Connex 3300HP

[Hawkeye351]

Got a Connex 3300hp on the desk today for a quick check. Owner said he bought it from the last tech around here which passed away a couple years ago and never hooked it up. He said he bought it used from the old tech. It has all new caps in it, someone recapped it before it got to me. Limiter has been removed, the resistor at R238 has been completely removed and a 1N4003 diode placed in the empty R238 location. This radio passthrough runs extremely hot within 15 minutes of rag chewing with a local. Either someone else or the factory put in a 2SB827 in as a passthrough regulator. I've never had much luck keeping those 827's cool. I like the 817 better.

Well, he recently hooked it up and noticed receive was way down and sounded off frequency, and the hi/lo band switch wasn't working.

After hooking it up and allowing to warm up for 30 minutes, I checked the alignment, yep, it was all way off.

Realigned the radio as it is, turned out beautiful on receive, xmit was already stought to begin with.

As it sits now, just recapped and completely aligned, the output is:
Lo power - 1w deadkey, swing up to 60w PEP on the watt meter and 52w on the oscilloscope.
Hi power - 8w deadkey, swing up to 60w PEP on the watt meter and 50w on the oscilloscope.
Average swing in both gears swings up to 35w.

Does that average seem too high to you guys? I know I still have to put R238 back stock and replace the limiter, but 60w really? No wonder it runs hotter than all get out in just a few minutes of talking.

 

[Hawkeye351]

Interesting....

Hmmm, normally in the R165 location there is a 220k up to 270k ohm resistor. Obviously it's not original according to almost all other resistors having tan coated leads.

68k (in this radios R165 location) is a far stretch from the typical 220k up to 270k normally found in the R165 location. Doesn't this create too much drive for the 4558 IC?

Any reasoning behind this change?

 

[Hawkeye351]

Update:

Replaced the diode in the R238 location with a 5.1k ohm 1% tolerance resistor (need to order more 5% tolerance resistors).

Reinstalled the limiter at the TR32 location with a new 2SC945.

Replaced both Chinese brand 1000uf caps with Nichicon 2200uf 25v caps.

Replaced the 330uf 16v Chinese brand cap beside the passthrough regulator (2SB827) with a Nichicon 330uf 16v cap.

I left R165 as it is, a 68k ohm. Typically in the R165 spot there is either a 220k or 270k ohm, but this one was replaced by someone, it's obvious by resistor leads compared to the other resistors in the radio. You can increase the value of this resistor slightly to get more audio drive, but I've never heard of decreasing the value of this resistor, especially by this much.

I replaced the AMC timing cap (C158) from the factory value of 10uf 16v to a 3.3uf 25v nichicon so the AMC won't be so aggressive.

I reset the keys for hi and lo gear, adjusted modulation for both gears.

Believe it or not, I lost no PEP swing, but average did change to a more sensible range.

Now:
Lo gear - deadkey at 1w, swings up to 45w pep, swing forward up to 18w average.
Hi gear - deadkey at 8w, swings up to 52w pep, swing forward up to 30w average.

By the way, the passthrough actually runs a lot cooler now. No one on the air can tell the difference, other than being more cleaner/crisper sounding.

 

[Shadetree Mechanic]

Did you leave R165 at 68k, or did you end up changing it? I guess if it has enough audio, it's fine.

 

[Hawkeye351]

I left it at 68k ohms. Doesn't seem to be harming anything and the radio runs cooler. Audio is very sensitive to every syllable, holds at max power the entire time speaking, no drop backs at all on certain words/syllables.