Peak and hold injector driver board

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Poolside
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Re: Peak and hold injector driver board

Post by Poolside »

linuxman51 wrote:ok i have corrected the issue with #4.without a chip in the socket on #1 it is still connected to ground.
What turned out to be the problem with the #4 output?

As for output #1 from the P&H board, a question. What does "the output is grounded" mean? You know, what are you measuring, between which points, and with what?

- Jim
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Re: Peak and hold injector driver board

Post by linuxman51 »

zero change with the extra ground. 2, 3 and 4 work fine. 1 is still grounded upon application of power with no IC.
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Re: Peak and hold injector driver board

Post by linuxman51 »

replaced the fet again without putting the driver back in the socket, and it still immediately grounds out. without the fet in place it doesnt (which really only rules out a short in the pcb right around the connector for the injector output). with power off i get a similar ohm reading from output to ground from all four circuits.

So what else do I need to look at here? the board won't take too much more de-soldering.
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Re: Peak and hold injector driver board

Post by linuxman51 »

Poolside wrote:
linuxman51 wrote:ok i have corrected the issue with #4.without a chip in the socket on #1 it is still connected to ground.
What turned out to be the problem with the #4 output?

As for output #1 from the P&H board, a question. What does "the output is grounded" mean? You know, what are you measuring, between which points, and with what?

- Jim
Its pretty straight forward, you turn the system (including the board) on, and output one is tied to ground 100% of the time. 4 was a loose joint upstream that simply manifested itself first as an intermittent functionality and then zero functionality (but not grounded on the output side).

I have injectors on my test bench with which I'm testing this stuff, this is not me just looking at a DMM scratching my head.
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Re: Peak and hold injector driver board

Post by racingmini_mtl »

So you're saying that with the LM1949 not installed (U1), the injector 1 output is grounded? Can you check the voltage at pin 2 of the U1 socket with the power on: it should be 0V. Then with the power off, can you check the continuity between pins 2 and 3 of the transistor Q2: you should not have continuity. And from what you say, you don't have continuity between the injector output and ground since you don't get a grounded output without Q2.

Let me know what you find out because this is definitely strange. There is a 5V trace that goes near pin 2 of U1 (between pins 1 and 2) and if there was a defect in the board that connected the 2 then you would get what you see. However, that would be quite a big defect and I'd be surprised if that was the cause.

Jean
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Re: Peak and hold injector driver board

Post by linuxman51 »

pin 2 power on gives me between .99 and 1.05 vdc without the chip installed.
powered off i get 1.75 m ohm between 2 and 3 (and a brief beep from the continuity function)
for reference i get 2.4 m ohm between 2 and 3 on #2

with power and no injector connected, i get 5.28 m ohm between inj 1 and inj1 grnd
with the injector (still no ic), it immediately clicks and the reading drops to a fairly constant 2.6 m ohm

with #2:
no inj : it floats between .6 m ohm and .7 m ohm (this number is dependent on how fast the stim is triggering the ms)
but with the injector it goes waaaay up to like 16 - 17 m ohm.
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Re: Peak and hold injector driver board

Post by racingmini_mtl »

Right away from the voltage you get at pin 2, there is a problem: this should be 0V (you could check what you get with the other drivers if it's easy to remove the LM1949). I think you have a short between pins 1 and 2 of Q2 which turns it on and grounds the injector output. That would also explain why you need the transistor to have the constant grounding.

Can you see anything between the pads for pins 1 and 2 either on the top or on the bottom of the board? Can you take a couple of pictures of these 2 spots?

Jean
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Re: Peak and hold injector driver board

Post by linuxman51 »

pin1 and pin2 gets me 6.5 m ohm with no power to anything, approx the same between pin 2 and ground
between pin 1 and ground i get 4.77 k ohm.
pin3 is .3 ohm to ground
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Re: Peak and hold injector driver board

Post by racingmini_mtl »

It is a bit confusing. When you talk about m ohm, do you mean M Ohm as in Mega-Ohm or m Ohm as in milli-Ohm? From your last post, I assume you mean MegaOhm.

What I don't get is that you say that when you connect the injector, it clicks and you still have 2.6 m Ohm. That doesn't make sense if it's MegaOhm and the 5.28 doesn't make sense if it's milliOhm. There is something about your measurements I don't get. With power on, try to take voltage measurements and if possible do them with and without any RPM input from the stim when doing the measurements on #2. And if you could take pictures of your board that would also help.

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Re: Peak and hold injector driver board

Post by linuxman51 »

I get pretty much the same voltage readings between 1 and 2 (edit to clarify, this is between output 1 and output 2, not pins 1 and 2 on output 1's fet) with the stim rpm turned off. I have noticed something while probing the IC socket however, and this may be normal, I get 5v on pins 7 and 8, whereas on the ic in #2, I get nothing on pin8, but I get 5v on pin 7. might this have something to do with it?

I can't seem to get any clear close up pictures, but I've looked in under and between & can't seem to find any solder bridges, i'll look closer @ the socket on the top. Just the odd bit of flux.
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Re: Peak and hold injector driver board

Post by linuxman51 »

Also, while reading 5v on pins 7 and 8, I don't get continuity between them or the 5v input, I'm assuming this reading is just residual from the other ICs grounding themselves.
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Re: Peak and hold injector driver board

Post by racingmini_mtl »

Pin 7 is the 5V supply pin so you would expect the 5V. Pin 8 is connected to pin 7 through the 39K resistor so if you don't have the chip in the socket you would also expect 5V (or very close to it) on it. With the chip in place, I haven't measured but it is not surprising to see a voltage around 0V on pin 8.

