TV22 MK1 Questions

[Panrock]

Originally Posted by mark pirate

Luckily, the wiring in my set is in very good condition, even the voltage tapping wiring is fine, the only wiring i will replace is the wire to the top cap of the PL38 & the EHT lead, as the insulation has gone hard.

Lots of perished insulation in mine! The voltage tappings have been replaced by new runs of red and green rubber wire, new eyetags at the ends with little sleeves.

I crumbled the insulation off my PL38 lead (by squeezing it in pliers) but was able to re-use the original inner lead by slipping on black silicone rubber 2mm sleeving: RS 399-423.

The original EHT lead could be retained, after first cleaning it then 'reconditioning' with waxoyl.

I spent a couple of hours cleaning the top chassis today, it was a pain cleaning all the melted pitch from the lopt, but at least half of the chassis is now shining!

Looks nice!

Steve

PS. The 'post preview' function here is now only rendering as plain text for me.

[murphyv310]

Hi.
The PL33 is not one of my favourite valves and suffers in a similar way the the UL41. Internal leaks are common and replacing the G1 coupling cap often is not a cure, I have often seen a good 5v on the G1 due to leaks, this of course in the TV22 is reduced at minimum volume as the G1 is effectively below cathode.
The 38 ohm as Boom says can be trouble it usually fails though due to the 0.7uf hum phasing cap going leaky or short.

[mark pirate]

I managed a little more progress today, the top deck is now finished bar 3 caps, so i made a start on the receiver, this has had no previous repairs since new, again, the wiring is all in good condition, so it has just been given a good clean.

I made a list of all the caps to be replaced, there are 23 in all!
After checking my stock, it turns out i am 9 short, and they are not on my order

So it looks like it will have to wait until after Christmas to be completed.


Mark

[Panrock]

This TV22 is now running nicely. The alignment issue was caused by something that's probably quite common - the cores of L3 and L4 had broken off and were flopping around inside their formers and the core of the L5 'channel adjuster' was found to be missing!

The ion trap broke during adjustment. I was able to fit its magnet to another one - lacking its magnet!

I noticed a 'kink' on the Test Card near the top of the frame. I've seen this before on TV22s. This was removed by deselecting the equalising pulses option in the Aurora. The TV22 prefers an original-spec signal in this regard.

Steve

[mark pirate]

I have now fitted all the capacitors in the top deck & fired it up, the LOPT looks OK, but I now have frame collaps. I have checked the frame output valve by subbing with a known good one, but no joy, the frame hold control has no effect, I am working from Trader Sheet 1003/T15.

Any ideas where to check would be most welcome.


Mark

[Boom]

Check the frame blocking transformer. It will almost certainly be o/c. Don't dispair there are ways around it.

The transformer is at the end of the paxolin panel on the right side of the set (from the front.) It should measure some 500-600 Ohms each winding and one winding will probably be o/c.

[mark pirate]

Dave, I am sure the frame blocking tx is ok (see post 11) if I measured it correctly.
I seem to remember taking the readings across the windings vertically as seen in the photo.
What voltage readings should be on the blocking tx?
There is plenty of EHT, and plenty of brightness, so hoping the tube is a goodun,

Mark

[Boom]

Right I have a board in front of me Mark and the windings are certainly as you say so (unusually I'd have thought) it doesn't seem to be the transformer.

A very nasty one I did come across a couple of times was if the tube has been taken out the wires from the scan coils can stick to the glass and get ripped. I'd think you would hear a buzzing from the FTB though if that had happened.

Did you get the caps' you need and have they been replaced on this board?

Sorry I don't have a set handy to measure the voltages from.

[mark pirate]

I have been reading the Bush manual, it has much better info than the Trader Sheet, I have just checked the readings again, a bit higher than the spec, but not o/c, (I took the measurements with the tx in circuit) the scan coils have not been disturbed, I have re-checked my work, and all appears fine, the set has never been messed with prior to my ownership.
This has got me baffled!
All the caps have been replaced apart from the smoother, which is fine.

Mark

[HamishBoxer]

Check voltages around the frame output valve.

David

[Ed_Dinning]

Frame op trans o/c pri? Check for volts on anode. Poor joints on trans tag panel?


Ed

[mark pirate]

This gets stranger by the minute, i have tried three different meters on the blocking tx, all give a comparable reading on the secondary, but quite a variation on the primary, so i have disconnected the primary from the tag strip, now it is reading o/c
The frame tx is spot on spec, so i now need to find a blocking tx, i have heard that most will work in the tv22, but ss law says i have nothing suitable to hand, i could get it rewound, as the chances of finding a good one are pretty slim, looks like it's going back on the shelf for a while....

Mark

[Boom]

Sounds like it was intermittent and just about to go Mark. Maybe volts from the meter saw it off?

I've never taken one apart but I wonder where they go? If it's at the end you might just be able to salvage it.

Just had a look at the circuit and I can't see any reason why the transfomer can't be tested in circuit.

[HamishBoxer]

The transformer is not too critical apart from not being o/c.Plenty of small similar transformers will work.

David

[mark pirate]

Dave, I think you are right, maybe one of my meters killed it, I wonder how much a rewind would be?

I don't really want to dismantle it, in case I decide to get it rewound.

the transformer is not too critical apart from not being o/c.Plenty of small similar transformers will work

I have plenty of small transformers, mainly from wall warts & audio output transformers, but sadly none from old tv's, I have read that a transformer from most sets will work, I supposeIi could borrow one from another of my sets?

Mark

[Boom]

Both Ed Dinning and Mike Barber rewind these. No idea of the cost but don't think it is a fortune.

[murphyv310]

Hi.
Absolutely NO way can your meter kill a transformer, I remember also posting a thread a year or two ago explaining that it also was impossible for the transformer to be destroyed by any fault in the set even if it not been recapped.
These transformers go O/C purely because of dampness and corrosion (Green spot) or physical damage, my TV22 and a shed load of repairs I have done for third parties use any other blocking osc transformers I have to hand and their DC resistances differ wildly.

[Boom]

Sorry Trevor but with great respect for your knowledge I'd disagree.

My understanding is that it is green spot that sees the wire off rather than any brute forced electrons under a fault condition.

If the wire is slowly getting eaten away there probably will come a point when the extremely small volts from a meter will be enough to blow apart what copper is left so it is very possible that Marks transformer did read ok first time around.

The wire could also have broke off when the transformer was being handled of coure

[murphyv310]

Hi Boom.
The point I am making is a "good" transformer can not be damaged by a meter or the set. An already badly corroded transformer could fail even it you sneezed at it!