02-16-2017, 01:05 PM
Hi Phorum,
I am restoring a 38-116, Code 121 which I picked up earlier in the month for $100. I am fortunate to have a 38-116 code 125 parts chassis to pull from too (understanding the circuitry differences between the code 121 and 125). The parts chassis is missing the on/off and magnetic tuning in/out knob as well as the dial mechanism but it includes the rest. I am in the process of checking the power transformer, audio interstage transformer (which appears bad from some leaked tar beneath it), the output transformer, and field coil for shorts and continuity. I am also using my Hickock 605A to test the tubes. I will also be replacing all electrolytic and tubular caps and all out of tolerance resistors and testing all the other chokes, coils and transformers along the way.
Anyhow, although I am a novice, I have been in the hobby long enough to know the great resources available on the Phorum and ARF. I have searched these boards and have compiled over 100 pages of commentary (from many of you!) on how to specifically repair and troubleshoot the 38-116. I am very grateful for all the knowledge that has been shared online and am carefully reviewing it before I submit a question to the Phorum - no need to ask something that has already been addressed.
I have gleaned a good deal of info on how to make the power supply safer and to better protect the 75+ year old tubes from power stresses. I was hoping that others whom have done this work before could double check my plan to make sure it is accurate. Here is what I would like to do (provided the transformers check out):
1) install a polarized plug with hot leg connected to a fuse before the power switch.
2) install a fuse on the hot leg of the power cord before the power switch. The radio draws 165 watts at 115 VAC (as listed on the blue label in the cabinet) so its amperage is 1.4. I will plan to use a 1.5 amp slow-blow fuse to keep it as close to the draw as possible.
3) Replace the 2 .015 caps in the bakelite block (part 145) that were originally on each side of the line to chassis ground with 1 .01 uf X1/Y2 safety cap - this would be after the switch across the line. I will continue to utilize the existing bakelite block as a tie-point for neutral side of the AC line cord and the primaries of the power transformer.
4) install a CL-90 in-rush current limiter after the power switch by adding a new 3 point terminal strip in an un-used existing hole on the chassis.
Below is a rough diagram on how I plan to do it. The yellow highlight is the hot lead of the AC line and the pink is the neutral side. The purple shows ground connections.
Are there any issues with my plan? Did I leave anything out? Thanks for your thoughts! -- Andy
I am restoring a 38-116, Code 121 which I picked up earlier in the month for $100. I am fortunate to have a 38-116 code 125 parts chassis to pull from too (understanding the circuitry differences between the code 121 and 125). The parts chassis is missing the on/off and magnetic tuning in/out knob as well as the dial mechanism but it includes the rest. I am in the process of checking the power transformer, audio interstage transformer (which appears bad from some leaked tar beneath it), the output transformer, and field coil for shorts and continuity. I am also using my Hickock 605A to test the tubes. I will also be replacing all electrolytic and tubular caps and all out of tolerance resistors and testing all the other chokes, coils and transformers along the way.
Anyhow, although I am a novice, I have been in the hobby long enough to know the great resources available on the Phorum and ARF. I have searched these boards and have compiled over 100 pages of commentary (from many of you!) on how to specifically repair and troubleshoot the 38-116. I am very grateful for all the knowledge that has been shared online and am carefully reviewing it before I submit a question to the Phorum - no need to ask something that has already been addressed.
I have gleaned a good deal of info on how to make the power supply safer and to better protect the 75+ year old tubes from power stresses. I was hoping that others whom have done this work before could double check my plan to make sure it is accurate. Here is what I would like to do (provided the transformers check out):
1) install a polarized plug with hot leg connected to a fuse before the power switch.
2) install a fuse on the hot leg of the power cord before the power switch. The radio draws 165 watts at 115 VAC (as listed on the blue label in the cabinet) so its amperage is 1.4. I will plan to use a 1.5 amp slow-blow fuse to keep it as close to the draw as possible.
3) Replace the 2 .015 caps in the bakelite block (part 145) that were originally on each side of the line to chassis ground with 1 .01 uf X1/Y2 safety cap - this would be after the switch across the line. I will continue to utilize the existing bakelite block as a tie-point for neutral side of the AC line cord and the primaries of the power transformer.
4) install a CL-90 in-rush current limiter after the power switch by adding a new 3 point terminal strip in an un-used existing hole on the chassis.
Below is a rough diagram on how I plan to do it. The yellow highlight is the hot lead of the AC line and the pink is the neutral side. The purple shows ground connections.
Are there any issues with my plan? Did I leave anything out? Thanks for your thoughts! -- Andy
Andy Sorrell
Palmyra, Virginia
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