Telefunken 711 - R567 overheats

[Welsh Anorak]

Hi
Not sure, but somewhere in the back of my mind I seem to remember the line driver transformer and the E/W transformers are prone to causing line output stage mayhem.
Good luck - you'll need it on a 711!!
Glyn

[Steve_P]

Welsh Anorak,

Have you got a decent copy of the manual that you can scan for me. The entry in the Newnes Books is barely readable.

Cheers,

Steve P.

[Welsh Anorak]

Hi
Sorry Steve - we never had one when we used to look after these sets! Eventually we did get a German one, but it got used so much it disintegrated....
Glyn

[Steve_P]

R567 is in the Line Output stage, after the Driver Transformer and before the Line Output Transistor (BU108).

Powered through 180v (U1) and 28V AC (U4).

The 28v is derived from the line transformer, and the AC part of it, at 15.625 kHz fed in by L561.

I would check C564, D561, R570. Change the BU108. Check L561 and L562 with an Ohmeter.

I've attached the diagram from Television Magazine for reference. Thanks to Brian Pateman for this.

Cheers,

Steve P.

[ben]

blimey, that's some response chaps! special thanks again to Mark, also to Steve for the scan which has helped a lot.

Steve - D561 tested ok, and i've replaced c564. will check the rest though. I'm now thinking the LOP transistor might have gone leaky, though in my experience they usually just go off with a pop!

hopefully over the w/e I'll find the time to knuckle down and solve this one. Wish me luck Glyn! Ben

[gec2110]

Now we have the correct resistor i would change the output transistor
along with the mica washer and some fresh dairylee heatsink compound
check for bad connections and the u1 voltage

[ben]

Have replaced the transistor with BU208A. I also want to replace a 2.2 nK disc (ceramic?) cap which was soldered between ground and via a small coil to the emitter of the BU208.will post again when done.

[gec2110]

Good luck with the 711 i hope it works if the crt is good you will get a good colour picture
the convergence was usually very good with these televisions when set up correctly

[Welsh Anorak]

...just remember to jump in the air when changing channels!!

[ben]

after replacing parts mentioned in post 27 and renewing the mica and heatsink, no smoke after a good 10 mins' use. Hopefully that part of the problem is now solved, will keep under observation.
Now I have the problem of no colour and black bars/shadow across the pic. I want to check the supply to the tuner first, as I'm working 'blind' I'd appreciate any pointers!
cheers, Ben

[Chris55000]

Hi!

This any help?

Chris Williams

PS! I'll be weeks and weeks scanning it all as my A3 scanner won't play ball with TWAIN editors, so please bear with me if you'd like more manual!!!

[Steve_P]

If the shadow or lines are a hum bar, check T421, T422, R442. If there is a picture then the tuner is OK, the channel switching on these sets is 33v and 12v. Tuning voltage comes out on pin 6 of the SAS560 chip.

Check the low voltage power supplies for hum.

Cheers,

Steve P.

[gec2110]

The tuners are usally quite good
it is the way its mounted in the chassis which causes problems
i would check the condition of c101 1uf it is on pin 3 of the tuner moduel on the
signal board
if you are having problems with the channel switching
check these out

d1109 1n4148 t1102 bc308a t1101bc238a