Galaxy Saturn Turbo power output ???

[Lkaskel]

Hi Gang,
Well the Galaxy Saturn Turbo that I replaced the power supply in and repaired one of the mini coax connections has returned to the bench. The owner used it for a day or so and it was running great. It was driving about 150 watts with good audio. Then......no power out. I have it on the bench and it has very low output power (8 on AM and 10 on SSB with very little modulation. I went over the amp board and it seems like everything is ok so I am wondering if the radio itself is not driving the amp board enough. I bypassed the amp (plugged the mini coax from the main board to the antenna) and I am only getting about 1/2 watt out of it. I cannot find any documentation about what the expected drive wattage should be. My thought is that it would do the normal 4 AM and 12 SSB into the amp board. Does anyone have any thoughts or experience with this unit? Because the original power supply failed and over volted the radio anything could be wrong......

Thanks as always!!!

 

[ExitThirteen]

It's possible that either the final failed or the 2SB754 pass regulator had failed, either one can cause the symptoms you're seeing. To check the pass regulator, turn the radio on and and in AM mode check for voltage to the center leg of the driver and final. The center leg is the collector of the transistor. Should be between 5-6 volts roughly. Switch to SSB mode and check again, should be 12.5-13.8V. If you are not getting these voltages, the regulator has failed, if you ARE getting those voltages, then I'd say the final could be suspect. Let us know how you get on.


~Cheers~

 

[Lkaskel]

It's possible that either the final failed or the 2SB754 pass regulator had failed, either one can cause the symptoms you're seeing. To check the pass regulator, turn the radio on and and in AM mode check for voltage to the center leg of the driver and final. The center leg is the collector of the transistor. Should be between 5-6 volts roughly. Switch to SSB mode and check again, should be 12.5-13.8V. If you are not getting these voltages, the regulator has failed, if you ARE getting those voltages, then I'd say the final could be suspect. Let us know how you get on.


~Cheers~

I was unsure if you meant t o take those readings in XMT or RX. Both the driver and final appear to be 7808A'a. Either way they both have readings in the 1.4 mv range on XMT and RX. Is that the regulator? One pin of the regulator has 13.8 and the othe 2 have 13.2 in RX. Thanks as always!!!

 

[ExitThirteen]

The driver/final in that radio are C2166 and C1969, they are located to the back left corner of the main PCB. The 7808's that you mentioned are the 8 volt regulators used elsewhere in the radio. The pass regulator I'm referring to is the big transistor in the back right corner of the board. It'll be labeled B754 (if it has not been replaced). Check the center legs on the C2166 (driver) and the C1969 (final). Those voltages I mentioned earlier should be present in RX mode. On my RCI 2990 (basically the exact same radio as the Turbo), I get 7.1V in AM mode, and 13.4V in SSB mode.


~Cheers~

 

[Lkaskel]

The driver/final in that radio are C2166 and C1969, they are located to the back left corner of the main PCB. The 7808's that you mentioned are the 8 volt regulators used elsewhere in the radio. The pass regulator I'm referring to is the big transistor in the back right corner of the board. It'll be labeled B754 (if it has not been replaced). Check the center legs on the C2166 (driver) and the C1969 (final). Those voltages I mentioned earlier should be present in RX mode. On my RCI 2990 (basically the exact same radio as the Turbo), I get 7.1V in AM mode, and 13.4V in SSB mode.


~Cheers~

Wow!!! Did I ever miss that one.... 6.12 on AM and 13.5 on SSB. Do you agree that I should be getting a higher output off of the main board? Something like 4 am and 12 SSB? I did have the regulator and the voltages right. Any other thoughts? Thanks for your patience!!!

 

[ExitThirteen]

Absolutely. You should be getting 4W AM, 12W SSB or better off the main PCB. The voltages look good, so the pass regulator is good. I would suspect a bad C1969 final.


