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Galaxy DX959 AM not working but SSB works as it should

C

Chris Lawrence

Active Member
Jul 9, 2021
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*On AM, frequency off (edit) 16kHz and clarifier does not affect it. However, on SSB it works fine. Example: ch20=27.221 but in SSB=27.205

*No TX RF Power on AM but SSB works. Keyup light lights up as it should.

*The RX meter shows a strong signal on RX (using dummy load). SSB receiving fine.

Channel 20:
TP3 shows 16.5264 instead of 16.5100 (note: L20 does not change reading—not sure if that is the culprit)
IC3 Pin 8 = 10.2400
TP2 2.8v
L20 only adjust about 30Hz
L7 does not affect TP3, as if a clarifier mod was done but it has not.

Help appreciated. What else can I provide?
 
Last edited:

Chris Lawrence said:
Thanks. I had done that. It’s how I got the results I posted.

I did make an edit to the original post. The reading at TP3 does not change when adjusting L20 as it should. Other than that, the PLL alignment was done.
Click to expand...
Its 16kHz high, not 4kHz That suggests the coil is not even part of the oscillator circuit. Look for a bad solder joint, ohm the coil, test D50 and then ensure bias voltage is present.
 
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Chris Lawrence said:
*On AM, frequency off 4000Hz and clarifier does not affect it. However, on SSB it works fine. Example: ch20=27.221 but in SSB=27.205

*No TX RF Power on AM but SSB works. Keyup light lights up as it should.

*The RX meter shows a strong signal on RX (using dummy load). SSB receiving fine.

Channel 20:
TP3 shows 16.5264 instead of 16.5100 (note: L20 does not change reading—not sure if that is the culprit)
IC3 10.2400
TP2 2.8v

Help appreciated. What else can I provide?
Click to expand...
If you followed the PLL alignment procedure via the service manual, you will see that you perform the AM BFO step on channel *1*, looking for 16.2700 +/- 20 Hz. Your findings in your post do not follow the procedure.

Try again and post the results from every step.

Have you looked at the BFO/carrier oscillator crystals with a sniffer that won't load them down? Do you see 10.695 at TP5 in TX? Is the REF OSC 10.240 MHz?

These are things I would be asking myself, if I were working on this.
 
brandon7861 said:
Its 16kHz high, not 4kHz That suggests the coil is not even part of the oscillator circuit. Look for a bad solder joint, ohm the coil, test D50 and then ensure bias voltage is present.
Click to expand...
Will do thanks.

When I said 4K, that was at the display. 27.205-27.201.

Will test shortly. Thanks again
 
Chris Lawrence said:
When I said 4K, that was at the display. 27.205-27.201.
Click to expand...
Chris Lawrence said:
*On AM, frequency off 4000Hz and clarifier does not affect it. However, on SSB it works fine. Example: ch20=27.221 but in SSB=27.205

*No TX RF Power on AM but SSB works. Keyup light lights up as it should.

*The RX meter shows a strong signal on RX (using dummy load). SSB receiving fine.

Channel 20:
TP3 shows 16.5264 instead of 16.5100 (note: L20 does not change reading—not sure if that is the culprit)
IC3 10.2400
TP2 2.8v

Help appreciated. What else can I provide?
Click to expand...
27.221 - 27.205 = 16kHz
16.5264 - 16.51 = 16.4kHz

At what point did you measure/see 27.201?

It would help if you specify the measurement point from now on. The frequency display on the radio does not have the resolution to show the response of some of the adjustments and it is not ok to be using it for alignments. I really hope you have a legit frequency counter in front of you. If not, put the cover back on.

If L20 is truly non-responsive, circle back to post #5 to track down why.

SuperLid said:
If you followed the PLL alignment procedure via the service manual, you will see that you perform the AM BFO step on channel *1*, looking for 16.2700 +/- 20 Hz. Your findings in your post do not follow the procedure.

Try again and post the results from every step.

Have you looked at the BFO/carrier oscillator crystals with a sniffer that won't load them down? Do you see 10.695 at TP5 in TX? Is the REF OSC 10.240 MHz?
Click to expand...
He is going by the PLL alignment as written in in the CBTricks stuff. And honestly, Id rather align in the middle of the band too.

I wouldn't be too concerned with the 10.695MHz oscillator right now. His problem is before 10.695 gets mixed in, so its best to sort that out before moving on.
 
SuperLid said:
If you followed the PLL alignment procedure via the service manual, you will see that you perform the AM BFO step on channel *1*, looking for 16.2700 +/- 20 Hz. Your findings in your post do not follow the procedure.

Try again and post the results from every step.

Have you looked at the BFO/carrier oscillator crystals with a sniffer that won't load them down? Do you see 10.695 at TP5 in TX? Is the REF OSC 10.240 MHz?

These are things I would be asking myself, if I were working on this.
Click to expand...
I’m following the alignment procedures on cbtricks (ch 20).

