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AZ1

 
Anonymous
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Having given forwarning of the sort of questions I'm likely to ask (ie stupid ones :) ) I shall start with an interesting one.

I have recently picked up a Philips BX480A and having opened her up the biggest valve in the box is an AZ1

It's a phone pic so not great:

Everything looks to be connected with no apparent filament breaks.

However the black base is loose and there are small fragments of either old glue or metal in the glass bowl at the bottom of the valve.

When looking closely it appears that the connections coming from the vacuum section into the bowl, and therefore presumably onto the connections at the base of the valve are all intact.
I can gently tighten the glass back into the base and it holds reasonably secure and it's strong enough to allow me to remove the valve from the chassis.

Do you think it's a gonner or is this common? Are you able to remove the base by de-soldering the connections thereby allowing the filings to be cleared?

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Topic starter Posted : 21/11/2012 3:32 pm
malcscott
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Araldite is ok for this job.

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Posted : 21/11/2012 4:05 pm
Terry
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... However the black base is loose and there are small fragments of either old glue or metal in the glass bowl at the bottom of the valve ...

Until I looked closely at the inverted image I thought for a moment that you meant bits of the glue were inside the envelope ...!

... is this common?

It is certainly not uncommon ...

... Are you able to remove the base by de-soldering the connections thereby allowing the filings to be cleared?

Yes, but it is a one way process ...!

Think about it - how would you get the wires back through the correct holes again afterwards ...?

If you can get any of the old glue out by shaking it, all well and good - but there probably isn't a big enough gap for them to pass through. Don't worry, they shouldn't do any harm where they are.

Being careful not to impose undue stress on it, try and dislodge any of the remaining glued on bits from between the glass and the base - hold it upside down so the bits fall out.

Wedge the envelope and base apart with two or three small pieces of card, folded paper or similar, then force adhesive into the cracks between the wedges - a two part epoxy might be a good idea as it also functions as a gap filler, but others may have alternative suggestions.

When this has set, remove the card wedges and fill those areas too.

Have you worked out what the valve is yet?

A = 4 volt heater
Z = Indirectly heated double diode rectifier
1 = Side contact base (can be any single digit number to indicate different valves of the same type)

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Posted : 21/11/2012 4:28 pm
Anonymous
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Thanks for the replies fellas.

So my lovely az1 is not dead, yet, and it can be removed from my office shelf and come home with me. (it is a lovely orniment at the moment :))

I will give the araldite/other 2 part epoxy glue method a try and also dislodge whatever remains of the glue currently in situe. If I can't find any glue at home tonight I'll get the wife to knock up a batch of her internationally famous custard. That'll stick anything that will.

Valve radio project number 2 can commence :)

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Topic starter Posted : 21/11/2012 4:39 pm
Anonymous
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AZ31 is Octal version.

The problem with unsoldering is you need to do tricky stuff to resolder as wires originally long and trimmed after soldering.

I had a base like that actually simply "fall off" 8))

Here I put it back together. I have not put the Epoxy yet (I want to test on Avo).

http://www.radiomuseum.org/forum/repair ... _base.html

I also had problem with loose DF1, the problem is these have external metallisation as screen rather than a can or mesh inside the glass as with the later Octal, rimlock and miniature (B7G and Noval) types. So I had to "repair" the connection to the metallisation or else the radio "motor boated".

Many early Mullard/Philips Octal are identical tubes to the edge connect version, simply a different base.

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Topic starter Posted : 21/11/2012 4:44 pm
Anonymous
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Have you worked out what the valve is yet?

A = 4 volt heater
Z = Indirectly heated double diode rectifier
1 = Side contact base (can be any single digit number to indicate different valves of the same type)

I had found out that it was a rectifier valve so I am expecting it to rectify something.

I also knew it was a side contact base by the way it connected to its housing (oh and it was loose already before I removed it thereby making its removal a very gentle carress using the base only)

The volt heater thing I don't know so I now have to investigate what the heater does and what it rectifies. See I said I wanted to learn.

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Topic starter Posted : 21/11/2012 4:46 pm
sideband
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I will give the araldite/other 2 part epoxy glue method a try and also dislodge whatever remains of the glue currently in situe. If I can't find any glue at home tonight I'll get the wife to knock up a batch of her internationally famous custard. That'll stick anything that will.

Be careful what glue you use. Assume that valves get hot (some get too hot to touch...rectifiers and output valves being typical), others just get warm. You want a glue that will allow expansion without cracking the glass. Never use superglue but if you don't have any epoxy, something like EvoStik (impact adhesive) will be OK.

