Some early Palomar 300A base linears had all 3 relays and the receive preamp on a plug-in circuit board.
Just one problem. When the relays go bad, you find that particular part hasn't been made in decades. The pins have a non-standard pattern. All the relays this size you can buy have a pin pattern that won't line up with the holes in the pc board.
Oops.
Haywiring a relay you can buy with wires that go into the circuit board holes is clumsy and time-consuming. First prototype of an outright replacement for the whole board was expedient, using a keying circuit board we make in quantity and sell on fleabay. Looks a bit clumsy, but it worked once I patched an error in the layout
Only takes two relays if you leave out the receiver preamp. Just don't need the grief I'll get from folks who try to use a preamp and don't like how it makes the noise level higher.
This project has had ups and downs. Getting the CAD software to remove the green solder-mask paint didn't exactly work the way it was meant to. The foil-trace "fingers" are supposed to be exposed metal, not covered in the green stuff.
Decided to move the keying circuit onto this board, rather than the piggy-back arrangement with the separate keying circuit board.
Got the partial exposed copper on the front side. The solder side is still totally exposed, but that's not really a problem.
I'd call this a production board, but some parts in the keying circuit are kinda crowded. Plenty of room, just didn't spread them out fully.
Not sure I want to revise it any further. Sale of the prototype boards hasn't exactly set the world on fire. Could be I just waited 20 years too long to come up with it?
Time will tell.
73
Just one problem. When the relays go bad, you find that particular part hasn't been made in decades. The pins have a non-standard pattern. All the relays this size you can buy have a pin pattern that won't line up with the holes in the pc board.
Oops.
Haywiring a relay you can buy with wires that go into the circuit board holes is clumsy and time-consuming. First prototype of an outright replacement for the whole board was expedient, using a keying circuit board we make in quantity and sell on fleabay. Looks a bit clumsy, but it worked once I patched an error in the layout
Only takes two relays if you leave out the receiver preamp. Just don't need the grief I'll get from folks who try to use a preamp and don't like how it makes the noise level higher.
This project has had ups and downs. Getting the CAD software to remove the green solder-mask paint didn't exactly work the way it was meant to. The foil-trace "fingers" are supposed to be exposed metal, not covered in the green stuff.
Decided to move the keying circuit onto this board, rather than the piggy-back arrangement with the separate keying circuit board.
Got the partial exposed copper on the front side. The solder side is still totally exposed, but that's not really a problem.
I'd call this a production board, but some parts in the keying circuit are kinda crowded. Plenty of room, just didn't spread them out fully.
Not sure I want to revise it any further. Sale of the prototype boards hasn't exactly set the world on fire. Could be I just waited 20 years too long to come up with it?
Time will tell.
73
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