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Cobra 89xlr

loosecannon said:
leapfrog, i didn't watch the video yet, as it seems like you got it handled.
let me know if you think i should still watch it.

the 2SC458 can be replaced by a regular old 2SC945 and they have been using a 945 in this application for a long while now.
(to the gurus: yes, i know some specs are a bit different, and that the 2SC458 will perform a bit differently in some applications, but for it's uses in a CB radio; the 2SC945 will work, and the manufacturers seem to agree)

TR14 is part of the AMC circuit and was probably clipped for a modulation increase.
definitely put it back in. these radios have great audio when just tuned right.

Ben Hebert, where did you order that 2SC1969 from? 99% of the places that sell them have fakes that will never give you the power output you want.

your best bet for a final for that radio would be the 2SC2078 since it's still being produced today. If only your driver transistor was blown, then do not replace the final "just because". replace the driver, confirm that the radio is now transmitting properly, and align the transmitter section.
if you are getting more than about 16 watts PEP from a 4 watt deadkey then you are all set and it's time to put the covers back on. simply adding a 1969 final, even a real one, rarely adds any significant power, and most times part values have to be changed to optimize it for the particular circuit it's in.
LC
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No sir no need, thank you for the advice on a substitute!
I have my own thread for an 89 XLR i have on the bench, low modulation. (if you wouldn't mind looking :notworthy::notworthy:)
These seem to be a real good AM only base station, when they are 100%.
 
Hey Ben; don't feel too bad. I've bought my share of phony 1969's myself. Even after I called BS on the 'Dalbani Corp' - a highly rated seller on eBay - for selling these phony parts - they still are selling them. So, beware.

Only 1969's that I know of that are 100% real are available from RF Parts.
Not cheap - tho . . .
 
there is one guy from california selling good used pulls and I have been buying them. about 40 or so used and are all good but one that the leg broke when I bent it to fit.
 
In your radio you have a power supply that changes ~110vac to 13.8vdc. Then the 13.8vdc is fed to the board and the voltage regulator, which changes it to 8vdc. So, there are two voltages on the board 13.8vdc and 8vdc. Which one did you trace out; 13.8vdc or 8vdc?
 
Capture.PNGCongrats, you traced thru the power supply. VR201/variable resistor on that same ac/dc power supply board will adjust the voltage output to the radio board. You will want to adjust VR201 with a voltmeter to read 13.8v. at the radio board. You can check the voltage output either on the emitter of transistor TR201; or where that wire goes to the radio board.

Capture.PNG
 
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ben hebert,

please don't take this the wrong way, but i have read through both of your threads on this radio (or both radios) and the impression i am left with is that you should not be tinkering around inside your radios. you have sooooo much learning to do, and so little experience that no matter how great the advice you get is, no one here can tell how it's being implemented.

my advice to you is to send the radio to a tech and have it restored.
that is all the advice i will be giving on this radio.
LC
 
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