Does any one know if it's normal for the heatsinked transistor for the power supply, in the radio, to get very warm to the touch. Just got the radio, was cleaning it up and checking over everything when I noticed it. It gets warm soon after the radio is turned on rather or not it's in TX or RX. Tried it on the air last night for a while and everything else appeared to work normally. Never saw any smoke.
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President Dwight D CB
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Hmmmm . . . Think I would first check the voltage out of the power supply and be sure that it is at ~13.8v. Since this an older radio (+25 yo) and I believe it used the 858 PLL chip; the electrolytic caps may be shorting or getting way out of spec. At least replace all of the electrolytic caps in the power supply circuit and the voltage regulator circuit on that board too. If there is an output voltage adjustment trimpot, turn it 13.8v. If the voltage is much higher and it won't adjust; then replace the voltage regulator and the zener diodes. Don't have a schematic for this radio's power supply; but if it is similar to the Cobra 142 GTL those are the parts I would check out.
Could also be any electrolytic cap that has shorted in the radio and causing a larger current draw. Look for other hot spots in the radio for a clue. My limited troubleshooting experience has taught me that an old radio has the greater chance of failures because the caps have outlived the odds of survival.
To replace all of the electrolytic caps in the entire radio would cost around $12-$15 and take anywhere from 2-3 hours to do. Worth it if this radio is a keeper/daily user.
You might also want to put new heat sink compound between all of chassis-mounted devices (final, driver, audio chip, etc . . .). Old compound will no longer transfer heat well if it has dried out. Can also lead to part failure too (some of these parts are difficult to find replacements for). Part of the aging process.
Think it uses the same basic schematic as the Cobra 29XLR if it has the 858 PLL chip. Could be wrong though. Compare the schematic to your radio; check it yourself and see:
http://www.cbtricks.com/radios/cobra/29xlr/graphics/cobra_29xlr_om_sch.pdf
If it is the later version with the 2816 PLL chip; then:
http://www.cbtricks.com/radios/president/dwight_d_new/index.htm
http://www.cbtricks.com/radios/president/dwight_d_new/graphics/dwight_d_new_sch.pdf
Could also be any electrolytic cap that has shorted in the radio and causing a larger current draw. Look for other hot spots in the radio for a clue. My limited troubleshooting experience has taught me that an old radio has the greater chance of failures because the caps have outlived the odds of survival.
To replace all of the electrolytic caps in the entire radio would cost around $12-$15 and take anywhere from 2-3 hours to do. Worth it if this radio is a keeper/daily user.
You might also want to put new heat sink compound between all of chassis-mounted devices (final, driver, audio chip, etc . . .). Old compound will no longer transfer heat well if it has dried out. Can also lead to part failure too (some of these parts are difficult to find replacements for). Part of the aging process.
Think it uses the same basic schematic as the Cobra 29XLR if it has the 858 PLL chip. Could be wrong though. Compare the schematic to your radio; check it yourself and see:
http://www.cbtricks.com/radios/cobra/29xlr/graphics/cobra_29xlr_om_sch.pdf
If it is the later version with the 2816 PLL chip; then:
http://www.cbtricks.com/radios/president/dwight_d_new/index.htm
http://www.cbtricks.com/radios/president/dwight_d_new/graphics/dwight_d_new_sch.pdf
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It has the 858 PLL. The other heatsinks, in the radio, stay at or about room temperature. Been a little hesitant to poke around in the radio with the power connected. 
As far as I can tell everything else appears fine.
Forgot to mention the previous owner(s) did the channel mod for "upper and Lower" or freeband channels and the limiter has been cut.
As far as I can tell everything else appears fine.Forgot to mention the previous owner(s) did the channel mod for "upper and Lower" or freeband channels and the limiter has been cut.
Had a new CB shop open in town and took the radio to him to look at. He told me it appeared fine and wouldn't mess with until it stops working. He further told me he has seen some radios' power supply get hot just by plugging in the radio.
So yesterday I used it for a while. Even talk to a radio shop in IL, off of I70 on channel 8 on it. Later that night I talked to some locals when I noticed the received audio sounded OK but not that great. One of the locals was pushing a two on the meter, a three when he turned on the foot warmer and sounded a little muffled. Another local, who uses a beam antenna was strong as ever. As the night went on I noticed some hash in the background when any of them transmitted. I turned on the Washington and everyone sounded clear as can be.
FWIW I was trying out the audio mixer, studio mic with the radio at the time. When I switched back to a CB power mic they said I sounded about the same. My Washington uses a five pin mic so I couldn't try the mixer on it.
So yesterday I used it for a while. Even talk to a radio shop in IL, off of I70 on channel 8 on it. Later that night I talked to some locals when I noticed the received audio sounded OK but not that great. One of the locals was pushing a two on the meter, a three when he turned on the foot warmer and sounded a little muffled. Another local, who uses a beam antenna was strong as ever. As the night went on I noticed some hash in the background when any of them transmitted. I turned on the Washington and everyone sounded clear as can be.
FWIW I was trying out the audio mixer, studio mic with the radio at the time. When I switched back to a CB power mic they said I sounded about the same. My Washington uses a five pin mic so I couldn't try the mixer on it.
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