TV22 in Italy restoration: first light

[Giulio Maiocco]

Hello,

This is a photo of the first light on the screen of Angelo (Ferrari on this forum)'s TV22. It seems quite OK, I played a DVD on it and the image quality is fairly good for such a small screen, I'm used to at least 17" screens

I have 2 questions:

- What control(s) should I touch to eliminate the "egg shaped" problem in the test pattern?
- I measured the boosted voltage, finding out it is only 265V, vs the 290/300V I read somewhere, is it a problem pointing to a weak PZ30? I made the mod Darius recommend (the 2K2 resistor between the boost voltage and the PL38 screen grid)

Please note that the CRT is very weak, this is about the maximum brightness you can obtain before the image goes negative!

Many thanks

Giulio Maiocco

[Dave Moll]

This looks like a line linearity problem. I hope I am correct in thinking this is the control labelled "horizontal form" (T5).

[yagosaga]

Originally Posted by Giulio Maiocco

Please note that the CRT is very weak, this is about the maximum brightness you can obtain before the image goes negative!

This is an excellent result for such a CRT. Conratulations.

Please don't try to improve the CRT performance, this might damage it.

Kind regards,
Eckhard

[Giulio Maiocco]

Hello,

Ok, I tried the "horizontal form" regulation, but it has a little effect only on the left side of the screen, is it possible that my problem has something to do with the hor. drive?

Also, it seems that with the hor. amplitude at the maximum, the image just barely fills the screen, I think it has something to do with the boosted voltage being a bit too low, but I'm not too sure about it. The filament string voltage is quite right on the money, being about 177V and the sum of the various filament voltages should be 176,7V so this "problem" is not caused by the filament string being underrun

Eckhard, I'm very happy with the results of this CRT and I know I can't do much about it, I think that the only solution is to find a better one

Once I have fixed these problems, the TV could return to Angelo.

Cheers

Giulio

[wiwior]

Hello Guilio,

Congratulations for the results. It appears that your picture is correct as Eckhard I think you don't improve crt.
Try to check it with a a crt controller; I had nearly the same problem with my Bush TV24 and I was sure that my crt was too weak; In fact the voltage wasn't perfectly correct.

You can also check your ion trap.

Sincerely as all

wilfrid

[Giulio Maiocco]

Hi Wilfrid

I also understand a little of French, so this in reality is not a big problem for me. Just don't ask me to speak French, or at least forgive me for the numerous and big errors, as I studied it over a decade ago!!

I used a CRT tester and the result is that the CRT is almost dead!

The voltages are about right, the plate voltages being a tad low all over the circuit!

I may try to move the ion trap, I haven't moved it just because it seems to be hold in place with some sort of glue and the raster is not bad. Honestly with such low result I had from the CRT tester, I was very surprised to have any light on the screen at all, let alone in the daylight!

Best regards

Giulio Maiocco

[yagosaga]

Hello Giulio,

Originally Posted by Giulio Maiocco

I'm very happy with the results of this CRT and I know I can't do much about it, I think that the only solution is to find a better one

This CRT is abolutely OK. I assume that the picture will become still better when using it regularly. And there is no need to search for another one. These early TV sets were used extensively, and therefore you probably won't find a better one.

Regarding picture width and centering: Paul Stenning provides the trader service sheet with all informations. You should purchase it. It is available also via email for a small amount of money.

Kind regards,
Eckhard

[beery]

Hi Guilio,
I would say the CRT looks ok.
Things to look out for...

Check that the vision interferance limiter is not causing a problem, it should be turned fully anti-clockwise.
Ensure that the brightness control works properly rather than being 'All or Nothing' due to an o/c brightness control.
Check that components are in the right place in the Line output stage, such as the 0.2uF connected to the Horizontal Form control.
For good line drive try replacing the ECL80 as the triode section of this valve is not up to much.
Try some other PL38 valves if you have any, their performance seems to vary in some work better in some models rather than others.
Check that the two 2uF 250V electrolytics in the Line output stage have been replaced (one is on the scan coils).

That's it for now...

Cheers
Andy

[murphyv310]

hello Guilio.
Thats a nice picture you have on your TV22.

I have done a few of these sets now and have found a few faults that may be your problem:
Even with 176v on the feed to the heater (filament) chain you may have only around 5.6v on the CRT instead of 6.3v, this could be for two reasons - A partial short on the CRT heater, or leaky decoupling capacitors that are in the RF unit.

Checks to make:
The CRT heater volts and the total current drawn for the heaters (breaking the chain at the live side of the PZ30)
The current drawn at the earthy end of the CRT heaters; the current drawn at the top of the chain and at the crt end should be the same, if it is lower at the CRT, change the capacitors that decouple the heaters. If the current drawn is the same both ends and the CRT volts are low you may have a partial short on the CRT heaters.

Regarding poor linearity on the horizontal deflection, all the settings are dependent on one another; eg linearity, width & drive.

One other thing to check - has the line transformer black pitch melted at any time?
It may have overheated and have shorted turns. Also are any visible laminations rusty (corroded)? This may explain low width and boost.

Trevor

[Giulio Maiocco]

Hi Trevor,

I replaced all the capacitors, well, except mica, so the "danger" of a leaky caps is greatly reduced! I could easily measure the filament string current simply unscrewing the wire from the mains dropper and putting an AC ammeter between these two points. The lamination on the LOPt is just a bit rusty, but it seems to work OK! The EY51 is not fully lit, I mean you can clearly see the filament lit, but the cathode is not the typical orange color. If you try to draw a spark from the PL38 top cap, it is practically non existent!

I don't know if this means something...

Cheers

Giulio Maiocco

[Giulio Maiocco]

Hello,

Now it seems that the hor linearity is much better than before, the ECL80 in the hor oscillator seems to be very healthy, as I had to reduce the drive quite a bit. I checked the filament string and all is fine, the CRT fil voltage is 6,7V, and the current is OK

[murphyv310]

Put the cabinet on, sit back and relax and enjoy.
Trevor

[Giulio Maiocco]

Hi,

Thanks a lot for your appreciations!! I'm happy you like my work!

Unfortunately I don't have the cabinet, I should ask Angelo if he can bring it next time we meet

Here are some more photos of the chassis, I THINK my work is presentable, but any remark is welcome!

[yagosaga]

Hi Giulio,

How did you bring the CRT back to life?

Cheers,
Eckhard

[Giulio Maiocco]

Hi Eckhard,

The emission on this CRT is still quite low, but my CRT tester has the rejuvenate function in 3 steps of "strength", in fact when I rejuvenate this CRT, I saw the corona you mention around the cathode and it seems quite watchable now! I hope to find a TV22 for myself, but the problem, aside the money, is the space, I have at least 30 TV sets at the moment!

Cheers

Giulio

[ferrari]

Hello
Congratulations to the great work Giulio has done! Wonderful results.
The cabinet will soon come, still needs some good wash, I'm reconditioning the original writing on front knobs (gold block letters writing) and the front central BUSH writing in gold too.
Cheers, Angelo