Galaxy saturn ept360014b vr16 low power will not adjust

[Hawkeye351]

So it's normal for that transistor to get hot in SSB mode on these galaxy style radios?

If so, then all I need to focus on now is the low sideband output, lights dimming and frequency counter going haywire when modulating in SSB mode.

Do you recommend upgrading any of the capacitors I listed above (or any other caps) from their factory values for better performance or cleaner signal?

Thank you nomad for the info on that trans issue. That's one issue I can stop worrying about.

 

[lulu]

bjr moi jai aussi une galaxy saturne jai tout changer elle reste 2w am et fm et 4 w blu jai suivi vos conseil mes rien a faire merci

 

[Cable Guy]

Benvenuto nel forum. Se puoi, traduci la tua richiesta in inglese.

 

[Xracerx13]

Benvenuto nel forum. Se puoi, traduci la tua richiesta in inglese.

That's Italian. He posted in French.

LuLu said: I change everything it stays 2W AM and FM and 4 W blu I followed your advice my nothing to do thank you

 

[Cable Guy]

So sorry

 

[Xracerx13]

So sorry

No need to be sorry. I'm Italian. It was nice to see some Italian on here.

 

[Cable Guy]

I'm trying out the Google translate as I only speak English and broken spanglish. See if you can get more information like what was changed and any original issues, etc.., you know...

 

[Hawkeye351]

Forgot to post the remedy for this issue:
It was the voltage regulator transistor mounted on the back left corner (behind power supply) of the radio.

Replaced that transistor with one from a spare Saturn and all issues were solved.

 

[nomadradio]

Rock on! Glad you found it.

Sometimes it really is just a simple failure.

73

 

[vswr]

Take out the 1n4148 and put the resistor end back in the hole and solder.
Check to see if TR32 had been removed (probably); replace with a 2sc945.
That should straighten out modulation issues.

You might start by checking the 50mA for the driver trans, then the final trans should be 50mA each for a total of 100mA.
For details, see:
http://www.cbtricks.com/radios/galaxy/dx99v/dx99v_trans_adj.htm

There is interaction between the low power VR and the high power VR; might check there first, since someone might have monkeyed with them.

In addition, the transmitter tuning coil chain (L43, L44, L42, and L40) may also need re-alignment.

One of the finals bias VRs may have been turned down.

Anyway, that should give you something to start looking at.

My VR 20 wont get me any current. Transistor is real and its good. Very strange. The transistor associated with vr 10 I can get way more idle current out of it. When adjusting the pot for 50ma, its very touchy. Hair rigger. Very jumpy. It easily can go way past the 50 from the looks if where 50 is on the trim pot. The other one does nothing. Swap both 2312 left to right and same deal. Not sure if its those 2 odd looking silver oxide brownish caps or a resistor. Looking at the schematic. Seems pretty straight forward. RF is magical. I can get over 10 watts on AM. Im driving a low watt input linear with it so its set for 2 watts with a swing to 5. Anyhow, the other issue is the rf power knob on the front. It does absolutely nothing. Its still connected. Any help would be appreciated.

 

[vswr]

There is your problem!
Gonna have to thrash thru the parts in the VR circuit to find the problem.
Might be a bad solder joint, VR10, or the MV1Y diode; be my first guesses.

View attachment 36607

For me its the opposite. Vr 20 does nothing. Transistor swap left to right still the same. Ugh.

 

[brandon7861]

If one has current and the other does not, that rules out the regulator as they are both using the same bias voltage source. Since the transistor has also been ruled out by swapping them, it must be in the bias circuit. With the pot being in parallel with another resistor, even if the pot went open, there would still be current flowing in that transistors collector (too much since the voltage at the base would go up). So with no current flowing, I would also rule out VR20.

If there is voltage to one side of R272 and not the other, either the diode D112 or capacitor C210 is shorted to ground. Lift one leg of each and test them. There is a chance that R272 is also bad because a short after it puts 8v directly across it. 8v^2/150Ω=430mW. That would be almost exactly the rated power of that bias resistor making it the next weakest link.

 

[brandon7861]

I am also concerned with the sensitivity of adjustment VR10. It shouldn't be that touchy, and the fact it is suggests that diode is either open or had been swapped out with one having a slightly higher turn on voltage compared to the transistor Vbe junction.

That diode does two things (when bolted to the heat sync). It starts turning on slightly before the transistor junction does. In this way, VR20 is controlling the current through the diode rather than the voltage of the transistor base. This allows the pot to have a much more controlled voltage level as the turn-on curve of the diode is traversed. The diode is also chosen to have the same Vforward change with temperature as the transistor, so when the transistor heats them both up, the diode Vf drops and lowers the bias point. These reasons combined are why you should not just toss in any random diode. You end up with touchy adjustments and thermally unstable bias points.

 

[nomadradio]

When one final shows bias current and the other one does not, next step is a coin toss. Either probe the base terminal of the one with the zero reading, or take the base and collector leads loose to connect a transistor tester.

If there is zero base voltage, this suggests one likely possibility. This final was previously replaced, but the previous final that failed also clobbered the bias diode and/or trimpot and/or the fixed resistor in the circuit. When a final fails, it will frequently short from collector to base inside the transistor. This will shoot 6 or12 Volts out the base terminal into the bias circuit. Croaks the bias diode, trimpot and a fixed resistor all three in some cases.

Just setting the bias trimpot to middle position, and then probing the transistor base with a volt meter is the easiest first next step. If it shows zero, you have failed parts upstream from there.

73