Switch feedback and power wiring issues in 9XR-P case mod project
Posted: Mon Aug 24, 2020 5:46 pm
My apologies for the long post. I have had some vexing issues past couple nights on this. I have spent so long staring at this particular issue, I have lost my starting point and confused myself... I HAD this working...
Background: (for those who somehow haven't stumbled across my other posts... LOL!)
I am stuffing a 9XR-Pro into a vintage Futaba FP Gold radio and modernizing it. Why? I got issues...
I am having a switch feedback issue. Swapping the Tunrnigy switch with the Futaba switch was pretty straightforward. Everything worked fine. I did some testing and managed to get the Futaba analog meter sorta working too, off the converted switch. Power up was pegging the meter though. Okay moving along...
Taking a closer look at the first Futaba donor radio mainboard, I noticed a trimmer pot. I needed a mounting board anyways, so I spent a few hours un-populating it, of course leaving that trimmer in place. I then flipped the input protection fuse over to the other side of the board (sticks up a LOT) so I could have double protection and hopefully safely slow charge the Futaba nicad pack maybe without involving the Turnigy charging circuit. Doing dumb stuff though so two fuses are probably still a good idea no matter what... I already popped the Futaba one once.
I am powering the radio off the Futaba transmitter pack. The Futaba pack plugs into original spot on Futaba mainboard. Constant b+ Power goes through Futaba fuse. Just two jump spots on the board, and to the trimmer pot for the analog meter. I have a JST plug off one of those points, with ground going to another jump point. I can put a diode here, but currently it is just jumped over to the ground plane. Removed the balance plug from the Turnigy RF and power board, and installed the JST mate there. Triple verified, polarity all correct and until I add meter back in, all works as it should.
The Futaba TX pack is a 9 cell nicad with charged voltage of 10.8v. This does appear to be kicking my low voltage alarms on, but that should be a simple matter to change in the radio setup (I haven't left anything powered up long enough to sort out since weird stuff is going on). I am wanting to run this pack due to how thin it is, and already the radio has a holder going for it. Room is at a premium. Pack appears to be fine, and I have a spare. So first question:
1) Is 10.8v good, or should I use a voltage booster circuit? The slight bump up I need shouldn't be too much of an inefficiency/power sink issue. Not my main issue though, more of a curiosity.
EDIT: Okay reading through one of the many many manuals available for this, YES I can use the 10.8 nicad pack. Well probably. Nimh is mentioned specifically, not nicad. Close enough. Voltage is WELL within tolerances so no need to bump it. Pretty sure my meter will fall off the scale well before TX stops working.
I am unsure as the wiring on the two donor radios is vastly different, but it appears that Futaba had the analog meter setup so that if the radio was off, but charging, the meter was powered up. I would have to buy a third complete radio to verify this (tempting, and cheap enough). They had negative side of the meter attached to the side of the charging jack that grounds when you plug in. And another wire to the the switched negative on power switch. Power is constant battery voltage, adjusted by the trimmer pot.
2) Should I continue with plan to charge the Futaba pack directly from the Futaba plug trying to get it working like original, or can I plug/wire Futaba power jack into the Turnigy mainboard charging jack? I figure the Turnigy charging circuit is set to cutoff at lipo cell voltage though...
Anyways before I added the Futaba mainboard power input and trimmer mod, the Futaba analog power meter was working (but hard pegging) with the negative on the black Turnigy switch lead. Radio powering on and off as it should. Ideally, if I have any chance of the meter showing when charging or just working safely, I need a safe switched ground point for the negative side of the meter when the system is powered up.
3) Any ideas what I should use?
I can likely pop a simple transistor into the Futaba board for this if I need to used a safe switched power source. If something pops the transistor, I only loose the analogue meter and not the actual system power. But just a simple switched ground would be nicer and easier....
Again, I had it working (before adding in the trimmer pot) using what I thought was switched ground on the switch. Mentero stated there is no switched ground though, and things were acting a bit off, so I figured I should post this up and get some guidance.
Oh as for the feedback problem I would have to verify again exactly what it was doing (and am real leery to do that now lol), but it wasn't powering back down right, or at all or something... If I plug it all back in and try again, I will edit this with exact specifics.
EDIT: Okay with the negative of the meter hooked to the black switch wire like it was, on initial battery plug in with the switch off, the meter powers up to basically full, although it is supposed to be off. Switch turns on, meter drops to zero and system powers up. Turn off, meter jumps up halfway, but system doesn't turn off. Unplug battery, plug back in, meter jumps up to full. I did this a few times to make sure of what was going on, then it booted up into bootloader mode. OOPS. Pulled battery, disconnected wire from switch. Powered up, all is good. WON'T do that again though LOL!!!
