Golborne Vintage Radio

I've found I have 2 of these sets and only want 1. They've been untouched since I bought them which is a good few years ago. So I thought I'd run them both up to see what the CRTs and LOPTs are like. Not too worried about anything else though I'd prefer not to have to deal with any other wound components that are faulty. Not planning restoration at the moment. The plan is to keep 1 set and flog the other at Harpenden or NVCF.

I put the one with the less good cabinet on the bench first. My usual way of running up a TV is cautious. Isolating transfomer so I can connect a scope safely. Aurora on Ch1 direct to aerial socket in case the set is rather deaf.

Look for caps across the mains. Both had been removed by a previous owner in this set.
Disconnect the HT and get the heater chain running, using a variac just in case. It worked immediately
Reform the main smoothers with HT PSU and resistor. The leakage dropped quickly to an acceptable level
Run up the HT gently with a variac. I actually used a 1N4007 here as it was easier to hook up to the variac and safebloc.
When all was OK I reconnected the HT in the set.

So far, without doing anything bar resoldering a detached lead to the line scan coils, the sound has appeared. Fair bit of hum/buzz but I don't care at this stage. Video present on the CRT cathode. Frame timebase running but not locked. Line timebase running but way high frequency, won't go below 25kHz. Plenty of drive to the LOP stage but as you'd expect it's not doing much at that frequency. Tiny sparks where you'd expect rather bigger ones and a few kV of EHT. The EY51 can't be doing very well at the high frequency. Nothing overheating or looking like it's unhappy.

Not a bad start. I need to manipulate the chassis so I can get at the 100pF preset horizontal hold control. Once the line oscillator is running at the right speed I reckon I'll get EHT and first light. Long time since I've played with an ion trap magnet but it looks like it's not been disturbed.

Not having looked at the VT4 circuit for a long time reminds me that it's a relatively complex set for its day, with flywheel sync and sophisticated AGC.

Service data available from http://www.thevalvepage.com/tvmanu/pye/body_pye.htm including a handy note on adjusting ion traps.

There is enough cable length to pull the chassis out to gain access to the trimmer. On the VT4 the tuner needs to be removed from what I remember. On any I've done its usually a component failure that upsets the line frequency, the discriminator diodes tend to go off on these with time and dampness, I fit IN4148's which work perfectly with a solid lock. Certainly don't need to tell you how to suck eggs but replace the 0.01uf coupling cap to the PL81 control grid and it's bias resistor as a matter of course.
Good luck

The chassis comes out quite nicely, even wit the tuner in situ but I had it stood on its side with the LOP downwards as this gave me good access to most of the circuitry. The line frquency trimmer was then inaccessible. When I get another chance I'll try again with the chassis normal side up.

There's ample drive to the PL81 and the grid is nicely -ve. Though as you say, replacing the coupler is an essential part of any restoration. I would also assume the discriminator diodes are duff. Thanks for confirming my first thoughts that 1N4148 are a good substitute. I also noted that nothing seemed to be stressed in the LOP (or anywhere else) with correct HT voltages and less than 100mA current though the LOP fuse.

My plan at this stage was simply to run up the sets to check that the CRTs and LOPTs were good, with absolute minimum component replacement. Then keep one set with a view to restoration at some point while disposing of the other at Harpenden or NVCF. It's part of a greater plan to dispose of sets that don't really interest me and make space for possible future acquisitions. While I'm not short of space in absolute terms I'm not a compulsive collector. I would rather have a few items that I really want than many that are of less interest. My Philips 563A will be arriving next weekend Thank you Jeremy.

There's a Philips 12" set lurking in the loft. It's either a 485A or 492A, probably the latter. The only reason I'm keeping it is because it might donate a 12" round CRT to some other more interesting project one day.

Hi Jeffrey.
All the interesting stuff appears south of the border and at impractical distances to collect. Pity as there are many sets I'd have bought or taken very happily.

