Bush TV22 with TC184 B3 converter.

[FERNSEH]

Hi Lloyd,
The CRT is the original Mullard MW22-16. Displays a very bright picture.

DFWB.

[peter_scott]

Originally Posted by FERNSEH

Another News Flash! The line output transformer is OK and the low EHT fault was caused by the 4mfd boost capacitor having gone low capacity.
DFWB.

David that's brilliant! But 4uF??

Peter

[FERNSEH]

Hi Peter,
Boost capacitor C21.
4 microfarads was the value of the old boost capacitor and I've seen other TV22 receivers with this value for C21.

DFWB.

[HamishBoxer]

Did some one say a while back to soak the over wind in WD40?

[wd40addict]

It was murphyv310:

https://www.vintage-radio.net/forum/...ad.php?t=24655

[beery]

Originally Posted by FERNSEH

Another News Flash! The line output transformer is OK and the low EHT fault was caused by the 4mfd boost capacitor having gone low capacity. It and the 2mfd scan coil coupling capacitor were replaced this morning. The latter replaced by a non polarised capacitor.

Turned out ok in the end then. I suppose that means there is no need to do any silly jellypot modifications

Cheers
Andy

[Argus25]

Originally Posted by HamishBoxer

Did some one say a while back to soak the over wind in WD40?

This is could be a viable option, pitch does dissolve in WD40 (not as readily as mineral turpentine) and therefore it is a possible solvent option for the pitch, and it obviously did work from the description, where the transformer in question was re-coated in pitch. So I guess, one could argue it would look original after that.

I only have a couple of misgivings, it appears that WD-40 is hygroscopic, see:

http://worldphaco.com/uploads/THE_WD.pdf

and pitch itself has a tacky surface. I prefer varnish (and I also coat my restored waxies with this) because dust doesn't stick to it after it dries.

[FERNSEH]

Because the Bush TV22 is becoming scarce I've found an alternative set to dump in the Biffa bin.

DFWB.

[Lloyd 1985]

I've got a couple of round Ekco's that can join it

Regards,
Lloyd

[peter_scott]

David, I think that's great news! I might then be able to find a scrap chassis to fill my empty cabinet.

Peter

[FERNSEH]

"I've got a couple of round Ekco's that can join it"
Hi Lloyd,
I've got one round Ekco that should really be put in the bin, but that's not going to happen, it's gong to be fixed.

"David, I think that's great news! I might then be able to find a scrap chassis to fill my empty cabinet."

Hi Peter, you've got an empty TV22 cabinet?

Meanwhile, my TV22 has been on for more than three hours and is working fine. But, it ain't half hot!

DFWB.

[Lloyd 1985]

Haha, yes, they must be fixed up, not binned! I'm getting there slowly with mine, it certainly is sounding good now!

Those TV22's do get a bit toasty, I had one running for a whole 8 hours at a vintage show once, and because I knew it had a bit of a tendency to get hot I removed the screening can from the LOPT, and fitted a 12V computer fan on the back cover in the ventilation slots, that kept it happy for the day, and it was still working well at the end of the show, sadly that set developed the shorted primary much later on, and is waiting for me to do something about it.

As for empty cabinets, I have a TV62 cabinet in the lock up!

Regards,
Lloyd

[peter_scott]

Originally Posted by FERNSEH

Hi Peter, you've got an empty TV22 cabinet?

No, not a TV22 but a Philco People's Set. If memory serves me correctly it's a 444.

Originally Posted by Lloyd 1985

Those TV22's do get a bit toasty,

I've now tidied up my TV22 LOPT and put the metalwork around it but I'm tempted to leave the lid off.

Peter

[mark pirate]

I've now tidied up my TV22 LOPT and put the metalwork around it but I'm tempted to leave the lid off.

I think that is a good idea, I run my TV22 with the side cover off as well.
I have never liked the heat generated by the PL36 & PZ30 in such an enclosed space, probably the reason all the sets I have seen have melted pitch from the LOPT around it's base, and some have dripped on to the receiver chassis!

Mark

[peter_scott]

Yes, with no surrounding metalwork it ran quite reasonably "cool", well warm anyway. Maybe I'll take the rear metalwork away too leaving the front/side to give better support to EHT lead.

Peter

[Argus25]

Originally Posted by FERNSEH

"I've got a couple of round Ekco's that can join it"

Meanwhile, my TV22 has been on for more than three hours and is working fine. But, it ain't half hot!

This is why in my set I re-wired with RS component's silicone rubber covered harsh environment hookup wire (looks like old fashioned wire too thankfully)Also in mine I replaced all/most of the valve sockets with ceramic versions. One other thing, it is important to replaced the aluminium heat foil reflector shield that lines the top of the inside of the cabinet, or the heat can be so severe it could damage the cabinet. I don't think that was there just as an electrostatic screen.

Maybe they should have put a slot in the back of these sets for a slice of toast.

[FERNSEH]

Hi Peter,
Many years ago I bought a Peoples set which turned out to have been made up from various bits and pieces. The bakelite cabinet is slightly larger than the regular 444 and the chassis came out of a model 296 woodie.
Getting back to the TV22. The interlace is not very good in my set, the problem being that there is line pairing irrespective of the frame hold setting.
Also, the set needs frame flyback blanking. The coupling between the video amplifier does not maintain the DC component thus on scenes with low contrast the black level rises and the flyback lines become apparent.

DFWB.

[Argus25]

I don't think this is correct. There is DC coupling in the TV22 all the way from the detector to the CRT's cathode, it (the DC component) is slightly divided down by the 47k and 270k resistor, only to about 270/(270 +47), so 85% of the original DC value is retained, which is more than adequate.

The reason why, on a TV-22 , or this type of design, the retrace blanking turns out to fail, is the nature of the RF modulation on the video carrier, not being stabilized/clamped. It is the consequence in some RF modulators of not clamping the DC axis of the sync tips (or black level) with respect to the RF carrier being modulated. So the effect of this is identical to having AC coupling in the video amplifier pathway, with no DC restorer and no DC coupling.

I mentioned this elsewhere, where people were seeing a lot of retrace lines on the TV22, and on mine (standard without internal retrace blanking added) I don't see them. My modulators have proper video clamping at the modulator.

Interestingly, in other video amp systems that are AC coupled, if they have a DC restorer at the CRT, it doesn't matter in those if the video signal in the RF modulator is not properly clamped, it makes no difference, even a poor modulator without clamping appears to work perfectly.

So the Bush TV 22 is an excellent set to test the quality of the design of an RF modulator, if you see the retrace lines at times after the contrast and brightness controls are correctly set, the RF modulator in use has poor clamping and its design is sub-optimal. The original transmitted signals from the TV station of course always had this issue attended to, so there were no issues for TV's that used direct coupling from the detector to the CRT.

[Ian - G4JQT]

Since the TV22 LOPT has been discussed in this thread, I'll drop in the detailed measurements I made of three of them a few years ago. I've since measured two more and they more or less agree with the table.

The TV22 and TV24 LOPTs are identical as far as I know, with minor component variations around them in the two sets.

(There are two different methods of mounting them to the chassis - in both models - but that's not relevant here.)

Ian

[Maarten]

Originally Posted by Argus25

I only have a couple of misgivings, it appears that WD-40 is hygroscopic, see:

http://worldphaco.com/uploads/THE_WD.pdf

If I read correctly, WD40 being hygroscopic is a hypothesis for follow-up research. It could also have trapped water underneath, for example.