken dwarfs the large 25" Ferguson 3700 (which is on its stand) console below it. Anyone who knows BRC 2K sets will know how big they are, It looks tiny underneath this German beast.

tfkn1.jpg


I have to say of all the TV's in my collection all the neighbours that have seen it, the delivery guys, strangers passing by as it sat on the drive and including my wife without exception are droolingl over it. The Ooo's and Arrrrr's, statements such as "How wonderful makes you wish TV's were like this now" etc. Just goes to show some of the population still appreciate style with a difference.

Anyway electrical assessment can be undertaken prior to application of power.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Terrykc » Sat Jul 16, 2016 3:40 pm

Very similar to the Keracolor sets but, as far as I know, they all used a Decca chassis. 

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Cathovisor » Sat Jul 16, 2016 4:12 pm

It's a beast and a half, isn't it?! :ccf

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by nuvistor » Sat Jul 16, 2016 6:20 pm

You'll need a step ladder to work on that :bbc , I will watch it's rebirth with much interest.

Frank

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Sun Jul 17, 2016 4:59 pm

Without the aid of a servicing manual I managed to figure out how the TFKN 712 chassis withdraws from the cabinet and folds. Underneath the main chassis I could see left and right were two substantial plastic side rails. Also underneath were two grooved bars, theses bars are pivoted on one end. These are swung left and right which unlocks the two plastic side rails. You then gently lift from the front and the side rails slip into the rails allowing the whole chassis to be extended out from the set by about a 1½ feet, this now gives plenty of clearance front, back and sides.

The two upright side panels have a locking hinge bar, when this is unlatched each panel can be swung down to a horizontal service position. Finally the Line stage cage can be hinged up giving access to the the components within. All in all superb access is afforded to the service engineer, I'm sure many who were called out to this type of chassis would have been grateful for the access give by the designers.

Now I can start to visually assess each panel and look for anything untoward, dry joints etc before applying first power. I won't be going down the variac route as I'm uncertain if this may cause problems, as we know the BRC 3000/3500 does not like coming up on the variac. It will be full mains unless anyone with TFKN knowledge knows otherwise or has some precautionary advice.

tfk1.jpg

tfk2.jpg

tfk3.jpg

tfk4.jpg

tfk5.jpg

tfk6.jpg

tfk9.jpg

tfk10.jpg

tfk11.jpg

tfk7.jpg

tfk8.jpg

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Sun Jul 17, 2016 5:26 pm

The TFKN 712 chassis like most sets of this period including British ones, employed a modular chassis design. I can now use the bench microscope to inspect all the daughter boards fro problems.

Some of the boards removed for inspection.

tfbd2.jpg

tfbd1.jpg

tfbd3.jpg

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by sideband » Sun Jul 17, 2016 7:23 pm

If it's anything like the few Telefunkens I've seen, it will be remarkably well preserved. Most of these and Saba sets (of this period anyway) had generously rated components and were incredibly reliable. It's full of good quality components and it wouldn't surprise me that all you find on the daughter boards was just tarnished contacts. Obviously some of the electrolytics may have suffered by now but running an ESR meter over them will show any dodgy ones .

I suggest that before you give it full mains, disconnect the tripler. These were one of the most common failures as with any set and it's probably a standard type fitted.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Sun Jul 17, 2016 7:31 pm

sideband wrote:I suggest that before you give it full mains, disconnect the tripler. These were one of the most common failures as with any set and it's probably a standard type fitted.

Hi Rich,

That was my thought too however that was until I noticed that the tripler connections unlike all my other sets, is fully soldered into the PCB. To isolate it I'm going to have to swot the R&TS circuit to see what connections are what. Nothing so simple as unplugging this one.

tfnktrip1.jpg

tfnktrip2.jpg

tfnktrip3.jpg

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Red_to_Black » Sun Jul 17, 2016 7:52 pm

sideband wrote: It's full of good quality components and it wouldn't surprise me that all you find on the daughter boards was just tarnished contacts. Obviously some of the electrolytics may have suffered by now but running an ESR meter over them will show any dodgy ones .

I suggest that before you give it full mains, disconnect the tripler. These were one of the most common failures as with any set and it's probably a standard type fitted.


