I recently acquired a vintage Collins 30S-1 console type HF amplifier. I've been considering one for quite some time, but due to it's 160 pound shipping weight, that made purchasing one outside of my area prohibitive. Fortunately, a few weeks ago, one was listed for sale near my home. Therefore, I decided to purchase that amplifier while I had the opportunity.
Several of my ham radio friends own a Collins 30S-1, and are very pleased with them. The 30S-1, I purchased is in good operating condition. Cosmetically, the amplifier is in good condition for it's age. It's been updated with new capacitors, diodes, and a Peter Dahl filament transformer. However, there are a few issues that require attention before I place the amplifier into the operating position.
The first issue, the front panel has two push switches, OFF and ON, and an indicator light for ready to operate condition. However, the off switch has been replaced with a generic switch. It works, but I would prefer to have a switch or a set of switches that are closer in appearance to the original. 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
The second issue is more critical. Mr. Warren Brune, designed 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 for 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 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 plan to replace the potentiometer. I was amazed to find the same part with the exact same part number was still available.
The final issue (I hope), the three minute HV timer has been deactivated as well, more than likely a quick fix, perhaps after the timer tube failed. I may build a simple solid state equivalent to interrupt any depression of the HV ON switch for three minutes.
Hopefully, I'll have the repairs completed soon and can give it a through shakedown.