04-11-2020, 04:26 PM
Working on a Philco 38-3.
Completely recapped, good tubes, new resistors.
It had been playing fine, now it's not.
Took the meter and ran pin voltage checks vs schematic. Here are the tubes with what they should read on left, and actual read on right:
Output 6Fg (with chassis upside down, this is the output tube on the left)
S 240v 226v
P 230v 198v
H 6.3 vac 6.7 vac
H 6.3 vac .025 vac
Output 6Fg (with chassis upside down, this is the output tube on the right)
S 220v 186v
P 235v 201v
H 6.3 vac 6.6 vac
H 6.3 vac .027 vac
RF 6U7G
P 235v 219v
S 90v -.316 (I thought I had crossed my probe wires here, but I took it several times. Same result)
H 6.3 vac .025 vac
H 6.3 vac 6.5 vac
IF 6K7G
H 6.3 vac 6.5 vac
H 6.3 vac ZERO
P 240v 215v
S 90v -.03 (See "S" under RF 6U7G above)
OSC Control 6N7G
P 180v -1.5 (See "S" under RF 6U7G above)
P 180 Could not reach this without removing one of the bathtub bakelite (all of which were gutted and recapped)
H 6.3 vac .022 vac
H 6.3 vac Could not reach without moving tub above
DET. OSC 6A8G
Osc. Plate 125v -1.65
H 6.3 vac 6.53 vac
H 6.3 vac .025 vac
P 230v 216v
S 90 v -0.32
2ND DET/1ST AUDIO 6Q7G
H 6.3vac 6.5 vac
H 6.3 vac ZERO
P 135v 94v
DISCRIM. 6H6G
H 6.3 vac ZERO
K 6.3 vac 6.5 vac
Now, all of that being said, I did have an incident with the power plug. The screws holding down the AC lines inside the plug came loose, with the result that plugging it in became a little fireworks show at the plug only. The power strip shut itself off, I replaced the plug and this time soldered the screws shut. The power cord goes into one of those oh-so-much-fun to get the goo out of and replace the caps inside bathtubs. In this particular tub where the power attaches I installed a pair of ceramic .015 mf ceramic safety caps. It had originally held a pair of 0.15 wax/paper factory installs that were buried in the tar.
When I had it playing I had alligator clip leads on some components (electrolytic caps that have to be installed in proper pos/neg orientation). I wonder if it's possible I reversed one of those caps when I soldered it together? Did a resistor fail?
I'm just stuck right now.
Thanks!
Completely recapped, good tubes, new resistors.
It had been playing fine, now it's not.
Took the meter and ran pin voltage checks vs schematic. Here are the tubes with what they should read on left, and actual read on right:
Output 6Fg (with chassis upside down, this is the output tube on the left)
S 240v 226v
P 230v 198v
H 6.3 vac 6.7 vac
H 6.3 vac .025 vac
Output 6Fg (with chassis upside down, this is the output tube on the right)
S 220v 186v
P 235v 201v
H 6.3 vac 6.6 vac
H 6.3 vac .027 vac
RF 6U7G
P 235v 219v
S 90v -.316 (I thought I had crossed my probe wires here, but I took it several times. Same result)
H 6.3 vac .025 vac
H 6.3 vac 6.5 vac
IF 6K7G
H 6.3 vac 6.5 vac
H 6.3 vac ZERO
P 240v 215v
S 90v -.03 (See "S" under RF 6U7G above)
OSC Control 6N7G
P 180v -1.5 (See "S" under RF 6U7G above)
P 180 Could not reach this without removing one of the bathtub bakelite (all of which were gutted and recapped)
H 6.3 vac .022 vac
H 6.3 vac Could not reach without moving tub above
DET. OSC 6A8G
Osc. Plate 125v -1.65
H 6.3 vac 6.53 vac
H 6.3 vac .025 vac
P 230v 216v
S 90 v -0.32
2ND DET/1ST AUDIO 6Q7G
H 6.3vac 6.5 vac
H 6.3 vac ZERO
P 135v 94v
DISCRIM. 6H6G
H 6.3 vac ZERO
K 6.3 vac 6.5 vac
Now, all of that being said, I did have an incident with the power plug. The screws holding down the AC lines inside the plug came loose, with the result that plugging it in became a little fireworks show at the plug only. The power strip shut itself off, I replaced the plug and this time soldered the screws shut. The power cord goes into one of those oh-so-much-fun to get the goo out of and replace the caps inside bathtubs. In this particular tub where the power attaches I installed a pair of ceramic .015 mf ceramic safety caps. It had originally held a pair of 0.15 wax/paper factory installs that were buried in the tar.
When I had it playing I had alligator clip leads on some components (electrolytic caps that have to be installed in proper pos/neg orientation). I wonder if it's possible I reversed one of those caps when I soldered it together? Did a resistor fail?
I'm just stuck right now.
Thanks!
