05-01-2012, 02:42 PM
(05-01-2012, 01:49 PM)Skywave Wrote: Lawrence: I've fitted a 100k-ohm resistor as an additional bleeder: +HT1 to chassis.
Mike: Yes, the HT will rise in TRANS - and by quite a lot too, since in that mode, the PSU is effectively on no-load. But I'm not too concerned about that in this receiver. I consider the chances of myself switching this set off at the a.c. supply whilst it is in TRANS to be remote. And even in TRANS, the existing 1 megohm resistor bleeder discharges the capacitors to 100-v in about 25 seconds. Moreover, I suspect that that is why the original bleeder was fitted to the input side of the L/C filter, as opposed to the filter's O/P - as is usually the case. So, you might ask, why not simply replace the 1 megohm bleeder with the 100k-ohm one? And the answer is: two bleeders are better than one!
Al.
Hi Al,
Having 2 "little bleeders" is better than one is good practice.
I think Lawrence was really wanting to know why they had fitted the 1 Meghm instead of a lower value like 100k. Having done a bit of surfing on t'internet it seems that the vibrator unit companion to the AR88 used an OZ4 valve for rectification. According to its spec the advised max current is 75ma, this will I guess be running at pretty near maximum rating. I wonder if the higher value bleeder is to sympathise with this.Of course battery duration would be improved by about 4 percent as well.
Mike
