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Thread: Need Palomar300A tubes for spares!

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    Quote Originally Posted by ARF2001 View Post
    I've managed to get a couple sets of outputs for the Palomar 90A on E-Bay for reasonable prices, but it's only a 2 tube amp. Seeing as the TV sweep tubes aren't nearly as robust as real transmitting tubes and these old amps tend to eat output tubes like candy, other than for the fun of it I'm questioning the worth of bothering with it too much longer. It won't take very many tube replacements to get to the cost of something like a new Dave Made base amp that not overdriven can be a lifetime investment without a lot of the headaches.

    Believe me I hear what your saying and I've thought of what your saying many times and that is why I haven't ordered 6 replacement tubes yet. I do that twice and I'm already on my way to buying a newer amp. I suppose a lot has to do with how much time you have to devote to being on the air. My unit has two external accessory cooling fans mounted on top to help dissipate the heat. How about it JJD how long do you get out of a tube set?

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    Quote Originally Posted by whiteastro View Post
    Believe me I hear what your saying and I've thought of what your saying many times and that is why I haven't ordered 6 replacement tubes yet. I do that twice and I'm already on my way to buying a newer amp. I suppose a lot has to do with how much time you have to devote to being on the air. My unit has two external accessory cooling fans mounted on top to help dissipate the heat. How about it JJD how long do you get out of a tube set?
    I have yet to burn up a set...I bought my "Kicker 500" back in 2012 used off ebay, and it had weak tubes in it when I bought it...So I replaced them with a New set, plus bought a extra set just to have as spares...The first set I bought are still working like new, so i'm not sure if I will ever use my spares.

    The Palomar 300A I have, has the original tubes still in it, and when I had the box in the shop having a rectifier diode replaced I had the tech check the tubes, and they all tested good and strong...

    IMO, if you run these type tube amps the way they were intended, they should last a long time...But if you over-drive them, or maybe have high SWR, then they won't last any longer than a pill box would being abused the same way.

    One other side note...Don't get too hung-up on tubes getting hot...That's what tubes do! These tubes were designed originally for old TV set's...Ever see a old TV set with a fan in the back to cool the tubes?..........no


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    The Palomar 300A is a better design than the 90A I have, and I can see by this that the 300A should have longer tube life and is likely more worthy investing in. I noticed with my spectrum analyzer that even with the cleanest signal input, the 90A pumps out a lot of harmonics and IMD. You might not give this any thought until neighbors or the FCC come to put a spear through your heart, just something to be aware of as these 1970's design CB grade amps don't have the filtering quality of a ham type linear. Along with excellent grounding a low pass filter IMHO is a must, I noticed it cleaned the harmonics above 30 MHz considerably as it should. Keeping reasonable modulation levels is a must too, or these amps turn themselves in to powerful wireless intercoms for home entertainment devices.
    Last edited by ARF2001; 12-10-2019 at 10:18 AM.

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    Quote Originally Posted by JesseJamesDallas View Post
    I have yet to burn up a set...I bought my "Kicker 500" back in 2012 used off ebay, and it had weak tubes in it when I bought it...So I replaced them with a New set, plus bought a extra set just to have as spares...The first set I bought are still working like new, so i'm not sure if I will ever use my spares.

    The Palomar 300A I have, has the original tubes still in it, and when I had the box in the shop having a rectifier diode replaced I had the tech check the tubes, and they all tested good and strong...

    IMO, if you run these type tube amps the way they were intended, they should last a long time...But if you over-drive them, or maybe have high SWR, then they won't last any longer than a pill box would being abused the same way.

    One other side note...Don't get too hung-up on tubes getting hot...That's what tubes do! These tubes were designed originally for old TV set's...Ever see a old TV set with a fan in the back to cool the tubes?..........no

    I was figuring on ordering 8 tubes in case some came thru shipment broken and I would go from there. I know and appreciate the theory why the man added the extra cooling fans on top of the amp case. It's called a once of prevention is worth a pound of cure Yes the tubes were made to get hot but how about the other resident electronic parts inside the cabinet. I think resistors, diodes, capacitors, transistors, and all the other parts that make the system work. How do they enjoy all that heat and what does it do to them. I'm no electronic wizard so I can't argue anything, I just read an try to learn. The guy installed the fans wrong in my opinion and I will change them. He put the fan in the 2 tube bay blowing down and the fan in the 4 tube bay blowing up. I want them both blowing up because heat rises!

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    Quote Originally Posted by whiteastro View Post
    I was figuring on ordering 8 tubes in case some came thru shipment broken and I would go from there. I know and appreciate the theory why the man added the extra cooling fans on top of the amp case. It's called a once of prevention is worth a pound of cure Yes the tubes were made to get hot but how about the other resident electronic parts inside the cabinet. I think resistors, diodes, capacitors, transistors, and all the other parts that make the system work. How do they enjoy all that heat and what does it do to them. I'm no electronic wizard so I can't argue anything, I just read an try to learn. The guy installed the fans wrong in my opinion and I will change them. He put the fan in the 2 tube bay blowing down and the fan in the 4 tube bay blowing up. I want them both blowing up because heat rises!
    So did the guy take out the factory fan then? Originally the 300A had a fan that sat between the driver tubes and the 4 final tubes...

