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Connex CX3300HP, ept360015c

Hawkeye351

Well-Known Member
Jun 27, 2021
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Got a Connex CX-3300HP dual final with a weird issue in receive, possibly xmit also:

Reason for coming to me:
Running hot, xmit sounds fine for a bit, then starts to muffle slightly. Receive is sluggish when in-keying mic.

All caps checked out fine, passthrough regulator was weak. Diode and resistor strapped across regulator. Swing mod at R238. TR32 removed. R249 removed.

1. Replaced all missing components, removed Swing mod at R238 and the one on the regulator.

2. Replaced passthrough reg.

3. Replaced AF reg.

4. Replaced 2 filter caps (1000uf).

5, Replaced 330uf cap beside passthrough.

6. Completely realigned.

7. Bias readjusted.

8. Dead Keys reset.

Results:
Receive still sluggish to recover after un-keying mic or nearby strong station un-keys.

Xmit sounds great now, regulator not running hot, warm, but not hot. Although I did notice after 20 seconds of holding the key down and modulating that the power drops. Anytime I key up after that incident, the power stays at that reduced level.

Turn radio on, let warm up for 15 minutes, key up first time and power swings to 32w peak from an 8w deadkey. After 20 seconds of holding that key and modulating, the swing drops down to 20w peak and a deadkey of 6w. Average power no noticeable change.

I've checked for loose, cracked, lifted solder joints. I've looked for loose ground connections. Bias stays stable. Power VR stays stable.

Noticed my power supply amperage scale jumps from 3.5a idle to 7a when I key up and goes to 10a when I modulate. Sounds like a short somewhere. Checked finals, and strap diodes, they check fine. All coils seem firm. So-239 firm.

Any suggestions?
 
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I had one do this and it was one of the 520's. Checked fine but once it heated up it would fail. Changed all 3 and she was up and running like new. Good luck!
 
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Ok, thank you crossbow...

I'll swap all 3 with new ones and go from there.

What's the typical wattage expected from one of these 3300hps with dual mosfets?

Would a bad final cause the receive to be sluggish to recover after unkeying? Still stumped on this...
 
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Well,
Had a rush job come through. It was the same kinda radio. Only issue was low power. Only 20w peak and 1w forward on average is all it would do. Dual final mosfet version. Swapped passthrough, AF, all 3 mosfets with new vishay brands, wattage back up. It's now doing 38w peak and 15w forward in average. Looks good on scope and analyzer, out the door. Now to finish this one up tomorrow. I'll give an update tomorrow on this one.

To this day, I still haven't seen 50w outta these radios. Factory connex 3300hp dual mosfet suppose to do 50w out the box isn't it?

Would an MFJ 871 not show those watts? That's the meter I use, but never seen anything over 42w peak. This meter is a peak/avg meter. Not a true peak reading meter from my understanding, that could be why.
 
Last edited:
40 watts is about average now. Back in the older models would do 50 but they changed things to make them a 40 watt radio.

Glad to hear you found the problem.
Don't throw away the old finals.
Find the bad one and pitch it then use the others for radios you want to mosfet like a cobra.
 
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Wasn't but one worth saving, the other 2 were just plain weak.

According to my oscope, the Vrms is 43.34v. If I convert that to watts using the following then it bout corresponds to my watt meter.

Vrms (squared) ÷ 50 = Power(w)
43.34 (squared) = 1878.3556
1878.3556 ÷ 50 = 37.567112 (37.57w)

Did I do that right?
Close to my watt meter.
 

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