Little Maestro T105.

[Joe]

I thought I'd better report on this one.

I had a nice morning listening to 6 Music through it. There's no point getting hung up about a 'Potentially Live Chassis' when there's an exposed Definitely Live main switch exposed for the touching. All I can say to Chris is a paraphrase of Queen: "Hey VanTickTock, you made a bad boy out of me."

I also had another look for bad connections or errors on my part but couldn't find any. I found that if I connected the aerial socket to the screen of the TV aerial cable and connected a crystal ear-piece to pin 2 of the UCH81 (V1) via an OA79 I could pick Virgin up well but have not gone to this bother for a crystal set!

Besides that I've checked the heater voltages but don't know if they indicate anything or not. They are:-

V4 (UY85) 35v
V3 (ULC83) 43v
V1 (UC81) 21v
V2 (UBF80) 16v

They all look as bright as each other.

I won't be doing anything wireless-wise tomorrow as I'm going out so hopefully by Sunday I'll have had some new ideas.

All the best
Joe

[OldTickTock]

UY85 38v
UCL83 38v
UCH81 19v
UBF80 17v

Something weird going on there me ole fruit bat all high some more than others

[OldTickTock]

Joe I've just checked my Radio & Television Servicing volumes and found the T105 listed in the 1957-1958. Ithas the schematic and clearly states V3 is a UCL82!!

Chris

[Joe]

That's part of the problem, Chris. I bought the service sheet and that's what that says as does the one Rob T has. This set has UCL83 stamped into the chassis and that's the valve that's fitted. Before I spotted it I could make no sense of the wiring and there are a few other differences beyond that. It's odd how that's the bit that works!

It hasn't been got at as all the joints still had anti-tamper paint on.

As I said yesterday, there's something odd about me and old wirelesses.

Thanks for at least looking.
- Joe

[OldTickTock]

Ah that will teach me to read the entire thread, just looked at post #6 where you showed the chassis. What is weird is that the ERT sheet and the Radio & Television Servicing manual both refer to UCL82 so I wonder what's with the 83 being used, a mystery.

Chris

[Joe]

I haven't done anything much with this in recent days but have been listening to my DAB radio through it and it's continued to perform very well in this role. In fact it's probably of more practical use to me as it is than as a working wireless.

I've been connecting it up via a 'Naughty Board' which consists of two 10K resistors to mix stereo to mono and then a pair of 0.1uF capacitors to block any DC that goes a wandering. I've never previously bothered with the resistors on these sort of jobs but they do no harm and provide a bit of extra isolation.

   

I know I nearly got lynched a few weeks ago for floating the idea of adding a Gram socket to a Bush AC91 but nobody said anything about croc-clips!

I've also been doing a bit more research. I've found another photo of this model on the Radio Museum web-site which is a different colour. That wasn't very surprising but the whole style of the tuning dial scale is different as well and I'm starting to wonder if I've got some type of rare variant which may be worth a few bob - in my dreams.

One thing I have checked is the current of the heater-chain. This is running at 97mA and is supposed to be 100mA so that is near as makes no odds and is wrong on the safe side.

I'd also had my doubts about the value of a resistor (R10 on the R&TS data) which is supposed to be 270K. The final band on the original looked green to me but I've found that it makes NO difference whether I use a 270K or 2.7M resistor n that position.

Besides that I've found that just powering up Rob T's signal injector will make it start bleeping without any physical connection so there's certainly life within the receiving bits.

I will continue to fiddle but have been doing other jobs in recent days, including extra dog-sitting which precludes doing much as I tend to get my arm jogged by heads which require patting which is not healthy when playing about with jump-leads.

All the best
Joe

[Joe]

Yesterday I made a careful comparison between my before and after photos, along with one I found of another restored set, but couldn't see anything wrong. I then compared it to the circuit diagram and couldn't find any errors that way either.

This leads me to think that the problem is either:-

Something amiss in one of the RF transformers
A duff small capacitor which I haven't changed
A faulty valve
The alignment being out despite it showing no signs of having been fiddled with

I've now given up on it until such time as I learn more about these areas so I can investigate properly. It's earning its corn as an amplifier for my DAB radio and I'm very pleased with it in that role.

Thanks to everybody for the assistance they've given to me.
- Joe

[Joe]

This thing is getting plain weird.

I've continued to use it basically as an amplified speaker but its not working properly has been bugging me, especially since I got my MW micro-transmitter working.

This morning I found that if I plug the aerial of the transmitter into the radio's aerial socket with no audio source connected (or even with the input shorted to ground) the radio picks up Absolute Radio load and clear across both bands.

I've also tried poking about with the injector/tracer that Rob T suggested but as soon as I power that up the radio speaker starts bleeping before I've even touched it.

Ideas most welcome!

- Joe

[tiv48]

could be low rf gain clutching at straws try r2(1meg) r4 (1meg) and c14 (0.1mf)
rob t

[Joe]

All those bits are new, Rob, though I still checked them and found they were OK. Interestingly my data says R4 is 47K and that was what was originally fitted. I tried a 1 meg but it made no noticeable difference.

Last night I had a look inside T1, chiefly to confirm what the connection are. Everything seemed fine in that.

I'll just have to wait until inspiration strikes one of us. No doubt it will be something simple when it is discovered.

Thanks for your assistance.

- Joe