[tongue-very-firmly-in-cheek-mode]

As I understand it, the freedom of movement within the UK enjoyed by the English, Welsh, Scots and Northern Irish was established so long ago that it can in no way be considered to be connected in any way with the EU's more recent diktat on the matter.

Therefore, I propose that, before noon on the 1st of April, we announce that, as that fishy woman keeps demanding independence for Scotland, all Scots in England will be required to return to their own country.

Perhaps Trevor might, during the ensuring outcry and publicity, be able to request volunteers amongst the returning Scots who would be prepared to bring with them the gems which he so coverts in the South back across the border with them?

[/tongue-very-firmly-in-cheek-mode]

(05-01-2019, 02:03 PM)Terry Wrote: [ -> ][tongue-very-firmly-in-cheek-mode]

Therefore, I propose that, before noon on the 1st of April, we announce that, as that fishy woman keeps demanding independence for Scotland, all Scots in England will be required to return to their own country.

[/tongue-very-firmly-in-cheek-mode]

I guess we'd need to give you back our Englishmen too. (I may be mistaken but I think Trevor is an Englishman by place of birth. )(Apologies in advance Trevor if my memory deceives me. )

Peter

The very first set I had was a Pye VT4, given to me when I started work. It had an excellent picture, as one might expect from the extras that Pye added but one night, while were watching it, the line frequency changed abruptly and shot off heaven knows where. It was quite late at night, so that was the end of play for the day.

The following night I started to look into it. First, I got the line speed correct but whether I had to adjust the trimmer, I can't remember  - well, it was 58 years ago!

No line sync, not the slightest trace. Ah, diodes I thought! No change! Feed from sync separator? Nope! Feedback pulse from the LOPT? Nope! Of course, no scope in those days - we didn't even have one at work! I was rapidly running out of ideas, resorting to changing components at random, even though I could see no logical reason for them being responsible.

Eventually, I had to admit defeat.  

One day my colleague Ray, 2 years my senior, asked "How are you getting on with you VT4?" "Given up". I said. So, he suggested we get it in and he'd take a look at it for me.

Of course, everything he thought of, I'd been there before him! Very soon too, he came up against a brick wall but he persevered. Fortunately, it was a slow day with nothing pressing that I couldn't handle.

Time passed and suddenly there was a cry: "Found it!"

I walked along the line of benches and there was the VT4, with a perfectly locked picture. *What was it?" Ray motioned toward an electrolytic lying on the bench with two wires connected to the  chassis. "Main smoothing" he said.

A hard earned lesson but one I'll never forget!

Ha Ha.
Yes I was born in Walton-on-Thames and lived there till we moved to Scotland in November 1957 so I was just three and a half.
There has been a lot of two way migration between Scotland & England and Scotland has a considerable number of retired English, we of course have sent England many as well so personally I think that is fair enough.
Without being political I'm not a supporter of Ms Sturgeon, the vote has been done so lets put it to bed.

Back on track. Yes the V4/VT4 does not like ripple on the HT, why it should be so fussy I haven't a clue but one that I was repairing for a friend in Dollar (Yes in Scotland) had the line way off, I did the same with the usual checks and eventually hooked up the scope only to see massive ripple, a quick stab with the test smoother and the line frequency dropped. New smoothing block cured the issue. So yes its an odd one and only reading this reply by Terry did it dawn on me Jeffrey may have the same problem and one that should have been firmly locked in the old brain.
Nice one

I wonder if the cause of the high line frequency was actually due to the poor decoupling rather than the high ripple?

Peter

(05-01-2019, 05:13 PM)Murphyv310 Wrote: [ -> ]Without being political I'm not a supporter of Ms Sturgeon, the vote has been done so lets put it to bed.

It wasn't intended to be in any way political, Trevor, just a highly improbable way of letting you get your hands on the goodies!

And, if anybody else has got any reservations about this, might I respectfully point them in the direction of the very precise timing of such an (improbable) announcement?

OK, yes, I know it's a tad early for this sort of thing but ...