Pye v4

[oldticktock]

Trying to ascertain volatges varied by the contrast pot are ok, does anyone with a V4 know if the below is normal

There are 3 tags on the contrast pot, but the query relates to voltages measured on just two.

1. The tag which is connected to pin7 of V2
2. The tag which is directly connected to R76 (15K)


Tag connected to pin7

When contrast rotated fully anti-clockwise (observerd from the back) voltage measures 17mV, screen is blank. When rotated fully clock-wise voltage measures 201V testcard displayed

Tag connected to R76

When contrast rotated fully anti-clockwise, voltage measures 198V, screen is blank. When rotated fully clock-wise voltage measures 200V testcard displayed.

Thanks
Chris

[Steve_P]

I hate to tell you this old boy, but those 3 pictures you posted a few messages back do look to me like a faulty tube.

There are a few drastic things you can do if you have the gear and the courage, but they are very much kill or cure. I know you have put a lot of work into this set, but you really do need to find a better tube or you will probably be wasting your time.

You could put an advert in Parts Wanted to try and find one, but I don't think you'll get it much better with that tube.

What do others think.

Cheers,

Steve P.

[Boom]

Originally Posted by Steve_P

I hate to tell you this old boy, but those 3 pictures you posted a few messages back do look to me like a faulty tube.

Two minds without a close up look but post #473 says maybe, maybe not. How about measuring the beam current on a testcard?

Dave

[oldticktock]

I defer to greater experience than mine, but one thing I've learnt from this set is, it has given the impression on more than one occasion of being ready for the knackers yard only to surprise us and come to life.

My diagnostic skills are exhausted as am I, but as I have said before I will fight this PYE into submission before I have to accept defeat. What I need is some pointers as to what test to carry forward with at this stage.

I still have not changed the remaining old diodes as I don't just want to poke and hope.
So we have, 1x Vision interference diode, 2 x interlace filter diodes,1 x sound demodulator diode, Electrolytics and a complete resistor scan to do. I did change R10 which had gone high and It might be wishful thinking but there did seem an improvement.

Chris

[murphyv310]

Hi
The tube looks low emission, I was under the impression David already told you the tube was only good for test purposes.

[oldticktock]

Hi Trevor,

Yes David did state that but remember, being new to this I did not really know what effects that would have on the picture. If low emission dictates what i'm getting then I understand and shall accept that I have done all I can do.

Time to move on to the TV22, hopefully the FCS will have sorted that today

Chris

[murphyv310]

Hi OTT
You might be able to give the tube a tickle, but dont consider a tube heater booster transformer as this tube has already shown that it has suffered with a partial shorted heater.
There are still issues with the set, poor LF response for one which is causing the bending verticals snd streaking, the AGC isn't right, there are feedback caps from the line that could be off value. Yet again I must ask have you set up the line oscillator as per the manual?

The reason I am asking is this is a LINE GATED AGC set and the correct adjustment and set up is paramount to correct operation of the AGC. If you havent done it well if you were my apprentice you would have been booted up the workshop! This IS the third time I have asked!

[oldticktock]

Hi
I have not set up the line oscillator from the manual as I don't know what manual you are refering to.

I recently got the R&TV servicing manuals from a chap but it would seem I had some poor luck there too. I asked for the manuals covering 1950-1960. I ended up with
1953-1954 (Vol V)
1955-1956 (models)
1956-1957 (Vol I)
1957-1958 (Vol II)
1958-1959 (models)
1959-1960 (Vol IV)
Radio post war (a-k)
Radio post war (l-z)
TV (a-k)
TV (l-z)

So the only reference I have to V4 is in the TV(l-z) I'm guessing the more detailed info is in the 1952-1953 book..... typical

I'm glad you mentioned the Testcard grid as I was thinking surely the non straight lines on grid cannot be down to low emission. Sorting out these issues are what I wish to do and then I can rest.

Last pic for tonight.

Edit:
Trevor please don't get angry, I have either missed your posting or forgotten we talked about it, I have no intention of ignoring your advice and I shall endeavour to find where it is detailed or where we discussed it. Hopefully from my endeavours you can see i'm trying to listen and learn and value all the input people offer.