*PLL Alignment
Tp2 2.8v good
Pin 8 IC3 10.2400 good
TP3 adjust L15 for max on scope. Done
TP3 USB 16.5125 good
TP3 LSB 16.5075 good
Tap3 AM 16.5100 fail. Actual 16.51240 ish (L20 adjust only about 30Hz or so).

*TX alignment:
TP3 LSB 16.5075 good however, L7 will NOT adjust (Note: No open clarifier mod done. Checked D68, D38, R113, D50, D51, D52)

TP6 USB 10.5925 good
TP6 LSB 10.6975 good
TP5 AM Fail. Cannot get good reading

At this point, I feel proceeding with alignment is futile as I won’t be able to perform tasks. If you suggest otherwise, let me know.

Symptom recap:
*Sideband performs flawlessly
*AM not on frequency by 1.6-1.8khz
*Clarifier works only on SSB. No change on AM
*AM no TX power
*V7 does not change frequency at TP3
*L20 does not change frequency at TP3

Replaced x3 w/ known working crystal. Is this the one you’re referring to?

Does this answer your questions?
 

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You say that both Side Bands work - yes.
Problem is on "AM":
* No "AM" TX.
* No adjustment to L20, or L23 possible (both used for "AM" settings).

Since your problem is only with "AM" I would blame the (LSB, USB, AM) MODE switch circuit while in "AM" mode or related parts in that circuit.
* There should be "approximately 8V" (8V) constant (always) to the MODE switch, then to the "AM" terminal, then to "D85", and ends at "D95" feeding L20 and L23 adjustments.
* In Receive .... With the MODE switch on "AM" check for the 8V at both sides of diode "D95" and "D85". (NOTE that the "AM" 8v also goes to "Q24" transistor before going to "D85" and "D95".)
* If there is no voltage on one side of "D95"..... "D95" is bad or a short to board ground on that circuit side (going towards L20 or L23) . (Check for solder blobs causing shorts on Trace side of board.)
* If there is no voltage either side of "D95" ...... check both sides of diode "D85" for 8V.
* If "D85" shows no voltage on both sides then check for 8v at the "AM" terminal of the "MODE" switch while still in the AM" setting.
** If there is no 8V at the MODE switch terminal of the "AM" side then the MODE switch is bad.
**If there is 8V at the MODE switch terminal of the "AM" side then check for cut trace or wiring problem going to "D85" and "Q24".
* If, at one time, the MODE switch was set to "AM", and having 8V at that terminal (that also goes to "D85" and "Q24"), was ever shorted to ground it could have burned out that contact tips (inside the MODE switch) for the "AM" side.
* If the MODE switch is bad (no 8V for "AM") you may be able to use another set of contacts on the same "MODE" switch assembly, just make sure you connect to the right contact tips.

At this point I should stop here, but the following is important too:

You have turned VR7 and made changes to the radio adjustments.
(VR7 is for the LOCKED TX only adjustment .... The Clarifier is for the Receive only adjustment (if you turn the clarifier for any reason, you're still off the TX frequency).
* VR7's adjustment is set once during the alignment process .... Transmit (TX) only (not Receive).
* Once set VR7 is locked to that setting, VR7's adjustment must be exact and is the only adjustment for being on frequency during TX on SSB, other wise you would sound like Donald Duck during TX to the rest of the world.
*** This is the reason why the clarifier should be UNLOCKED letting the "Clarifier" control both Transmit and Receive at the same time (at all times) with VR7 no longer used and out of the circuit. (All previous adjustments need to be redone once the Clarifier is UNLOCKED to make sure that the Clarifier knob is centered at the 12o'clock position.)

You say that SSB works fine so this means that the "VR7" circuit should also be fine since it's common to all modes .... in case you want to check the circuit ........
If the clarifier is stock, VR7 should work to change TX MODE frequency only:
* While in TX (Mic keyed):
* Check for 8V at one side of VR7.
* If there, adjust to make sure that the TX frequency changes.
* If there and no change in frequency .... Check for bad VR7 or shorts at wiper wire back to the board connection. (But you don't have this problem if SSB is working.)

For accurate checks and adjustments make sure that you do not short any connections (especially making any voltage checks), which may cause more problems.

73
 
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Dr. Frankenstein said:
You say that both Side Bands work - yes.
Problem is on "AM":
* No "AM" TX.
* No adjustment to L20, or L23 possible (both used for "AM" settings).

