5V ---> 6.3V

A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
tmoble
Posts: 55
Joined: Fri Nov 25, 2011 1:01 pm
Location: Glendale, Az

5V ---> 6.3V

Post by tmoble »

well, I thought I had my TCU about done.

now checking it with a transtim I find that the 5V has somehow become 6.32V. It's hooked up to a 12V SLA battery that currently has about 12.5V. What could cause this? is the regulator toast? Previously it actually was showing 4.99V on my Fluke 175.

it shows 11.9 on the 12V of the regulator, noting on the center, 6.3 on the output. I didn't that regulator would go over 5V?
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: 5V ---> 6.3V

Post by Bernard Fife »

It could be the regulator, or it might be that you have more than 5V (such as a 12V source) connected to the 5V supply downstream of the regulator. Did you follow the transstim build instructions here: http://www.msgpio.com/manuals/mshift/v2 ... build.html ?
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
tmoble
Posts: 55
Joined: Fri Nov 25, 2011 1:01 pm
Location: Glendale, Az

Re: 5V ---> 6.3V

Post by tmoble »

yeah, I'm asking about the TCU, not the stim. I'm connecting the 12V battery to Pin1 of the connector. I'm using the pad marked as ground just to the right of Q8 for ground. I temporarily soldered a jumper wire on there. Seems to work, I think it's the same ground as the 4 pins 17-19.

Are those regulator known to fail? I've thought over everything I've done lately, nothing comes to mind. I do recall smelling something nasty a couple days ago.

Could I buy one of those at DIY AT?

Processor fried by getting 6.32V? I went through all the checks during the build, I had 4.99 every time
tmoble
Posts: 55
Joined: Fri Nov 25, 2011 1:01 pm
Location: Glendale, Az

Re: 5V ---> 6.3V

Post by tmoble »

Well, I bought a few of the 5V regulator from DIYAT. I guess I'll see when they get here.
tmoble
Posts: 55
Joined: Fri Nov 25, 2011 1:01 pm
Location: Glendale, Az

Re: 5V ---> 6.3V

Post by tmoble »

well, update. pulled the old regulator off, installed a new one from DIY AT. power up the board, still have 6.29 volts on the right-most Pin #3 on the regulator. IOW, no change.

So, it must have a short between the 5V rail and the 12V rail somehow. It was OK when I buttoned it up in the case, but I forgot that last step where it wanted me to install a resistor in one of the vias for D7, near Q1. I did that and connected the other end to 12V at AMP1 as given. It was something about a pull-up for the VSS, IIRC. That's actually when things went wrong, I think. I had and have 6.3V on pin3 of the U1 or Vreg. I have now disconnected that wire, but no help. Now I can't find that instruction anywhere.

A couple questions:

if there's a leak or short from the 12V rail across to the 5V wouldn't I have 12V on the 5 volt rail, not 6.3? where is that 6.3 number coming from?

The transistor at JP3 in the GP02 section is getting very hot, way too hot. There's nothing connected to the board but power and ground from a 12V SLA battery that has about 12.5V. It burnt my finger when I was poking around looking for the source of the warmth I felt around the middle of the board.

Any bright ideas? Should I pull all the 25x2 jumpers to keep from feeding 6.3 to the processor?
tmoble
Posts: 55
Joined: Fri Nov 25, 2011 1:01 pm
Location: Glendale, Az

Re: 5V ---> 6.3V

Post by tmoble »

that's interesting, looks like the 12V and 5V sides of things meet at JP3, which is where the egg-frying transistor mounts. That's in GPO2 section. Looks like GPO2 goes AMP7 which goes to LED3 on the stim. IIRC I never did get those LEDs to work with the big pot for the gears.

I wonder if that transistor met some cruel fate causing it to short out the 12V and 5v sides.

Anybody think it would be worthwhile to take it out, see what happens?
tmoble
Posts: 55
Joined: Fri Nov 25, 2011 1:01 pm
Location: Glendale, Az

Re: 5V ---> 6.3V

Post by tmoble »

anybody home?
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: 5V ---> 6.3V

Post by Bernard Fife »

if there's a leak or short from the 12V rail across to the 5V wouldn't I have 12V on the 5 volt rail, not 6.3? where is that 6.3 number coming from?
The regulator will be trying to bring the 12V output down to 5V (and it may be partially succeeding). As well, even if the regulator wasn't there, but there was some resistance between the 12V and 5V supply, you could get an intermediate voltage value.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
tmoble
Posts: 55
Joined: Fri Nov 25, 2011 1:01 pm
Location: Glendale, Az

Re: 5V ---> 6.3V

Post by tmoble »

OK, I've replaced the regulator, still have 6.3V. That transistor in the GPO2 section at JP3 seems to be the leading suspect. it has legs on the 12V rail and 5V rail. I've looked at the schematic, it seems to match the physical layout OK. or vice-versa.

What would make it get so hot? Something internal to the transistor or is it maybe being overworked by something external to it?

What does it bring to the party? possible to just cut it off?
tmoble
Posts: 55
Joined: Fri Nov 25, 2011 1:01 pm
Location: Glendale, Az

Re: 5V ---> 6.3V

Post by tmoble »

Well, I clipped off JP3, no difference. So then, in a fit of pique I clipped the other 3 off too. Yes, I graduated from the self-foot-shoot school of technology.

Anyway, now I have 5.001V on the 5V rail. !2V rail still at about 12.35.

Now, I checked the four JPx's and found all 4 to have 12V and 5V where they should, all four have close to zero on the middle leg.

3 of the 4 of the clipped off components are marked ZTX 450. The last one seems to ventured off on it's own, probably based on the velocity imparted by the clipping operation. I think I may have heard it bouncing somewhere.

in the GPIO section of the manual it sez: "The default transistor for the GPOx circuits is the ZTX450." So that would seem to be correct. It would seem that the most likely explanation of the issue is that I installed one or more of the transistors backward. Would that cause 6.3V to appear where 5V was expected?

So now, the question is: unsolder the dozen clipped off legs and re-install install transistors? Is that all these do is run the gear LEDs if installed?
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