Been using my Megawatt 30 amp PSU now for over a year with the fine adjust pot, when mxwanderer suggested a 500 ohm 2 watt 10 screw potientiometer to replace the rather touchy one screw micro pot.
Not having the means to solder the new 500ohm 10 screw $6 Bourne pot in place With micromeasure counter on top, I sought the services of a ham radio guru, who also happens to build antenna's for digital TV stations, for a living. Namely SCVJeff, as we've met and camped together at Quartzsite, and in general, the guy plays with electronic stuff that would make my head spin, so a solder job for him was child's play.
Since he was curious, we measured the micro pot on the unit as a 900 ohm resistance unit. Replacement was a 500 ohm unit.
This is the voltage range now with the 500 ohm unit.
Circuit board from a Megawatt S-350-12
Top side.
Finished, haven't decided how I will attach yet the new 10 screw pot, but numerical locking dial settings will make voltage output repeatable.
Another view.
Note the zip ties, extensive use of heat shrink wrap and professional grade quality of all the connections. The heat transfer paste from the factory was, at best, marginal. Jeff made sure to use the good stuff, and in generous quantity, to get the heat out of the electronics, and transferred to the external aluminum case.
BTW, it took 4 pair of hands to remove the circuit board out of the chassis, it is a tight fit.
I'd like to express a deep level of gratitude and thanks to SCVJeff for helping this old hack carpenter that's only ever worked pretty much with 120V and 240V with some minute, clean circuit board soldering repair and replace, since I don't own the tools or knowledge to do work at this level. Special thanks is also due to mexicowanderer, who first found this PSU, saw the fit to dry campers or off the grid campers needs, and used my money and me as the successful guinea pig to even attempt this Rogue venture. I find it some of the best money spent by me for doing exactly what I need in a bulk charging timed battery charger. It will be effortless for me to dial in the exact 13.50 + -.02V I need now for my exotic Telecom 158 AH AGM battery, and it's exotic voltage needs for properly recharging.
If you are in the same boat as me, there is probably none better that an old hand Ham Radio operator or pro to touch soldering on your circuit boards without botching the job. BTW, the Bourne pot terminals needed some serious scraping and cleaning up to get the solder to adhere to them. When it comes to electronics and circuit boards, it's not worth it to cut corners, do it right, the first time. His attention to detail, and having all the tools there to measure, a variac, Fluke DMM, copper weave for wicking solder off the old pot and off the circuit board, cleaning up terminals before resoldering, tie wraps, heat shrink, etc, etc is what is the sign of a person that takes pride in their craftsmenship.
I hope this helps some of you that are on the fence about building your own 14.8V MANUAL timed bulk charger for your dry camping applications off the grid.
Not having the means to solder the new 500ohm 10 screw $6 Bourne pot in place With micromeasure counter on top, I sought the services of a ham radio guru, who also happens to build antenna's for digital TV stations, for a living. Namely SCVJeff, as we've met and camped together at Quartzsite, and in general, the guy plays with electronic stuff that would make my head spin, so a solder job for him was child's play.
Since he was curious, we measured the micro pot on the unit as a 900 ohm resistance unit. Replacement was a 500 ohm unit.
This is the voltage range now with the 500 ohm unit.
Circuit board from a Megawatt S-350-12
Top side.
Finished, haven't decided how I will attach yet the new 10 screw pot, but numerical locking dial settings will make voltage output repeatable.
Another view.
Note the zip ties, extensive use of heat shrink wrap and professional grade quality of all the connections. The heat transfer paste from the factory was, at best, marginal. Jeff made sure to use the good stuff, and in generous quantity, to get the heat out of the electronics, and transferred to the external aluminum case.
BTW, it took 4 pair of hands to remove the circuit board out of the chassis, it is a tight fit.
I'd like to express a deep level of gratitude and thanks to SCVJeff for helping this old hack carpenter that's only ever worked pretty much with 120V and 240V with some minute, clean circuit board soldering repair and replace, since I don't own the tools or knowledge to do work at this level. Special thanks is also due to mexicowanderer, who first found this PSU, saw the fit to dry campers or off the grid campers needs, and used my money and me as the successful guinea pig to even attempt this Rogue venture. I find it some of the best money spent by me for doing exactly what I need in a bulk charging timed battery charger. It will be effortless for me to dial in the exact 13.50 + -.02V I need now for my exotic Telecom 158 AH AGM battery, and it's exotic voltage needs for properly recharging.
If you are in the same boat as me, there is probably none better that an old hand Ham Radio operator or pro to touch soldering on your circuit boards without botching the job. BTW, the Bourne pot terminals needed some serious scraping and cleaning up to get the solder to adhere to them. When it comes to electronics and circuit boards, it's not worth it to cut corners, do it right, the first time. His attention to detail, and having all the tools there to measure, a variac, Fluke DMM, copper weave for wicking solder off the old pot and off the circuit board, cleaning up terminals before resoldering, tie wraps, heat shrink, etc, etc is what is the sign of a person that takes pride in their craftsmenship.
I hope this helps some of you that are on the fence about building your own 14.8V MANUAL timed bulk charger for your dry camping applications off the grid.
