Ekco A28 wiring replacement

[Andrewausfa]

I won an Ekco A28 in the recent Harpenden auction which I've managed to get going again. It was making an awful sputtering noise which, it turned out, was the 10k resistor HT potential divider. I'll be asking for some help and advice on getting it working fully but that's for another day.

The wiring on the underside looks in good condition. However above looks decidedly bad, particularly the wiring close to the magic eye which is dry and crumbling and looking as if the covering's got a little hot. My problem is that this wiring is in a loom and is bound along its length with a cotton cord and I don't feel confident enough to disconnect the original loom, remake it and replace it whilst still getting the connections right. If you saw the underside of the chassis you'd possibly understand why! Spaghetti junction. I was contemplating pulling each length of wire out in turn and replacing it but the binding is quite tight.

Is there an alternative way of repairing the wiring without replacing? Any thoughts or ideas would be most welcome.

Thanks _Andrew

[boxdoctor]

Hi Andrew,
Would it not be possible for you to undo the wiring harness in situ, and then draw a rough sketch of the underside of the chassis and follow the individual leads to the magic eye, marking on the sketch where they are connected underneath the chassis, and the pin number on the magic eye socket. You could then make up a new harness with ease, and if you use different colour wires for each pin of the socket, connect it with no problems. Good luck, Tony.

[yestertech]

Hi Andrew,

I can understand your reluctance, especially when you add in the real pain that is trying to get old solder to flow and not transposing connections.
How about this ?

Carefully cut off the lacing cord
Remove one end of each wire at a time from the magic eye base
Oversleeve with silicon insulation back to the point where it connects below chassis.
Reconnect wire and repeat for all others.

This can make an unholy mess as the insulation crumbles off all over the chassis, but this can be vacuumed up afterwards
In the case of Philips sets where the wire has been solid, I have removed all the crumbling insulation first, which makes re-sleeving neater, as you can use a smaller bore.

At a later date, if indeed necessary you can replace the whole loom.


Andy

[Brian4radio]

Hi Andrew, I have waxed lacing twine you could have to re-lace the repaired loom once rewired. I too have an Ekco A28 so if you get stuck let me know. If you want any help or twine (off cream in colour) PM me regards Brian.

[Andrewausfa]

Thanks for all the advice gents. I wanted to hear some thoughts on this as I'd no doubts that most of you have had to repair this sort of thing before. The wires in the loom seem to go off everywhere, over and under other wires and components and I'm not brave enough to tackle a full re-wire yet

One thing I was reluctant to lose is that binding, someone must have sat there all day endlessly tying loops around bundles of wire but I will have a go at what Andy suggests. Brian thanks for your very kind offer, I will no doubt be begging you to see some inside shots of your A28 in the next couple of weeks.

That cap on the magic eye base looks a bit toasted doesn't it?!

Thanks - Andrew

[Tim]

Lacing is very easy and quick to do once you get the hang of it. You only have to tie one knot at the start, the rest are loops until you get to the other end.

[ColinB]

Have you got a service sheet for this set, the connections of the eye must be detailed in there??

Probably available from this site if you need one.

Grab some surplus wires and have a go at lacing, it's not as hard as it looks (once you get started...)

Cheers,

Colin

[Andrewausfa]

Hi Colin, yes I have the Trader for this thanks. I could re-make the harness, in fact I may well do anyway as a side project, it's just being brave enough to take the original out

[M0FYA Andy]

Here is a very useful link on how to do wire lacing -

http://www.dairiki.org/hammond/cable-lacing-howto/

Andy

[Billy T]

Originally Posted by setsappeal

I can understand your reluctance, especially when you add in the real pain that is trying to get old solder to flow and not transposing connections.

The easiest way to get old solder joints flowing is to start by 'resoldering' them using resin-cored solder. The old and new solders mix and it becomes much easier to either clean the joint with a solder-sucker or with solderwick.

The solder sucker is the most economic to use, and you can improve the sucking power significantly by keeping the cylinder lubricaied with CRC 2-26 or 5-56, or maybe WD40, though I've never tried using the latter. Squirt some into the sucker nozzle via the usual thin tube supplied with the spray can and repeat after every two or three joints. It also make cleaning out the sucked up solder much easier.

To avoid transposing connections, take photographs and/or make diagrams of connections. Use a meter with a 'tracing buzzer' or make up a buzzer with battery and sounder unit plus probes so that you can positively identify the two ends of each conductor. Many meter-based buzzers will vary their tone if there is any extra impedance in the test path, even if it is just an ohm or so.

If old conductor coverings have faded and all look much the same colour, nip the insulation close to a joint with a pair of sidecutters and you will usually find that the colour is stronger below the surface.

If practicable, replace wire by wire, it reduces the number of opportunities for mistakes.

Cheers

Billy

[Andrewausfa]

Thanks for everyones advice on this.

On Saturday, I took the plunge and decided to re-wire the whole lot. I cut the lacing, undid the u-clip which holds the loom to the chassis and unsoldered one wire at a time from the EM34 base and waveband selection lamp. The wire was then pulled back through to the under-chassis, traced to its connection, unsoldered and a new length of wire added trying to follow its original path back up through to the magic eye base/lamp holder.

I took the opportunity to replace the eyes decoupling cap at the same time. I then had a go at the lacing which I may well have another go at with some modern thread actually as the original has lost a lot of its strength.

A couple of shots showing before and after (or after and before!).

Andrew