..more Monster-'scope discoveries, specially for any Cossor or 1049 fans:
See pics and thanks again to Ken, who also provided resources towards fix
(BTW, these go with the running success story here:
https://www.vintage-radio.net/forum/showthread.php?t=49496)
:
(1)
alternative to v22?? (a bit whacky, I admit) Cossor seemed keen on the 61BT tube. Yet to find easy replacements! (unless I want to waste EL38's with 3X power-handling). With little to lose, I spotted 6BQ6 has decent plate-volts (hurrah!).. but almost 2x I-fil (boo)...
So I tried 12BQ6 just for fun (yes, I know, a 12V tube in place of a 6V one... but I always did prefer experimental physics to precision engineering).
Results are so far so good in v22, but perhaps I should try swapping v15 this way instead... on basis it pulls less current?? Will keep you posted
(2)
More gone-hi carbon power resistors. This time, to my surprise, both 15W glazed 56K's gone o/c. Both identical. These are R77 and R79, so result was no A1 trace. Now trace almost restored.. just too far -ve, so more resistors gone-hi I expect.
(3)
Same again, EHT arcing is still a problem. Cotton-buds and meths must come out again but it's a bit hit and miss!
(4) Yet again, all caps seem fine... once again the famous Cossor electrolytic-less scope wins-out in this round.
Bottom line: if you restore a cossor of this era, expect to replace a LOT of fat carbon resistors. (See also first installment in link above).
Have fun!
Dave