Agreed :aad regarding those purple electrolytics though I would definitely pay close attention to those, they were leaking/corroding and/or going dry enmasse years ago in any sets that used them, in fact in Panasonic TV sets of the day it was known as "purple cap syndrome" :bba , I had them fail in the ITT sets where they were used as well.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Red_to_Black » Sun Jul 17, 2016 7:59 pm

CrustyTV wrote:That was my thought too however that was until I noticed that the tripler connections unlike all my other sets, is fully soldered into the PCB. To isolate it I'm going to have to swot the R&TS circuit to see what connections are what. Nothing so simple as unplugging this one.


You only really need to disconnect/unsolder this bit (ringed) for testing purposes
Attachments
tfnktrip1-.jpg
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Cathovisor » Sun Jul 17, 2016 8:02 pm

Not entirely dissimilar mechanically to the 711 I had, except that didn't have the vertical line timebase PCB and had a separate convergence PCB in the front lower section of the set.

On the 711 you pulled the main chassis back in much the same way you did, swung the signals PCB down and then lifted and rotated the whole PCB assembly. From memory it sat at 45 and 90 degrees for servicing. A lovely chassis to work on; miles away from the evil that was the RBM A823 I have to say :aaj

And as R2B has rightly pointed out, you only need disconnect the pulse input from the tripler for testing.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Sun Jul 17, 2016 9:05 pm

As mentioned above the chassis is modular design, the modules being grouped in three main assemblies.

1) The signals board which has Video, I/F, sound, Tuner Chroma I, Chroma II and RGB
2) The deflection board which has the vertical output, vertical oscillator, E/W pincushion, Sync and power supply module
3) The Line output board

And yes as Rich suspected all the interconnect pins on all these daughter boards across the entire set are tarnished, a clean-up will be required.

tfkdec1.jpg

tfkdec2.jpg

tfkrgb.jpg

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by sideband » Sun Jul 17, 2016 9:08 pm

CrustyTV wrote:
That was my thought too however that was until I noticed that the tripler connections unlike all my other sets, is fully soldered into the PCB. To isolate it I'm going to have to swot the R&TS circuit to see what connections are what. Nothing so simple as unplugging this one.


As R-B says, you only need to disconnect the input to the tripler.....the lead that connects to the LOPT overwind.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Sun Jul 17, 2016 9:18 pm

OK thanks for confirming guys, I'd sussed the blue wire was the primary one to disconnect, what I was not sure and was a tad worried was if any of the others would need removing also. Guess I've been spoilt with working on so many Thorn 3K sets where you just unplug everything. I have to admit after working on so many 3k sets recently and especially the PSU's, I'm feeling rather out of depth with this chassis which is a totally different beast.

Well I'll be busy over the next day inspecting all these boards and familiarising myself with the layout, components and circuit in R&TS, then I will be ready for the power up. As mentioned in the blog the A56 500X is looking great, emission is good on all guns, tracking spot on and life tests show it to be a corker.

Fingers crossed there are a few faults but not show stoppers :qq1 Spending this afternoon looking over the boards it does seem to be in very good condition. The only section which looks a tad rough is the Thyristor power supply. The T/X and a few components look to have surface rust. The three fuses ( 240V, 20V and 6.3V) are intact which is a good sign.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Katie Bush » Sun Jul 17, 2016 10:59 pm

I'm almost certain someone on eBay was selling a set of "Service Extension Leads" for this, or similar set, not so long ago?

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Tue Jul 19, 2016 5:27 pm

For those interested I have just uploaded service data for the Telefunken 712 Chassis.

I've created a 18 page PDF, it combines the thee part Trader data. If I do get the manufacturers, that will be appended also.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Wed Jul 20, 2016 11:55 am

I've held back on board testing whilst I awaited delivery of a new piece of test equipment that will make life a lot simpler. The equipment in question being a Peak Atlas ESR70+. This device will now allow me to quickly blitz the entire condition of this sets electrolytics with regards to *ESR ( equivalent series resistance) status.

I'm sure everyone here is well aware of what this device is capable of but for those looking in who may not it tells you the capacitance of the electrolytic under test and its ESR. Out of circuit you will get an accurate reading of the capacitance, in circuit you will not. In or out of circuit you will get a true ESR reading, this means I can quickly go around all the boards checking the ESR of the electrolytics, replacing those which are shown to be faulty.

