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Old 19th Dec 2016, 10:57 am   #1
Voxophone
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Default Bush TV22 Mk 1

Hi all,

I’ve finally made my first foray into vintage tellies by picking up a Bush TV22 Mk 1! It’s in untouched condition with all the original components and appears to be in pretty good order, despite some minor corrosion on some parts. I’ve been searching the net and forums for some restoration tips, but I have a couple of questions:

Does anyone have a link for the Mk 1 trader sheet 1003/T15? I have the sheet for the later models but I can’t seem to find this one anywhere.

The top cap wire of the PL38 is very brittle and I think will need replacing. This seems to be the same type of wire as the EHT wire to the CRT, although this seems to be okay. Is there a preferred type of wire for replacing EHT connections? Obviously voltage rating will be important.

One of the first things I wanted to check was the LOPT. I managed to measure two windings from below the chassis, both of which are okay, but I haven’t been able to measure the other windings accessible from above as the tags are covered with pitch. Is it worth chipping the pitch off these tags to confirm winding resistances, or does this run an unnecessary risk of breaking the lead out wires? The area around the LOPT is stained with black soot so if possible I’d like to confirm that it won’t go up in smoke when I eventually power it up!

My set seems to have the common problem of an o/c frame transformer, so this will either be a rewind or a replacement. In the short term however, would it be okay to test the set with this fault in place just to see if I can get a raster? I suppose the fault would just restrict it to a vertical line?

Aside from the above, are there any real danger points to be addressed when bringing one of these back to life? I've restored a few radios by now, so I'm familiar with live chassis, 'that' capacitor etc. But I'd like to avoid a bang when it eventually gets near the mains!

Any advice would be much appreciated.

Cheers

Liam
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Old 19th Dec 2016, 11:30 am   #2
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Default Re: Bush TV22 Mk 1

I use the internal core and clear insulation from the old network coax cable for EHT cable replacement. You may be ok with the lopt but only really find this once the set is up and running upto temperature. The lopts can fail in a variety of ways ranging from a shorted primary to secondary or the overwind could be an issue.
Operating the set with the frame transformer open will produce a collapsed frame in the form of a horizontal line, an aurora will be an essential for testing too.
Apart from the mains capacitor next to the dropper there isn't anything that's likely to go bang. its worth identifying the correct orientation of the mains plug to ensure the neutral is to chassis and not live.
You would have undoubtedly found this but its an excellent guide to a restoration
http://www.radiocraft.co.uk/902.htm
Have a look on http://elektrotanya.com/?q=showresult service info for all the tv22`s is here
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Last edited by Freya; 19th Dec 2016 at 11:37 am.
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Old 19th Dec 2016, 12:57 pm   #3
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Default Re: Bush TV22 Mk 1

Thanks. I have some quite large coax lying around somewhere. I might give that a try, although it may be too big to fit through the hole in the shield.

Unfortunately the link you supplied doesn't seem to have the Trader sheet I'm after, although it does have the manufacturer's data. I have a few bits and pieces printed off already, but I always liked the layout of the Traders for some reason. Maybe one will turn up.

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Old 19th Dec 2016, 1:09 pm   #4
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Default Re: Bush TV22 Mk 1

PM me and I will email it. Note though there is an error on this sheet showing a hard link between windings d & e of the lopt that shouldn't be there.
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Old 19th Dec 2016, 1:20 pm   #5
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Default Re: Bush TV22 Mk 1

Thanks. PM sent.
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Old 19th Dec 2016, 3:03 pm   #6
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Default Re: Bush TV22 Mk 1

Stephen will be emailing it to you, but for general information Trader sheets 1 - 1600 are issued to BVWS members as part of the joining pack.
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Old 19th Dec 2016, 8:49 pm   #7
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Default Re: Bush TV22 Mk 1

Hi Liam, as others have said, a faulty lopt unless really bad will not show up until the set is powered, usually due to leakage between the 2 primary windings. Even if the lams are really rusty they are still OK.
Faulty FBOT will give a horizontal line on the screen and should be OK for tests as long as the brightness is not advanced too far. Easily re-wound.