I REALLY want this analog power meter to work. Super big part of this radio's vintage feel.
Background: (for those who somehow haven't stumbled across my other posts... LOL!)
I am stuffing a 9XR-Pro into a vintage Futaba FP Gold radio and modernizing it. Why? I got issues...
I am having a switch feedback issue. Swapping the Tunrnigy switch with the Futaba switch was pretty straightforward. Everything worked fine. I did some testing and managed to get the Futaba analog meter sorta working too, off the converted switch. Power up was pegging the meter though. Okay moving along...
Taking a closer look at the first Futaba donor radio mainboard, I noticed a trimmer pot. I needed a mounting board anyways, so I spent a few hours un-populating it, of course leaving that trimmer in place. I then flipped the input protection fuse over to the other side of the board (sticks up a LOT) so I could have double protection and hopefully safely slow charge the Futaba nicad pack maybe without involving the Turnigy charging circuit. Doing dumb stuff though so two fuses are probably still a good idea no matter what... I already popped the Futaba one once.
I am powering the radio off the Futaba transmitter pack. The Futaba pack plugs into original spot on Futaba mainboard. Constant b+ Power goes through Futaba fuse. Just two jump spots on the board, and to the trimmer pot for the analog meter. I have a JST plug off one of those points, with ground going to another jump point. I can put a diode here, but currently it is just jumped over to the ground plane. Removed the balance plug from the Turnigy RF and power board, and installed the JST mate there. Triple verified, polarity all correct and until I add meter back in, all works as it should.
The Futaba TX pack is a 9 cell nicad with charged voltage of 10.8v. This does appear to be kicking my low voltage alarms on, but that should be a simple matter to change in the radio setup (I haven't left anything powered up long enough to sort out since weird stuff is going on). I am wanting to run this pack due to how thin it is, and already the radio has a holder going for it. Room is at a premium. Pack appears to be fine, and I have a spare. So first question:
1) Is 10.8v good, or should I use a voltage booster circuit? The slight bump up I need shouldn't be too much of an inefficiency/power sink issue. Not my main issue though, more of a curiosity.
EDIT: Okay reading through one of the many many manuals available for this, YES I can use the 10.8 nicad pack. Well probably. Nimh is mentioned specifically, not nicad. Close enough. Voltage is WELL within tolerances so no need to bump it. Pretty sure my meter will fall off the scale well before TX stops working.
I am unsure as the wiring on the two donor radios is vastly different, but it appears that Futaba had the analog meter setup so that if the radio was off, but charging, the meter was powered up. I would have to buy a third complete radio to verify this (tempting, and cheap enough). They had negative side of the meter attached to the side of the charging jack that grounds when you plug in. And another wire to the the switched negative on power switch. Power is constant battery voltage, adjusted by the trimmer pot.
2) Should I continue with plan to charge the Futaba pack directly from the Futaba plug trying to get it working like original, or can I plug/wire Futaba power jack into the Turnigy mainboard charging jack? I figure the Turnigy charging circuit is set to cutoff at lipo cell voltage though...
Anyways before I added the Futaba mainboard power input and trimmer mod, the Futaba analog power meter was working (but hard pegging) with the negative on the black Turnigy switch lead. Radio powering on and off as it should. Ideally, if I have any chance of the meter showing when charging or just working safely, I need a safe switched ground point for the negative side of the meter when the system is powered up.
3) Any ideas what I should use?
I can likely pop a simple transistor into the Futaba board for this if I need to used a safe switched power source. If something pops the transistor, I only loose the analogue meter and not the actual system power. But just a simple switched ground would be nicer and easier....
Again, I had it working (before adding in the trimmer pot) using what I thought was switched ground on the switch. Mentero stated there is no switched ground though, and things were acting a bit off, so I figured I should post this up and get some guidance.
Oh as for the feedback problem I would have to verify again exactly what it was doing (and am real leery to do that now lol), but it wasn't powering back down right, or at all or something... If I plug it all back in and try again, I will edit this with exact specifics.
EDIT: Okay with the negative of the meter hooked to the black switch wire like it was, on initial battery plug in with the switch off, the meter powers up to basically full, although it is supposed to be off. Switch turns on, meter drops to zero and system powers up. Turn off, meter jumps up halfway, but system doesn't turn off. Unplug battery, plug back in, meter jumps up to full. I did this a few times to make sure of what was going on, then it booted up into bootloader mode. OOPS. Pulled battery, disconnected wire from switch. Powered up, all is good. WON'T do that again though LOL!!!
I REALLY want this analog power meter to work. Super big part of this radio's vintage feel.