Originally Posted by hank
Intermitant loss of out put power radio keys but only does 1/4 of a watt has audio checked driver and finals voltage reg. ect: ALL check ok. Sometimes it works ok swings 40 watts other times keys up has audio but wont do any watts.
BEST REGUARDS HANK
Repairing any electronics is 60% symptom analysis (recognizing what's not working) and 40% troubleshooting.
So just knowing exactly what's not working is over half the battle.
Below you'll find enough info to repair any Galaxy radio with good receive and no transmit power.
You only need two things for these radios to produce power.
1. Proper voltage
2. Proper drive.
Checking proper voltage is easy with only needing a voltmeter.
Since you are testing the transmit section always make sure your voltage checks are done in TX
Make sure front panel controls are properly set before testing, Mode SW - AM
, RF Pwr button to HI, etc...
Key radio and check collectors of TR51 (2SB754), TR44 (2SC2166), TR43&TR56 (2SC2312) all for approx. 6.5 volts.
Checking for proper drive is a bit more involved and requires a good 100Mhz scope with a (x10) scope probe.
Below are the AC/RF voltages peak to peak starting from TR45 out to the antenna.
TR45 collector - 10v peak to peak in TX
TR44 collector - 15v peak to peak in TX
TR43/56 collectors - 25v peak to peak in TX
Output side of L33 - 80v peak to peak in TX
Output side of C166 - 40v peak to peak in TX
Output to antenna - 60v peak to peak in TX
If you do not have the approx voltages at TR45 then you must troubleshoot the transmit oscillator circuit of X4 (10.695mhz) crystal and TR30.
In transmit check the emitter of TR30 for 10.695mhz.
Next check IC3 pin 7 for 10.695mhz in TX
Next check IC9 pins 7&8 for 10.695mhz in TX
. - very small signal, will only see this with a good scope and switch the probe to x1.
The last troubleshooting aid that can help would be to have a known good DX88 setting on the bench plugged into DC so you can use it
for comparison checks.