06-24-2018, 06:54 AM
FULLY MISSION CAPABLE!!! FMC
READY FOR ISSUE (RFI)
working, done, in service!!!!
the one remaining cap was a direct short , its value was .25uf, i replaced with a .33uf.
it was the cap on the second 6sk7 pin 6. if you short it on the schematic, my rectifier dc output would have a direct shot to ground with the only load being the inductor off pin 4/8 of the 25z6.
order of happenings........
i got the set free
i recap and retest on cap at a time
i kept the .25uf cap from the second 6sk6 installed as i did not have a replacement yet,, did not check it either. it physically appeared as though it never once saw any harm or battle, looked really new and i made an assumption.
as i was on the phone and the set playing,, it self destructed out of the blue.
i ordered up caps & 2ea spare tubes.
i muddled through making a correction to the input ac power section & installed the missing 25ohm resistor on the cold side of the on/off sw.
undid & corrected the previous work done that compensated for the lack of this 25ohm resistor.
added correct size filter caps.
powered up and no sound at all even when i touched the tone & vol pot leads.
eventually my power up and power down events started to cause my rect tube to almost instantly glow blue.
found that the one remaining cap .25uf was shorted.
replaced the cap, powered up and like a tesla coil , the rectifier tube provided a quick show of force, i swear i heard the whole radio even vibrate! but...... it was in a linear way getting stronger and stronger like sumthin's gonna BLOW!
i unplug the cord and consider putting it up for a while...but no.
i used my last resort redneck troubleshooting tactic. i power up one more time , my plan is to look for the smoke and let the darn thing show me where it hurts,, and it did.
the rect tube took another breath of life then went dark.
still having no idea what to do since my short to ground was gone and i wired the set corectly, i consider another trick which was a risk to my wallet.
i installed all brand new tubes.,,, thinking that the affect the rect tube had on other things, putting new unbeaten down tubes in would help reveal the "weaker link".
power and and there she is,, playing all good and fine.
i backed out one at a time my new tubes in trade for the orginals that were in the set(excluding the rectifier). i migrated all the way down to both 50L6's and all the originals were working great. my new spares are all mostly metal type and even though the metals are supposed to be better, i like the look of being able to see the tube working.
all is well in my small collection of working sets.
missing in this pic of my repaired sets (notice i dont say resto cause im not really doing purist work), are 4) s38's, 1) s53, & 1) philco 46-1226 which is in the master bedroom.
heading out to add an antenna relay to the minerva and a fuse on the power cord.
all is well.
Note to anyone who see's one of these.............. if your a armed forces supporter!
-If the set has the letter "M" in the speaker grill *AND* is occupied by the schematic showing series 50L6's,
~~~civilian sets had a louver grill over the speaker.
-then the set was only found for sale in a military exchange army/navy.
**this means that the set "should" have been on the front lines as the moral radio of the minerva line.
if the radio schematic has parallel audio output push/pull's & other rectifier tubes, then it was civilian ordered.
READY FOR ISSUE (RFI)
working, done, in service!!!!
the one remaining cap was a direct short , its value was .25uf, i replaced with a .33uf.
it was the cap on the second 6sk7 pin 6. if you short it on the schematic, my rectifier dc output would have a direct shot to ground with the only load being the inductor off pin 4/8 of the 25z6.
order of happenings........
i got the set free
i recap and retest on cap at a time
i kept the .25uf cap from the second 6sk6 installed as i did not have a replacement yet,, did not check it either. it physically appeared as though it never once saw any harm or battle, looked really new and i made an assumption.
as i was on the phone and the set playing,, it self destructed out of the blue.
i ordered up caps & 2ea spare tubes.
i muddled through making a correction to the input ac power section & installed the missing 25ohm resistor on the cold side of the on/off sw.
undid & corrected the previous work done that compensated for the lack of this 25ohm resistor.
added correct size filter caps.
powered up and no sound at all even when i touched the tone & vol pot leads.
eventually my power up and power down events started to cause my rect tube to almost instantly glow blue.
found that the one remaining cap .25uf was shorted.
replaced the cap, powered up and like a tesla coil , the rectifier tube provided a quick show of force, i swear i heard the whole radio even vibrate! but...... it was in a linear way getting stronger and stronger like sumthin's gonna BLOW!
i unplug the cord and consider putting it up for a while...but no.
i used my last resort redneck troubleshooting tactic. i power up one more time , my plan is to look for the smoke and let the darn thing show me where it hurts,, and it did.
the rect tube took another breath of life then went dark.
still having no idea what to do since my short to ground was gone and i wired the set corectly, i consider another trick which was a risk to my wallet.
i installed all brand new tubes.,,, thinking that the affect the rect tube had on other things, putting new unbeaten down tubes in would help reveal the "weaker link".
power and and there she is,, playing all good and fine.
i backed out one at a time my new tubes in trade for the orginals that were in the set(excluding the rectifier). i migrated all the way down to both 50L6's and all the originals were working great. my new spares are all mostly metal type and even though the metals are supposed to be better, i like the look of being able to see the tube working.
all is well in my small collection of working sets.
missing in this pic of my repaired sets (notice i dont say resto cause im not really doing purist work), are 4) s38's, 1) s53, & 1) philco 46-1226 which is in the master bedroom.
heading out to add an antenna relay to the minerva and a fuse on the power cord.
all is well.
Note to anyone who see's one of these.............. if your a armed forces supporter!
-If the set has the letter "M" in the speaker grill *AND* is occupied by the schematic showing series 50L6's,
~~~civilian sets had a louver grill over the speaker.
-then the set was only found for sale in a military exchange army/navy.
**this means that the set "should" have been on the front lines as the moral radio of the minerva line.
if the radio schematic has parallel audio output push/pull's & other rectifier tubes, then it was civilian ordered.
