04-30-2017, 07:40 AM
I have a Philco 37-650 chassis that I'm restoring and it is working other than the volume going down shortly after it warms up. I checked and subbed the 6K5 & 6F6 tubes and that didn't fix the problem. Two odd things I noticed is one the plate of the 6K5 goes from 200 V down to 90 V and the volume goes down as well and the tone switch has very little effect on the tone---the tone/on-off switch is good and the tone cap block #54/54A is recapped and connected properly. The bias voltage on the 6F6 tubes is -16.5 V and the plate/screen voltages are very close according to the service literature. The voltages on the voltage divider are -17.2 v & -2.7V. The RF/IF section is working great and the shadow meter is working. I checked the output transformer on the H-26 speaker and the primary is measuring 660 ohms/970 ohms compared to 330/370 ohms that is shown on the schematic. The field is measuring 465 ohms--wondering if the output transformer might be the issue or if it is something else--I have fully recapped the chassis and checked/rechecked all connections and I can't find any other problems. I've restored other 37-650 chassis before but this one is the worst one I ever worked on. Thanks, Ken