Another bonus, I can go through my draws of NOS unmarked ( due to markings rubbing off) Philips electrolytics and get the capacitance values sorted.

Now off to test the boards, once done I'll report findings, replace what needs replacing then power up.

* https://wiki.xtronics.com/index.php/Capacitors_and_ESR

esr70+.jpg

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Terrykc » Wed Jul 20, 2016 1:54 pm

CrustyTV wrote:Another bonus, I can go through my draws of NOS unmarked ( due to markings rubbing off) Philips electrolytics and get the capacitance values sorted.
Do you have the data on the Philips electrolytics, Chris?

I'm sure I can find it if you haven't.

When you have both the value AND the can size, you should be able to determine  the working voltage from the data.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Wed Jul 20, 2016 5:23 pm

Terrykc wrote:Do you have the data on the Philips electrolytics, Chris?


Yes thanks Terry, thanks to your prior efforts its here :thumb

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Thu Jul 21, 2016 2:55 pm

Thought it might help to visualise where everything is for those like me, who are new to the Telefunken 712 Chassis, layout and modules detailed below.

layout.jpg

Found and replaced one of those notorious WIMA's (C401) in Power supply module I, which was blown. Tested the main smoother (C403) which is looking good. Next onto Power supply module II

tf6.jpg
PSU module I schematic

tf7.jpg
PSU module I removed

tf1.jpg
C403 under test, ESR reads good

tf2.jpg
PSU Module

tf3.jpg
Faulty cap

tf4.jpg
Close up

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by sideband » Thu Jul 21, 2016 6:30 pm

Now....did that capacitor fail under load or did the casing just split while it was stored due to moisture ingress? These things like the Refa types seem to split and disintegrate even when not used. Normally if it fails under load, there would be soot and smoke damage and probably some melted plastic. Not that it matters...it's duff anyway! Just idle thoughts.

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by crustytv » Thu Jul 21, 2016 8:42 pm

Onto Power Supply II, the Thyristor regulator module. An in circuit test revealed C427 10uF @ 100V was o/c. Removed and confirmed. I've fitted a 10uF 400V. Also The large can C441 2200uF @ 40V read as leaky everything else checks out OK. Perhaps these 3 cap failures in the power supply modules are the reason the set was retired.

Sods law dictates I have every voltage of a 2200uF below 40V but not 40V :bbd Will order some up and continue this once fitted.

Edit: checked C441 on the bridge at rated voltage yep its totally o/c.

tf10.jpg

tf9.jpg
The tower/Chimney at the left rear is the heat-sink for TY421, the Thyristor. Also showing C427 removed from circuit. Also duff C441 bottom left can

tf8.jpg
That's a duff one then (C427)

tf11.jpg
And another (C441)

tf12.jpg
Just to be sure as the peak cannot apply rated, Yep the bridge with rated voltage applied agrees and as McCoy would say to Kirk, "Its dead Jim"

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Cathovisor » Thu Jul 21, 2016 11:01 pm

The large cylindrical thyristor also featured on the 711 chassis. Another quirky feature of the 711 was what Telefunken called "active smoothing" - it was merely an R/C network of large R and smallish C that supplied base drive to a Darlington pair, so the low current provided a smooth voltage to the base as there was next to no ripple, which was then reflected at the emitter of the output stage. AFAICR it didn't actually regulate - it just smoothed.

Very Telefunken!

 
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Re: Telefunken Mystery : Model unknown : Chassis Telefunken

Post by Red_to_Black » Thu Jul 21, 2016 11:11 pm

I see the purple electrolytics are performing as expected then. :bba

That German capacitor or a very similar type was used extensively in Grundig sets of the day, and rather than going leaky or low ESR, they could fail either completely O/C or completely S/C, most odd!

Another type of cap that did similar to the German types mentioned above was the Philips light metallic blue electrolytics which ( I think) you mentioned earlier, again most failures in various Philips kit I came across the caps were again either completely open, or short circuit.
I don't know if Rich (Sideband) came across this a lot ? or if his experiences while he was at Philips were similar to mine ?

:thumb for the ESR meter btw.

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