Finals for older Connex 3300hp?

[codeman]

I have a 12 year old Connex 3300HP. About a month ago I noticed a buzz when I had the power switch on low. Well, I took it to a cb shop and he told me he replaced the finals. I checked it on my meter and I was getting 40-45 watts. Reports on the radio said it was very loud and clear.

Well, earlier this week I was trying to do some some skip talk when I began to smell that horrible smell of electronics burning up. The heat sink on my radio was HOT. Now on low power I get a terrible buzz and on high I do as well but it is not as bad. Now I am only getting maybe 8 watts swing on high.

I took the cover off and I see the finals are Mitsubishi c2312's. Are these the correct finals for this radio? I thought the Connex 3300s came with 1969 finals.

Also, what would have caused my finals to burn up? Assuming that is my problem. My SWRs are 1.4 or lower.

Since I do not use my internal speaker, is there a fan I can have mounted under the radio to help with cooling or possibly one inside where the internal speaker is? I really enjoy this radio and i will get her back up and running again. I just don't understand why I had this problem to begin with.

 

[Robb]

2312's have slightly more output than a 1969 and make a fine replacement. However, I wouldn't run them at full output all of the time, as this is hard on even a dual final radios as well. 35 watts is plenty and another station you may talk to can't really tell any difference between the output and 45 watt output either. Better to run them a little lower and cooler too.

Take it back to your repair guy and see what he says . . .

 

[jazzsinger]

as robb says the 2sc2312 is a superior replacement to the 2sc1969,

the pep rating of them is about 16w pep each.

so running a radio with 2 x 16w pep capable transistors at 40-45w should give you a good indication of why your finals disintegrated.

instead of worrying about cooling fans, try setting your AM/FM deadkey to about 8w max, which will give around 32w swing at 100% modulation, which is perfect for that radio and those transistors, as soon as you go over that you start to sound rough and also increase the likelihood of causing thermal runaway in your finals.

also as Robb says no-one can tell the difference between 32w and 45w except from the piss poor audio it creates, as the AM modulator transistor is incapable of supplying the power necessary to drive the audio at those levels. Not to mention god knows what else the tech at the shop you took it to may or may not have done.

think about it this way, if the 2sc2312 or 2sc1969 was capable of cleanly supplying that type of power, why do companies like, ranger, uniden,magnum etc all state their radios (even single final exports) are 4w am/fm 12w ssb pep?

because in radio, due to the amount of dodo's that don't understand power, power itself is THE main selling point of most cb/export radios. if these manufacturers could get more clean power then they definately would. the keyword in the last sentence is "CLEAN".

adding a fan to a radio set for proper power is a great idea and destresses the finals more, but adding a fan to a radio woefully overset for power, may help but its like sticking a sticking plaster on a gunshot wound.

 

[codeman]

Thanks guys, I will take the advice. When I get the finals replaced I will tell the
CB shop to set it to a maximum of 30-35 watts. When I had this radio set up initially it was doing about 38 watts and it lasted for years that way.