01-27-2006, 06:06 AM
Ok, I'm still having issues with the 37-650. I just finished the extensive teardown of the RF subchassis- anything that wasn't addressed before, was this time. However- I still have no audio output. If you all recall, last we heard, the radio had gone from low volume to no volume. However, I am better equipped to check things now- I have my oscilliscope, my RF generator and my Precision Model 654 Tube Tester and High Sensitivity Set Checker...
So I am making power checks. With the black probe aggie clipped to the case of the chassis, and touching the indicated spots on the underside of the tube sockets, with tubes in place, I am getting some spurious readings: What should be 6-6.5vac is between 6 and 7. This is reasonable. However- all my 100 vac points are running around 200vac-225vac, my 250vacs are running around 510-520vac! I've switched the radio off for the night, and until I get some ideas...
The power transformer is the stock 32-7606N, for 110vac50/60hz. Power here is about 120vac, 55hz. I have a spare transformer I pulled out of the 38-3 I tore down last week, but the number on it is 32-7853N. Is this a suitable substitute?
All my tubes check out fine on the Precision tube tester(this is the type that powers them up, and checks them- not just a filiment checker) I am going to test them again, to be sure they were not damaged by the higher than standard voltage.
I replaced all the condensors, resistors, bakelite and micas as well, and all the electrolytics. I also replaced the hard wiring with new- the insulation was decayed and flaking off, so it only made sense. I used 20ga. stranded for most of it, except where smaller was called for. The two large wire-wrapped resistors were replaced with similar spec. metal oxide ones- could this be my problem?
So now I am looking at two issues: too high a power on the high AC circuits, and no volume. I am suspecting the volume control, and will pull it later today to check it out. It looks like the 38-3 uses the same one,(I checked the numbers) so I will probably give it a swap-out, and see the result- once the power issue is addressed.
Help? Please?
Thanks!
Scott
So I am making power checks. With the black probe aggie clipped to the case of the chassis, and touching the indicated spots on the underside of the tube sockets, with tubes in place, I am getting some spurious readings: What should be 6-6.5vac is between 6 and 7. This is reasonable. However- all my 100 vac points are running around 200vac-225vac, my 250vacs are running around 510-520vac! I've switched the radio off for the night, and until I get some ideas...
The power transformer is the stock 32-7606N, for 110vac50/60hz. Power here is about 120vac, 55hz. I have a spare transformer I pulled out of the 38-3 I tore down last week, but the number on it is 32-7853N. Is this a suitable substitute?
All my tubes check out fine on the Precision tube tester(this is the type that powers them up, and checks them- not just a filiment checker) I am going to test them again, to be sure they were not damaged by the higher than standard voltage.
I replaced all the condensors, resistors, bakelite and micas as well, and all the electrolytics. I also replaced the hard wiring with new- the insulation was decayed and flaking off, so it only made sense. I used 20ga. stranded for most of it, except where smaller was called for. The two large wire-wrapped resistors were replaced with similar spec. metal oxide ones- could this be my problem?
So now I am looking at two issues: too high a power on the high AC circuits, and no volume. I am suspecting the volume control, and will pull it later today to check it out. It looks like the 38-3 uses the same one,(I checked the numbers) so I will probably give it a swap-out, and see the result- once the power issue is addressed.
Help? Please?
Thanks!
Scott
Old Cars, Old Radios, Old Pipes and Young Women... What more is there?
