Several of my ham radio friends own a Collins 30S-1, and are very pleased with them. The 30S-1, I purchased had two know issues , but otherwise was supposed to be in good operating condition. However, I discovered a few more issues after I became more familiar with it's operation. Cosmetically, the amplifier is in good condition for it's age. It's been updated with new capacitors and diodes in the 1990's, and a Peter Dahl filament transformer. However, the amplifier has enough significant issues, that it now qualifies as a project.
The first known issue, the front panel had two push switches to control the high voltage, OFF and ON, and an indicator light for ready to operate condition. However, the off switch had been replaced with an unattractive generic switch. It worked, but I preferred to have a switch or a set of switches that are closer in appearance to the originals. The original switches are no longer available, but there are similar switches available from Newark Electronics, manufactured by EAO. I found the following information on the website of Al Waschka.
Newark # EAO # Description
50F8257 31.121.025 Series 31 Rectangular Switch, Snap Action, Momentary
50F8263 31.040.005 Series 31 Rectangular Indicator
50F8264 31.901.2 Series 31 Rectangular Lens, Red
NS/Order 31.901.0 Series 31 Rectangular Lens, Black
NS/Order 31.963.1 Bulb, 14V
50F8269 02.905 Lens Removal Tool
50F8270 02.906 Lamp Removal Tool
50F8273 01.927 Series 31 Rectangular Protection Guard
I've replaced the switches and indicator, and they look great. Unfortunately, the original switch and indicator were very fragile, and literally fell apart during the replacement process.
The second issue is more critical. Mr. Warren Brune, participated in the design of the amplifier for Collins in the late 1950's. To protect the 4CX-1000 tetrode tube from over heating. A mechanical method was utilized using a normally closed, heated bi-metal sensor, that is connected in series with the interlock circuit. A 250 volt/2 watt 500 ohm potentiometer is used in series with the 120 Volt supply to control the heating circuit, to vary the temperature of the sensor, thus setting the activation threshold for when the sensor will open to protect the tube.
When I purchased the amplifier, the seller indicated, that the previous owner had deactivated the tube protection circuit, because one lead on the temperature potentiometer was arcing the 120 Volt AC supply to ground. I found a replacement potentiometer, and was amazed to find nearly the same part with the exact same part number was still available. I have the temperature sensor working, but the amplifier goes off line occasionally, so more investigation is required. I may update that circuit to use a modern temperature sensor relay.
As I mentioned, there were other issues that were not revealed or perhaps unknown by the seller. The third issue, the three minute HV timer has been deactivated, likely a quick fix after the timer tube failed. To address that issue. I may build a simple solid state timer equivalent.
I've had an opportunity to use the amplifier, and discovered a few additional problems. The grid current is not being displayed on the meter. On the higher bands, the output power is way down, despite trying several known good tubes. This may end up being a wintertime project for me.