Rich.

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Posted : 21/11/2012 5:19 pm
Anonymous
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Another couple of suggestions, a very quick one is to cut a section from an old bicycle tyre inner tube about 1.5 inches long so that it forms a rather fat elastic band. Open it out with your fingers and slip it over the valve base so it overlaps roughly half and half with the glass envelope, hope that make sense :).

If you want to use adhesive, the original 'glue' was shellac. Try injecting knotting solution or french polish between the base and the glass. It has the advantage that as the glass envelope heats up, the shellac softens and allows for expansion.

Keith

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Topic starter Posted : 21/11/2012 6:11 pm
Anonymous
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Another couple of suggestions, a very quick one is to cut a section from an old bicycle tyre inner tube about 1.5 inches long so that it forms a rather fat elastic band. Open it out with your fingers and slip it over the valve base so it overlaps roughly half and half with the glass envelope, hope that make sense :).

If you want to use adhesive, the original 'glue' was shellac. Try injecting knotting solution or french polish between the base and the glass. It has the advantage that as the glass envelope heats up, the shellac softens and allows for expansion.

Keith

Makes perfect sense and I like that Heath Robinson style of fixing but as I don't have a spare inner tube the only other option would be a pair of the wife's rubber gloves and if I ruined them I might end up having to do the washing up!!!!

It's gonna have to be the araldite.

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Topic starter Posted : 21/11/2012 7:25 pm
Kalee20
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Another couple of suggestions, a very quick one is to cut a section from an old bicycle tyre inner tube about 1.5 inches long so that it forms a rather fat elastic band. Open it out with your fingers and slip it over the valve base so it overlaps roughly half and half with the glass envelope

I don't think that will work very well with a side-contact base. Akmost all of the base disappears into the valveholder, on all the types I've seen.

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Posted : 21/11/2012 7:26 pm
Terry
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Actually, if you study the photographs, you'll see that is most definitely notthe case here!

In fact, the shape of the base above the bit that fits in the valveholder would probably help to secure the tubing!

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Posted : 21/11/2012 8:40 pm
Anonymous
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It's certainly a quick fix on most valves and worth a go to stop them being wobbly. I think the idea was in one of Mr F.J. Camm's books. Anyway Squiffything hasn't got an inner tube so it's rather hypothetical :) .

Another way of fixing valves I've seen is to use a strip of Empire tape to bind the glass to the base. Don't know if you can still get Empire tape though, or what it's intended use was

Keith

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Topic starter Posted : 21/11/2012 8:50 pm
Refugee
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I will vote for the Araldite method.
The two parts can be varied to produce a slightly more flexible result.
Mix it at 2 parts hardener to one part resin or 3 parts to 2. This makes it set slightly more rubbery so giving flexibility of the joint.
When cleaning the old glue out i would tie a length of "butcher's string" to a solid object and run it up and down the joint between the glass and the base. Avoid anything that may scratch the glass as this might make the valve go to air.
Superglue almost always makes the valve go to air and can crack car window glass.

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Posted : 21/11/2012 9:01 pm
sideband
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I've decided to split this into a new thread here seeing as the AZ1 question has been answered.

Rich

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Posted : 22/11/2012 8:46 pm
Terry
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... The idea is to extend the leads, I normally do this by twisting the lead out wire with single core wire of the same gauge as far along the original as I can ...

Yes Trevor, that did occur to me but would you have attempted it the very first time you touched a valve which, as I understand it, is the situation here?

You and I will barely need to glance at the valve pinch to correctly identify which wire goes to which electrode - although I'm sure we'd both take a bit more care! - and then correctly get each extended wire down the right hole but you are expecting rather too much, I think, of someone who has clearly stated that his level of experience is zero!

Perhaps he could try with the next valve he touches ....? 8))

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Posted : 22/11/2012 9:33 pm
Anonymous
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I poked wires UP from underneath and soldered them to the original wires. Deciding which is the heater is easy of course.

I've repaired octals the way Trevor suggests as the long hollow pin holds the twisted connection. But the Edge Connect are just eyelets.

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Topic starter Posted : 22/11/2012 10:35 pm
Anonymous
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Well I picked up some epoxy glue and got to work on the AZ1. Careful application with a cocktail stick avoiding the main glass of the valve and arter letting it stand for a few hours and its as good as new, almost. A few bits of old glue rattling around inside but doesn't affect the tube.

Plugged it in and after carrying out the checks and tests switched on and watched as it started to glow into life. Once again a very happy bunny.

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Topic starter Posted : 03/12/2012 11:07 pm