05-04-2013, 05:27 PM
Update:
Well, the entire chassis has been rewired, e-caps replaced (I did not change any of the mica caps, as I have no clue how to even test them...) All resistors more than 3% off value were replaced (I even tested the brand new replacements to that spec, Radio Shack quality was, well... Everything is clean, shiny and new looking. All points and contacts have been cleaned.
The only wires I did not replace are coming off the transformer, the AC power switch, the bandswitch light and the speaker (more about this in a minute)
So I took a deep breath and plugged it in, with my wife standing by; nervously holding a fire extinguisher aimed at me.
No sparks, no smoke; so I went ahead and turned on the power. I had already done dim bulb tests at 60, 100 and 120W, which is how I discovered that the output transformer was shot, but this was the first full power up with the bulb taken out of series and that big shiny resistor in its place.
Dials lit up, and the 2 41 tubes, the 6X5 (going to order an 84 to replace it soon!) and the 2 XXL tubes all started heating up and cheerfully glowing -none of the 7 series tubes did (7A6, 7C6 and 2 7B7's).
Then I smelled burned insulation and a trickle of smoke came up by the dial lamp.
I unplugged it, turned the chassis on its side and tried again.
Turned out that the wire from the Bakelite block to the power switch (one of the few wires along with the power transformer wiring that I did Not replace, even though I re capped the bakelite block itself) was burning up right at the switch, so I clipped it off and soldered on a new wire. No more smoke, no more burnt insulation smell. The switch performs flawlessly.
But now I am second guessing myself; should I remove the transformer and replace those last few wires? They are braided and seem to be in pretty decent shape, but so did the one running into the switch block... Should I replace the switch altogether?
Next: What should I expect to have coming from the speaker with only the 2 41's the 2 XXL's and the 6X5 (84) tube operational? Is there any troubleshooting or work I can accomplish without the other tubes?
It will be another month before I can afford to buy tubes (have had an unwelcome houseguest since Christmas -which is why I couldn't buy grill cloth -I carefully counted the pattern threads bought more than a Mile of various yarn and thread and made my own on a 1970's craft loom, pics soon!- and had to wait 2 months to order my new Hammond output transformer.)
As for the gimmick cap from posts 5 & 7 on the antenna coil -I am saving that for last, as I want to hear the difference with/without it.
I still have the original grill cloth carefully stored, and as I said somewhere else, it has some cat damage and a stain or two. Hopefully tomorrow I can post pics of it and the replacement I made.
Ron or Arran or anybody interested in the 2'X2' original? Plenty of usable cloth for smaller applications. Just let me know what you think I should do after you see it.
Again, thanks for all your patience with me guys; this is my very first project of this kind (wow -tubes and stuff!) and without these and the other forums where I see you posting I would be completely lost.
Well, the entire chassis has been rewired, e-caps replaced (I did not change any of the mica caps, as I have no clue how to even test them...) All resistors more than 3% off value were replaced (I even tested the brand new replacements to that spec, Radio Shack quality was, well... Everything is clean, shiny and new looking. All points and contacts have been cleaned.
The only wires I did not replace are coming off the transformer, the AC power switch, the bandswitch light and the speaker (more about this in a minute)
So I took a deep breath and plugged it in, with my wife standing by; nervously holding a fire extinguisher aimed at me.
No sparks, no smoke; so I went ahead and turned on the power. I had already done dim bulb tests at 60, 100 and 120W, which is how I discovered that the output transformer was shot, but this was the first full power up with the bulb taken out of series and that big shiny resistor in its place.
Dials lit up, and the 2 41 tubes, the 6X5 (going to order an 84 to replace it soon!) and the 2 XXL tubes all started heating up and cheerfully glowing -none of the 7 series tubes did (7A6, 7C6 and 2 7B7's).
Then I smelled burned insulation and a trickle of smoke came up by the dial lamp.
I unplugged it, turned the chassis on its side and tried again.
Turned out that the wire from the Bakelite block to the power switch (one of the few wires along with the power transformer wiring that I did Not replace, even though I re capped the bakelite block itself) was burning up right at the switch, so I clipped it off and soldered on a new wire. No more smoke, no more burnt insulation smell. The switch performs flawlessly.
But now I am second guessing myself; should I remove the transformer and replace those last few wires? They are braided and seem to be in pretty decent shape, but so did the one running into the switch block... Should I replace the switch altogether?
Next: What should I expect to have coming from the speaker with only the 2 41's the 2 XXL's and the 6X5 (84) tube operational? Is there any troubleshooting or work I can accomplish without the other tubes?
It will be another month before I can afford to buy tubes (have had an unwelcome houseguest since Christmas -which is why I couldn't buy grill cloth -I carefully counted the pattern threads bought more than a Mile of various yarn and thread and made my own on a 1970's craft loom, pics soon!- and had to wait 2 months to order my new Hammond output transformer.)
As for the gimmick cap from posts 5 & 7 on the antenna coil -I am saving that for last, as I want to hear the difference with/without it.
I still have the original grill cloth carefully stored, and as I said somewhere else, it has some cat damage and a stain or two. Hopefully tomorrow I can post pics of it and the replacement I made.
Ron or Arran or anybody interested in the 2'X2' original? Plenty of usable cloth for smaller applications. Just let me know what you think I should do after you see it.
Again, thanks for all your patience with me guys; this is my very first project of this kind (wow -tubes and stuff!) and without these and the other forums where I see you posting I would be completely lost.
