Re: Capehart 500M with automatic record changer (Restoration Topic)
Posted: Sun Oct 01, 2023 9:56 am
Thank you for your comments Richard. Glad you are enjoying the restoration.
Jon
Jon
Continuing service on the amplifiers I have noticed most all carbon resistors are out of tolerance. I have new carbon resistors similar to the originals to use in both the 1942 amplifiers as well as the 1937 amplifier if needed. I am rounding completion of all three amps with major service on only one left to perform. Both 1942 amplifiers have 5V4 rectifier tubes in place of the factory specified 5Y3 rectifiers. It appears the original owner had these swapped to 5V4's in 1942 for some initial reasoning I was not aware of. After researching more and studying my tube charts it appears the 5V4 is almost similar in all respects to a 5Y3 tube. The added benefit to the 5V4 is that it boosts B+ by a small factor and provides less sag to overall performance of the amplifier. I may decide to test and monitor with the 5V4's installed to see if they improve performance of the 1942 amplifiers. All three amp's were modified by the dealer in 1942 so I am most interested in replicating those mod's to a T. I will have to monitor B+ on the push pull output circuit as a result and also monitor the power transformer and filter capacitors as ratings with the sub tube will change the overall circuit.
Below is part one of the electrical restoration on the amplifiers for those whom are interested:
Video 4: https://www.youtube.com/watch?v=mmx4cajkwWA