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Palomar 300a amplifier
- Thread starter Tweetybird
- Start date
The one on top was made in 1976.
The lower one was made in 1979.
With any luck the last 40 years have been kind to it.
73
The lower one was made in 1979.
With any luck the last 40 years have been kind to it.
73
The R50 was originally sold as a "sealed" relay. This meant that you could safely immerse the circuit board in a cleaning solution to clean off the excess flux from a wave-soldering process. They don't build it "sealed" just to keep out dirt and schmoo, but to protect it from cleaning solutions in the pcb-manufacturing process.
Just one problem. The plastic they used for the thing would "outgas", or leach vapor into the interior of the relay. This vapor would build up and then condense onto the contact surfaces. This makes an insulating layer on the contact points causing that circuit to become intermittent.
It's common for the glue to come loose where the top cover attaches to the bottom plate of the relay. So long as this happens soon enough, the life of the relay will be longer than you would get if the thing had remained fully sealed up. Odd, but a poor glue job will make it last longer.
Later production of this part was revised to have a vent hole at one corner, like the one in this pic.
This would prevent that vapor from building up and causing trouble. A small piece of yellow tape covers this hole when the part is made, so you can still safely clean the pc board by immersion. You're supposed to peel off this tape after the part is installed.
What this means to a relay built 40 years ago is that it's a total tossup whether or not it will work reliably.
Have a look at the glue seal around the bottom of the thing. If it's separated, the part may be okay to use. If it's still fully sealed, maybe not so likely.
73
Just one problem. The plastic they used for the thing would "outgas", or leach vapor into the interior of the relay. This vapor would build up and then condense onto the contact surfaces. This makes an insulating layer on the contact points causing that circuit to become intermittent.
It's common for the glue to come loose where the top cover attaches to the bottom plate of the relay. So long as this happens soon enough, the life of the relay will be longer than you would get if the thing had remained fully sealed up. Odd, but a poor glue job will make it last longer.
Later production of this part was revised to have a vent hole at one corner, like the one in this pic.
This would prevent that vapor from building up and causing trouble. A small piece of yellow tape covers this hole when the part is made, so you can still safely clean the pc board by immersion. You're supposed to peel off this tape after the part is installed.
What this means to a relay built 40 years ago is that it's a total tossup whether or not it will work reliably.
Have a look at the glue seal around the bottom of the thing. If it's separated, the part may be okay to use. If it's still fully sealed, maybe not so likely.
73
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Mounting components to a green board triples their value. No one does a good shoehorn job anymore. The local surplus store usually has something better than new for a couple of bucks.
Saw the BC321. Don't have any experience with that version of the radio. I do have a BC348 in the basement that I inherited from a buddy 30-plus years ago. He was lightening his load before moving to California. Looked like a fun retirement project. But decades later I have no plans to retire. Should probably unload it some day.
Fixed a handful of BC348 radios in the 80s for local hams, but haven't looked inside one since then. My wife gets amused when a WW2 movie takes place in a B17 or B24. She really doesn't care if they dressed the set with the right liason radio or not, but I'll point it out anyway. A restored B24 visited our local general-aviation airport a few years back. Got to walk through it and they not only had the right liaison receiver, but all the original AAF manuals next to it. Very cool!
Good luck with yours. It's a good AM receiver, but not so swift for CW and sideband.
73
Fixed a handful of BC348 radios in the 80s for local hams, but haven't looked inside one since then. My wife gets amused when a WW2 movie takes place in a B17 or B24. She really doesn't care if they dressed the set with the right liason radio or not, but I'll point it out anyway. A restored B24 visited our local general-aviation airport a few years back. Got to walk through it and they not only had the right liaison receiver, but all the original AAF manuals next to it. Very cool!
Good luck with yours. It's a good AM receiver, but not so swift for CW and sideband.
73
Here in the South Duct Tape fixes anything.I never saw any RED duct tape because RED is my Favorite color I would have purchased at least two or three rolls. LOL
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