Connex 3400 HP problems

[trucker]

Hi, a good friend of mine just gave me his Connex 3400 HP today. He has had it less than three months. And in that time, it has blown the finals twice!!
The first time he took it back to the shop where he got it. (after about a week)
And paid to have the finals replaced. Repairman said his antenna or coax was bad. He bought a new antenna and coax. Seemed to work just fine for a little over a month. Then, one day it blew the finals again! Took it to a different shop and the tech there said yep, the finals are toast. Installed new ones and it seemed to be working fine. Today, it blew the fuses (10amp) twice. And the radio was HOT (almost to the point of being untouchable) by the power connector. The second time he replaced the fuse, the radio stayed working, but, again, it was HOT near the power connector. He was so mad at the radio
that he pulled it out this evening (we drive rock trucks at the same company)
and handed it to me. I offered to buy it, but no dice. Give away he said. He said he was reinstalling his old Cobra 25, which has never had a problem.
(he even used it when he put it in the shop the first time and never a problem)
I guess what I need to find is a good schematic of the radio(if it exists).
i have done a Google search and come up empty handed for a schematic , much less, any good info on known problems with this radio.
Any suggestions (such as known voltages at test points.....haven't opened the radio up yet) would be appreciated.
Trucker

 

[Superidgit]

I remeber somewhere that Connex uses same boards as Ranger but I am unsure of this. Also I wouldn't know what radio you would compare it too if it were true.

I hoped I helped.

 

[Robb]

Chance are, that the tech that replaced the finals had to re-set the bias on the transistor as well. Well; one would hope that he did - anyway. So, either your friend set up his antenna that a) compromised the integrity of the coax (smashed it down flat or gave it too sharp of a bend while installing it) or b) put the antenna in such a place that gave it too high amount of reflected power back into the final.

Just for starters . . .

 

[mackmobile43]

Chance are, that the tech that replaced the finals had to re-set the bias on the transistor as well. Well; one would hope that he did - anyway. So, either your friend set up his antenna that a) compromised the integrity of the coax (smashed it down flat or gave it too sharp of a bend while installing it) or b) put the antenna in such a place that gave it too high amount of reflected power back into the final.

Just for starters . . .

My bet is on some "bozo" twisting a screw driver in the bias regulator also and has the voltage way to high and just fries the transistors.

 

[Superidgit]

Chance are, that the tech that replaced the finals had to re-set the bias on the transistor as well. Well; one would hope that he did - anyway. So, either your friend set up his antenna that a) compromised the integrity of the coax (smashed it down flat or gave it too sharp of a bend while installing it) or b) put the antenna in such a place that gave it too high amount of reflected power back into the final.

Just for starters . . .

My bet is on some "bozo" twisting a screw driver in the bias regulator also and has the voltage way to high and just fries the transistors.

Not to bust balls here mack or robb but how does that get him a schematics? Or what he needs to adjust or where to look?

 

[Robb]

CB tricks doesn't have that info either - I checked. Don't know what to tell ya. The best one can do is make sure that the cause is found - regardless if it is internal problem or an external installation problem. Or else it will happen again.

Replacing the finals without checking and adjusting the bias is one sure way to make the same thing happen again. They could be over-biased; in which case they will heat up and cause failure. Send it to a decent tech. After all; you don't have anything invested in it. So having the right person to fix it and troubleshoot it would be the smart move at this point - IMO.

 

[AudioShockwav]

Can you pull the cover, and see what board it has in it?
A lot of these radios use the same main board, with a different case/face.
How high was the power output?
You probably know this already, but it is not a good idea to run them balls to the wall and stay on the key all day.

73
Jeff

 

[AudioShockwav]

If that radio has a Ranger EPT 3600 14-C board in it you can use the Schematic and the service manual for one of the other radios that use the same board if available.
Also is it using the 1 2sc2166 driver into dual 2sc2312 finals....or is it the model using all IRF 520`s?
At least it will give you something to work with.

That board is used in several radio`s

73
Jeff

 

[triple nickel]

Not to sour the grapes, But all new radios have Mosfet Finals, And they are cheaply made. And high Swr's will blow the Finals. If you ever decide to get a good radio, Look for an early Connex 3300hp or an early General Lee that have the older non-Mosfit Finals. JMO. They are built better.

 

[jon666]

your not alone

Thread connex cx-4300 hp problem? | Sparkys CB Shack Forum | BoardReader

sorry i could not find anything on line to help.