~Cheers~

 

[Lkaskel]

Absolutely. You should be getting 4W AM, 12W SSB or better off the main PCB. The voltages look good, so the pass regulator is good. I would suspect a bad C1969 final.


~Cheers~

I will order new drivers and finals tomorrow and go from there. I really want to re-cap this radio but the owner cannot afford that right now. I am wondering if a cap is shorted as well.
Thanks so much for your council thus far ExitThirteen!!!!!

 

[ExitThirteen]

It's possible that you may have a cap shorted, if the radio got "volted" when the power supply failed, the first caps to go are the 10V or 16V ones... If there are any 10V or 16V caps, you should replace those first for sure. Let us know how you get on.


~Cheers~

 

[Lkaskel]

It's possible that you may have a cap shorted, if the radio got "volted" when the power supply failed, the first caps to go are the 10V or 16V ones... If there are any 10V or 16V caps, you should replace those first for sure. Let us know how you get on.


~Cheers~

Well, here is the update. I received new drivers and finals. I did test the transistors before I installed any of them. The driver was open and the final tested fine. I replaced the driver and....nothing. I went back to the beginning and checked for voltage at the center pin of both. On AM I have 4.77vdc and the same on SSB. I did check for voltage at the 3 pins of the regulator and I had 13.5 on 2 and 14.11 (power supply voltage) on one. Man this stuff is hard!!!!! I need to ask a question about a GE mobile but I'll start a new thread for that. Thanks as always!!!!

 

[Lkaskel]

It's possible that you may have a cap shorted, if the radio got "volted" when the power supply failed, the first caps to go are the 10V or 16V ones... If there are any 10V or 16V caps, you should replace those first for sure. Let us know how you get on.


~Cheers~

Hi Everyone,
Here is an update with some questions. The owner of this radio asked if he could purchase the capacitor kit on his own. He recently dropped off the kit and I have put the radio back on the bench. The capacitor kit is not great as most of the caps in it are 3 times the size of the caps on the board and will not fit into the area needed. My caps (Nichicon) have the same issue as all of mine are 50 volt. I am going to order exact voltage replacements so I will have what is needed.

Now to the question, as a troubleshooting method I removed the driver and final and tested the voltages at the center pins without them in place. I am still getting ~4.7VDC on the center pins on both AM and SSB. I also checked the regulator as explained above and the voltages are 13.5V the rear pin, 6.1V(AM) and 13.5V(SSB) on the center pin, and 14.1V on the front pin. It sounds like the regulator is working correctly as it is switching on AM and SSB. Because I receive 4.7 on the center pins of the driver and final on both AM and SSB my guess id something is shorted like a cap. Do you agree or would I look for something else?

All the best!!!

 

[Lkaskel]

It's possible that you may have a cap shorted, if the radio got "volted" when the power supply failed, the first caps to go are the 10V or 16V ones... If there are any 10V or 16V caps, you should replace those first for sure. Let us know how you get on.


~Cheers~

Hey my friend,
You may have read this on another post of mine but this radio is now fixed. In the end, I had purchased a number of fake drivers and finals off of E-Bay. Last weekend I bought some from RF Parts and the radio transmitted on the 1st try. Lesson learned. Thanks for your help in diagnosing this!!! The radio is now re-capped, replacement power supply new driver and final and an alignment. The owner should have a nice radio for years to come!!!

Thanks again!!!

 

[OldTech03]

Hey my friend,
You may have read this on another post of mine but this radio is now fixed. In the end, I had purchased a number of fake drivers and finals off of E-Bay. Last weekend I bought some from RF Parts and the radio transmitted on the 1st try. Lesson learned. Thanks for your help in diagnosing this!!! The radio is now re-capped, replacement power supply new driver and final and an alignment. The owner should have a nice radio for years to come!!!

Thanks again!!!

Good deal.

 

[nomadradio]

Rock on!

Always good to hear a success story. Congratulations for sticking with it.

73