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Cobra 29 LTD
- Thread starter kaos513
- Start date
That cap would be my choice also and like Andy said, make sure the negative end is towards TR18. Hard to say if the original cap is a non-polarity type, even with your photo. I believe there's a testing method for determining if it's a non-polarity type and another test to determine the negative lead on a polarized type, but I never had the need for that type of testing.
I only caution because I've seen nearly brand new radios come across my desk with just two parts swapped out - and one of the electrolytic blew up - exploding it's guts - aluminum shrapnel - everywhere - shorting out several paths.
All because the owner reworked two caps and not sure if their tech did this or they did this to their radio - all for an audio upgrade. But putting in wrong rated or in the wrong direction it will make a mess and ruin a good radio real quick if you use wrong rated parts and / or - they're installed wrong direction.
Can't stress that enough.
All because the owner reworked two caps and not sure if their tech did this or they did this to their radio - all for an audio upgrade. But putting in wrong rated or in the wrong direction it will make a mess and ruin a good radio real quick if you use wrong rated parts and / or - they're installed wrong direction.
Can't stress that enough.
Yet another variation. C68 looks like it has a Ceramic Disk cap. I bet that one is non-polarity.
I finally found the right parts list it’s from sams I paid 20 bucks even shows c68 as a aluminum electrolytic and the right alignment, this radio seems was from1978.
Tr23 - main Regulator...
R117 - Bright / Dim dropping resistor - works with TR22 - so R117 SUPPLIES power thru TR22 for the Bright and Dim function.
TR23 supplies regulated power to many sections - including the 5 volts PLL regulation and the 10.240MHz Delta Tune and the SWR ANT warn light.
Since it covers a large area of traces - any spots causing this heating problem? Else some heat is normal - but tarnishing silver and the smell of hot electric, is not...
Best way to look for this is to put a meter on the power input to the radio and adjust volume, squelch, Bright Dim - various functions and watch the meter to see if a section, when it comes up powered, makes the meter climb drastically.
Since you've found one old cap questionable, this radio may have seem a spike in voltage and or current to the power leads into the radio - this may indicate a problem with age and or power reversal. So caps may still be in the cards as far as needing replacement.
R117 - Bright / Dim dropping resistor - works with TR22 - so R117 SUPPLIES power thru TR22 for the Bright and Dim function.
TR23 supplies regulated power to many sections - including the 5 volts PLL regulation and the 10.240MHz Delta Tune and the SWR ANT warn light.
Since it covers a large area of traces - any spots causing this heating problem? Else some heat is normal - but tarnishing silver and the smell of hot electric, is not...
Best way to look for this is to put a meter on the power input to the radio and adjust volume, squelch, Bright Dim - various functions and watch the meter to see if a section, when it comes up powered, makes the meter climb drastically.
Since you've found one old cap questionable, this radio may have seem a spike in voltage and or current to the power leads into the radio - this may indicate a problem with age and or power reversal. So caps may still be in the cards as far as needing replacement.
I tried balancing the power so far so good and also replaced the final will keep an eye on the heat issue
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