Galaxy DX959 AM not working but SSB works as it should

[Chris Lawrence]

Either you have a misprint, or you did the "L23" adjustment wrong....

"L23" (in TX mode) is adjusted using test point TP5 not TP3.

Correct. TP5 is the test point and L23 is working. Aligned to 10.695 in TX.

I should have typed a bullet point * at the beginning of the next sentence stating that L20 is not effecting TP3. Will edit.

 

[Chris Lawrence]

Let's not worry about crystal reading until you get the "AM" adjustment section working since both side bands are working.

Copy that. As mentioned, edited previous reply for clarity. Other info I can provide for you?

 

[Dr. Frankenstein]

@Chris Lawrence

NOTE: Make sure your radio is connected to an antenna or dummy load.

You said that the "L20" adjustment wasn't working, but "AM" TX does work?

Can you read the actual transmitted (ch.20) "AM" carrier (dead key) frequency going to the antenna (from inside your radio) with your frequency counter? (Don't care about SSB since it works.)

** Check for the 8V from R154 to both sides of "D50".
** If there is voltage at both sides of "D50"; continue, or fix.
** If you notice that it's still not working change D49. (but I doubt it)
** There is a chance that you may be having a problem reading TP3 with your frequency counter while in the "AM" mode:
* Try putting a 0.1uf or 0.01uf ceramic capacitor between TP3 and the positive lead of your frequency counter.
* If that doesn't work try a 100Ω resistor instead.
* Always with the negative lead to board ground.

Since the "Clarifier" controls the Receive (RX) frequency, and "VR7" controls the TX frequency ....... with both going to X3, try this:
* Connect your Frequency counter to TP3 (with cap or resistor, whichever works, or fix D50 "no voltage" whatever works).

* Instead of adjusting "L20" at this time ..... wait:
* Step-1. In RX mode, turn the Clarifier (both ways) to see if the frequency at TP3 changes. (Make sure that the Clarifier is set to "12 o'clock" when done and record that frequency.)
* Step-2. Key up (TX), turn VR7 (both ways) to see if the frequency at TP3 changes.
* Step-3. Key up (TX), adjust VR7 frequency to match (recorded frequency)
from "Step-1".

* At this point the "Clarifier" and "VR7" are "LOCKED" together (RX&TX), but not on "center frequency". (If the clarifier is touched TX and RX are off from each other.)

* Step-4a. This is the time to adjust "L20", as you would have done using the instructions in the RX "AM" mode, to whatever numbers you are using for ch.20 ........... Check the Frequency Display (on the front of the radio) for 27.205.
(When "L21 & L22" were adjusted the front Display should also read 27.205 for both Side Bands.)

or:​

* Step-4b. Connect your frequency counter to the inside of the radio to "sniff" the actual TX frequency of the radio at the SO-239 (with antenna or dummy load connected):
* Key up (TX) and adjust "L20" for 27.205.00MHz while in "AM" mode on your frequency counter.

My concern at this point is if the radio's Display reads right (27.205 on ch. 20)? ....... or ....... If your frequency counter is accurate?

Get it working, and figure that out later...........

I would "UNLOCK" the Clarifier and just get VR7 out of the equation.........
"Close enough only counts in Horse Shoes and Hand Grenades, but not SSB."

73

 

[Chris Lawrence]

@Chris Lawrence

NOTE: Make sure your radio is connected to an antenna or dummy load.

You said that the "L20" adjustment wasn't working, but "AM" TX does work?

Can you read the actual transmitted (ch.20) "AM" carrier (dead key) frequency going to the antenna (from inside your radio) with your frequency counter? (Don't care about SSB since it works.)

** Check for the 8V from R154 to both sides of "D50".
** If there is voltage at both sides of "D50"; continue, or fix.
** If you notice that it's still not working change D49. (but I doubt it)
** There is a chance that you may be having a problem reading TP3 with your frequency counter while in the "AM" mode:
* Try putting a 0.1uf or 0.01uf ceramic capacitor between TP3 and the positive lead of your frequency counter.
* If that doesn't work try a 100Ω resistor instead.
* Always with the negative lead to board ground.

Since the "Clarifier" controls the Receive (RX) frequency, and "VR7" controls the TX frequency ....... with both going to X3, try this:
* Connect your Frequency counter to TP3 (with cap or resistor, whichever works, or fix D50 "no voltage" whatever works).

I’ll tackle this section first because it may change further instructions. I’ll log my process here while testing.

*TP3 = 16.5288xx on all of the following:
-BK 1856D
-BK1823A
linked to 10mHz oscillator-if that helps at all.

*RF Output on ch20 = 27.2238xx on:
-Both BK’s
-Rigol spectrum analyzer
-Icom bench radio scope

So, it looks like TP3 reading and at antenna are high by 18,800 Hz. Does that sound right. So I believe my equipment is reading correctly.

*R154 = 7.5v
**D50 = 0.0v on both sides. Good grief. I tested the diode earlier but didn’t test voltage while in the circuit.

BRB

 

[Chris Lawrence]

Found it!

Turns out the trace between D50 and L20 was pulled up. It was almost unnoticeable until I put on my magnifying head set. SMH

Undoubtedly that was my fault. The original problem was the lead from the mode switch. I got ahead of myself when diagnosing; reflowed solder joints and testing L20. I removed it for testing. That was dumb. Sometimes when you’re tired…well, that’s my excuse.

Restored trace and it’s fixed. That explains why restoring the lead to mode switch did not fix everything.

Full alignment and open clarifier coming.

Thanks so much.

 

[Dr. Frankenstein]

@Chris Lawrence

So I was right, "** If there is voltage at both sides of "D50"; continue, or fix." was your problem. (You're lucky you didn't have a bad "L20".)

Glad you found it, and all is well again!

Does the radio's display match the Frequency counter now?

These radios are known to drift (like a sail boat) when cold.
Make sure that you do the final adjustments to "L20 ~ L25" after the radio has warmed up with the covers on, and that the clarifier at "12 o'clock".

About the "Clarifier"......... on mine:
I replace R114 (2.2K) with a 10Ω and R153 (2.7K) with either a 10K or 12K resistor
to set my "Slide" to just over 10Kc, enough to go between channels. You can also replace the clarifier pot with a 10K/10 turn pot, for a nice fine adjustment.

Glad I could help......
73

 

[Chris Lawrence]

@Chris Lawrence

So I was right, "** If there is voltage at both sides of "D50"; continue, or fix." was your problem. (You're lucky you didn't have a bad "L20".)

Glad you found it, and all is well again!

Does the radio's display match the Frequency counter now?

These radios are known to drift (like a sail boat) when cold.
Make sure that you do the final adjustments to "L20 ~ L25" after the radio has warmed up with the covers on, and that the clarifier at "12 o'clock".

About the "Clarifier"......... on mine:
I replace R114 (2.2K) with a 10Ω and R153 (2.7K) with either a 10K or 12K resistor
to set my "Slide" to just over 10Kc, enough to go between channels. You can also replace the clarifier pot with a 10K/10 turn pot, for a nice fine adjustment.

Glad I could help......
73

All aligned. Opened clarifier. Yes, Frequency display matches. The vr on the display always takes about a 1/4 turn clockwise to read correctly. Like to see it flip from 4 to 5 right when the clarifier moves right on frequency.

Not a fan of the big slide as they’re already touchy. The 10 turn is a nice touch though.