I doubt the 8 volt reg is bad, but I cant say the same for the PA devices. I don;t recall if you did, but have you checked the gate voltages on the IRF520's? Oh, and don't use 13N10's
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Anytone at-5555n II (version 2)
- Thread starter Eldorado828
- Start date
Sorry but time for another dumb question... Can the IRF520 gate voltage be tested with them still soldered in place or do they have to be removed to do this?
Yes, in place while transmitting on SSB, no modulation.
I am looking at the IRF520 in Q104 as an example of measuring the gate voltage with the mosfet still soldered in place.
I switched the multimeter to diode mode.
With the radio off, I connected the red lead to Source leg and black to Drain. Then I turned the radio on, keyed the mic on SSB, no modulation. Voltage dropped from .5201 to 0. Similar initial values and drop to 0 were observed on the other three IRF520s as well
Is this close to being the correct way to do it? No smoke or dimming of house lighting was observed, which in win by itself.
I did subsequently replace the voltage regulator L7808CV with a new one but as you expected, it made no difference.
It's looking more and more like this is headed to eBay under the Repairable Radio group. Darn I was hoping I could get this sorted out. If this was a mechanical device, it would already be blown apart to its component parts on the workbench. Except if it was an automatic transmission. The valve bodies in them are voodoo / black magic.
I switched the multimeter to diode mode.
With the radio off, I connected the red lead to Source leg and black to Drain. Then I turned the radio on, keyed the mic on SSB, no modulation. Voltage dropped from .5201 to 0. Similar initial values and drop to 0 were observed on the other three IRF520s as well
Is this close to being the correct way to do it? No smoke or dimming of house lighting was observed, which in win by itself.
I did subsequently replace the voltage regulator L7808CV with a new one but as you expected, it made no difference.
It's looking more and more like this is headed to eBay under the Repairable Radio group. Darn I was hoping I could get this sorted out. If this was a mechanical device, it would already be blown apart to its component parts on the workbench. Except if it was an automatic transmission. The valve bodies in them are voodoo / black magic.
Red to gate, black to source or a ground point. In SSB TX, you should be seeing around 4V give or take a few tenths of a volt.
I have several calibers of "tools" available to me here but none from the shotgun family. But I have thought about introducing this radio to one of my little friends.
However, I have a feeling that shotgunning the FETs might mean something else to electronics tech/experts. I will say that the original MOSFETS are still in place and have not been removed/replaced by me.
Shotgunning = replace everything and hope for the best.
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Here are the readings. I tested both with black to source and again black to ground. Same results.
Q101 3.595 volts
Q102 3.595 volts
Q103 4.058 volts
Q104 3.854 volts
Q109 1.2991 volts
109 is not a FET....but the other gate voltages look somewhat right. Maybe finals are a bit low and driver a bit high and I mean a bit.
That's what we mechanics call igniting the parts cannon.
Hitting the end of the road on my ability to further diagnose the root cause of this radio's SSB modulation quality issue means from here on out I would just be blindly throwing parts at it. No thank you. The soldering iron has been holstered. I'm definitely not one to throw parts at my project cars/motorcycles/snowmobiles/etc. I try to stay within the project plan, budget and timeline, more or less. My current Mustang project has had enough required stuff thrown at/on it, much more than was supposed to be needed. Oh well, at least it's nearly done now.
Maybe someone else would judge this radio's sound to be just fine and I am just too picky. I'm sure I will find a buyer for it on CL or FB Marketplace. And I will be fully disclosing my concerns about how I think it sounds on SSB.
Maybe someone else would judge this radio's sound to be just fine and I am just too picky. I'm sure I will find a buyer for it on CL or FB Marketplace. And I will be fully disclosing my concerns about how I think it sounds on SSB.
Perhaps go through the bias alignment procedure, before you pack it in.
I would love to see this radio repaired, I just read the entire 53 pages of this thread.