UK Vintage Radio Repair and Restoration Discussion Forum

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-   -   My first telly TV22 (https://www.vintage-radio.net/forum/showthread.php?t=174941)

Travellingwave 7th Jan 2021 4:14 pm

Re: My first telly TV22
 
1 Attachment(s)
I've measured most of the resistors and put the results on attached spreadsheet. Im inclined to wait and see when I get power on before changing any - even though some are quite a long way off

Any views ? are any values especially critical on this set?

Need to get an order off for new Caps and any resistors I may need

Helder Crespo 7th Jan 2021 4:24 pm

Re: My first telly TV22
 
Quote:

Originally Posted by Travellingwave (Post 1328087)
Thanks Helder
So is it best not to heat the lopt after treating with white spirit but rather leave it to help with varnish impregnation?

Yes, this is what Argus25 (Hugo Holden) recommended, and what I did with my second LOPT. White spirit is also the solvent for marine spar varnish, as well as for transformer varnish, and will be gradually replaced by the thicker varnish. In the first dip I left the transformer immersed in varnish overnight, as had been recommended by Hugo. This method has been used by several forum members, who vouch for its effectiveness. The tradeoffs: it takes some time to do as the LOPT should be left to dry after the last coating for at least one week. I used 10 consecutive dips with some time (1-2 hours) in between to allow the varnish to become tacky and less runny, which typically results in a final thickness of 0.5mm). Also, it will not look the same as the original pitch coating, but it does look good and Hugo's LOPT has been working for many years without problems. This was first reported here: https://www.vintage-radio.net/forum/...d.php?t=141634
The advice to dip the LOPT in varnish while still wet was given elsewhere (maybe a post or a PM).

stevehertz 7th Jan 2021 4:26 pm

Re: My first telly TV22
 
Quote:

Originally Posted by Travellingwave (Post 1328089)
I've measured most of the resistors and put the results on attached spreadsheet. Im inclined to wait and see when I get power on before changing any - even though some are quite a long way off

Any views ? are any values especially critical on this set?

Need to get an order off for new Caps and any resistors I may need

Nice listing. My own 'mantra' is replace resistors that are more than 20% outside the stated value. Ok, in some places it may be more critical, but in general up to 20% won't make much difference, especially when there are pots to adjust many settings.

Helder Crespo 7th Jan 2021 4:37 pm

Re: My first telly TV22
 
Quote:

Originally Posted by Travellingwave (Post 1328087)
Thanks Helder
So is it best not to heat the lopt after treating with white spirit but rather leave it to help with varnish impregnation?

To complement my previous reply, this is the thread where Hugo refers to dipping the LOPT in varnish while only superficially dry, so there is still white spirit deep within the windings:
https://www.vintage-radio.net/forum/...=157811&page=2
So no heat required prior to the varnishing step as water/humidity has already been displaced by the white spirit.

Travellingwave 12th Jan 2021 4:02 pm

Re: My first telly TV22
 
1 Attachment(s)
Just dipping my Lopt in transformer varnish

Helder Crespo 12th Jan 2021 4:34 pm

Re: My first telly TV22
 
Quote:

Originally Posted by Travellingwave (Post 1329996)
Just dipping my Lopt in transformer varnish

I think it's looking very good. Note that it's also important to varnish the primary/secondary windings "hidden" inside the former (the ones that usually fail).

Travellingwave 12th Jan 2021 5:13 pm

Re: My first telly TV22
 
So should I pull out the primary? I was planning to leave well alone unless I find a problem with them. I was thinking it best not to get varnish inside the core incase the primary windings do need to come out at some point.

Helder Crespo 12th Jan 2021 5:32 pm

Re: My first telly TV22
 
Quote:

Originally Posted by Travellingwave (Post 1330009)
So should I pull out the primary? I was planning to leave well alone unless I find a problem with them. I was thinking it best not to get varnish inside the core incase the primary windings do need to come out at some point.

If left untreated its insulation may fail. There are several reported cases in the forum of LOPTs developing S/C primaries after a few hours of operation, which then required rewinding. This is what happened to the LOPT in my first TV22. As for the one that I recently repaired and varnished, I never fully disassembled it and simply dipped it in varnish too. I agree that varnishing will make future rewinds difficult, but I see this as an effective way of preventing failure.

Helder Crespo 12th Jan 2021 6:04 pm

Re: My first telly TV22
 
...
And the idea of preventing failure is also to avoid a rewind, hence keeping the LOPT as original as possible (same interwinding capacitance, same coupling, etc.)

Travellingwave 14th Jan 2021 7:31 pm

Re: My first telly TV22
 
4 Attachment(s)
Caps have arrived , having a go at restuffing some waxies. Ten min in the bottom oven of the AGA melts the wax nicely but don’t tell the missus. Been trying to work out which side of the new capacitors is the outer foil , not sure how critical this is.

ekcopyephilips 14th Jan 2021 7:50 pm

Re: My first telly TV22
 
To tell which is the outer foil connect to a scope and touch the body of the cap between thumb and finger. The orientation that gives less amplitude on the display mean the lead connected to ground on the scope is the negative.

