What have I broken and fried!

Megajolt Kit assembly Question and Answers. Be sure to review the <a href="http://www.autosportlabs.net/MJLJ_V4_kit_assembly_guide">Kit assembly guide</a>

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Ethel
Posts: 18
Joined: Sun Feb 10, 2008 11:17 pm

What have I broken and fried!

Post by Ethel »

Couldn't decide which of the 2 existing and doubtless popular categories are most apt so thought a new one was best :shock:

V3 'jolt was working until my muppety actions hooking it to my PC on the bench. I couldn't find enough AA batteries to put in my pack to give 6v so I stupidly trusted the labelling on a mains power pack (12.5v) instead of fetching my multimeter from the garage. When my PC crashed on hook up I realised this wasn't the best idea. I since discovered my MJ was being fed closer to 18v (I don't think this should have been a problem on its own so maybe the connections also shorted?).

My (spare) PC no longer "sees" the MJ, the voltage regulator is regulating correctly, as per assembly guide. All the diodes and resistors seem ok too. Running the dos firmware update does register the hard reset when I hook up a battery.

Are there any other tests I can try? I'm hoping I just fried the MAX232A but my electronics skills don't extend far beyond swapping old for new 'n crossing my fingers. Can I get a new processor if I toasted that too?

Many Thanks,

The Muppet



p.s. if there are any computer whizzes about, after this little escapade my PeeCee will post & boot, sometimes for several minutes, but not every time & when it crashes it dies as if the power is cut followed by bouts of whirring and flashed leds as if its trying to reboot. What are the chances it just needs a new PSU? It like to report an overclocking failure, although it isn't clocked.

brentp
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Post by brentp »

Hello,

18V fed into the MJLJ should not damage anything on the MJLJ. Can you tell me the label on the voltage regulator? On a V3 if it's a LF50 or similar the voltage regulator will go into "shut down" mode if near or over 18V, and not supply power to the MJLJ circuit.

Also, no excessive voltages would be applied to your PC as well- the MAX232A is behind the voltage regulator, and will never see a voltage above 5V. I believe what happened with your computer was coincidence only.

If you have run the firmware update program and it "sees" the MJLJ, then it shows the MAX232A is also working correctly.

Have you hooked the MJLJ back up to the engine to verify it's controlling ignition advance correctly?
Brent Picasso
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Ethel
Posts: 18
Joined: Sun Feb 10, 2008 11:17 pm

Thanks for the prompt reply Brent,

Post by Ethel »

I wonder if the fault could have originated on the pc? It did it first via the usb port, so a few volts on offer there. I have also tried with a DB9 cable.

The regulator is marked LF50APB. It has previously been possible to communicate via the usb adapter, which still installs correctly, and was used for the firmware "ping" but won't read off the MJ now. I'll try and rig up yet another PC with a RS232 port and report back. I don't have an assembled engine to run at the mo & I had recently (successfully) flashed the firmware to 3.3. so not even sure what the configuration is - I was intending to flash 3.32 when I had my mishap.

brentp
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Post by brentp »

If you're upgrading to the new 3.3.x firmware then you should download the new, matching configuration software.

Keep us posted!
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Ethel
Posts: 18
Joined: Sun Feb 10, 2008 11:17 pm

still no dice

Post by Ethel »

I dug out pc number 3 and managed to successfully run the firmware flash in dos to 3.3.1 but it still reports a timeout with 3.3.2 configurator. :?

brentp
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Post by brentp »

As a test, can you convert back to the 3.2.1 firmware and try the corresponding 3.2.1 configuration software?
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Ethel
Posts: 18
Joined: Sun Feb 10, 2008 11:17 pm

Post by Ethel »

I could but I've already had it talking to a PC with 3.3. and it failed to do the same after the incident, but before I could upgrade the upgrade so I'd be surprised if it will make a difference. Does the firmware upgrade involve the MJ confirming the processor has been written to....

Well this time there's nothing - no ack signal :(
Last edited by Ethel on Sat Aug 29, 2009 8:01 pm, edited 1 time in total.

brentp
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Post by brentp »

Hi Ethel,

Yes, it does verify the firmware upgrade.

You can install the 3.2.1 and the 3.3.x configuration software side-by-side, fyi.
Brent Picasso
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Ethel
Posts: 18
Joined: Sun Feb 10, 2008 11:17 pm

Post by Ethel »

As above, taken a backward step now won't acknowledge the reset with hc08sprg

Quicky recap:

Worked
PC crash with 18volts
Configurator timeout - can't read/write to MJ
hc08 reset worked (with USB - so no firmware write)
firmware write to 3.3.2 via proper serial port
Nothing - no hc08 reset acknowledge

brentp
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Post by brentp »

Ethel,

Have you most recently been using a usb-serial adapter when flashing the firmware? it's not 100% clear from your post.

If possible, test using a PC with a regular serial port- both flashing firmware and testing with config software. Also, be sure you have a fresh 9V battery connected to the unit's power input- this could also contribute to the inconsistent behaviour you're seeing.
Brent Picasso
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Ethel
Posts: 18
Joined: Sun Feb 10, 2008 11:17 pm

Post by Ethel »

I know of the usb issue - mine worked, but wasn't up to flashing the processor so I have also tried a motherboard serial port 'n cable.

I don't think it's the battery, I've been using 4 AA's which have shown just over 6 volts when connected & I also whipped the PP9 out of my meter to try.

Are there any hardware tests I can try to confirm the chips are functioning? I can't be sure how the processor is configured even if I had a running engine to test it on - the last thing I managed was to flash 3.3.1 which ran ok in Dos but I can't confirm in the config software, obviously. Is it worth geting a meter to check the capacitors?

brentp
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Post by brentp »

Hi Ethel,

6V is a bit too close to the target 5V, and the voltage regulator might not be able to work correctly as a result. Do try a 9V battery and see if that makes a difference.
Brent Picasso
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Ethel
Posts: 18
Joined: Sun Feb 10, 2008 11:17 pm

Post by Ethel »

New new9v battery tried still nothing. :(

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