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The radio's chassis shows +12v - yeticom optima
- Thread starter CbRadiosPRONTO
- Start date
if the chassis (body) is showing +12v then you have your power wires around the wrong way ..
however your description is some what vague and can be interpreted several ways
L405 is from the negative lead directly to ground (and therefore chassis as the radio is a dc ground radio not floating earth )
d416 is the protection diode..close to L405 ..it is no doubt blown with possible finals shorted
send it back to your vendor for repairs however removing the lids has voided any warranty you had with them
you have not even mentioned if the radio powers up also..details help others to help you
however your description is some what vague and can be interpreted several ways
L405 is from the negative lead directly to ground (and therefore chassis as the radio is a dc ground radio not floating earth )
d416 is the protection diode..close to L405 ..it is no doubt blown with possible finals shorted
send it back to your vendor for repairs however removing the lids has voided any warranty you had with them
you have not even mentioned if the radio powers up also..details help others to help you
I hope you got it from Mike and Dave at Yeticomnz, never buy Optima's from any place else.
Thanks for the input. Sorry, I'm not so versed in these boards. I was hoping to get a "no brainier" type of response. So, I'll have to do a little work I guess.
Radio will power up only if L405 is in the circuit, but, of course, it will then just smoke because the L405 pad furthest away from the chassis is shorted to power some where. This pad, of course, is chassis ground, thus the problem.
*Would like to start with checking the protection diode. I cannot find d416. Can you point me in that direction?
I don't know, however, if a protection diode could cause this directly, or if it caused something else to fail which is causing the short. Final transistor and AM regulator legs have been lifted so as to eliminate them from the equation.
Radio will power up only if L405 is in the circuit, but, of course, it will then just smoke because the L405 pad furthest away from the chassis is shorted to power some where. This pad, of course, is chassis ground, thus the problem.
*Would like to start with checking the protection diode. I cannot find d416. Can you point me in that direction?
I don't know, however, if a protection diode could cause this directly, or if it caused something else to fail which is causing the short. Final transistor and AM regulator legs have been lifted so as to eliminate them from the equation.
D416 is right beside L405 between the two electrolytic's in the corner
Sounds like a classic case where using a simple 25 cent fuse could have saved $$$.
I had the same issue on a different radio not long ago. A guy plugged it in (no fuse) with the polarity reversed. It blew the protection diode and burned the trace coming from the negative dc power wire. It was actually his son and this happened twice. Somehow the radio survived both times.
Traces on the circuit board can act like a fuse, sometimes.... otherwise deeper damage can happen.
Protection diodes will blow a small and quick acting fuse before damage can happen, most times the protective diode will be ok but best to replace it after a reverse polarity event.
If the fuse is bypassed then all components along the B+ rail can be damaged. These include the AM regulator, both final (FET or Bipolar) and driver, audio amp, power capacitors and in newer computer controlled radios, the power switch diodes and transistors. Most B+ rail sources have smaller polarity diodes, this would be on newer style rigs.
mechanic
Protection diodes will blow a small and quick acting fuse before damage can happen, most times the protective diode will be ok but best to replace it after a reverse polarity event.
If the fuse is bypassed then all components along the B+ rail can be damaged. These include the AM regulator, both final (FET or Bipolar) and driver, audio amp, power capacitors and in newer computer controlled radios, the power switch diodes and transistors. Most B+ rail sources have smaller polarity diodes, this would be on newer style rigs.
mechanic
If the diode is shorted or another component and the choke on the negative is open you will measure positive on the chassis of none floating chassis rigs,
small silicon diodes are a cheap & poor method of protecting your radio in the event of cross polarity,
their turn on voltage is relatively high while their switching speed is relatively slow,
they sort of work if the correct fuse is installed but not always,
fitting them to the circuit board is a stupid idea as it often burns traces and or chokes if somebody put a larger than stock fuse in the power chord,
a large amp fast switching low volt drop schottky diode connected directly across the power socket before the chokes where they should be installed works more effectively,
don't use a shottky large enough to smoke the power chord and cause a fire,
small silicon diodes are a cheap & poor method of protecting your radio in the event of cross polarity,
their turn on voltage is relatively high while their switching speed is relatively slow,
they sort of work if the correct fuse is installed but not always,
fitting them to the circuit board is a stupid idea as it often burns traces and or chokes if somebody put a larger than stock fuse in the power chord,
a large amp fast switching low volt drop schottky diode connected directly across the power socket before the chokes where they should be installed works more effectively,
don't use a shottky large enough to smoke the power chord and cause a fire,
The bottom line is to always use a fuse in the power lead like the manufacturer intended and make sure it is the proper rating. Above all else PAY ATTENTION to which lead goes where. AFAIK all power cords are colour coded so it is really hard to mess up if you pay the least bit of attention. Of the several times someone has brought a radio to me that they hooked up with the wrong polarity without a fuse I refused to even look at it. IMHO it was a waste of my time and their money even if I did it free of charge. IC chips really don't like reverse polarity.