Sorry
Chris

[Alistair D]

Tut tut Trevor. If you were my journeyman and had kicked me up the workshop for not doing something you had not properly explained how to do ( I am an apprentice after all) I would have kicked you back down the workshop and the some more. Please lets get this wonderful thread back on track.

[murphyv310]

Hi.
Apprentices should always say why they didn't do something But this was a wee joke lets not get serious, I did say to Chris where it was explained and the manufacturers VT4 manual explains the best.

Why I did ask it to be done is for this reason.
The V4 line osc has to be correct with no phase errors, if this happens the picture will not basically be in step with the oscillator it can be shifted to the left or right with foldover seen on either the left or right, this means the returning pulse from tghe line stage does not tie in with incoming sync from the video amp/sync seperator, this then leads to the AGC not operating correctly.
I am just about to leave for work so from memory there are to shorting links to be applied to the osc one removes sync and the other shorts the coil out on the cathode of the osc, the set is turned on and left for 15 mins the hold is set mid position and the trimmer set for slow running through of the picture, the short is then removed from the coil and this is then set to do the same as well the short is remove to restore sync feed and hay presto.

[Heatercathodeshort]

Have you replaced our old friend the sync coupling capacitor? Still looks a bit cogged and this can upset the sync with this model more than a standard receiver. Odd operation of the contrast control is normally due to a fault in the APC circuit. The tube looks fine for test purposes but don't expect it to give a brighter picture. The picture should however be of good shape and stability. J.

[oldticktock]

Hi John,

If that's C36 then yes, already changed that a while back, I remembered cogging was related to the sync decoupling cap but still learning to recognise the correct components from schematics.

Hi Trevor,

With regards to the setup of the line osc. I checked back through the thread your first mention was #421, I responded vaguely in #423 but was side tracked by a cap in that area.

Next mention was #453 I responded directly to that in #455 and made reference to your previous request (#421) to perform line setup.

Then there was your third request, I was not ignoring you as can been seen, your apprentice was communicating and responded to all requests about line setup, maybe not loud enough but it was there, that i did not have access to the data to perform the setup.

To make it very clear I do not have access to the line setup procedure, and I do not have the PYE manual. If anyone has a copy I would be grateful or can list the steps required.

Please remember I am new to TV's only started on March 25th 2010 not even 2 months yet, what were apprentices like at that stage, maybe i'm doing badly in which case I will try harder. I bet most of them you sent off to the stores to ask the storeman for a component called "long wait" to which he obliged



Chris

[oldticktock]

Until I get some info regarding the line setup or I find the PYE manual and if C36 is the sync decoupling cap, I decided to go over my notes. I found after all the issues with the CRT heater and then the neck tapping I had never revisited the ION trap to see if it was aligned to it's optimum, It was not. It seems to be in the best position now and brightness was greatly improved.


When the set is first turned on it takes a while for the testcard to grow and fill the entire screen, Geometry is still off, also as time passes and it's left on the picture increases in height a tad which has to be reduced using the rear vertical linear and amp pots. I guess this maybe all sorted out once I do as Trevor suggests, and or components.

Chris

[PJL]

What happens if you tweak the sensitivity? Did you ever find C14?

[oldticktock]

Hi Peter,

C14 replaced, sensitivity is full anti, if I advance it picture gets worse

[ppppenguin]

I'm wondering about putting an attenuator in the Aurora output. I know the set should be able to cope with the nice strong signal but it's worth a go.

[oldticktock]

Hi Jeffrey but would any of that effect geometry of the test card? thats what I feel I need to get sorted.

about 36 hours ago I had to operate with two stacked attenuators 2x6db then some components were changes and I had to reduce to 1 then some more and I found that it was better with none. I just don't know anymore I'm in the wood with the trees at the moment. I can try putting them back in. Like I said is the going to asist with geometry if not then maybe it should wait.

[Steve_P]

No it wouldn't.

Cheers,

Steve P.

[ppppenguin]

Won't help the geometry but that's good enough for now. The real problem is all the bent verticals and smearing. This can be affected by overloading, hence the attenuator suggestion.

[Boom]

Chris, I'm puzzled as the geometry seems fine. Just needs adjusting for the bottom lin'.

Dave