The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

anyone have a schematic for the stonewall jackson power supply area.I need to know what transisters and transformer it has in it.

What is the PCB Number? and PLL?

See www.radiomods.co.nz/forum/viewtopic.php?t=312

Rick.

you can not read the board number at all I had already tried this.I believe the 2995 is about the same board.so far it looks to be.the radio puts out about 150 watts when done right.thanks Rick for trying to help.

Ranger USA's site used to have a 2995DX service manual in a PDF file to download. It's a 2 and a half meg file, so I'm not going to try to post it here.

Same 'linear-regulated' power supply and pc boards.

Output transistors are usually 2N3771, rated for 30 Amps each. Not the only number the factory has used, but it's easy to get from Mouser, and the one we use. Other types with current ratings of only 15 or 20 Amps never last very long in this radio.

You probably found two mica-sheet insulators under each of the large metal regulator transistors. I'm convinced this is done to make the radio blow up some time after the warranty is up. They hope.

The regulator circuit lacks any "ballast" resistors to force the two large transistors to split the current evenly. The factory uses a matched pair of transistors in an effort to skip having to include those two parts. We cut the trace to the base pin of each large transistor, and place a 2.2-ohm resistor across the gap. Seems to extend the life of the large transistors in a big way.

The rectifier (or both of them in later models) will also have this bogus second mica insulator under each, with one side of one insulator "dry" with no compound on it. The extra bogus insulator gets removed and a proper layer of compound on both sides of the single insulator that goes back under each rectifier flange.

If you can't track down Ranger USA's web site with this file, speak up and I'll figure out how to get you a copy.

The regulator circuit is pretty simple. It uses a 7808T 8-Volt 3-terminal regulator, with a 5-Volt zener diode between its "ground" pin and the circuit ground. A small trimpot is between the zener diode and ground and serves to set the output voltage. The 2SB754 alongside the 7808T on the small U-shaped heat sink drives the base current into the two large regulator transistors.

It works okay until something fails. There is no current limit built in to protect the regulator. An overload tends to damage some part or another.

And, if one or both of the large regulator transistors shorts inside, there is NO protection for the radio from over voltage.

If you see the lights get REALLY BRIGHT all of a sudden, unplug the thing. Right away. 22 or 23 Volts will fry the main radio PC board and the linear both before long.

Any time this model radio shows up here, we strongly recommend that the owner have the "suicide intervention" done, in the interest of making it last longer. Involves removing the bogus 'extra' mica insulators, adding the ballast resistors, and making sure sufficient heat-conducting compound is under all the power components. The factory gets stingy with the stuff. You figure out why.

Not sure what you need to know about the transformer. It seldom fails unless someone used an excessive-size fuse with the radio. The stock 5-Amp fuse tends to protect the transformer pretty well. Pretty sure its rating is 16 Volts at about 25 Amps. Gets you more like 20 Amps from the regulator's DC output.

If the transformer really HAS been damaged, you'll play the devil using a substitute. Just won't fit. The size and shape of the original are pretty unique.

73

thanks Nomadradio,
I copied the service manual from rci last night.I am in the process of checking all the parts in the circuit.looks as if the output for the finals is bad also.I found the 2n5301 that came in the radio but I will look for the 2n3771 that you said are better.never had one of these radios here to work on before so taking my time.will due the mod you wrote down also with cutting the circuit board.
if you have anyother suggestions for me would be great.
thanks
Sonoma

Haven't seen a lot of that model around here. One thing I found odd was with the pc board that bolts flat against the inside of the large heat sink This is the board that the metal regulator transistors' pins are soldered to.

Other models have a brass 'eyelet' installed in each pair of holes that accept the pins on the regulator transistors. The pins on the metal TO-3 transistors are barely long enough to meet the hole in each eyelet, but will solder okay.

The last S.Jackson I saw had no eyelets. Just a bare hole in the board for each pair of power-transistor's pins. I have some pics I took of the procedure. Ended up soldering "crutch" wires onto the pins of each regulator transistor. They poke through the holes in this board when the transistors are installed. Green mask paint is scraped from the pc trace for each hole, and the end of each crutch wire is lap-soldered to the foil trace.

This is the only RCI-made high-power base I have seen that lacks the eyelets on that board. Might have been a fluke for that batch of radios. Like I said, haven't seen enough of them to be sure.

I'll rustle up some pics and get them uploaded to Imageshack so I can post them here.

73

thanks nomadradio,
that is the way with me this is the 1st one I have seen.I ordered all the parts just waiting for them to get here.a lot of strange thinks on this radio.

another big problem I am having is I just moved about 1000 miles to michigan and I still am having a problem finding all of my books and repair parts and am still unpacking things.most of my parts were lost in the move from the moving lines.I had 2 -34 foot moving vans full of stuff and my good items did not show up.I told them make sure they had everything marked on the boxes but that did not happen and a lot of my power tools did not show up.the insurance paid off on the lost items but after they depreciated everything that was lost I only got pennies on the dollar.My scope did not show up either.so I am lost with out some items.
thanks
sonoma