pye 76f

[Yorkie]

I've never been happy with the modern little ones as reservoirs, but they seem to survive.

Alan

Thats's a view which I'm sure is shared by many Alan.

The one bit of info we never seem to be able to get hold of is the ripple ratings - only very rarely is the ripple rating stated on caps. Modern ones look so puny, I do sometimes wonder if they're up to the task of smoothing/reservoir caps, passing maybe up to 100mA at 300V and 100Hz (with a full wave rectifier), but that said, I've not heard of any going pop. Modern tiny caps are fair enough for undemanding roles as say an audio valve cathode bypass (as often as not 25uF/25V), which I usually stuff, especially if the cap is mounted in a can above the chassis. Modern ones look quite comical when compared to the originals.

[Joe]

What surprised me when I re-stuffed the can in my ivory DAC90a was how small the actual capacitors were; a good third of the can was full of pitch. The replacements had a 500mA ripple rating.

- Joe

[tiv48]

work is realy getting in the way of my radio work still a bit of progress today.
had to make a bracket to mount the new smothing cap.and changed the wireing to how i think it should be .
i found the output valve has been changed from an el41 to an el84 and as i dont fancy changing the socket i will leave it .the next step will be to change the dc blocking cap to the controle grid of el84.next check/change the other wax caps
then power up on variac and see what happens.
rob t

[tiv48]

not much time today but have now changed all wax caps all failed leakage test.
i have found more work has been done as there was was melted plastic sleaving and wires that had just been tacked on and would fall off if breathed on.
before i power up i am going to have to trace the wireing to the output stage as it does not look right.
i still find it stange that so much work was done and yet none of the caps were changed.
pics of work done and c37 leakage test
rob t

[Joe]

The Phantom is a strange creature indeed.

- Joe

[Andrewausfa]

I'm sure you're more than capable of tracing a circuit but here's a couple of shots of mine taken of the same area as yours in case they are useful. Mine is untouched here bar the yellow AF coupling cap and the temporary main lead.

Andrew

[tiv48]

many thanks Andrew .I can already see that there are discrepenceys .the bigest problem i have is the mods done to the output valve (now el84) the cathode bypass cap is disconected ,infact the lead won't reach the valve holder.mind you this cap is leaky so will need changing.i think i will try and sketch out the circuit as it is and see where i go from there.
it was not unusual to change output valves eg cbl31 for an el84 + a couple of diodes .but an el 41 was/is not rare so i dont understand why it was done in this case?
rob t

[Joe]

I did it in my P75 because I had an EL84 to hand. Initially my idea was just to test that all was well with the rest of the set; there'd be no point buying an EL41 if the OPT was up the spout. It worked so well that I changed the base and made it permanent.

- Joe

[AlanBeckett]

Heathen!

Alan

[tiv48]

hi joe i think i to will leave it unless i have to rewire the base.
alan .i dont have a base to change it back but i do have some el81's
i will order some bases just in case.
rob t