Tiny Tim and the Unitra D-400

[Steve_P]

Tiny Tim looked down from the stool in the workshop and moved his legs idly back and forth. It was turning into one of those days. From when his wife Tinkerbell brought him his breakfast in bed and walked off with his paper. Tim liked his morning paper as it gave him things to moan about through the day.

Washed and dressed, he took up his position at his bench, and fixed two Signal Generators in quick succession, one was off frequency and one wanted a new mains lead. So there he was, looking with worry at Mark the Mender's McMichael, which probably had something easy wrong with it, but he couldn't find out what. He eyed it with a mixture of panic and fear and looked back towards his feet. He looked as his feet moved back and forth and wondered if it was worth having another go at it.

His long suffering wife Tinkerbell came in with a parcel that the nice courier man had delivered. She'd unwrapped it. It was his Unitra D-400. He had the D-401 on the shelf above him, but this was different entirely. 4 wavebands and a gram setting on the front control, nice and clean and the bloke he'd bought it from said it works.

He never took this at face value, so he opened the set up. It had a white colourless lead and plugs at either end, so he carefully made sure the chassis was at neutral and marked the lead so he would always plug it in the right way. Otherwise he would get a shock and use lots of naughty words and Tinkerbell would be cross with him.

The speaker had been replaced quite badly, so he tidied this up and looked at the valves. The output valve was an ECL86, and this had been replaced already. The phantom who had been here had not replaced the grid capacitor however and it was acting more like a resistor. He replaced the capacitor and said a prayer for the valve. Some valves tolerate this better than others and the ECL86's don't tolerate this very well. And they aren't cheap.

It was time for Tiny Tim to apply power and see what happens. All the valves lit and after a minute there was hiss but nothing else. Select LW and in came Radio 4 in the right place. Medium wave worked too, but the wavechange switch was varying the volume every time it was touched. He gave it a thorough clean and this problem was sorted.

When he scanned up and down the dial, it stopped with a crackle two thirds across. It was the same on both Medium and Long waves, but there was nothing at all on Short Wave. This was because the tuning cap was shorting out, due to dirt or bent plates. He attacked it with his air duster and it still did the same thing. So using his meter he found which one of the two variable capacitors was faulty and then tuned it until it failed. He then turned it out and moved the outer plates outward slightly. One was too far in, and this was causing the oscillator to fail.

There were now stations up and down the bands on Medium and Long waves. Still nothing on Short Wave. He cleaned the wavechange switch again and there was no joy. Nor was there any when he tried another ECH81, but he didn't think it would. Life isn't that easy.

He also had nothing on VHF, so he left the Short Wave problem for now and looked at the VHF. 10.7 Mhz got through OK, so he tried another ECC85. Now he got Radio 2 but it was quiet all over the dial. There was no aerial, just a socket for a dipole. He plugged in his big antenna and it was much better, but he soon found that the ECL86 was past it's best..It was OK on AM but the distortion was evident on FM. So a new one went in and the old one had 'AM set only' written on the box and was put on the shelf.

Now he turned his attention back to Short Wave and the lack of signal.

The wavechange switch was on a separate board, which had a few bits attached to it, including two trimmers and a few caps. The trimmers hadn't been touched so he traced through the Short Wave setting through and found a small cap that was in two. This was a tiny cap and it looked like 51pF. A look at a Unitra Circuit he did have for one of their sets gave the same value, so he fitted one from a scrap set, resoldered the whole board, switched on and crossed his fingers.

It came up on Short Wave now, and he spent the next few minutes listening to signals around the world.

The set now performed well on all bands, so it was time to reassemble it. He carefully put the set back together and left it running on the kitchen table, in the hope that Tinkerbell would be pleased with him and bring back his newspaper, hopefully with tea and chocolate biscuits.

She did as a matter of fact, and he ate them while reading the newspaper full of things to moan about. She did say something about a McMichael, but he wasn't listening. He was in fact wondering how Postman Pat had got in charge of a football team and wondering how good a coach Jess the Monochrome Cat was.....

Cheers,

Steve P.

P.S. Mark the Mender gave permission and the use of Tiny Tim and Tinkerbell came from Television Magazine and Les Lawry Johns.

[Tazman1966]

Beatifully written Thanks for sharing it with us Steve and of course another of your faves restored

[Tim]

Nice one Steve!
Large print dial for hard of hearing listeners?

[Mike Phelan]

Excellent, Steve; LLJ would have been proud of you.

[Mark the Mender]

Ah Mr Pendlelebury.............I trust Tinkerbell approves!
That McMichael is an itch that requires some scratching,gets right under the skin that set!

Well done old bean the magic has not left you

cheers Mark

[Sideband]

Classic LLJ Steve especially the bit about the naughty words!! Well done.


Rich.

[igranic]

LLJ & Unitra - This man has taste & talent!

[petervk2mlg]

Great work Steve! You brightened my morning with that whimsical piece.
Nice radio that Unitra. Can you tell me how heavy it is? (Thinking about shipping one out to Oz!)
Peter