The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Hello, I have a 2980(EPT360014B) that received a lightning shot. The radio receives fine, but has no TX. The red light does turn on at TX. This same thing happened a few years back and a local shop replaced the finals to repair it. I can hear a slight carrier on a nearby radio when I push the mike button. It has no mod on AM, but does on FM. Where do I start on taking voltage measurements? I have limited tech skills.
Thanks in advance
Lou

Remove the jumper PCB, this is at the back of the radio (A small vertical PCB that connects TP7, TP8, and TP9), then check the voltage at TP9 in AM Mode TX.

Hi Rick, the voltage is 6.85

Looks like the finals have gone south.

Rick, I am waiting on the new finals, but have noticed TR51 measures 6.8v. Is this because of the bad finals?

Remove the jumper PCB, this is at the back of the radio (A small vertical PCB that connects TP7, TP8, and TP9), then check the voltage at TP9 in USB or LSB Mode TX and you should have about 13.2 volts.

In AM it should be only 5.60 volts, you can reset this by adjusting VR13 in AM Mod TX, so that the voltage at TP9 is 5.60 volts.

TP9=USB 6.8v
AM 6.8v
Measurements with jumper removed and TX
Next

Ok then it looks like TR51 is also bad.
Check the voltage on the Base, Collector and Emitter of TR51 and let us know what you find.

With jumper out: TR51 B=13.81 C=6.82 E=13.81

With jumper in and TX on AM and USB: B=13.80 C=0 E=13.81

If you are taking the voltage reading correctly?
If so then it looks like you have a bit more than just the finals and TR51 bad.
I would check the voltages at TR49 and TR50 in AM TX with the jumper out.
I would check the voltages at TR52 in SSB TX with the jumper out.

TR49=E 6.79 C 13.79 B 6.42
TR50=B 13.79 C 6.81 E 13.81
TR52=E 7.22 C 13.72 B 7.22

Correction on TR52=E 7.26 C 13.72 B 7.82

The voltage are not right, so before you do any more reset VR13 in AM TX so the voltage at TP9 5.60 volts with the jumper out.

Then check the voltages at TR49, TR50, TR51, and TR52 in AM TX with the jumper out.

Also check the voltages at TR49, TR50, TR51, and TR52 in SSB TX with the jumper out.

Rick, VR13 will not make any changes to the voltage. The pot does show changes in resistance when I checked with the radio unplugged.

Make sure the RF power control on the front of the radio is turned fully CW.
Then try adjusting VR13 while checking the voltage at each side of R238.

If I am at the right location, below VR13, someone has changed that resistor to 2 100k resistors solder together. The schematic I am looking at shows a 5.6k at R238. Anyway the voltage is 6.21 one one side and .11 on the other.
Looks like TR51 has been changed before.

When you post can you put the reference in the Subject line as it make it easy to track the post.

R238 and R239 should both be 5K6, you need to put this right as this will through all the voltage reading out.
Also, check the voltage at each side of R237 in the TX mode.

Ok, replaced R238, but VR13 will only turn down to 5.94. R237 reads 8.52-8.70.

Ok try adjust VR13 and check to see if the voltage at the base, collector, and emitter of TR50 is now changing has you adjust VR13.

Yes, voltages adjust at TR50. Lowest at C is 5.92

Ok it maybe right now but before you replace any parts you need to make sure that the Pass regulator TR51 is working ok.

1. Make sure the RF power control on the front of the radio is turned fully CW.
2. Remove the jumper PCB from TP7, TP8, and TP9.
3. Check the voltage at the collector of TR51 in AM TX, it should be 5.60 volts, if not try adjusting VR13.
4. Check the voltage at the collector of TR51 in SSB TX, it should be 13.50 to 13.70 volts.

Still have problems. At TR51C, voltage stays at 5.94 in AM and SSB. VR13 only turns down to 5.94. Jumper is out.

If it would be best to go and checkout the transistor voltage, TR49, TR50, TR,51, TR52, TR53, and TR54.

You will find a voltage chart at the link below, this is for a Galaxy DX88, but this is the same main PCB EPT360014B and all voltage are the same.
http://www.cbtricks.com/radios/galaxy/d ... _chart.htm

Let us know which ones are not right and take a note of the transistors and there voltages.

Rick, should I take the voltage readings with jumper out? On TR52 I have C=13.82 in AM and SSB. At TR54 C=0 in AM and FM. The Galaxy 88 chart shows 5.6 at both. Is the Galaxy Saturn the same board? It shows 0 volts at C on TR54.

Do not go of the Galaxy Saturn voltage chart as it as a few errors.

All test should be done with the jumper board out and the RF power control to fully CW.

It looks like TR51 is bad and is why you are getting bad voltage readings.
It would be best to test TR51 before you do any more, you can find the info on testing transistors at http://www.elexp.com/t_test.htm
TR50 and TR51 are PNP type transistors.
TR49, TR52, TR53 and TR54 are NPN type transistors.

Rick, it looks like TR51 is bad. I unsolder it to test it. Will have to order a replacement. Will get back with you when it is installed
Thanks for your help. I didn't think you would hang in this long with a rookie.

Back again Rick. I replaced TR51 and TR 50 with higher wattage tr's and the voltages are now correct at those 2. VR13 will now adjust correctly. TR52 still shows 13.82 at C and TR54 shows 0 at C(FM). The charts say 5.6 at those locations. These tests were made with jumper out.
Your serve

TR54 is only switch on in the FM mode.

Have you removed the finals as they was bad?

I think you need to gover the voltage chart again.

You will find a voltage chart at the link below, this is for a Galaxy DX88, but this is the same main PCB EPT360014B and all voltage are the same.
http://www.cbtricks.com/radios/galaxy/d ... _chart.htm

Success. I tested the finals and the driver, and they were ok. Adjusted bias on the driver and finals to spec. I now have transmit. It looks like TR51 was the trouble all along.
I want to thank you Rick, without your help this was on it's way to the shop and a big repair bill. This experience wants me to tinker a little more.
Thanks again.