Pye v4

[oldticktock]

I'm not certain about this but it would seem I have overload as without the 12dB attenuator the testcard is hard to resolve.

Which brings me to wonder about MR3 (overload diode) a CG5E which I should be able to replace with another OA91 as carried out earlier on the MR2 (vision demodulator diode)

Is it worth a try or is the just a wasted component change.

[Boom]

I was still in short trousers when these things were being serviced Chris so have no direct experience of working on them but from what I can read and trust here from those who know far better that I do is that you have to imagine these MRX things as a diodes equivalent of a waxxie. One out all out.

Dave

[oldticktock]

I see Dave, thanks I was not aware of their status duly noted now

[oldticktock]

Whilst on the subject of diode what's the modern equiv of CG6E would that be OA80/81 not 90/91

[FERNSEH]

The germanium diodes OA90 and OA91 are the miniature versions of the OA80 and OA81.
These diodes are real old timers having been around since 1957.
There was an earlier diode, the OA70.

I'd say the the CG6 can be replaced by the OA70/80 or 90. Also consider the GEX34.

DFWB.

[oldticktock]

not 91 then? I ask as I have those in stock.

[FERNSEH]

Try the OA91, it should be OK.

DFWB.

[oldticktock]

Thanks David, I think for tonight I will just replace MR3 and see if the overload is reduced, then do the others tomorrow, another long day today.

[oldticktock]

Final report for the night, the overload has been reduced I do not need the Atten now.

One observation of the test card is as follows when the control is turned anti-clockwise (looking from back) there comes a point when the screen goes blank. If you then slowly advance clockwise, there is for a brief moment, before going negative, a prefect B&W picture the sides of the testcard are still distorted etc but what i'm seeing is the definition resolved not negative.

I have a feeling this means something quite what I have not yet figured out, maybe look again around the ECC82 (V2 osc & APC amp) & EB91(V13 APC samp & rect)


Tomorrow I will replace MR1 (Vision Interference diode) with an OA91 and observe the results.

[Red to black]

Well done so far! mate
Is this your tenth day?
What a marathon.

[oldticktock]

In 20mins it's the 10th day.................... it's a public example of my lack of experience, other more capable people would have dusted this off long ago. I may come close to it but I will not give in, this set is going to give up the fight and work whether it likes it or not.

[Red to black]

No don't give in!.
I have been following your battles throughout the days/day, but did not want to post, and disturb the proceedings
You have done really well especially without some of the test gear req.
Have a.
until tomorrow.

[oldticktock]

and on the 10th Day.......

More work needed, but I think the battle of will's between me and this PYE are starting to turn in my favour.

p.s.

The really sad thing is, this was resolved in my sleep,I was dreaming of diodes!!! woke up had a cuppa did the necessary and result. Even when asleep im still working on this Damm PYE!!!!!

[Lloyd 1985]

Fantastic!!!! very well done on getting it to work, I have to say this set would have tried my patience and ended up on the pile of 'stuff to look at later'!
I'm off to the nvcf in a bit, and if I see one of these I might still be tempted

regards,
Lloyd.

[Steve_P]

You have discovered a trick used in Exams and Repairs alike. When you leave a set, the mind continues to work on it, even in your sleep. I have a pen and paper beside the bed!!

There is an old saying among engineers with sets like this - leave it, have a cup of tea and time away from it. You also return to it fresh and something that was obvious when you return jumps out at you.

Now, sitting here in bed unable to move, there is a set opposite me that I really must look at when I am finally allowed to move....

Nearly there old boy....

Cheers,

Steve P.

[ekcopyephilips]

Hi OTT

That looks great. It inspires me to carry on when i hit a snag. Incidently am i right in thinking that Charles Orr Stanley (Head of Pye at the time) described these as 'shockingly bad sets' when they were released ? And that Pye was so slow to respond to complaints about the performance that from that point onwards lost a lot of dealerships and their technical dominance and that finances also surrered as a result.

Mike

[Mr Hoover]

Originally Posted by ekcopyephilips

Hi OTT

That looks great. It inspires me to carry on when i hit a snag. Incidently am i right in thinking that Charles Orr Stanley (Head of Pye at the time) described these as 'shockingly bad sets' when they were released ? And that Pye was so slow to respond to complaints about the performance that from that point onwards lost a lot of dealerships and their technical dominance and that finances also surrered as a result.

No,fairly sure that was the subsequent model,the V14 I believe,had trouble with a PCF80 as a line oscillator drifting out of tolerance.
There was a quote in "The Setmakers" book that making the V4 and VT4 was like "Shelling Peas" in the end.

I restored my VT4 last year,no major problems,changed a lot of capscitors.
The band 1/3 tuner valve pins needed cleaning,symptom
intermittent/low gain.

Hugh

[oldticktock]

I think I'm going to spend the next 10 days trying to sort out the niggling issues! still not as good as the Bush's yet.

The test card definitions is ok-ish, but when a film is played it was way to dark so had to adjust. When you go back to the test card it's washed out.

This is such a tricky set.

I still think there is an issue around the contrast and maybe the A.P.C. as when the contrast is turned anit-clock-wise the screen goes blank, I believe this is supposed to happen with the A.P.C. When it is turned clock-wise there is a point when the screen returns, but from then on the contrast seems to have little effect. Reading the R&TV book it would seem that the vision sensitivity and contrast need to be set in conjunction with each other, white-spot suppresor control seems to have an effect. This is what I mean anbout being a fiddly contraption.

Will continue to check the circuit, I still have a couple of diodes to dispense with, if they need it, such as MR1 "Vision interference surpressor"

[oldticktock]

MR8 & MR9 the "Interlace filters" which are WX6's, would anybody know what are the modern equiv's of these.

Also

R10 which is connected to pin2 of the Oscillator should be 33K but is 44K that's outside of the 20%(6600 OHMS) tollerance is that ok. I'm still unsure of when you should bring values back in-line.

[Steve_P]

Stick an OA91 in their place and try that.

If you think that resistor being high might be a problem, change it.

Many such parts as WX6's are hard/impossible to get these days, so try an ordinary diode. Experimentation is a vital part of restoring old sets you know. What you find out by experimentation could be of use in the next set.

Cheers,

Steve P.