A good choice of set to start with

Ed
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Old 19th Dec 2016, 11:53 pm   #8
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Default Re: Bush TV22 Mk 1

Watch out for the decoupling caps on the heater chain as if any of these suddenly decide to go short they could really spoil your day by taking out / stressing a load of filaments.

There are several grid caps (AKA that cap), but C27 (trader 1003) is probably the most important to spare the PL38 & LOPT from any extra stress.
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Old 20th Dec 2016, 11:02 am   #9
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Default Re: Bush TV22 Mk 1

Thanks. I think I’ll replace those before powering up. Not worth risking the filaments.

I now have the tube removed to make working easier. The scan coils measure ok which is a relief. Not sure whether these tend to fail but they look like they’d be a nightmare to repair. The focus assembly is covered with black slime which appears to be dust adhering to old lubricant. A bit of a cleaning job ahead I think…

The tube is labelled as an MW22-18, hence should not have an ion trap according to the Trader sheet. It does have a circular clamp around the base of the neck however. What is this for if it isn’t a trap magnet?

Unfortunately the PL38 is already having a bad time as the top connector is broken off! There is a miniscule stump of wire emerging from the glass pip, but I doubt it would be possible to solder to it without chipping off more of the glass. Is it worth trying this or am I basically looking for a new valve?
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Old 20th Dec 2016, 11:32 am   #10
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Default Re: Bush TV22 Mk 1

You've got nothing to lose by attempting a top cap connection but grinding rather than chipping might be more controlled.

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Old 20th Dec 2016, 12:06 pm   #11
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Default Re: Bush TV22 Mk 1

I have used silver loaded paint to fix top cap connections like this but only on RF valves which either have the grid on the top cap or have low anode currents.

The PL38 gets very hot so I would look for a new valve rather than try to repair it. They do wear out so go for a NOS one or at least one that has been tested.
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Old 20th Dec 2016, 1:35 pm   #12
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Default Re: Bush TV22 Mk 1

Use a small diamond file to work the pinched piece of glass, hold the valve in a teacloth or similar in case of failure. once enough of the wire is exposed then make up a tiny curly spiral of single core wire like a resistor end. slide over the exposed end and gently squeeze the coil onto the wire. then solder.
the new long end can then be passed through the cap, glue with epoxy and solder when set.
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Old 20th Dec 2016, 2:08 pm   #13
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Default Re: Bush TV22 Mk 1

I have successfully repaired a few PL38's using the same method as Freya, the only thing I would say is that I tend to use cheap epoxy glue (like that available from pound shops etc) as it never seems to fully harden like the top brand stuff so therefore there is less stress on the glass as the valves heat causes expansion and contraction.

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Old 20th Dec 2016, 2:27 pm   #14
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Default Re: Bush TV22 Mk 1

I wrote a two-part rebuild article on a TV22 mk2. Only the RF deck differs between the two.

If you like I can email you the pdf. Will need your email address via pm.
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Old 20th Dec 2016, 2:36 pm   #15
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Default Re: Bush TV22 Mk 1

Hello Voxophone,

I have restored a TV22. In my view to do this job properly there are no shortcuts.

It is tempting to patch up this and that and try to save resistors and capacitors here and there. Usually in these sets most of the capacitors, the electrolytics and others really need to be replaced. Most of the carbon composition resistors go out of spec too. Often the wiring insulation is brittle from heat cycling and the the tube sockets are worn & corroded.

Modern 2W metal film resistors are about the same physical size as 1950's vintage 1/4 watt ones. New higher voltage rated electros can be put in the large capacitor canister.

In mine the transformer brackets were removed for re-plating as they were rusty and the rusted laminations treated with rust converter and the transformers re-varnished.

