Little Maestro T105.

[tiv48]

having a look at the underside before restoration it does look like 25mf goes to pin 7 witch would be the pentode cathode on a ucl83
so i now belive the corect valve to be ucl83
robt

[tiv48]

is this the circuit you have the radio you have apart from useing a different valve also seams to use different circuit topoligy as pin 3 on a ucl83 is the triode grid
rob t

[Joe]

Sorry for being a bit thick earlier. I was trying to cook my tea, or actually a much-delayed dinner at the same time.

We seem to have wondered off my initial question a bit which was is the 2.7 meg resistor likely to be that size? I'm sure the final band is green but I wouldn't argue if somebody said it's more likely to be 270k.

Thanks for your help and patience.

- Joe

[Joe]

The last two postings crossed.

Yes, Rob, that's the sheet I've got. It's even got the same line going through "C25 C26."

It's just my luck to land on an odd-ball radio.

- Joe

[tiv48]

the resisistor is r 10 and should be 270 k
rob t

[tiv48]

here is the pin out of ucl83

[Joe]

Thanks, Rob. I think I've got some of those. 2.7M seemed way to high even with my minimal knowledge.

Cheers
Joe

[Joe]

I found a couple of resistors which were the right size to finish this off but looked a bit puny as regards power. I thought they'd at least do for a brief test and have just tried it.

I stepped up through various light-bulbs and finally connected it direct.

There was a bit of crackling but, glory of glories, NO HUM. There was no audio either.

There's a bit of noise when the volume is adjusted and prodding the connection with an (insulated!) screw-driver made a crackle so the audio stage seems to be working.

I'd like to know what the most obvious things to check are. Is there any safe way of injecting an external audio signal into it just to confirm that that part is working.

Actually this test has gone much better than I was expecting given the state of the components I've replaced.

As ever, many thanks.
- Joe

[tiv48]

knock up one of these

   

rob t

[OldTickTock]

You can make quick N dirty sig injector with an MP3 player. Connect your head phones rip the hearing end off, insert 0.1uF caps on each lead one in series for ground/earth, the other one in series for live, use croc clips if you want to keep hands out. Use music, anything, won't matter you can work your way through the circuit tracing until you hear it from the set should be able to trace the faulty stage

Chris