01-20-2013, 08:55 PM
Well, it plays now. Loud, clear.
Pulls many stations on BC Band, very sensitive.
First I almost killed it. Shame on me.
I powered it without speaker first, all was normal, so I plugged the speaker, heard the low "boooo".
measured the B+, and it was about 80V, so I pulled all the tubes, and it was still the same, so I simply measured the resistance to Chassis from the Filter choke and so it go to Zero when the speaker was plugged.
I traced it to a wire that I jammed when putting a rebuilt backelite cap back. And I always watched for that, and still missed one. Well, I put two layers of heatshrink over the damaged insulation, plugged it again, measured the B+, saw it being OK, turned the volume.....voila!
Praise the Lord for the Impedance and for oversize transformers! The 80 tube was starting to glow just a bit....that told me something.
Now I have to:
1. Fix the wiring from the tone control: they used rubber wires and they are cracked all over.
2. Add more rubber washers under the tuning cap. I found many grommets in Lowe's, but none was high enough (there is a metal cylinder inside the grommet, so when fully compressed it has to still remain under the top of the grommet to allow compression/damping) so I used extra rubber washers...still not enough, need two more per screw.
3. Need to start looking at the shadow meter. The bulb is OK, but I don't see any action....maybe I still don't know how to operate it.
4. Replace the power cord: it seems to be OK mostly, but in one place it is damaged. I will buy some together with the speaker cloth and wiring for Tone Control.
OK, well....it is moving!
Pulls many stations on BC Band, very sensitive.
First I almost killed it. Shame on me.
I powered it without speaker first, all was normal, so I plugged the speaker, heard the low "boooo".
measured the B+, and it was about 80V, so I pulled all the tubes, and it was still the same, so I simply measured the resistance to Chassis from the Filter choke and so it go to Zero when the speaker was plugged.
I traced it to a wire that I jammed when putting a rebuilt backelite cap back. And I always watched for that, and still missed one. Well, I put two layers of heatshrink over the damaged insulation, plugged it again, measured the B+, saw it being OK, turned the volume.....voila!
Praise the Lord for the Impedance and for oversize transformers! The 80 tube was starting to glow just a bit....that told me something.
Now I have to:
1. Fix the wiring from the tone control: they used rubber wires and they are cracked all over.
2. Add more rubber washers under the tuning cap. I found many grommets in Lowe's, but none was high enough (there is a metal cylinder inside the grommet, so when fully compressed it has to still remain under the top of the grommet to allow compression/damping) so I used extra rubber washers...still not enough, need two more per screw.
3. Need to start looking at the shadow meter. The bulb is OK, but I don't see any action....maybe I still don't know how to operate it.
4. Replace the power cord: it seems to be OK mostly, but in one place it is damaged. I will buy some together with the speaker cloth and wiring for Tone Control.
OK, well....it is moving!