An old fashioned B/W TV has a single vertical line - what part has failed ?

Question

I am OK at repairing most minor electronic items, so if this likely to be say the line output transistor, I can replace it. However I seem to remember that a line output tranny failing gives a horizontal line, not a vertical one !! The sound works fine by the way - Any thought folks... Oh yes and I know about EHT and how to safely discharge the tube with a bleed resistor.

Hi Bill and Pete
Great stuff, brings back memories for me too !

But, silly of me I should have stated "Old TV but SS not valves" (tubes for those across the pond)

OK, so we are poss looking for a bad conx rather than a blown tranny - I will get tapping then !!

Keep up the good work, and I will report back soon.

All the best, John in the N.W. UK

Answer 1

OK then I will address your fault first ----- A vertical line down the screen that is top to bottom ! can only be a bad joint from the line out transistor to the deflection yoke or something basic in that area !.
Explanation-- eht is present so that means that the line tranny is good as well as the line amp transistor, vertical deflection is good ( this confuses some ) with no vert def then you have a horizontal line ! ( side to side ) .Cheers Pete
Hi Bill ! gee you must be as old as me ! I well remember the old EY 51 s etc but I think the PCL 82s were used as sound o/p and 85s were frame o/p !! Anyway nice to know that I am not alone !!!!
Cheers Pete

Answer 2

Hi My name is Bill Saint. I am a qualified teleivision engineer and teacher. Old School)

The problem with you tv is not the line output stage but waht we call. THE FRAME OUTPUT..

If it is a valve tv it will have what is known as a triade/pentode type. It is 2 valves in one glss enveloe. A triode valve ( three electrodes) andf tyhje pentode part which has six.

The tiode part controls the osccilation of the frames and the pentode amplifies itv so it vhas enough power to defelctb the bem up and down across the screen.


Different tv's had different valves. It will probably start with the number PCL THEN POSSIBLE 82.....

PCL 82/83 84 85 86 VAVES WERE ALL COMMON FRAM OUTPUT VALVES./

The fact that you have a line open the screen shows all the eht and line output is working Also the rectifier which canhges the high voltrage output from the line output from ac to dc. Ypoun probably have a the littel glass tube soldered on top of the Line output transformer.Was EY51 TYPE BUT LATER WAS REPLACED WITH A PLUG IN VALVE RECTIFIER EY86 / 87 ETC.

The output voltage on the side of the tube is Dc about 15KV.

If you touch it it will make you jump but wont hatm you. Best way to discharge it.. if you have to.. is to just short circuit it out to the chassis somewhere with a long screwdriver.

Theres no real need to touch this part or discharge it. though.

Sometimes giving tjhe valve a clump with the plastic end of a screwdriver gets it working... ..

Hope this helps.. nice to rack my brain again. Come back if I can be any further help.

By the way just check this out as well. Arouing the neck of the tube is a large coil.. these are the SCANNING COILS. Make sure no leads have come off. The coils carry high voltage so turn it off first.No need to discharge these coils..

Call me on 07803 071001 if you like.

Bill