25-03-2019, 01:13 PM
(21-03-2019, 05:43 PM)markandrewberry Wrote: There is something slightly unsatisfactory about diverging from the intended design. (Not that I'm hung up over originality, it isn't as if I've got the last one!)
I agree. However, there is also evidence of cost-cutting in the intended design, such as the UL41 Pin 4 used instead of sticking in another tagstrip. Saves cost, but builds in a latent problem. The mods were aimed at getting better results, for a bit of time and expense, without changing things massively.
Who knows whether the original designers wanted to design it exactly as the aforementioned mods, but were overruled because it would have put the DAC90a cost just above their nearest competitor, instead of just below? We will never know. Maybe that's why the DAC90a is so plentiful! We do have something to thank the bean counters for, after all!
Agree with most of the previous posts. The valves will probably be OK. If 'that capacitor' waxy has leaked, it may have given the UL41 a hammering, and the rectifier too, but unlikely to have killed them.
You can operate the radio without the mains filter capacitor. The worst that will happen is there may be a bit more interference.
The mains dropper is unlikely to have failed. The dial lamps, more likely - but check they are screwed in properly.
The output transformer is a showstopper! But a cheap mains transformer with 9V secondary will get you going. Make sure, even if just a lash-up, that connections are secure - trying to operate with an open-circuit anode connection to the UL41 means all its current is diverted to the screen-grid, which can overheat. It won't kill it, but it's bad for it all the same.
One thing which has not been said, is the loudspeaker suspension has a habit of becoming unglued in these radios. It might sound scratchy is so.
It's an easy chassis to work on. Have fun!
