air tuning cap - VHF90

[Bushbaby]

HI All,
I'm really getting on with the restoration if this radio. It does appear that I've replaced most of the wiring as it was in such poor condition - this set has run hot for a long time and the wiring has suffered very badly as a result.

I'm stuck in rewiring the air tuning cap. I cant seem to get the soldering iron bit hot enough to take the wires of the cap end off and I can only assume that the cap itelf is acting a heat shunt!! Anyone got any useful tips etc how I can unsolder the leads to replace them?

Thanks

Rob

[Steve_P]

Bring it to the Golborne event. I have an RF iron and that will do most things. Or see if anyone nearer to you has one.

Cheers,

Steve P.

[AlanBeckett]

Rob,

Get a bigger iron

Seriously, I assume these are the connections to the fixed vanes and Trimmers. I've never had any problems with a Weller and a decent sized bit. You can usually suck most of the solder off then wiggle the wire out of the hole. On the other hand the connections to the Frame can be a bit problematic, although they are usually braid and don't need changing.

Alan

[Skywave]

This is my general method for solving problems such as what you describe. It'll need adapting to any specific chassis, model - and the particular job to be done. In a phrase, "How do I get this *^$* thing hot enough?"

If you haven't already done so, remove the tuning capacitor from the chassis, making a note of its wire connections: cut them away from the cap. Usually, removing a tuning cap. means disturbing the drive cord: I usually fix the cord to the various pulleys, etc. with Blue-Tack; perhaps Plasticine will do, or even sticky plastic insulating tape. Now you can put the chassis aside and concentrate on cleaning up the solder connections to the tuning cap. You may find that as it is now out of the chassis, the unwanted heat-sinking effect has gone, enabling you to proceed with the clean-up. Otherwise use a hot-air gun - I use a paint stripper - and heat up the solder joints. Don't apply excessive heat, since that will dry out the tuning cap's. bearings. Then to make the job worthwhile, since the tuning cap. is out of the chassis, give it a good clean using any of the established methods. Finally re-assemble and re-wire.
Of course, a lot of that work can be avoided if you are able - and are prepared to take the risks - of heating the tuning cap. solder lugs with the tuning cap. in situ: all depends on the construction of the particular radio.

The ideal approach - which isn't any help to you right now - is to acquire a 'Metcal' soldering iron: with its 1/4" bit, I can solder direct to 18 s.w.g. steel plate. Failing that, keep a lookout for a big soldering iron - something like a 200-watt job. Occasionally I've seen those at car boot sales, auctions and house clearance sales: usually they are remarkably cheap: I've got two! But sometimes the heat-gun approach (and a really hot iron) is the only answer - and it's a lot quicker.

Al.

[Joe]

What I've done in cases like this is to snip the old wire off leaving a long enough bit to solder the new to and then cover the joint with heat-shrink.

- Joe

[Bushbaby]

is it appropriate to get out the old Weller soldering gun?? I've never liked using it but it does get very hot!

R

[Skywave]

As with so many questions like that, the only way to get the answer is to give it a try! That's the way to learn by practical knowledge. But be careful that you don't burn anything that the element of the gun gets near to.

Al.

[Bushbaby]

Hi Al,
No problem there! I've just tried the gun on both heat settings - the bulbs lighting up on the gun, and its buzzing as its always done BUT its not getting hot.

Oh dear!
Rob

[Radio Fixer]

Rob

You live near me and I have a huge 200W Weller iron with a large bit, its never failed me on jobs like yours. You are welcome to borrow it. Give me a PM for phone number but thats in the BVWS book if you have it.

Cheers Gary

[pwdrive]

My 50 watt Antex does more or less everything including chassis tags and braiding to the earth springs on tuning gangs, does not do wide flat braiding direct to chassis etc or ditto to tuning gang main frame, I used to have an iron with a three quarter inch chisle bit, that would tackle anything.
If still no good then I would favour Joe's suggestion.

Lawrence.