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89xlr
- Thread starter Ben Hebert
- Start date
Obviously do not leave the built-in power supply connected while you use the DC in jack, as far as I remember these radios don't have an ac/dc switch.
Make the radio work correctly on a separate supply, or fix the power supply before attempting to talk on the radio.
Replaced tr14 but that still not working. Tr12 tr15 tr16 not working. Should r85 have power on both sides on it
R85 is 3.3 k Ohm, if i'm reading the schematic correctly it should have 2.2V by the base of TR14 and the wiper of VR5 & 7.6 volts on the other end, less the voltage drop across R91 (1k ohm resistor) the voltage comes from pin 7 of IC2.
http://www.cbtricks.com/radios/cobra/89xlr/graphics/cobra_89xlr_sm_sch.jpg
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What voltage is present on the other end of R85?
Make sure your negative lead of the volt meter is on PCB ground, not the chassis/frame.
if you have 13.77 volts @ pin 7 of IC2, ic2 has failed..... I would say anyway without looking at the radio. It is kind of hard to follow all the things about two or three 89 XLR radios, you a few threads going my man, all on this model of radio.
What is the DC power supply voltage you are running the radio off of? 13.77?
You may need to plainly state what has been done to the radio since you got it, and what all works/doesn't work. So that people can help, anyway how how many 89 XLR radios have you got Ben?
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If i'm reading the schematic correctly, that should be 7.6v.
What power supply is the radio running off of?
What power supply is the radio running off of?
Cool, ok so this radio has already been re-capped?
If you know you have a problem in the a.c. supply, why risk damage to the radio?
Do you not have a lil 4 or 5 amp power supply yet, that's okay if you don't I'm just trying to figure out how to help.
If the radio is running off of the incorrect voltage to start with, you cannot test anything and expect proper measurements. ~Shut it off, those old parts are not made anymore, would not want to burn up those IC's.
A failed resistor on the PSU board, can mess up the range of the VR.
In the 89XLR I worked on, the psu board needed two or three resistors replaced..
They had gotten hot after the power transistor failed short circuit and this caused them to change in value..
After replacing the transistor I could not dial the supply voltage in; until I changed the bummed resistors out also.
If It was me I'd change all the resistors for new ones of the appropriate size, the psu pc board is small if you have the parts on hand, rebuild it; replace what is not new on the board.
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