Since your problem is only with "AM" I would blame the (LSB, USB, AM) MODE switch circuit while in "AM" mode or related parts in that circuit.
* There should be "approximately 8V" (8V) constant (always) to the MODE switch, then to the "AM" terminal, then to "D85", and ends at "D95" feeding L20 and L23 adjustments.
* In Receive .... With the MODE switch on "AM" check for the 8V at both sides of diode "D95" and "D85". (NOTE that the "AM" 8v also goes to "Q24" transistor before going to "D85" and "D95".)
* If there is no voltage on one side of "D95"..... "D95" is bad or a short to board ground on that circuit side (going towards L20 or L23) . (Check for solder blobs causing shorts on Trace side of board.)
* If there is no voltage either side of "D95" ...... check both sides of diode "D85" for 8V.
* If "D85" shows no voltage on both sides then check for 8v at the "AM" terminal of the "MODE" switch while still in the AM" setting.
** If there is no 8V at the MODE switch terminal of the "AM" side then the MODE switch is bad.
**If there is 8V at the MODE switch terminal of the "AM" side then check for cut trace or wiring problem going to "D85" and "Q24".
* If, at one time, the MODE switch was set to "AM", and having 8V at that terminal (that also goes to "D85" and "Q24"), was ever shorted to ground it could have burned out that contact tips (inside the MODE switch) for the "AM" side.
* If the MODE switch is bad (no 8V for "AM") you may be able to use another set of contacts on the same "MODE" switch assembly, just make sure you connect to the right contact tips.

At this point I should stop here, but the following is important too:

You have turned VR7 and made changes to the radio adjustments.
(VR7 is for the LOCKED TX only adjustment .... The Clarifier is for the Receive only adjustment (if you turn the clarifier for any reason, you're still off the TX frequency).
* VR7's adjustment is set once during the alignment process .... Transmit (TX) only (not Receive).
* Once set VR7 is locked to that setting, VR7's adjustment must be exact and is the only adjustment for being on frequency during TX on SSB, other wise you would sound like Donald Duck during TX to the rest of the world.
*** This is the reason why the clarifier should be UNLOCKED letting the "Clarifier" control both Transmit and Receive at the same time (at all times) with VR7 no longer used and out of the circuit. (All previous adjustments need to be redone once the Clarifier is UNLOCKED to make sure that the Clarifier knob is centered at the 12o'clock position.)

You say that SSB works fine so this means that the "VR7" circuit should also be fine since it's common to all modes .... in case you want to check the circuit ........
If the clarifier is stock, VR7 should work to change TX MODE frequency only:
* While in TX (Mic keyed):
* Check for 8V at one side of VR7.
* If there, adjust to make sure that the TX frequency changes.
* If there and no change in frequency .... Check for bad VR7 or shorts at wiper wire back to the board connection. (But you don't have this problem if SSB is working.)

For accurate checks and adjustments make sure that you do not short any connections (especially making any voltage checks), which may cause more problems.

73
Click to expand...
Copy that, Doc. Makes perfect sense. I’ll go through it.m hopefully tomorrow. With regard to VR7, I’ll be opening the clarifier anyway. Step one is just to resolve this issue in stock condition.

Thanks.
 
Dr. Frankenstein said:
You say that both Side Bands work - yes.
Problem is on "AM":
* No "AM" TX.
* No adjustment to L20, or L23 possible (both used for "AM" settings).
Click to expand...
Dr. Frankenstein said:
Since your problem is only with "AM" I would blame the (LSB, USB, AM) MODE switch circuit while in "AM" mode or related parts in that circuit.
* There should be "approximately 8V" (8V) constant (always) to the MODE switch, then to the "AM" terminal, then to "D85", and ends at "D95" feeding L20 and L23 adjustments.
* In Receive .... With the MODE switch on "AM" check for the 8V at both sides of diode "D95" and "D85". (NOTE that the "AM" 8v also goes to "Q24" transistor before going to "D85" and "D95".)
* If there is no voltage on one side of "D95"..... "D95" is bad or a short to board ground on that circuit side (going towards L20 or L23) . (Check for solder blobs causing shorts on Trace side of board.)
* If there is no voltage either side of "D95" ...... check both sides of diode "D85" for 8V.
* If "D85" shows no voltage on both sides then check for 8v at the "AM" terminal of the "MODE" switch while still in the AM" setting.
** If there is no 8V at the MODE switch terminal of the "AM" side then the MODE switch is bad.
**If there is 8V at the MODE switch terminal of the "AM" side then check for cut trace or wiring problem going to "D85" and "Q24".
* If, at one time, the MODE switch was set to "AM", and having 8V at that terminal (that also goes to "D85" and "Q24"), was ever shorted to ground it could have burned out that contact tips (inside the MODE switch) for the "AM" side.
* If the MODE switch is bad (no 8V for "AM") you may be able to use another set of contacts on the same "MODE" switch assembly, just make sure you connect to the right contact tips.
Click to expand...
8v wire at Mode Switch was torn at plug. Looks like it was holding on by a strand or two and finally broke loose. New radio smh.

*Once 8v was restored at mode switch, AM now has RF power out.
[edit] *L23 does adjust TX @TP5 on TX
[edit] *L20 does NOT adjust frequency @TP3.

*8v to d85, d95, r164
*D53 = 5.4v at anode
*D53 = 4.7v at cathole

X4?
Cannot get a reading on x4 using BK Precision 1856d frequency counter.
Just FYI: Checking x3 I get a reading of 15.370Mhz (15.360Mhz crystal).

I do have parts radios :)
 
Last edited:
Either you have a misprint, or you did the "L23" adjustment wrong....

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

"L20" (in RX mode) is adjusted using test point TP3.

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