Tag Archives: W9KR

Brass Pin on the side of 811A and 572B Tubes

Not every power tube installation uses a simple push-in tube socket.

A straight-push insert replacement socket

Some older ham gear, audio gear and military/avionic sockets are twist-type.

Twist-Insert Socket – look for the pin guide slot in the collar

As something has to fit the index slot, a Brass Pin on the side of 811A and 572B Tubes is a mechanical index and retention pin.

Brass Indexing Pin (on an 811A)

These sockets where you have you insert the tube base with the pin in an L-shaped slot, Push in And then Rotate are kind of neat.

Looking down into a twist-type socket

Most old tubes have a pin that sticks out about 60-70/1000th of an inch.   A small group of original 811A tubes from my amps that W9KR measured showed .062” to .071”.

The pin length on new tubes may vary, as I received 572B tubes with an exposed 94/1000th of an inch of pin which is sticks out too far for one  of the socket locations in my amps, as the overly long pin doesn’t quite clear other components and chassis in my amplifiers.  The 572B tubes W9KR measured .091” to .094” pin extension lengths.

I have not been able to find an original specification for pin length.

When confronted with an overly long pin that hits chassis or components, a bit of Dremel tool time, relieving the excess pin length or sanding away the entire projecting pin, will sort things out.



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Digging Deeper – Collins S-Line work after Mice Tried to Move In

Some more great work by Chuck W9KR, this time on my Washington Island Collins Station where during my absence from the Island during the CCP-19 Virus “lockdowns” a mouse family tried to build their new home in my KWM-2A Transceiver.

Lots of shells (and poo)

Well packed during their brief residency

I get mice into the radio shack area regularly, and have traps set.  But traps are useless if you are are not there to clear them out, meaning the mice were second or third wave while we were absent from the island for the extended period of the initial virus lockdowns.

While I captured the mice easily once we could tend our mousetraps, it wasn’t until last year that I realized they had taken up residence and created their own warehouse of food inside the Collins gear.

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Collins Progress Update 1

Some in progress pictures as Chuck W9KR does his magic on the Collins 32S1/75S1 station.

Digging in at W9KR’s very well equipped workbench

Testing found some weak and failed tubes, all which are being replaced. I had bought tube kits for some of the units, and others have been sourced. All told about 8-10 tubes across the equipment are being replaced.

After a prolonged period of increasing voltages controlled by a variac, good meter readings

Prolonged means a lot longer than I would have thought, a gentle process.
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Disposition of radios (2) – Collins S-Line Station

Collins S-Line (32/75/312-4…) Station Loaded for Service Work

Over the last 12 years I’d accumulated enough Collins S-Line equipment to not only complete the 32s/75s station started when George W9EVT gave me a 75S1 receiver with a shopping list of what I needed to complete an operating S-Line station, but a second KWM-2A transceiver based station which I will come back to in another post.

The 32S/75S setup was never fully setup once collected and consists of:

  • 32S1 – transmitter
  • 75S1 – receiver
  • 30L1 – amplifier
  • 312B4 – remote VFO
  • 516F2 – power supply
  • 312B3 – speaker
  • DL-1 – dummy load
  • Matching SWR Meter
  • SM-1 – microphone
  • SM-2 – microphone
  • Voice processor
  • Digital frequency Display
  • necessary interconnect cables, manuals, some spare tubes, and so on

At no one time has the entire station been in operation.

I reached out via the reflector to fellow members of the Collins Collectors Association asking for help checking over the gear, and more importantly helping me with some issues with the other S-Line station (the one that I will come back to in a later post).

Chuck W9KR reached out to me, as we are just over an hour apart, offing to help me out.

So the station made it way to Chuck’s QTH for review, tune-up and any catch-up work/mods.

We opened up the 30L1 amp to test the tubes, as replacing these tubes has become rather pricy. W9KR has awesomely kept tube testers that outshine a typical museum piece which were put to duty testing the four tubes.

All of the power tubes tested great, and digging a bit further we discovered this particular 30L1 had already had a power supply upgrade board and kit installed.

We spent some time with my describing how I wanted to end up with a robust station that I and others who didn’t have much of a chance to operate tube radios could work with learning these skills.

The station was left with Chuck W9KR to be systematically gone through. Planes are to bring in the KWM-2A station from Washington Island so Chuck can help me sort that station out as well.



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