As I recall I soaked the pitch off the lopty over about a week in a mineral turps bath (M. turps is the solvent for pitch, but when the pitch is very dry the process is slow), brushing it gently with an artist's brush each day. This got rid of all the cracked old pitch. After that I varnished the lopty winding heavily with transformer varnish before putting it back into service. I would not recommend you attempt that, unless you were very confident. Pitch was a bad choice for an insulator on EHT windings, it always dries excessively, ages and cracks and in its early years it is tacky and attracts dust. It is better dispensed with.

So, for a full restoration I would recommend the view that most/all of the carbon resistors & capacitors & sockets & wire in the set are disposable, that is if you want a reliable long lasting result without drifts and intermittent faults cropping up. Hopefully the input wire wound dropping resistor is OK. Not everyone will agree with this view and think it's too radical (it is just my view). Use 630V rated poly caps everywhere, including the yoke coupling. (the black one you see in the photo near the yoke is a Solen Fast brand) For the RF capacitors, 500V silver mica mil types are best.

The metalwork requires a lot of attention to bring back a good finish. When I finished mine I lacquered it to prevent future corrosion. It gets Toaster Oven hot in these sets and I would recommend using ceramic tube sockets and high temp hookup wire. Also replace the aluminium foil heat shield that lines the inner top of the cabinet to prevent long term thermal damage to that too.

Also, I know you know about the hot chassis issue, it really is best to use a mains isolating transformer and ground the chassis, especially if you are attaching test instruments to it.

My set is here; but it did take a lot of work to get it like this, but it is worth it for one of these wonderful sets:

http://worldphaco.com/uploads/BUSH_TV22.pdf

I didn't take any pre-restoration photos, it looked very similar to the one on the radiocraft site when I first got it.

Last edited by Argus25; 20th Dec 2016 at 2:43 pm. Reason: add info
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Old 20th Dec 2016, 3:04 pm   #16
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Default Re: Bush TV22 Mk 1

Quote:
Originally Posted by Argus25 View Post
I found your article on google before. That's a truly amazing result! I doubt if mine will ever look that pristine, but I hope I can at least get a picture out of it. Unfortunately there appears to be more corrosion on mine, although it’s nowhere near as bad as others I've seen. The case is in very good condition.

The dropper resistor has already tested OK. I currently have it removed for cleaning and to replace the mains wiring. I'm checking the other resistors as I go. No bad ones so far.

I'll probably replace all the waxies and electrolytics in the end, but at the moment I'm focusing on doing only what is necessary for a safe initial power up and test. Basically the following is on my to-do list:

- Replace vital wax capacitors (mains r.f. bypass, heater bypass, output valve grid coupling etc.)
- Replace smoothing electrolytics, as I don’t have the facility to reform these.
- Replace perished wiring. On my set this includes the mains wiring, the scan coil plug wiring and possibly also the r.f. deck and CRT base plug wiring to be safe.
- Replace perished EHT connection to PL38.
- Repair or replace PL38 valve.
- Remove all valves. Test filaments, clean pins and bases, then reinsert.

I might have missed a couple of points here, but that’s the essence of what I’m trying to do before applying the mains.

Ian - I've sent you a PM as suggested. It would be very useful to read your experience with this set.

Cheers

Liam
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Old 20th Dec 2016, 7:24 pm   #17
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Default Re: Bush TV22 Mk 1

Hi Argus 25 , just clicked on the link to your restored TV22.
Wow that is one really shiny TV22 chassis , I can imagine that took a long time to restore to that standard.

Robin
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Old 21st Dec 2016, 5:36 am   #18
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Default Re: Bush TV22 Mk 1

Thank you Line Sync and Voxophone for the remarks about my TV22 set.

Most sets I have restored (HMV904, Andrea KTE-5, RCA621TS etc) were steel chassis types, requiring fine glass bead blasting to remove all rust, then plating with Electro-less nickel that goes down holes and into corners to get a good restoration.(this does not use an electric field in the plating process so there are no holes in the plating)

The TV22 being all aluminium is a different challenge. But I could say that the only way to restore a chassis is to completely strip it down. It is not possible otherwise to get a uniform finish when screws, sockets transformers etc are still in place.

