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i took the dive and got it

1iwilly

Sr. Member
Dec 7, 2008
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just bought a Palomar 300A in excellent condition from a local here in fl older-gen
the top cover has never been removed and still has the rivets on it.
any good recommendation on a fan outside to dissipate heat quicker
 

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Um, the top cover is secured by the three quarter-inch hex-head bolts on each side, one below each rivet.

The rivets serve to secure a metal strip to the top cover. This strip extends below the lower edge of the top cover and serves to anchor the three hex-head sheet-metal screws that hold the case halves together.

Remove those six screws and the top cover comes off. Remove the four screws on the underside and the lower half of the cabinet comes off.

Unless you fetched it out of a time machine fresh from 1977, there will be age issues as a rule. Removing the bottom cover will permit you to check for visible signs of impending doom, like swollen electrolytic capacitors. If yours has the white PVC-plastic 1000uf 25-Volt axial-lead capacitors (one wire out each end) make sure none of them are beginning to swell up. This is the first sign that the part is going to short out and cause mayhem some time soon.

With any luck, you'll hear similar advice from other folks about 45 year-old electrolytic capacitors and how they tend to fail soon after they are awakened from a long sleep. Doesn't mean it won't appear to work fine as you found it. But the statistical reality doesn't lean in your favor for the long run.

You have a rare find here. Would be a shame to see it go poof in a week or three because of a predictable issue.

73
 
Um, the top cover is secured by the three quarter-inch hex-head bolts on each side, one below each rivet.

The rivets serve to secure a metal strip to the top cover. This strip extends below the lower edge of the top cover and serves to anchor the three hex-head sheet-metal screws that hold the case halves together.

Remove those six screws and the top cover comes off. Remove the four screws on the underside and the lower half of the cabinet comes off.

Unless you fetched it out of a time machine fresh from 1977, there will be age issues as a rule. Removing the bottom cover will permit you to check for visible signs of impending doom, like swollen electrolytic capacitors. If yours has the white PVC-plastic 1000uf 25-Volt axial-lead capacitors (one wire out each end) make sure none of them are beginning to swell up. This is the first sign that the part is going to short out and cause mayhem some time soon.

With any luck, you'll hear similar advice from other folks about 45 year-old electrolytic capacitors and how they tend to fail soon after they are awakened from a long sleep. Doesn't mean it won't appear to work fine as you found it. But the statistical reality doesn't lean in your favor for the long run.

You have a rare find here. Would be a shame to see it go poof in a week or three because of a predictable issue.

73
i took the bottom cover off the 2 caps in the middle where change very clean i was able to remove the top cover and looks clean and tight only thing lose i found was the 2 long screws on the blower motor tighten them up good to go driving it my my cobra 2000 so far good reports 20220704_141005.jpg
 
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My brother has a Thunderbolt 305 sitting on his desk right now.
It is pristine, no dirt or dust, and the tubes that came with it were new looking in the boxes.
I told him.
He said, but it looks like new.
Worked awesome for almost 3 months.
He is now cleaning up fuzzy leftover spluge, burnt traces on the HV board and waiting for replacement caps.
Then we will see if anything else it toasty.
It happens.

( on edit)
It does look like some one has replaced one of the 450 volt caps in that one, see were they just cut the leads and cobbled the new one in.


73
Jeff
 
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My brother has a Thunderbolt 305 sitting on his desk right now.
It is pristine, no dirt or dust, and the tubes that came with it were new looking in the boxes.
I told him.
He said, but it looks like new.
Worked awesome for almost 3 months.
He is now cleaning up fuzzy leftover spluge, burnt traces on the HV board and waiting for replacement caps.
Then we will see if anything else it toasty.
It happens.

( on edit)
It does look like some one has replaced one of the 450 volt caps in that one, see were they just cut the leads and cobbled the new one in.


73
Jeff
I am not sure about those caps they look like the same ones as of of my Palomar's in my collection that i know are originals.
 
I am not sure about those caps they look like the same ones as of of my Palomar's in my collection that i know are originals.
Look closely at the leads of the bottom high voltage cap.
Sometime in the past they changed one if them. If it was original the leads would go down through the holes in the board and are soldered on the bottom. Someone clipped the leads and left a tag end sticking up from the old cap. They then twisted the new replacement in and soldered it. Did not want to remove the board to properly replace it.
So I looks like one old cap and one replacement of unknown age.

73
Jeff
 
02513BA5-9579-4DEE-8C89-C12EC1E3A3B5.jpeg
I only use these now, run off of the old school lamp dimmer (adjustable) switch. These plugged straight to 120v will rattle your teeth with noise. But, throttled down they move much more air than I ever needed and are rather quiet overall. The last one I bought was this particular one. It was brand new in the box off of fleabay for 20.00.
 
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Actually if you look, both have been done that way, on my phone it looked like just one, but I got home and both look like they have been done that way.

73
Jeff
looks like very first thing is DO AS TOLD your right so is nomad radio. shame to see fine electronics ruined
 
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went thru the whole amp everything is very tight and clean nothing looks discolored tubes sit tight no kind of looseness so now waiting on some good skip
i'm not the long-winded type
The guy I bought mine from was a middle aged guy getting into radio repair and he claimed he got about 600 watts out of it and from what I used it that was about right He was getting a bigger amp but he was a AM skip talker. Claimed he really didn't like SSB. My Palomar is in limbo waiting for me to get some time to look at it and install a part I received from Nomad Radio. Like they say No Rest For The Wicked ! LOL
 

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