Galaxy 959 no Tx

[griz]

Hello need some help i have a Galaxy dx959 that has no output on AM and SSB i have changed Q54,55 ,37 , The radio has good RX and when you key the mic the TX light lights up and the talkback works , the pa works anybody have any ideas what to check , I even checked with another radio can not hear anything on the other radio, And i forgot to say i was doing a alignment and was trying to set the bias on vr12 and no current on vr12 the other one i can set

 

[Handy Andy]

See if you still have power going to the Transmit strip.​

 

[griz]

View attachment 41491

See if you still have power going to the Transmit strip.​

Checked L39 and L41 both have 8.9 volt both sides and continuity

 

[Handy Andy]

Good, that means the strip is functioning...

​

You located L41 - locate the line that traces down to the 150 ohms resistor (a buffer) R245 and R244 - see if they still pass voltage - if one side is dead, lift that leg of the resistor and measure leg again - make sure the Resistor didn't burn up.

If you get NO voltage on the side of the resistor - yet it has voltage on the leg when lifted - either going to the DRIVER and/or FINAL - then the section at the bias for that section - has a short - it's killing your bias...

 

[griz]

Good, that means the strip is functioning...

View attachment 41500​

You located L41 - locate the line that traces down to the 150 ohms resistor (a buffer) R245 and R244 - see if they still pass voltage - if one side is dead, lift that leg of the resistor and measure leg again - make sure the Resistor didn't burn up.

If you get NO voltage on the side of the resistor - yet it has voltage on the leg when lifted - either going to the DRIVER and/or FINAL - then the section at the bias for that section - has a short - it's killing your bias...

I checked the voltage on R245 and it was 8.90v on one side and 5.24v on the other side and checked R244 and it was 8.90v the other side was .739 so i lifted that side and retested voltage and it was 8.90v

 

[Handy Andy]

I checked the voltage on R245 and it was 8.90v on one side and 5.24v on the other side and checked R244 and it was 8.90v the other side was .739 so i lifted that side and retested voltage and it was 8.90v

Your section - using R244 Is correct for BIPOLAR.

Now let's stop here...and ask, are you using MOSFET or Bipolar? for Driver and or Final?

Why do you get 5.24 volts on the Driver? VR12 won't adjust - is it the short? But R245 is BEFORE (in power feeding) VR12 - so review the work in that area...PAST R245 into the section If you use MOSFET - D93 and associated parts highlited above as Asymmetry Mod need to go, remove - if you use MOSFET

 

[griz]

Your section - using R244 Is correct for BIPOLAR.

Now let's stop here...and ask, are you using MOSFET or Bipolar? for Driver and or Final?

Why do you get 5.24 volts on the Driver? VR12 won't adjust - is it the short? But R245 is BEFORE (in power feeding) VR12 - so review the work in that area...PAST R245 into the section If you use MOSFET - D93 and associated parts highlited above as Asymmetry Mod need to go, remove - if you use MOSFET

The radio has 2166 and 1969 in it

 

[Handy Andy]

Ok, Bipolar, more than likely the Driver is blown - the Bias diode is also gone - blown the 2166 open too

 

[griz]

Ok, Bipolar, more than likely the Driver is blown - the Bias diode is also gone - blown the 2166 open too

Ok i will check it later will let you know

 

[griz]

Ok i will check it later will let you know

Ok i replaced D93 ,D92 , C214, R244 ,and Q49 ,Q51 now i can set the the bias on tp 7,8,9 but no tx output

 

[nomadradio]

Ah, do you have another radio you can tune in the channel the 959 is on when it's keyed?

Would be good to know if a weak signal is leaking out of it. A coax jumper on the receiver will get you a half-inch long "sniffing" antenna at the other end with the sleeve backed off the plug.

If you can't get any signal on the monitor radio, this means your on-channel signal isn't being generated at all when the 959 is keyed. No point troubleshooting the power sections if no drive is feeding into them.

And if you can hear only a weak signal this tells us the transmit-mixer chip is working, and the tracks are blocked downstream from it.

73

 

[griz]

Ah, do you have another radio you can tune in the channel the 959 is on when it's keyed?

Would be good to know if a weak signal is leaking out of it. A coax jumper on the receiver will get you a half-inch long "sniffing" antenna at the other end with the sleeve backed off the plug.

If you can't get any signal on the monitor radio, this means your on-channel signal isn't being generated at all when the 959 is keyed. No point troubleshooting the power sections if no drive is feeding into them.

And if you can hear only a weak signal this tells us the transmit-mixer chip is working, and the tracks are blocked downstream from it.

73

Nomadradio i did check that right a way and i have no sound at all in the other radio

 

[Handy Andy]

(...Sorry this post never got "posted" yesterday due to SOE declarations - had to help Wife with stuff...)

You have a scope?

Will need to see if you have output from Driver now, going into Final - if Driver is ok, but no power out - check Final.

You will need to look for output from the Predrivers into the Driver section.

Continuity checks thru the coils into the stages.

Caps? Not much unless you can pull them and verify their values...but then too - if your radio has blown final and driver - you'll need to look downstream, further thru the output network to the antenna connector - continuity checks here too as possible. - You DO NOT want to recreate what made the Radio fail the first time - from happening again.

ADDENDUM - Follow @nomadradio with the "sniffer" even an old AM only radio and a dummy load on it's antenna jack can help provide signal both from that radio and to that radio from it to help you find the "break"

Best advce is to use; or make/create a 50 ohm dummy load for BOTH radios and keep it in place (installed on the antenna jack) while you use it to fix and test - your equipment .

 

[Crossbow]

Would have been nice to see the outcome of this as I have a 959 with the same problem. Both driver and final was blown. Installed new ones but still no TX power out.

 

[griz]

Would have been nice to see the outcome of this as I have a 959 with the same problem. Both driver and final was blown. Installed new ones but still no TX power out.[/QUOTE I am not done with it have not had time was hoping some would give me more ideas i am sure i am not getting any signal from transmit mixer