Palomar TX-75 Bi Linear Solid State with tuner on back

[Onelasttime]

First I purchased this 1-2 year ago along with a Palomar TX-150 solid state NOS from RF Parts for $149 each.

I have not done anything with them yet.

I opened the case of the TX-75 and found a red wire going to the power switch wedged between the case and the cover with a chunk of insulation missing. I should hook them both up and function check them. Always open those boxes up and check them out before you power them up!

So I was wondering if the Pi network on back marked 10-15, 20, 40, 80 actually works? It is just a sticker and does not have an m after the numbers but clearly it is meant to be 10-15m, 20m, 40m, 80m. I am imagining it works since it is a sizable box on the back and it would be silly to build a circuit board and populate it with parts if it was not intended to work. Then again it is CB amp and that box and parts inside could be lipstick on a pig so thought I would ask.

It has two old school CTC CD2545 transistors. Outside of the tuning network on back appears to be just like any other Palomar TX-75. I have to say I was surprised to see Arco's and Silver Dipped Mica's making up 1/2 of the cap's in the box.

I bought both units becasue they where NOS and the price for new American made or Japanese made transistors is equal to or is higher than the price I paid for the each 2 transistor complete amplifier. Plus how can you go wrong with NOS SSB ready 2xtransistor mobile amp full of 100% American made parts for $149 each?

Be interesting to hear peoples experience with the built in band tuning box on back!

 

[AudioShockwav]

The old Palamar built a couple amps with band pass filters on them, I had the 4 transistor 5200 .
They did this to try to skirt around the FCC.
It may very well be a filter.
Can you post pictures of the inside?
73
Jeff

 

[Onelasttime]

I can. I took photo's with my new phone and having issues putting in my email to send photo's to my PC. I did not take photo's of the tuning section.

At the time I did not have a flat tip small enough to remove the knob on the tuning section hand. All kinds of Phillips. The wife and kids are always taking my tools out of the junk draw. I will have to go out to garage and get a small flat tip.

It looks like a solid little amp but the wire inside is so tiny. Not a big fan of the relays they used inside but in 1976 I am sure they where as common as pigeons and dogs in Berlin!

 

[AudioShockwav]

I can. I took photo's with my new phone and having issues putting in my email to send photo's to my PC. I did not take photo's of the tuning section.

At the time I did not have a flat tip small enough to remove the knob on the tuning section hand. All kinds of Phillips. The wife and kids are always taking my tools out of the junk draw. I will have to go out to garage and get a small flat tip.

It looks like a solid little amp but the wire inside is so tiny. Not a big fan of the relays they used inside but in 1976 I am sure they where as common as pigeons and dogs in Berlin!

Here is the inside of the 5200 showing the band pass filter.

73
Jeff

 

[nomadradio]

This appears to be the version without a single relay in it.

Uses PIN diodes to switch RF. This was a bleeding-edge hi-tech wocka-wocka feature 40 plus years ago.

Just one problem. You need 12 Volt power to make it act like a barrel connector.

And that's what an amplifier should do when it's turned off, right?

But a relay's metal contacts will carry the receive signal and the radio's barefoot power directly to the antenna, power or not.

PIN diodes require power to pass any RF through them. Either barefoot OR with the amplifier active. I saw my share of this model back in the day, blown out because someone tried to talk barefoot with it in line and no power applied.

Always make sure there's DC power to the amplifier's power leads before you key the mike, whether the power switch is on or off.

73

 

[Onelasttime]

Sorry guys been busy working on cars and house before winter hits!

 

[Onelasttime]

Sorry I have been to busy to get back to this!

 

[DelR]

First I purchased this 1-2 year ago along with a Palomar TX-150 solid state NOS from RF Parts for $149 each.

I have not done anything with them yet.

I opened the case of the TX-75 and found a red wire going to the power switch wedged between the case and the cover with a chunk of insulation missing. I should hook them both up and function check them. Always open those boxes up and check them out before you power them up!

So I was wondering if the Pi network on back marked 10-15, 20, 40, 80 actually works? It is just a sticker and does not have an m after the numbers but clearly it is meant to be 10-15m, 20m, 40m, 80m. I am imagining it works since it is a sizable box on the back and it would be silly to build a circuit board and populate it with parts if it was not intended to work. Then again it is CB amp and that box and parts inside could be lipstick on a pig so thought I would ask.

It has two old school CTC CD2545 transistors. Outside of the tuning network on back appears to be just like any other Palomar TX-75. I have to say I was surprised to see Arco's and Silver Dipped Mica's making up 1/2 of the cap's in the box.

I bought both units becasue they where NOS and the price for new American made or Japanese made transistors is equal to or is higher than the price I paid for the each 2 transistor complete amplifier. Plus how can you go wrong with NOS SSB ready 2xtransistor mobile amp full of 100% American made parts for $149 each?

