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Pre Amp Not Working on Palomar 300 Amp
- Thread starter bgosper
- Start date
I could not tell from the diagram if you have the Skipper 300 or, the Palomar 300a.
There are 2 PNP transistors in the Palomar amp, one is the keying circuit and, the other is the receive preamp.
Locate the transistor with the 220 ohm resistor, the 1000 ohm resistor and, the 68K resistor associated with it; that is the preamp transistor. Change it out, you need a 2n2905 PNP transistor.
.
There are 2 PNP transistors in the Palomar amp, one is the keying circuit and, the other is the receive preamp.
Locate the transistor with the 220 ohm resistor, the 1000 ohm resistor and, the 68K resistor associated with it; that is the preamp transistor. Change it out, you need a 2n2905 PNP transistor.
.
Toll_Free
Well-Known Member
The 300A is MUCH more complicated.
That's a Skipper he has the schematic posted to... It's a 1X3.
The 300A was a 2X4, and had associated switching to switch the driver in and out of the circuit.
4 tubes = Skipper. 6 tubes = 300A or 350Z.
--Toll_Free
Ide love to get another350Z I had a restored 350Z in the late 1990s I should never have sold it 
. I had a 300 A in the mid 1990s that thing was crazy it had a seperate transformer that plugged into the wall with another cord running to the box or head unit.
. I had a 300 A in the mid 1990s that thing was crazy it had a seperate transformer that plugged into the wall with another cord running to the box or head unit.Toll_Free
Well-Known Member
Ide love to get another350Z I had a restored 350Z in the late 1990s I should never have sold it
The 350Z and the 300A are the same amp, for all intents and purposes...
The 300A was the same physical size, and as you pointed out, had the transformer in an external chassis.
Guess which one has a problem cooking plate transformers? BOTH!
The 300A doesn't come with air cooling holes factory (a few late runs did, right before the change to the 350Z), and the 350Z cooked the thing in between 6 tubes.
The best thing you can do for the 350Z is pull the driver tubes, and drive it with a 100 watt PEP driver.
The 300A, just mount a fan above the transformer box, and put some holes in the bottom. NEVER lay the power supply on the floor, and you'll have a happy amp for years to come.
--Toll_Free
Just curious the comment on the transformer up off the floor. I get this thread is old and likely will go unanswered, but I was wondering why that is a bad idea?
No air flow to the transformer. Might be a problem if it were on carpet. A top mounted fan on the transformer pulling air from the bottom and out of the top should keep it happy.
I have one of these (300A) but have not noticed the transformer getting hot but I only use SSB and not all that often. I just may check it out the next time it is powered up.
73
David
I have one of these (300A) but have not noticed the transformer getting hot but I only use SSB and not all that often. I just may check it out the next time it is powered up.
73
David
Ahh that makes sense. The transformer for my 300a doesn't have any ventilation slots. Is that something that was added in the later versions or a mod folks do? I have it sitting on the floor below the desk on a tile floor, never noticed it getting overly hot.
I had a chance to test the 300A transformer for heat this past weekend. None noticed after driving with 90w on SSB for several hours talk time.
My transformer sits on the bottom shelf of my radio bench. The shelf is made of wood and sits off the floor about 8-10 inches.
73
David
My transformer sits on the bottom shelf of my radio bench. The shelf is made of wood and sits off the floor about 8-10 inches.
73
David