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41-285 phono switch addition?
#5

It made sense to remove it. I did and replaced the .01 cap on the volume pot. I also found several issues and repaired them. The most important was at the junction of the 1 meg resistors R54 & R53. The leads were cracked, so I've replaced both resistors with new ones (the old ones had measured within tolerance, so I'd left them in place). I re-measured the output transformer from CT to each side and it is higher than the Philco part, but not by much (Philco is 170 and 190 ohms per side and the Thoradson is right at 210 or so per side). I measured each chassis ground and got continuity at each one. Retested the tubes...I wanted to see if there was an issue with the rectifier. All good. Lowest rating was a 7B7 at 60% with 50% as marginal on my Triplett.

Took some voltages, and voltages show some issues for sure:

junction of R30, R28, and R26=3.8v (should be 100v??)
pin 4 of the rectifier 84=217 (the pin the filter cap connects to)
grid of osc. XXL=0
C27A positive side=217 (should be 180v).

Just wrong. I wonder that I can hear the signal generator.

Charlie in San Antonio


Messages In This Thread
41-285 phono switch addition? - by ccomer1955 - 09-11-2015, 06:41 PM
RE: 41-285 phono switch addition? - by Raleigh - 09-13-2015, 12:48 PM
RE: 41-285 phono switch addition? - by ccomer1955 - 09-13-2015, 03:17 PM
RE: 41-285 phono switch addition? - by Arran - 09-14-2015, 12:46 AM
RE: 41-285 phono switch addition? - by ccomer1955 - 09-14-2015, 10:26 PM
RE: 41-285 phono switch addition? - by ccomer1955 - 09-15-2015, 01:59 PM



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