I done a search on this problem on this site and did not find any info about this issue so thought it would be nice to share some info how what the problem could be. I talked to Andy after I repaired this problem to see if he would like to make us some of his cool graphics to help others understand the area that needed to be checked to figure this problem out. Keep in mind there is many things that can be the culprit so if you have had this issue before and fixed the problem then feel free to post up your results. Here is what I found.
Galaxy 33 HTML EPT3600148 board. No TX and the light does not change to red when keyed.
First thing I checked was for anything that looked burned, Broke traces or bad soldier joints. All was good.
Next step was to check the Alignment. Right off the bat TP2 I noticed R116 was showing 8 volts and L17 would not adjust the voltage at all. This tells me something has shorted out so now the fun begins to hunt this down.
Here are the most common parts we need to check for this problem.
Common faulty parts are C101, C102, C108, C90, TR25, TR26, L22 and L17
First off lets check that the 10.240 MHz frequency is present on the pin 4 of the PLL. Yep it is there!
First step I took was to make sure this problem was on the PLL / VCO side.
I checked the voltage on D66 and found 2.4 volts on both sides. OK we know the cath side of this diode goes to pin 8 of IC5 PLL chip and should be around 8.10 volts and the other side of this diode goes to pin 6 of IC4 should be around 3.2 volts. By lifting one end of D66 to break the circuit allowed the radio to key with the light turning from green to red. No TX power but at least the light now changes letting us know the problem was on the PLL side.
Now lets do what we call a VCO Loop Test.
Unsolder pin 7 of the IC5 PLL chip.
Inject 3 volts into TP2
Connect freq counter to TP3
Adjust L17 for 16.270 MHz If you can not get this to adjust then look at TR25 emitter and collector should have 16.270 MHz and TR26 on the collector. You can also check the voltages on these transistors as followed.
TR25 is the VCO Transistor = B 2.10, C 7.30, E 1.40
TR26 VCO Buffer = B 0.60, C 3.80, E 0.00
On both transistors checked out fine but still could not adjust L17 so this was the faulty part. Changed out L17 and the problem was fixed.
There is a lot more that could been the problem like IC10 and IC5 that could cause this problem but I will not go into those area's as L17 is where this problem was.
Andy will come in and do some of his awesome graphics to show these problem area's.
Hope this will help someone else down the road that may need help on this problem.
Galaxy 33 HTML EPT3600148 board. No TX and the light does not change to red when keyed.
First thing I checked was for anything that looked burned, Broke traces or bad soldier joints. All was good.
Next step was to check the Alignment. Right off the bat TP2 I noticed R116 was showing 8 volts and L17 would not adjust the voltage at all. This tells me something has shorted out so now the fun begins to hunt this down.
Here are the most common parts we need to check for this problem.
Common faulty parts are C101, C102, C108, C90, TR25, TR26, L22 and L17
First off lets check that the 10.240 MHz frequency is present on the pin 4 of the PLL. Yep it is there!
First step I took was to make sure this problem was on the PLL / VCO side.
I checked the voltage on D66 and found 2.4 volts on both sides. OK we know the cath side of this diode goes to pin 8 of IC5 PLL chip and should be around 8.10 volts and the other side of this diode goes to pin 6 of IC4 should be around 3.2 volts. By lifting one end of D66 to break the circuit allowed the radio to key with the light turning from green to red. No TX power but at least the light now changes letting us know the problem was on the PLL side.
Now lets do what we call a VCO Loop Test.
Unsolder pin 7 of the IC5 PLL chip.
Inject 3 volts into TP2
Connect freq counter to TP3
Adjust L17 for 16.270 MHz If you can not get this to adjust then look at TR25 emitter and collector should have 16.270 MHz and TR26 on the collector. You can also check the voltages on these transistors as followed.
TR25 is the VCO Transistor = B 2.10, C 7.30, E 1.40
TR26 VCO Buffer = B 0.60, C 3.80, E 0.00
On both transistors checked out fine but still could not adjust L17 so this was the faulty part. Changed out L17 and the problem was fixed.
There is a lot more that could been the problem like IC10 and IC5 that could cause this problem but I will not go into those area's as L17 is where this problem was.
Andy will come in and do some of his awesome graphics to show these problem area's.
Hope this will help someone else down the road that may need help on this problem.
