I am sorry to read of your troubles.? Here are some thoughts interspersed in our post:
Evan?
? So I have had everything functional for a few days. I managed to get the bias set, spent a good deal of time calibrating the output, which I also have a question about that I will mention further down. No sooner than I was about to put it together and in service, I blew a final.
What were you doing when the final blew?
I replaced the 510, and as I was considering what caused the last 510 to die, all went dark.
As there is variability between batches and manufacturers, it is best always to replace the IRF510s as a pair from the same order.
Sitting in steady state receive, I managed to get a short to ground.
Do you have any idea where the short may have occurred?? What were you doing when this happened?
I have pulled and checked Q9, Q101, and both IRF510s. All checked out, even though one of the 510s began to smoke.
If one of the IRF510s smoked, I would replace both after figuring out the reason for the overload.? Maybe the bias is set too high.
With these still removed, I have checked Q22 and Q29, both drains show continuity to ground as well as Q22 having continuity to source. I've been checking paths for shorts/opens, etc.?
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It would be difficult to measure the resistance of Q22 and Q29 in the circuit as D32 and D33 are across the Q22 source to drain.? To verify, you can take out the diodes or remove the MOSFETs for testing.
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You can verify that the resistance across the MOSFET source to drain is very high with no power.
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?I found that checking the pads for the 510s source, that there is brief continuity to ground, milliseconds, before opening. Is this possibly the string of caps , C104,106,107,110 between the T7 primary and the +12v supply?
Do you mean the drains of the IRF510?? The source is connected to ground.
?Next question, this last attempt to set the bias resulted in no change when adjusting the pot. Current is ~.9A in receive and bounces around 1-1.3A ptt engaged, no drive, 40m, usb. Removed pot, checked okay.
Did you start with the PABIAS1 Pot fully counterclockwise, note the current, and then SLOWLY adjust the pot until the current starts to increase?? A .3A current variation seems high.? Without audio in USB mode, the current should not vary more than .1A.
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Now, the calibration question. This supposed to be a scale adjustment as I understand, but relative to what? Which signal is being adjusted? Going from the default values, direction and amount of adjustment is very erratic from band to band. Some have had to be be adjusted by a factor of 10.
The scale value is used to set the gain of the signal inside the software.? The higher the value, the more audio IF is sent to the modulator.? This is the AUDIO-MOD signal.
So I am going to clean the board up the best I can and look at it again?tomorrow. Since I have quite a few of the components removed, I will leave them until I hear back from you, in case I need to pull anymore.?
?Don't feel to pressed to think about this right away, I know it's mouthful! I'm definitely learning a good deal with this project though, as frustrating as it may be. Thanks again.?
What software are you running?? The 64-bit upgrade from JJ (W9JES) has a toolbox app that helps adjust the scaling factor.? It is still a tedious task.? I start from the default settings in the hw_settings_v3.ini file and adjust by no more than 10% each time.? The power will not increase at some point, and going higher can decrease the output.??Note that the higher frequency bands cannot get to 25 watts.? The output starts to drop at 20 meters for some of my rigs.
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Others in the group may have suggestions as well.
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I hope the above helps.
73
Evan
AC9TU
