Here is a calculator to determine the resistor value.
<http://www.calculatoredge.com/electronics/zener.htm>
You will probably have to provide an external supply, at the zener
voltage, to know what the current draw is for the calculator.
You might find that the original resistor value was too low or the zener
wattage was too low for the circuit draw.
You might also find a leaky filter capacitor down stream causing the
current to be too high.
There may be a leaky filter capacitor up stream causing the zener to
draw too much current as the peak voltage may have exceeded the original
calculations.
73
Glenn
On 4/23/2017 2:31 PM, Dave Wood wrote:
Bill, actually what happened is the zener diode that the resistor fed
shorted and that's the reason it burned up. I have two units with this
issue and I cannot read the resistor value since it burned up. What I
would love to know is what the original value of the dropping resistor
was? 73 Dave
On Sat, Apr 22, 2017 at 11:39 PM, Bill Hawkins <[email protected]> wrote:
There is usually a power dissipation reason why a resistor becomes
toast, and the reason is frequently a shorted bypass cap or a shorted
device.
Have you measured the resistance to ground of the end of the resistor
opposite the power supply?
Sometimes inputs get high voltages and short the amplifying device.
Sometimes that is reason the units were for sale.
Hope I'm wrong.
Bill Hawkins
-----Original Message-----
From: time-nuts [mailto:[email protected]] On Behalf Of Dave
Wood
Sent: Saturday, April 22, 2017 8:43 PM
Anyone on the list own the above Time Code Readesr. I have one of each,
they are identical with the same issue. I need to identify the correct
value of a resistor in the power supply that provides 27 volts to the
input amp. They are both toast in my units and I do not have a manual.
Thanks in advance! Dave _______________________________________________
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QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
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