Kenwood TS-510S (Trio)

This radio was marketed also as Allied A-2517 in North America and was manufactured in the late 1960's.  It followed earlier model TS-500 remaining same cabinet styling. A new feature was a solid state VFO giving good stability. Features include RIT, VOX, 25 kHz calibrator and side tone oscillator. Meter indicates Ip, RF, HV ALC and signal strength.

The receiver is dual conversion super heterodyne. IF frequencies are  3395 and 8595 kHz. It has an RF-amplifier and 1.2 kHz crystal filter (+ optional 250 Hz CW filter).

The transmitter  has one 12BY7A driving the final amplifier. That has two S1001s operating at class AB1. S2001 is same tube as 6146B

Repair notes

General cleaning, I used Q-tips dipped in water to clean PCB-boards.

After some general alignment the receiver started to sound a little better but it was still very quiet in CW. Perhaps that was the reason why someone had installed an extra switch to use SSB filter on CW. I removed the switch and checked carrier frequencies with a frequency counter. And they were not right! The CW filter had not been installed correctly. After adjusting all frequencies CW reception was much improved.

Many aluminum shields around valves were missing. I made new ones using Al from a beer can (I scratched the paint of using steel wool). Don't know how important those shields are but added them anyway.

The receiver is now adequate on 80 meters (I don't have a proper antenna yet) but almost deaf on all other bands. I suspect there's something wrong with the tuning coils. There are individual tuning coils for 3.5 MHz, but coils for other bands are connected in series.

The transmitter is basically working. I got something out to a dummy load at 3.5 MHz.

Still a lot to do!