Pye v4

[murphyv310]

Looks as if there are two faults line speed is out and possibly no line sync, as Jeffrey says the two diodes (discriminator diodes) could be duff, but the 1N4148 is a perfect diode in this position.
There is also a correct way to set up the line oscillator in a V4 and this just may be the problem. Pye's own manual for the later VT4 explains how to do it and I would try doing this first.

[Boom]

Looking very good Chris. You'll have a picture on it by tonight. Looks to me like the line speed is way off. Maybe the sync' seperator has cap' trouble.

Dave

[oldticktock]

I will try and find the cap you are taking about. I just got my set of red books this morning covering 1950-1960, so I shall try and find the circuit in there and see if its got better info than the trader, so far I can only find V2

[Kevin19]

Hi Chris

It is in the Red books its in Volume 11 Television data page 432 Funny enough in mine it looks really well used and some one has written little bits about the set in pencil and certain caps! looking like they had big troubles way back then. Yours starting to look v good.

Kevin

[oldticktock]

Just managed to get some bench time and fiddled again, with controls, the are all so sensitive the slightest turn and whoa its all goes haywire. This was the best I got and it just scolled sideways.

Need to check the caps as mentioned in the line osc and sync

[murphyv310]

The picture looks negative, try reducing the contrast and even the sensitivity.

[oldticktock]

Hi a question,

V7a output is fed via a R42(10K) which now reads 12K & C36 (which has been changed) to the control grid of sync seperator (V8) a 4.7M resistor which now reads 5.3M on pin2 can these resistors that have gone high cause issues?

Chris

[murphyv310]

Most of the resistors in the set will be 20% tolerance but the major thing with valve circuits is how forgiving they are so its unlikely that is the problem.
Your Picture looks very negative which is severe overloadind these sets will "invert" quite easily under too strong signal conditions so backing off either sensitivity or contrast should return the picture to normal. If you back off the contrast, etc and everything dissapears try retuning the thumbwheel to get a stronger picture wih you gradually reducing the contrast, if you cant get an improvement there may be an agc fault or a misplaced component either in the wrong place or not fitted to the original earth point, any oscillator caps replaced "must" be fitted in the same position as the originals.

[oldticktock]

I had a feeling that the resistors would not make much difference unless they were sky high from base value.

I have noticed when contrast backed off the picture goes blank, other times I find with certain settings it seems to do nothing. A very finicky set to adjust unlike the Bush Tv's

Two components .001 caps those ones I thought were resistors the earth tag had to be moved but by only a little. It was impossible to get the soldering iron in to access without burning everything or removing so much as to run the risk of more distubance and potential error, these were around V1.

I know both you and John W say these sets a excellent when working I hope the effort/ input is rewarded this side of Xmas and it offers equal or better picture than the Bush? I remain to be convinced as the pictures on both the TV62 and 63 are superb. I may just put this to one side when the TV22 turns up.

[murphyv310]

Good job the customer is not in a hurry
All joking aside these sets are not in the least way fiddly, they give a wonderful picture with proper blacks that no Bush can do anyway I have already said about their performance, The video detector diode may be playing up, its MR2 it may just need a whacking signal to partially work so that might be worth subbing, An OA90/91 will work fine, Pity that scope wasn't higher bandwidth, the set would be sorted in half an hour!

[oldticktock]

Luckily I have a load OA91's.

Scope is pants then? maybe I put that away then, its a huge beast taking up bench space

[MALC SCOTT]

Spare scope here if you want to borrow it.

[murphyv310]

Originally Posted by oldticktock

Scope is pants then? maybe I put that away then, its a huge beast taking up bench space

Not Pants but no good for tracing IF and RF signals in a TV, OK for Video, line, frame, Sync & Audio.

[oldticktock]

Hi Malc,
Thanks for the offer, lets see how I get on.

Trevor I take it the CG5E + and the OA91 red is > the equiv

[murphyv310]

Originally Posted by oldticktock

Hi Malc,
Thanks for the offer, lets see how I get on.

Trevor I take it the CG5E + and the OA91 red is > the equiv

Sure is

[oldticktock]

OA91 is in for MR2

its not static, it constantly moving

[Heatercathodeshort]

The picture appears to be negative. I suspect that the contrast control has little or no effect due to the APC circuit that does not appear to be working and there is no line sync. Check all the aluminium pea sized diodes known as 'M3'. These use selinium discs and go open circuit. Replace with IN4148 diodes. From memory I think they are also used in the AGC clamp circuit and if faulty would certainly give the symtoms you receiver displays. J.

[murphyv310]

OK, It looks like that wasnt the fault, this is really a scope job! Perhaps you could borrow Malcs scope as we need to look at the IF signals.
Have you changed any IF valves, it may be an idea to replace V1-V6 & V13, don't do them en-block just one at a time

[oldticktock]

spot on John just checked MR4 & MR5 no continuity. This is where I stop until I get some IN4148

Chris

[oldticktock]

Tried the valves as stated a little better but still same result. Shame you cannot use IN4007 got a whole load of them