Travellingwave 14th Jan 2021 8:24 pm

Re: My first telly TV22
 
Thanks, don’t have access to a scope at the moment , I think this will be my next present to myself. Tried connecting to my amplifier and judge hum level but not very satisfactory , I guess depends a lot on the value of the capacitor

beery 15th Jan 2021 3:24 pm

Re: My first telly TV22
 
Hi Travellingwave,
It is really not critical in the TV22. Generally the outer foil of new capacitors is marked by a thin vertical line at onea end a the label area, but some capacitors are not marked at all. You might be OK jus making sure that the writing is the same way round as on the original capacitor.
However, like I said I've never had a problem with capacitor orientation in a TV22. I restored my first TV22 by using polyester X2 caps (dives for cover from the backlash), seriously though they are cheap and reliable replacements for waxies, but being rectangular, they just look wrong. However they never have outer foil markings.

Cheers
Andy

Travellingwave 16th Jan 2021 6:59 pm

Re: My first telly TV22
 
1 Attachment(s)
I’ve completed first tag board on the main deck. I managed to restuff all the waxies bar two in which the new ones were bigger than the Origionals . One of these was under the tag board so not visible, the other I covered with black sleeve. The audio output valve cathode bypass cap will be replaced with the restuffed origional when I have a more suitable replacement. The big waxy clamped to the chassis was fun. These big chunky tag boards are much easier to work with than the flimsy vertical ones on the couple of Phillips sets I’ve worked on.

beery 16th Jan 2021 10:35 pm

Re: My first telly TV22
 
Hi Travellingwave,
I take my hat off to you for restuffing the caps in your first TV restoration.
My first TV22 which I restored 25 years ago was not as neat as that. However I've since redeemed myself by obtaining another chassis and restuffing the caps in that.
People have suggested that I was mad to restuff the caps in such a common set as the TV22, however I do like my sets to look old, even on the inside. Anyway, there will evenyually be a time when TV22s that are not full of bright yellow poly caps, although strangely the supply of TV22s never seems to dry up.
Also practicing the skill of restuffing capacitors in common sets has enabled me to gain a reputation that has opened up oportunities for me to restore other people's rare sets.

A couple of points:-
I see you have an electrolytic next to the big green resistor, it might get a bit too hot being that close.
If the warm up time seems a bit long then you have to carefully bend the big green resistor closer to the thermistor (the black rod that looks like an unpainted resistor), you may have to melt the solder on the tags to achive this.
The 16uF capacitor to the bottom right of your picture is probably open circuit. I'm not sure why they fail when the main smothing block is usually fine.
Regarding those tiny 1nF waxies, what I do is slit along the length of them and unwrap the cardboard label. I then glue this around the new slightly larger capacitor, fill the ends with wax and solder them o the set with the gap in the label facing the tagboard in order to hide it.

Ah yes, the Bush tag boards. Whilst I often say that the TV22 is not the best set to have as your first restoration from a technical point of view, it is at least very easy to service. If you had started on the equally common PYE B18T/LV20 you would have had a set with more reliable wound components, but with hard to service point-to-point construction built up in layers. It is much easier to connect a new component to the wrong place in such a set and not notice your mistake.

Keep up the good work.

Cheers
Andy

Travellingwave 17th Jan 2021 10:59 am

Re: My first telly TV22
 
Thanks Beery
I’ve read quite a bit on pros and cons of restuffing- I guess it’s the origional old axe story. As you say one day these TV22 will become rarer - like unmolested MG midgets so I think it’s worth preserving what can be preserved.

Will have a go at slitting the small waxies.

I think the blue electrolytic is more or less where it was when I found it , though it may have had longer leads and been standing further away from the tag board , I’ll have a look at it.

Travellingwave 17th Jan 2021 11:01 am

Re: My first telly TV22
 
Re stuffing also forces me to slow down and work more methodically which is not my normal MO

Travellingwave 17th Jan 2021 11:10 am

Re: My first telly TV22
 
Sorry just realised you are talking about the black electrolytic , that’s a temporary job till I get a better replacement , just don’t like to leave completely loose ends

lightning 17th Jan 2021 6:16 pm

Re: My first telly TV22
 
1 Attachment(s)
My first (and only) vintage TV was a Bush TV24 which is very similar to the TV22.

Although l did have some knowledge l don't know much about vintage TV sets so l started by replacing all the wax covered capacitors, including a couple of hidden ones that are easy to miss.

These TV sets seem to last the decades of non-use very well, after replacing the wax capacitors mine powered up, with HT, but there was no picture.

My friend who knows a lot more about these TV sets let me sweat for a week or so, trying various things, and then came round and got a raster (light on the screen) within thirty seconds.

There's a little magnet on the neck of the tube called an "ion trap magnet" and it was 180deg out, turning it round brought the picture straight on.

Also l expected a "snowstorm" on the screen and it was just white. I thought it must be faulty but apparently this is normal. When l eventually bought a converter the picture was very good.

That was back in 2009 and the TV is still working, l turn it on every few months. Remarkably the tube is good, after 67 years.

Travellingwave 17th Jan 2021 6:46 pm

Re: My first telly TV22
 
3 Attachment(s)
I’ve been chasing down more waxies. Discovered that there are some differences between my set and the trader sheet I have. There appears to be some additional components on the tag board that is mounted on the left side (looking from the front). The 8k resistor appears to be open circuit - it’s quite big any idea what power it is likely to be?
I guess this would have stopped the thing working.


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