And another Bush TV22.

[FERNSEH]

The "Biffa Bin" TV22 is working perfectly so I'm inspired to do another.
The set to be the subject of this topic is another Mark 1 model and was made in early 1953. The 1952 Biffa Bush employed EF91 pentodes in the signals deck, this one has EF80s instead. Note the Eau de Nil mask. It would seem that the 1950-51 models had the white mask and those sets made in 1952 and onwards had the coloured mask.
Just my opinion, but I think the Mark 1 version is the better set. The Mark two has the modified timebase deck employing the PL81 and PY81 valves.
The frame timebase is not as good as the early version. Again just my opinion.

Let's find out if this set is any good.

DFWB.

[Courtney Louise]

Are you breeding them?

[peter_scott]

Originally Posted by FERNSEH

The 1952 Biffa Bush employed EF91 pentodes in the signals deck, this one has EF80s instead.

What was the motivation to change? I have an EF91 Biffa and its RF stuff is no problem. Was there a big price advantage with EF80?

Peter

[wd40addict]

Surely this is a Mk2 because it has EF80s and the externally mounted tag strip, on the left of the RF chassis? This is covered by Trader 1091, whilst the Mk1 (EF91s and no tag strip) is Trader 1003.

I think the very last Mk2s had PL81 and PY81. Before they introduced the TV22A.

Are you getting EHT droop on 'Biffa'

Regards,

Paul

[radiotircoed]

Another great restoration. I'd love one in my Play Room...

[FERNSEH]

Hi WD40addict, The Biffa Bush is holding up really well, so well in fact it has been working for up to six hours without any focus drift and no readjustment of any controls. One thing is sure though, it gets mighty hot.
There seems to be some confusion about what defines a Mark 2 model. I was always under the impression that the TV22A was the Mark 2, however, that might be incorrect and the TV22 models with EF80s are the Mark 2 sets.
Hi Peter,
Bush actually used the EF91 again in the 1953 14 and 17" BBC only models. Perhaps it is more likely that by 1953 Mullard did not consider the EF91 as a "current equipment type" and suggested to TV set designers the valve to use was the EF80.
The EF91 continued to be used in industrial and military equipment.

Returning to the set which is the subject of this topic. Pre switch on tests revealed that the on-off switch was OC. This part was brought back into service by employing that old trick of spraying switch cleaner over it, actually WD40, and heating the connection tags with a soldering iron. This creates a switch cleaner vapour inside the switch and this helps to remove the tarnish on the contacts.
Contact resistance is down to 0.2 ohms.
The mains filter capacitor has been clipped out. The set was plugged in to the mains. No fizzes or bangs and in due course the heaters lit up, the measured HT crept up to 175 volts, then after a while the HT volts started to fall back and there was a funny smell and smoke appearing from somewhere on the upper deck. Switch off. more tests necessary.

DfWB.

[Heatercathodeshort]

Originally Posted by Courtney Louise

Are you breeding them?

They do breed. It all started when a rampant TV12 broke into the TV assembly shop at the factory overnight in 1950 and created havoc. It may have been this one, I've named him 'Benjie.' He can be seen hiding on the top shelf..
These two appeared in my 'museum' together with the one with the pink mask. It took me six weeks to notice there were additions to the family. J.

[FERNSEH]

I've got other TV12 and TV22s hiding somewhere in the shop.
Looks I might have to change my avatar, why not dump a Masteradio TV in the Biffa bin?

DFWB.

[mark pirate]

I always thought the mark 2 had the EF80 RF deck, but the upper deck was the same as the mark 1?

Not too sure about them breeding, but I have two Pye LV20's looking at me as I type, there was only one there yesterday
I will restore these as a breeding pair!

Mark

[Stubble]

I just love them, I'm on the look out for a tv12 or 24 we must save as many as we can from the Biffa bin.

[FERNSEH]

I think we have cleared up what defines as the mark two version. It is the TV22 fitted with the RF deck with EF80 valves. The TV22A is therefore considered as a different model.
Some late production TV22 sets employ a PL81 instead of the PL38 line output valve. My favourite device, an adaptor plate, is used in order that the B9A valveholder can be fitted in place of the octal socket.
I have tried with no success a PL36 as a substitute for the PL38 although another Forum member tells me that he has tried the 30P19 successfully.
The base connections of the 30P19 differ from those of the PL38 so the valveholder has to be rewired. The alternative is to make an adaptor.

DFWB.

[FERNSEH]

OK, it's Monday, Monday and I'm back in the shop so let's get it it on and fix this thing.
I gotta feeling this one is going to be an easy fix.

Let's find it that is the case.

DFWB.

[yesnaby]

Hello,

Is this you (or HKS?) after secretly restuffing a Visconol?

Michael

[FERNSEH]

This is too good to be true, results already.

DFWB.

[FERNSEH]

Originally Posted by yesnaby

Is this you (or HKS?) after secretly restuffing a Visconol?

A green Biffa bin. I'll have to have one of those.

Well I've got a picture of sorts. All the usual capacitors will have to be replaced. The sync coupler for starters, the verticals are ragged depending on picture content. The HT voltage is a bit low at 168 volts, the PZ30 rectifier could be low emission or something is dragging the HT voltage down.

DFWB.

[mark pirate]

Looks very promising, should be a straightforward recap. I hope to see this finished by the end of today

Mark

[FERNSEH]

This set is a Mark 2 model and has the PL81 line output valve. The valve is a yellow label sixties replacement dated B4D2, that's April 1964, so like the other TV22 I serviced recently this set was obviously still in use eleven years after it was purchased. Perhaps it was used as a second set?
Replacing the 0.01mfd coupling capacitor between the line oscillator and the control grid of the PL81 has resulted in an increase of EHT voltage, up from 5KV to 7.5KV. I've replaced the sync coupling capacitor and now the line and frame lock is improved, but it could be better so there is still more work to do in that department.
I'll now turn my attention to the frame timebase. Recapping required there for sure.
A picture of the line timebase compartment and the PL81 on it's adaptor plate.

DFWB

[FERNSEH]

Getting better. I changed the four 0.1mfd capacitors in the frame timebase without testing them, they'd almost certainly would have been leaky. Also, replacing screen grid decoupling capacitor of the sync separator valve has improved the line and frame lock.

DFWB.

[Valve'n'vinyl]

Coming along nicely ! Well done !

[FERNSEH]

I've signed this job off for the time being. Picture and sound quality are fine but I can't squeeze out enough width. The valves are OK, the HT is up to 195 volts and the line drive conditions are correct. This could possibly be the line output transformer.
Any ideas?

DFWB.