I have seen sets that have claimed to be restored, but if you look closely, there is still rust or corrosion, or paint over rust etc as the set was never disassembled to enable a proper chassis treatment or proper cleaning and re-finishing of structures mounted to the chassis.

Also I could add, I think its much better to take 4 times as long to restore one set properly, than restoring 4 sets in the same time frame but not doing all that was needed on each one.

For the aluminium on the TV22 I used fine grade paper (2000) to remove the corrosion from the surfaces, then an aluminium polish product, they sell in marine stores, made by 3M. It is a thick white paste. It is a messy business with black hands, but once it has been polished I then wash the aluminium parts with a concentrated solution of laundry powder and water. This removes all the polish residue and slightly flattens the gloss of the surface due to the alkaline nature of the solution and micro etching. That way it is possible to get a horrible corroded looking aluminium chassis (like the TV22 chassis when I got it) looking quite respectable again, like it was when it was new.

Never go below 1000 grade paper as this leaves surface marks that are very difficult to polish out. 2000 grade is as coarse as I use for this job mostly.

One interesting thing about the 3M polish, on the label, in fine print, it said something like "3M will not be responsible for any damage caused by this product regardless of any theory put forward by a lawyer". That really made me laugh, 3M must have been burnt in the past by ridiculous product liability claims. Mind you my wife has a sweater that says on its label "do not iron while wearing". I wonder how that label got there ?

Last edited by Argus25; 21st Dec 2016 at 5:45 am.
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Old 23rd Dec 2016, 12:21 pm   #19
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Default Re: Bush TV22 Mk 1

A quick update and a couple more questions:

I've started replacing selected wax capacitors with 630V Polypropylene, focusing on the r.f. deck and heater decouplers for now. I've received some silicone wire from RS to replace the perished originals as I doubted my usual PVC would stand the heat.

One of the wiring assemblies in need of replacement is the scan coil lead from the tube. I'd like to avoid removing the coils if possible. Is there any reason why I can't replace the wires to the tag board with it still on the neck of the CRT?

On the subject of the CRT, I'd also like to clean the focus assembly. Mine is the polar opposite of Argus's nice clean effort above, and I can't move the handle without feeling like I'm forcing something. What's the best way to clean this without demagnetising anything?
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Old 26th Dec 2016, 11:51 am   #20
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Default Re: Bush TV22 Mk 1

That wire from RS is a good move. Once you have used that its hard to go back, because it is completely resistant to soldering iron temperatures and doesn't melt or retract near the soldering and it even looks like old fashioned rubber covered wire.

There is no real need to remove the yoke from the crt if you don't want to. It would only need to be loosened for cleaning or adjustment/rotation.

For permanent magnet focus assemblies it is best not to take the magnets out of the pole-pieces as they can loose magnetism. The pole piece assembly acts like a Keeper. So try to clean up the assembly as best possible and lubricate it without pulling it completely apart.

In cases where the assembly did have to come apart and be put back together, it is awkward and difficult to re-magnetize individual magnets or with them "out of the Keeper" so to speak, but there is a way to re-magnetize these if they go weak:

I have done this and it works; by wrapping about 30 to 50 turns of very thick (about 1.5mm) diameter enameled copper wire circumferentially around the focus magnet assembly (removed from the set of course) and taking the Right Hand rule into consideration and checking the North and South polarity of the magnetic field with a compass for both the field magnets and the coil (with a low applied test current on the coil in isolation) so the field produced by the coil reinforces the permanent magnet's field (otherwise you could de-magnetize the magnets by mistake).

Once the polarity is certain, connect the thick coil across a car battery's terminal for a brief episode (sparks momentarily flying and safety goggles on). The very large Ampere-Turns will re-magnetize a weak focus magnet assembly and it will hold the magnetism. Don't connect it so long the coil overheats. Hopefully you will not have to resort to this.

Then if the field is too high the assembly can be partially disassembled a few times to adjust the field strength downwards until the field drops to a level where the CRT is focused properly with the mechanical arm at about half travel or the gap in the mechanical part of the focus magnet about half open/closed.
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