Hi, Mr. Solar Guppy! I pulled the jumper off JP3. There was no change in the inverter's operation. It was still in mode "Variable Power Mode Is Enabled". So, I gave the pot a slight turn; the power output increased. Another slight turn, more power. This pot seems to adjust the Pmax as displayed on the LCD. Turned it all the way up to Pmax=1500. Inverter went to about 1200 watts, normal for this time of day. The inverter seems to work fine, so far. Tracks the sun/clouds and recovers. The displayed mppt and Vin are very close almost all the time. Vin is still very close to the DVM reading. I think you fixed it. But is the "Variable Power Mode Enabled" considered a "normal" mode of operation? Is there another jumper? To me, from a board layout standpoint, JP3 looks like it "wants" to be closed, not open. Thanks, Barry, thudman149

Oops! I meant JP4 looks like it wants to be closed, not open. Thanks!

Re-read my last post on what to check. Being in the variable power mode when at it maximum power won't effect generation but the screens are different. The PIC chip is seeing the sense for the special mode, so check the voltage. Another thing you might want to do is hook-up fish bowl and see if the reported temperatures, voltage and current are correct. You can connect to an isolated computer ( like a laptop )

Sound like its been this way since it was shipped, without the gnd on the regulator the PIC chip would be regulation thru th e I/O pins, maybe damaging the mux that the ADC reads some things thru.

So check the voltages as I describe the the last post, hook up Fishbowl to see if other reading are off or just use as is ... it will harvest the power even though is not in the correct mode

on JP3 check all the pins

2 pins should be ground ( #1 & #3 ) , one about 2.5V ( #4 ) another ( #3 ) ~4v. the ~4V one when grounded by the jumper selects variable power mode

Also the fact the POT works means U6 is working ( the 8 to 1 mux ) , pin #5 of U6 is the sense for variable power mode and should be ~4v. R42 should be a 357k, R30 a 100k which divide down a 12V source for the ~4v signal. When jumper on JP3 is installed between pins 1 & 2, it shorts to gorund and enables the mode

Hi, Mr. Solar Guppy!
Ok, I will check those voltages next week. I want to watch it over the weekend and see if it goes up to max power when it should and to make sure it doesn't stop harvesting. But I think the "stop harvesting" effect was, as you said, due to the incorrect voltages as displayed on the LCD. When you told me that the CPU used this same number and that if it was incorrect the operation would be affected, then I knew we were onto something. Finding the missing ground was simply good bench-tech work on my part. I will hook-up fish bowl when I can find a cheap isocoupler. I am looking. I DO have a laptop, but I am afraid to try it without an isocoupler. A few more things. 1) What kind of bench supplies do I need to play with the CPU board on the bench? 2) Will Xantrex sell me a new PIC? 3) What does JP4 do? 4) The previous owner had the same problem; that is why he sold it. It had been back to the factory at least once since the UPG. Have a nice weekend. Thanks, Barry, thudman149

Xantrex won't do anything, its been discontinued since 2003

I would use an ohm meter and check to see if something got botched, check to see if the sense used is shorted to ground, and find out why. I figured it was never right, glad to see you may get some use out of it, but when it dies, you will have no where to get it fixed.

Good work on your part, glad I could help you get it going

Hi, Mr. Guppy!
I will definitely check all of the voltages you recommended checking. I guess I need a 5 volt and a 12 volt bench supply to power the CPU board by itself, right? I have both of those and many more (15, 24, 28, 32, 48, etc). I am a little reluctant to poke around too much, since your last post indicates that the PICs are not available from Xantrex (16C or 16F series?) Would hate to blow up the only one I have. The inverter performed flawlessly all weekend. Nice design, sad that they discontinued it. Guess they went to IGBTs in the GT and XW series? MOSFETS in the SunTie? Maybe I should post on this site for a non-working 2500UPG so I can get the PIC out of it? thanks, Barry, thudman149

None of the Xantrex products use IGBT's everything is mosfets, mosfets have come along way since the Suntie was designed in 1999. the GT series is an excellent gridtie design ... nice also that you can get 5kw in a single unit

If you happy with the performance as is, even though is in manual mode, I'd leave it as is and not risk damaging the unit

Hi, Mr. Solar Guppy!
I think you are right---since no spare parts are available, I better not play with it. It really works fine the way it is. I really, really don't want to blow up the PIC. Other stuff is generic, but the PIC is unique. Think I will post for parts. Many thanks for helping me fix it. Barry, thudman149