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Anyone ever adjust driver bias on a connex 4300hp
- Thread starter Low_Boy
- Start date
Same way hundreds of other radios with EPTxxxx board.
TP6-TP8 50mA driver, for final no way to set, hardwired on vertical board it is soldered to.
Mike
TP6-TP8 50mA driver, for final no way to set, hardwired on vertical board it is soldered to.
Mike
Pull the main jumper where bias board usually sits.
Thank you Mike. I should have known that. I feel stupid.
Thank you Mike. I should have known that. I feel stupid.
still not right. Feed to final 2sc2290 comes in at TP7. TP9 goes over to TP8. TP9 voltage veries with variable power. From 1V to about 1.5V without mic keyed . With mic keyed .96V to 1.3V. Still not sure what connection should be broken. And is this still set im mA or volts?
Umm, the whole thing about breaking a connection to read the driver transistor's supply current only applies to a sideband radio. In that case, you set bias for "idle" current, transmitting in sideband mode with no drive power applied to the driver.
But this is an AM/FM model. Can't key it with no carrier driving the driver transistor. Pretty sure that's why the fork terminals and "mirror" board are replaced with jumper wires on this model.
We settled for turning the bias trimpot first to zero. Easy to tell which direction to turn the trimpot, just watch for minimum power. Next, it gets slowly turned up, watching the modulation peaks on the 'scope, and set it where the peaks just begin to drop off.
Not very scientific, but seems to work.
73
But this is an AM/FM model. Can't key it with no carrier driving the driver transistor. Pretty sure that's why the fork terminals and "mirror" board are replaced with jumper wires on this model.
We settled for turning the bias trimpot first to zero. Easy to tell which direction to turn the trimpot, just watch for minimum power. Next, it gets slowly turned up, watching the modulation peaks on the 'scope, and set it where the peaks just begin to drop off.
Not very scientific, but seems to work.
73
10-4 nomad. I ended up sort of doing the same thing I think. Turned it from lowest power to highest power and backed it off a bit. The 4300 looks terrible on the scope and I had to have one. Now I have 3 lol. And I am not impressed. 1 2290 transistor and to run it clean it puts out about as much power as a cobra 29.
TRPC nailed it 100%... that's why 95% of exports are junk. Get a good CB and call it day. 
I will say this, though.... if anyone has a 4300HP that they want to get rid of on the cheap, working or non-working but complete, let me know.
~Cheers~
I will say this, though.... if anyone has a 4300HP that they want to get rid of on the cheap, working or non-working but complete, let me know.
~Cheers~
Such a mixed message.TRPC nailed it 100%... that's why 95% of exports are junk. Get a good CB and call it day.
I will say this, though.... if anyone has a 4300HP that they want to get rid of on the cheap, working or non-working but complete, let me know.
~Cheers~
TRPC nailed it 100%... that's why 95% of exports are junk. Get a good CB and call it day.
I will say this, though.... if anyone has a 4300HP that they want to get rid of on the cheap, working or non-working but complete, let me know.
~Cheers~
Well, I wouldn’t exactly call it junk. I think we’ll all mostly agree they’re drifty and they certainly aren’t built to the standards of “real” ham radios. You either love them or hate them, personally I like them but I know what they are.
Some will say they can be made to perform to Icom or Yaesu standards (or exceed) but I’ll just laugh and say “ok”. The worst thing I think they have against them is the cold solder joint issues that seem to plaque a bunch of these types of radios (or did).
I’m not a Connex fan at all but I like the 4300HP and I have one myself, fully restored to like-out-of-the-box quality.
But it’s no huge secret that they come from the factory with minimal alignments and other quirks. I was really ribbin’ at Rabbi more than anything else, I figured he could take a joke.
So I was working on a seismic support and asked where I could find the torque spec for a 4" nut/bolt I had to "torque to spec". An old hand told me...
"Heave on it 'till it breaks and back off a quarter turn"
Not very scientific, but seems to work
*approx 30,000 Ft/Lbs ASTM-354 BD lubed/waxed
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It's a mixed message only because I'd use it for parts. More specifically, the PCB that houses the 2290 final on it. That's what I'm after. But I would gut the chassis and keep a fair bit of the parts.
~Cheers~