The main issue here is that you get voltage on pin 2 of the socket (which is the same as pin 1 of the transistor Q2) which turns on the transistor to ground the injector. Since you say that the problem is not there with Q2 removed, you either have something that makes contact between pins 1 and 2 of Q2 or between pin 2 of U1 and 5V.

Jean
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Re: Peak and hold injector driver board

Post by linuxman51 »

ok, now i have found a (possibly) significant variance:
between pin 1 of Q2 and pin2 of the IC i get 8K ohm resistance (no power)

between pin 1 of the fets and pin 2 of the ics on the other circuits I get a minimum of 11.9K ohm resistance

I have gone over it closely under a bright light, re-touched everything, and scrubbed the board down to get rid of any flux. when it dries I will get new readings and see what things are. Next thing i guess would be to isolate that pin on the ic and connect it directly to the fet?
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Re: Peak and hold injector driver board

Post by racingmini_mtl »

Between pin 1 of Q2 and pin 2 of U1, you should have continuity (0 Ohm) because they're directly connected together. Pin 2 of U1 is the second from the bottom on the right (slightly above the work Peak on the board). Pin 1 of Q2 is the first one one the left. You should be able to see the trace on the top of the board.

If you see some significant resistance (and 8K is more than significant) there is either a major problem or there is a problem with your measurements. Since the other drivers are working and you see 11.9K then I suspect your measurement (either the wrong pin or the wrong setup on your meter).

Also, it is possible that your solders are fine and that there is no solder bridge or flux but if there is some copper on the board that should not be there (manufacturing defect). Look to see if there is clearance around the pad on the 2 suspect pins.

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Re: Peak and hold injector driver board

Post by linuxman51 »

Sorry, the measure was between pin 7 and pin 1.
circuit 1 pin1 q2: (no IC in socket)
IC pin 1: 59.0 k ohm
IC pin 2: .4 ohm
IC pin 3: 22.2 M ohm
IC pin 4: 4.79 k ohm
IC pin 5: 4.8 k ohm
IC pin 6: 9.26 k ohm
IC pin 7: 8.85 k ohm
IC pin 8: 47.1 k ohm

with ic in socket:
IC pin 1: 51.0 k ohm
IC pin 2: 1.4 ohm
IC pin 3: 11.9 k ohm
IC pin 4: 4.79 k ohm
IC pin 5: 4.8 k ohm
IC pin 6: 8.2 k ohm
IC pin 7: 7.85 k ohm
IC pin 8: 46.1 k ohm


Q3 pin1 with ic:
IC2 pin 1: 61.5 k ohm
IC2 pin 2: 1.2 ohm
IC2 pin 3: 15.8 k ohm
IC2 pin 4: 8.25 k ohm
IC2 pin 5: 8.25 k ohm
IC2 pin 6: 12.73k ohm
IC2 pin 7: 12.33k ohm
IC2 pin 8: 50.8 k ohm

IC1 powered (chip installed)
pin 1 32.7 ohm
pin 2 0.5 ohm
pin 3 .512m ohm
pin 4 1.949m ohm
pin 5 1.949m ohm
pin 6 28.2 ohm
pin 7 14.34m ohm
pin 8 3.03m ohm

ic2 powered
pin 1 31.8 ohm
pin 2 0.3 ohm
pin 3 .5m ohm
pin 4 1.954m ohm
pin 5 1.95m ohm
pin 6 27.3 ohm
pin 7 14.34m ohm
pin 8 3.03m ohm


pin 2 to ground on Q2 : 40k omh
pin 2 to ground on Q3: 1.2m ohm
:-/ no visible outhangers on the socket or solder pads for the fet. is there any way to bypass the the board for the trigger to the fet?
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Re: Peak and hold injector driver board

Post by racingmini_mtl »

I should have thought of that before but the problem may be that Q2's metal tab is grounded. Can you check that the mica insulator is correctly placed and that you don't have continuity between the tab and ground (or at least a very high resistance). The fact you get a relatively low resistance on pin 2 makes me think that is the problem because pin 2 is connected to the metal tab.

If you just do a test with Q2 not bolted on but just free in the air that should tell you if that is the problem. Don't run it like that because it needs the heat sink.

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Re: Peak and hold injector driver board

Post by linuxman51 »

its not attached to anything right now (Free air) as the very first thing I thought i'd done wrong.
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Re: Peak and hold injector driver board

Post by racingmini_mtl »

You could try to test with pin 1 of Q2 not connected to see if the injector still gets grounded. This would help pinpoint the problem.

By the way, checking Ohms on a complete circuit is somewhat misleading especially when powered. You should try to measure voltage or ideally check with a scope (but I understand that this last one may not be possible).

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Re: Peak and hold injector driver board

Post by linuxman51 »

cut pin 1, still grounds the injector. (with the ic in) no drastic differences in voltage readings between circuit 1 and 2 with pin1 cut on #1.

and just tested again, grounds injector without chip in. I'm lost.
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Re: Peak and hold injector driver board

Post by Poolside »

A common failure mode for a FET is to fail with the drain and source shorted. Though it sounds like you swapped/replaced the FET in question a few times with the same results.

- Jim
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