MSX/v3.0 with p&h boards - back through db37 connector?

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MSX/v3.0 with p&h boards - back through db37 connector?

Postby snorkels51 » Wed Sep 26, 2018 5:56 am

I have a MS/v3.0 with MSX self assembled to be used to control a Jaguar V12 engine. I will be using the factory low impedance injectors and have ordered three v1.1 p&h boards which should arrive shortly, intending full sequential on ignition and injectors.
I will be using the injector pins from the 10 pin J1 header on the MS3 board for the InjA to H, and H1 to H4 on the MSX board for InjI to L to the three p&h boards.

My question is, since I will not be using the 8 injector drivers on the MSX board and I have a harness to connect to the DB37 connector there with those 8 injector leads already wired, can I either solder jumpers to a leg of the VND5N07 mosfets from the 2 p&h boards outputs for InjA to H and be able to use the db37 connector and harness as is?
If this is feasible, would it be better to remove the mosfets completely and just run the jumpers to the appropriate terminal on the board to achieve the same outcome?

If this is doable it would mean a much physically smaller connector for the IgnI to L and InjI to L wires and require less room in the enclosure I will be using.

Any input will be gratefully received.
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Re: MSX/v3.0 with p&h boards - back through db37 connector?

Postby jbelanger » Wed Sep 26, 2018 3:44 pm

You should be able to connect to the leg of the VND5N07 that goes to the DB37 or to the DB37 pin itself without having to remove the VND5N07.

And if I understand correctly, your second option would consists of using the header on the MS3X and removing the VND5N07. That one is not a good option because you would also need to remove 2 resistors per driver (1k and 100k) and bridge the series resistor (1k resistor). Moreover, the board traces on that side of the driver are not designed to handle the current from the injectors.

If you do connect to the transistor or the DB37 directly without removing the transistor, you might want to pay attention to any unexpected behaviour from the p&h drivers. The presence of the original drivers should not affect the p&h drivers but I cannot guarantee that this will always be the case. So you may need to remove the VND5N07 to get a properly functioning p&h driver.

Jean
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Re: MSX/v3.0 with p&h boards - back through db37 connector?

Postby snorkels51 » Wed Sep 26, 2018 6:01 pm

Thank you Jean for your prompt reply.

My first thought was to go directly to the pins on the db37 on the underside of the MSX board but decided that the wires would be considerably shorter by going to the leg of the vnd5n07.
I had reasoned that since there would be no connection to those circuits on the MSX there should be no gremlins there but electronics are funny things.

Actually my alternative thought with the removal of the mosfets was to solder directly to the contact pad that the mosfet uses (if that is feasible) which would not require the removal of any other components.

Since I am a fan of the ‘KISS’ principle, I think I will go for option 1 and if I get any odd behaviour I will then decide whether to go directly to the db37 pins or start removing mosfets.
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Re: MSX/v3.0 with p&h boards - back through db37 connector?

Postby jbelanger » Wed Sep 26, 2018 7:24 pm

Using the pads from the removed mosfet would work and has been done before. Soldering to the pads would be easier than soldering to the DB37 but removing the transistor may not be that easy. You also have to be careful not to damage the board.

Jean
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Re: MSX/v3.0 with p&h boards - back through db37 connector?

Postby snorkels51 » Thu Sep 27, 2018 5:33 am

All good then, thank you.

I should have the boards in the next few days so I'll give it a go and see how it works out. It does seem like the logical way to go.
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