 

[trucker]

Can you pull the cover, and see what board it has in it?
A lot of these radios use the same main board, with a different case/face.
How high was the power output?
You probably know this already, but it is not a good idea to run them balls to the wall and stay on the key all day.

73
Jeff

Hi, sorry for not getting back sooner. (working 14+ hr days is a killer!)
I will in the next day or so pull the cover and see which board it is. I had looked at CBTricks and couldn't find a schematic there. I agree that the first
time the finals were blown that the culprit was most likely the antenna or coax. But, the second time, was with all new hardware. And we tuned his antenna using my MFJ 259b antenna analyzer. (I love that thing)
The second tech who replaced the finals told him that the voltage on the
original finals was 1 volt too high. And that he had readjusted it to the correct setting. I'm guessing (and that's all it is , a guess) that it was the bias voltage he was talking about. But, would being one volt over the correct setting cause the radio to blow fuses and heat up like that? Are the
mosfet finals that sensitive? Both times that the fuses blew, he wasn't talking on the radio. (we work for a company that builds gas & oil well drilling sites.......truck drivers) I would think that there would be little to no voltage applied to the driver and finals until the radio was keyed up.
Anyway, I will remove the cover(s) and check it out and get back with what results I can come up with.
Thanks to everyone for all the helpful hints and replys.
Trucker

Oh, and as to the suggestion of taking it in to a good tech, the second one is held in quite high regard (well, in this area anyway) and that really surprised me when my friend called me and told me his radio was blowing fuses. The last fuse he put in, has not blown (yet) and he had only transmitted with the radio a little bit. (he turned the variable power all the way down....about 1 watt dead key.......) But, still the radio was quite hot
around the power connector. Almost too hot to touch.
Thanks again everyone!

 

[trucker]

Ok, I hooked the radio up to my power supply(47 amp) on my bench and ran it thru a watt meter to a dummy load. No output at all now! I can hear the transmit relay keying
but, no output. And the band indicator next to the channel indicator no longer shows which band the radio is on. The board is a Ranger EPT 360015C. It has two IFR 520's on the rear(behind the rear heatsink) with a third with no markings on it. The voltage regulator doesn't have markings(that I can see) on it nor does the two other regulators. I'm guessing that's what they are since they are not marked either, but are on the side of the chassis towards the front of the radio on the same side as the voltage regulator. The voltage regulator is much larger than the other two and looks more like the finals but smaller. And both are attached to the chassis with screws and as all the devices attached, uses thermal compound to help dissipate heat into the chassis. No obvious burn marks or damage that I can see. Just no RF output and very little receive when hooked up to an outside antenna. My thoughts, without having the schematic with voltage testpoints to look at, is the regulator has all but died and it only powering a small portion of the radio. ( I get audio hiss and can vary the volume, but, no reception and no RF out anymore)
I Googled the board number and got lots of hits. That board is used in a LOT of radios.
But, I still did not find a schematic.
Trucker

 

[trucker]

Well, the voltage regulator does have markings on it, but, I cannot see what it is in spite of what angle I try using my lighted magnifying glass. And also, with the radio connected
to an outside antenna, no reception at all. I carried it out to my pickup and the same results. I just might take it to the first tech that my friend took it to. (the one that originally sold the radio to him) I have used that particular guy in the past when I have not had time (or the inclination) to mess with radios and he has always done a good job.
trucker

Forgot to mention, I found a schematic for the radio at CB Tricks after all. Not for the radio itself but, one that uses the same board.
Ranger EPT360015C. I was surprised when I got a lot of hits on that board. And how many different radios it is found in.

 

[triple nickel]

Sorry for the sad news. JMO But Older radios are built better.

 

[trucker]

Sorry for the sad news. JMO But Older radios are built better.

No doubt on that one!! My old (4+ year old) Connex 3300HP is still going strong!!
I broke down and took it by the last shop that looked at it and he said he didn't remember working on it, but, believed me if I said he had. He said he would not charge me labor , just for parts to fix it. He found (as I suspected) the regulator was bad, as was one of the finals. He also replaced the trimmer for the final that was bad because he was having trouble getting the BIAS voltage to stay put. He thought the trimmer might be bad. Well, replacing the trimmer helped, but, still the voltage tends to vary on it's own. So, he is keeping it for a day or so and tracing the problem down. So far, I owe him $30 for 1, regulator and 2 finals (I'd rather have matched finals even though one of the old ones was good) Also, owe him for the memory battery(for the processor) that he had to replace.
I could have done the replacement on the regulator and finals and the adjustment, but, given my work hours lately, (16hrs a day!!) I would never get to it! Easier in this case to just let this guy do it.
trucker