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Palomar 350Z

oldgeezer

New Member
Aug 13, 2017
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I bought this amp and rebuilt it. New power supply capacitors & a relay to switch the 600 volt secondary. Palomar had the tubes drawing B+ continuously- not good. I had four new 6LF6, driver 6LF6 tubes were like new. Anyways on low drive I could get only 300 watts out with a swing to 350 watts. Radio dead keyed 4 watts and swing to 16 watts. To have any forward swing on the amp I detuned the driver circuit and it dead keyed 200 watts to 350 watts. I think this amp is a dog. I was expecting 500+ watts swing on low drive. I did sell it & buyer is happy- go figure.

With two 6LF6 driving four 6LF6 it should make more power. B+ was around 850 volts. Is this amp simply a dog or what?
 

BTW- My low class Hy-Gain model 480 with two tiny 6JU6 tubes dead keys 60 watts and swings to 180 watts with same radio having the 16 watt swing.
 
Never did figure out why the 350Z would never stack up to a 300A.

The problems with unobtainable relays, a wacky "overdrive protect" circuit, and tubes that push a hundred Watts of heat on standby make the "wimpy power" problem seem kind of irrelevant.

Wish I had some useful wisdom to offer.

73
 
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I picked a 350z up this summer mine does 300 pep on low and 500 pep on high with a 2-12 pep radio. I did not remember what dead key of amp was. I am going to dig it back out and drive it with a JB150 and see what it will do.
 
Amplifiers running old TV sweep tubes should be avoided like the plague!!! It is crazy to buy any amp with sweep tubes these days. You are much better off having an amp use something like a 3-500z or a pair of them or even an 8877, An 8877? Now your talking big time!! Ever thought about running a "special" SB-220?
 
I do not believe for a minute it will blow up I have about 20 old tube amplifiers and almost all have sweep tubes in them. This 350z will work just fine like all the rest do with a little drive put to it and tuned properly. They do not make the sweep tubes anymore but with a good set in a amp you should see 25 years of service if amp tuned right and taken care of . Been driving the snot out of my Phantom triple stage for 4 years now and it works great still. The 350z is basically a 4 tube amp the other 2 tubes are drivers.500 to 600 watts from 4 tubes is pretty good I would say.
 
I've had all kinds of sweep tube amps over the years and never had issues with them "blowing up" or failing. Just drive it conservatively and you'll be okay......
 
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I do not believe for a minute it will blow up I have about 20 old tube amplifiers and almost all have sweep tubes in them. This 350z will work just fine like all the rest do with a little drive put to it and tuned properly. They do not make the sweep tubes anymore but with a good set in a amp you should see 25 years of service if amp tuned right and taken care of . Been driving the snot out of my Phantom triple stage for 4 years now and it works great still. The 350z is basically a 4 tube amp the other 2 tubes are drivers.500 to 600 watts from 4 tubes is pretty good I would say.
I have seen sweep tubes in amps last that long too. These "techs" tell you sweep tubes are bad when most of the tubes are older than I am and will last if you take care of them.
 
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will last if you take care of them.

Roger that!

My experience is mainly with the folks who don't.

"Just a little more drive", And then "just a little" more. Eventually they find the "kaboom" drive level.

And if your stuff runs for years without trouble it's because you're treating it right.

73
 
They run high output export and ten meter radios into them and the input is too much. Back the drive down to standard cb level and you'll do ok.
 
Never did figure out why the 350Z would never stack up to a 300A.

The problems with unobtainable relays, a wacky "overdrive protect" circuit, and tubes that push a hundred Watts of heat on standby make the "wimpy power" problem seem kind of irrelevant.

Wish I had some useful wisdom to offer.

73
Cathodes on the tubes in the 350Z have resistors inline with them to ground for the DC bias path. As the positive peaks draw more current, this pulls the cathode voltage more negative and destroys the amplifiers ability to reproduce peaks as strong as the 300A. Probably done to keep the transformer from cooking.
 
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