Be interesting to hear peoples experience with the built in band tuning box on back!

I found a Palomar DX-75 at a flea market for $20USD, works great, My elcheapo meter shows somewhere around 150-175W with my Cobra 139XLR and D-104 mic.

 

[BC Coyote]

My elcheapo meter shows somewhere around 150-175W

You probably need to get a new meter.
A Palomar TX-75 maxes out at about 60 to 65 watts.
I have several Palomar amps.....my TX-100 makes about 85 watts PEP, and my TX-200 can eke out 180 watts PEP.
Either your meter is giving you bullshit readings, or the amp is spewing massive amounts of harmonics because it is being over-driven or over-volted.
How much are you driving it with ? 4 or 5 watts drive would be the most you'd want.
That amp will sound like crap on sideband due to its class C biasing, but it should sound OK on AM or FM mode.

 

[DelR]

You probably need to get a new meter.
A Palomar TX-75 maxes out at about 60 to 65 watts.
I have several Palomar amps.....my TX-100 makes about 85 watts PEP, and my TX-200 can eke out 180 watts PEP.
Either your meter is giving you bullshit readings, or the amp is spewing massive amounts of harmonics because it is being over-driven or over-volted.
How much are you driving it with ? 4 or 5 watts drive would be the most you'd want.
That amp will sound like crap on sideband due to its class C biasing, but it should sound OK on AM or FM mode.

You are probably correct on the meter. I thought that was too much also. I figured that would get a faster response than just asking about it.LOL. I was thinking that is what the "75" is about. While on the subject, what should a Kris 300, 2 tube put out?

 

[BC Coyote]

I was thinking that is what the "75" is about

The numbers don't really mean squat. It's no different than stereo gear or appliances. The manufacturers insinuation is that the "75" or "100" is the output, but it's really just a model number. I find the sweet spot for most solid state amps is about 75 to 80% of the "model" number LOL!

what should a Kris 300, 2 tube put out?

About 200 watts with a medium amount of splatter, or 250 with a LOT of splatter.
People often claimed more than 300 watts That's assuming new-ish tubes. Are they 6LQ6's in there ?
Those things are real old-school splatterboxes using TV sweep tubes!
If it hasn't been run for several years you would want to bring it up to full voltage slowly on a variac to make sure nothing is going to go bang.

I'm sure the tube amp guys will be along now shortly to correct me LOL!

 

[DelR]

You are probably correct on the meter. I thought that was too much also. I figured that would get a faster response than just asking about it.LOL. I was thinking that is what the "75" is about. While on the subject, what should a Kris 300, 2 tube put out?

I an going to start a Kris 300m thread for this.
Thanks
2112

 

[DelR]

The numbers don't really mean squat. It's no different than stereo gear or appliances. The manufacturers insinuation is that the "75" or "100" is the output, but it's really just a model number. I find the sweet spot for most solid state amps is about 75 to 80% of the "model" number LOL!

About 200 watts with a medium amount of splatter, or 250 with a LOT of splatter.
People often claimed more than 300 watts That's assuming new-ish tubes. Are they 6LQ6's in there ?
Those things are real old-school splatterboxes using TV sweep tubes!
If it hasn't been run for several years you would want to bring it up to full voltage slowly on a variac to make sure nothing is going to go bang.

I'm sure the tube amp guys will be along now shortly to correct me LOL!

Well, I have to admit to you. I changed meters and 75w pep, it is.

 

[linearone]

This appears to be the version without a single relay in it.

Uses PIN diodes to switch RF. This was a bleeding-edge hi-tech wocka-wocka feature 40 plus years ago.

Just one problem. You need 12 Volt power to make it act like a barrel connector.

And that's what an amplifier should do when it's turned off, right?

But a relay's metal contacts will carry the receive signal and the radio's barefoot power directly to the antenna, power or not.

PIN diodes require power to pass any RF through them. Either barefoot OR with the amplifier active. I saw my share of this model back in the day, blown out because someone tried to talk barefoot with it in line and no power applied.

Always make sure there's DC power to the amplifier's power leads before you key the mike, whether the power switch is on or off.

73

I've heard of this pin diode switching thing before, can you show me a schematic of how this actually works? I'd love to learn

 

[nomadradio]

a schematic of how this actually works?

There's got to be somebody out there who has covered the design info for this trick.

I gave up trying to fool with it, just trying to find specs on high-power PIN diodes. This was before the internet, and it was an uphill struggle.

Never was a proper schemo of the 5200 amp shown above that I have found.

Besides, an amplifier that commits hari-kari if you transmit through it with no DC power just doesn't appeal to me.

73