    You would be surprised at just how much heat all those parts inside can handle...Even with fans blowing, tube amps still get plenty warm...And one thing i've noticed with mine, is the hotter it gets, the more watts show up on the meter...Now that could just be harmonics playing with the meter, but at any-rate, it put's a smile on your face watching the needle on the meter swing!


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    Quote Originally Posted by JesseJamesDallas View Post
    So did the guy take out the factory fan then? Originally the 300A had a fan that sat between the driver tubes and the 4 final tubes...

    You would be surprised at just how much heat all those parts inside can handle...Even with fans blowing, tube amps still get plenty warm...And one thing i've noticed with mine, is the hotter it gets, the more watts show up on the meter...Now that could just be harmonics playing with the meter, but at any-rate, it put's a smile on your face watching the needle on the meter swing!

    To be honest with you JJD I will have to take the top off and check to see if the internal fan is working or if the other two fans are just his way of not fixing the internal fan. I really laughed when I read about you smiling as you watched the watt meter rise. That's the way you know you have the radio sickness Really Bad. LOL

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    Quote Originally Posted by ARF2001 View Post
    The Palomar 300A is a better design than the 90A I have, and I can see by this that the 300A should have longer tube life and is likely more worthy investing in. I noticed with my spectrum analyzer that even with the cleanest signal input, the 90A pumps out a lot of harmonics and IMD. You might not give this any thought until neighbors or the FCC come to put a spear through your heart, just something to be aware of as these 1970's design CB grade amps don't have the filtering quality of a ham type linear. Along with excellent grounding a low pass filter IMHO is a must, I noticed it cleaned the harmonics above 30 MHz considerably as it should. Keeping reasonable modulation levels is a must too, or these amps turn themselves in to powerful wireless intercoms for home entertainment devices.

    That's why I enjoy this forum because there is a lot of people in here with a lot more experience in the radio field than I have and they save me from making expensive mistakes. I only give $150.00 for the amp so I'll get a set of spare tubes once and go from there. What little I've used it I have got good reports. I'll never be a Ratchet Jaw, that is not my style. Back in the 70s I always wish I could talk skip but couldn't afford to so now I have a little more to play with. LOL

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    The transistors used in the 300A look to be in a similar configuration to the 90A, in that they are only part of the preamp and relay switching thus shouldn’t run hot at all. The high wattage dropping resistors in the power supply likely get really toasty, but are made to convert the extra power to heat with their inefficient 1970’s design. Power supply rectifier diodes might get a bit warm, but not excessively hot. These amps did sound good, little question to that. They were also built a little less as Saturday night specials than many, so they get some respect. Again, not ham level amps but they fill the outlaw CB’er bill which was Palomar's intent at their price level.

    I think I have most of the garbage filtered out of the 90A’s transmissions, at least I haven’t heard the neighbors complaining about it. In knowing the distortion was there I think a bit of prevention went a long way before really using it. (Of course if you live in a remote area with no neighbors, this won't be an issue.) DX was booming for a little while especially on 6 and 28 last night, and I was getting some good signal copy far away so yeah, these amps work!
    Last edited by ARF2001; 12-11-2019 at 11:13 AM.

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    Quote Originally Posted by ARF2001 View Post
    The transistors used in the 300A look to be in a similar configuration to the 90A, in that they are only part of the preamp and relay switching thus shouldn’t run hot at all. The high wattage dropping resistors in the power supply likely get really toasty, but are made to convert the extra power to heat with their inefficient 1970’s design. Power supply rectifier diodes might get a bit warm, but not excessively hot. These amps did sound good, little question to that. They were also built a little less as Saturday night specials than many, so they get some respect. Again, not ham level amps but they fill the outlaw CB’er bill which was Palomar's intent at their price level.

    I think I have most of the garbage filtered out of the 90A’s transmissions, at least I haven’t heard the neighbors complaining about it. In knowing the distortion was there I think a bit of prevention went a long way before really using it. (Of course if you live in a remote area with no neighbors, this won't be an issue.) DX was booming for a little while especially on 6 and 28 last night, and I was getting some good signal copy far away so yeah, these amps work!
    Yes I have read that the 300A was frowned on by the Ham operator people and thanks for the run down on my amps insides. All of life is a learning process and we try to learn from our mistakes if we can admit we make them. I'm not a real blabber mouth so that amp will probably suit me as long as age doesn't start taking it's toll on it. I pulled off the cover and the internal cooling fan is working. So far the only thing that doesn't work is the tuning meter and I use my Dosy meter to do that. I'm glad your amp is working for you and you can have some fun. I usually stick to 38LSB because tuning the amp every time you jump around would be a Pain. If your out by Erie PA you probably do get more CB traffic. If you hear PA50 that will be me waving. Good luck Mike

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