Hi, I just finished building a TSE-II amp. Parts include:
Edcor XPWR131-120 PT using the 330V taps
C-14X choke
Toroidy TTG-KT88SE OPT using 3K
Raytheon 5842WA tubes
Psvane HiFi 300B tubes
Chinese 5AR4 rectifier - test tube
All standard components from the BOM + 100uF motor run cap
Yesterday I went through the Checkout procedure and set the tube bias to 61ma. It plays and sounds good. Not as much volume as expected, but that’s maybe my crappy test speakers. However, I’m worried about my running voltage readings:
B+ 424V
B- -258V
Wall outlet is 117V
Edcor PT 660V red/orange tap putting out 679V to board - a bit high
R 5842 set to 173V
L 5842 set to 174V
L 300B set to 61ma
R 300B set to 62ma
The B+ looks to be too high to run 300B tubes for any length of time, so I shut it down after 15 minutes even though the tubes weren't glowing at all. I have the standard 47uF 500V cap for C4. Isn’t B+ of around +375 better for the 300B tubes longevity?
I boosted the bias on the 300B tubes to 70ma, but B+ didn’t hardly go down any. So, would lowering C4 to a 4uF – 10uF range lower it enough?
Any thoughts would be appreciated, thanks.
Mike
Edcor XPWR131-120 PT using the 330V taps
C-14X choke
Toroidy TTG-KT88SE OPT using 3K
Raytheon 5842WA tubes
Psvane HiFi 300B tubes
Chinese 5AR4 rectifier - test tube
All standard components from the BOM + 100uF motor run cap
Yesterday I went through the Checkout procedure and set the tube bias to 61ma. It plays and sounds good. Not as much volume as expected, but that’s maybe my crappy test speakers. However, I’m worried about my running voltage readings:
B+ 424V
B- -258V
Wall outlet is 117V
Edcor PT 660V red/orange tap putting out 679V to board - a bit high
R 5842 set to 173V
L 5842 set to 174V
L 300B set to 61ma
R 300B set to 62ma
The B+ looks to be too high to run 300B tubes for any length of time, so I shut it down after 15 minutes even though the tubes weren't glowing at all. I have the standard 47uF 500V cap for C4. Isn’t B+ of around +375 better for the 300B tubes longevity?
I boosted the bias on the 300B tubes to 70ma, but B+ didn’t hardly go down any. So, would lowering C4 to a 4uF – 10uF range lower it enough?
Any thoughts would be appreciated, thanks.
Mike
Oops, rookie mistake. I’ve never set a bias on an amp before. I initially used the 200m setting looking for 61.0mv. I Just changed to 2000m setting and set to 610mv and works just fine now. B+ is a more acceptable+374V. And way more volume!