Commander 150A AB linear amp schematic?

[Robb]

I have seen many of these amps floating around in my day. Used to be very common. Long ago, I had the 250A(?) model, IIRC. But I cannot seem to find a schematic for one.

Someone brought me two of them to go thru and make them work. If I had a schematic, I might have a chance. CBTricks doesn't have one, as I have looked thru their amp schemes.

Anyone have a schematic?
Thanks in advance!

 

[YR Mason FL]

I looked too. Is it possible it may have been built by Palstar? Do you have a picture of it?

 

[Robb]

Found a smoked 68 ohm resistor that I think goes to a 2N4401 transistor.
That transistor is probably cactus - along with that resistor.
The TX keying circuit?
Dunno . . .
Haven't checked the relays yet; but it sure would be cool to have the schemo for it.
Not making any money on it, just helping a local CBer/forum member because he asked for help.

 

[nomadradio]

Never have had a diagram for this one. I remember it for the double-sided pc board and the tendency of the foil pads to lift. Don't know if it was just cheap glue or what but unsoldering a component from one of these seemed almost guaranteed to lift a foil pad.

Not a favorite.

And a diagram would still be better than not having one.

73

 

[AudioShockwav]

I think this is it Robb, take a look.

http://www.cbtricks.com/Amp/palomar_other/250R 600p landscape B.gif

73
Jeff

 

[YR Mason FL]

It does look very similar to the old Palomar Red Devil mobile 10/11 meter amplifier. There is no doubt that the case is identical.

I will keep looking periodically. I did see where a couple of them had been listed and sold on eBay back in 2018 but there was no link to technical specs or schematics.

 

[Robb]

I think this it Robb, take a look.

http://www.cbtricks.com/Amp/palomar_other/250R 600p landscape B.gif

73
Jeff

Thanks once again Jeff!
Looks pretty close to me.

 

[Robb]

Findings:

The smoked 68 ohm resistor in one amp showed a value of 114k ohms; so it was replaced (doh!); the 2N4401 transistor was OK - strangely enough.
Found three caps (one 10uf and two 470uf's) that were marginal/bad and were replaced.
Rec Amp indicator led needed to be resoldered and now works.
Removed two finals in one amp and tested them - both good.
Cleaned off the old paste, filed them flat with a smooth flat file and re-installed them with new paste.
Adjusted RV1 pot in both amps.
Cleaned the relays in both amps; one was pretty badly carboned up, but cleaned up well (both were dirty).
Both amps are working.
DK was set to 3w on a President Grant test radio and both amps saw ~140w/pep @13.8v on a 100w dummy load.

Thanks to all who chimed in!

 

[Robb]

BTW - are those Macom branded MRF-455's transistors any good?
Or are they junk?

Both of these amp here have the original Motorola transistors in them - no problem there.

Was just wondering about the Macom output power, build consistency, and quality . . .

 

[YR Mason FL]

Findings:

The smoked 68 ohm resistor in one amp showed a value of 114k ohms; so it was replaced.
Found three filter caps (one 10uf and two 470uf's) that were marginal/bad and were replaced.
Rec Amp led needed to be resoldered and now works.
Removed two finals and tested them - both good.
Cleaned off the old paste, filed them flat with a smooth flat file and re-installed them with new paste.
Adjusted RV1 in both amps.
Cleaned the relays in both amps; one was pretty badly carboned up, but cleaned up well.
Both amps are working.
DK was set to 3w on a Uniden Grant and both amps saw ~140w/pep.

Thanks to all who chimed in!

It is always awesome to hear good news!
I am glad that you got them both working.