CPI 400/2000 radio MM5221ESD chip availability?

[VK3RX]

You had to plug it in then do something else like install a jumper or make a change on the board.

Now that you mention it I didn't just swap chips, I recall I swapped the whole board from the junker to mine because it seemed a later revision.

Yes, junker CPIs are hard to get hold of because people are hanging onto them for spares. I have a working CP2000 here and a junker CP300.

Working final transistors for one thing are handy to have, because it seems many CP300/400 units had the power cranked up, with some having a heatsink bolted to the outside rear of the chassis to theoretically dissipate the heat

 

[prcguy]

When my CP300 was brand new in the late 70s I had a guy machine me a heatsink for the PA transistor. He had it black anodized and it was beautiful.

Now that you mention it I didn't just swap chips, I recall I swapped the whole board from the junker to mine because it seemed a later revision.

Yes, junker CPIs are hard to get hold of because people are hanging onto them for spares. I have a working CP2000 here and a junker CP300.

Working final transistors for one thing are handy to have, because it seems many CP300/400 units had the power cranked up, with some having a heatsink bolted to the outside rear of the chassis to theoretically dissipate the heat

 

[VK3RX]

Nice

The two studs on the rear of the PA module were often "tweaked" by the screwdriver brigade to try and adjust the power, not realizing they were just mounting studs for the transistors. When "adjusted" the studs usually broke off the transistors and rendered them useless.

I recall CPI used a few rivets in addition to screws to attach the PA module to the chassis, to discourage fiddling.