Old Connex 3300 AMC Disabled.

[LeapFrog]

Just bought an old connex with the EPT360011Z board.
Looking for clipped parts I found D80 was snipped, this enables talkback with the echo on or off.

I saw a resistor was snipped but cannot find it now, if you could point me in the right direction to re-enable the amc I would be very greatful. So far all the info online i have found is for the ept360014b and nothing for this older single final pc board.

 

[LeapFrog]

TR53 was removed, I think this is the amc limiter on the old ept3600 boards, any idea what transistor will work?
Edit: They yanked TR32 also... Arggghhh. :/

 

[sonoma]

the resister that can be pulled is up by the VR's. do not remember the number

 

[Robb]

TR53 was removed, I think this is the amc limiter on the old ept3600 boards, any idea what transistor will work?

2sc945?

 

[LeapFrog]

Thanks Rob, that's what I was thinking, most likely the same for tr32 that I just saw was removed also.. Dangit, I guess for $20 I still have an oldschool "black box" radio, for some reason I keep collecting these exports, the r.c.i. radios are interesting to me..

I will look at an ept360014b in one of my galaxy radios to confirm they may use the 2sc945 transistor across the years.

 

[LeapFrog]

I might play with this one on the dummy load with a 100ohm + 1N4148 npc to see if it cleans up the signal on the scope as she is pretty nasty right now!

 

[Robb]

I would also remove the NPC mod and just give the radio a decent TX can peaking. These radios are already pretty much bodacious as far as AM performance goes. Don't really need to push it into distortion - IMO .

 

[LeapFrog]

Very well Robb thank you for the suggestion!
! ~Clean can be mean~ !
After I get the two transistors replaced I will see how much of a clean signal I can get without going into distortion land!
125% on the positives and 98% on the negatives wouldn't cause bleed-over on the adjacent channels would it?

Almost every "LOUD" radio I here can be heard one channel up and one channel down from the frequency they are centered on, this makes want to build a detector and see what the modulation looks like!

The npc mod has not yet been done to this radio, nor has the diode swing mod..
(I only run exports on a dummy load)
But this how I learn, in practice along with theory.

 

[Robb]

The NPC mod could be done but with no other mod. This is a tricky mod, in that it is often done wrong with a nasty signal resulting. A scope should be used so as to make sure that the positive peaks remain symmetrical. Of course, the dead key wattage should also need to be reduced.

 

[LeapFrog]

The NPC mod could be done but with no other mod. This is a tricky mod, in that it is often done wrong with a nasty signal resulting. A scope should be used so as to make sure that the positive peaks remain symmetrical. Of course, the dead key wattage should also need to be reduced.

One would turn down AM power adjustment pot?.
I'm about to power the rig up now, if I burn up tr51 im only going to blame myself lol!

 

[Robb]

Yeah, 2w.

 

[LeapFrog]

I didn't know if this wire was factory so i clipped it, initial key up was over 10 watts, turned the am vr down to 2watts, any ideas on the heck that wire was?

 

[LeapFrog]

The scope looks much better now, no more saw teeth and the carrier is not pinched like it was before, I have not figured out the trigger setting on my scope yet to save the wave form for a nice picure. The radio is better than it was before, I removed that unknown wire, everything seems to function still. I see the trace cut by the p.a. / ext. speaker area, for a talkback mod no doubt.

It looks much better on the 'scope!

 

[222DBFL]

If it was a red wire, it might have been power for something?? Not sure what, if anything. Did it appear to be a stock wire or wwe is not listed on any of the schematics?

 

[LeapFrog]

I did some image searching on Google and the other ept360011z boards I found did not have that wire so I removed it.

I did the Bill Eitner / Billy Dean Ward NPC-RC mod and the radio is a real screamer without the nasty signal I originally recorded when I first got the radio.

I am super pleased with the outcome of the mod, it's just too bad the exports only will sit on my shelf!