Step 69 part C - something to take notice of.
#1
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Part C says to install Q9 and Q12. These transistors have to sit on mica insulators and have a resistance of greater then 60k ohm between it and the heatsink.
Last night I got done with my build, plugged it in, lights flickered for 10 seconds and died. I started to get really really upset and panicky, I said **** it and went to sleep pissed off. The only thing I discovered last night was that the battery or the adapter got very very hot and there was no power on the cpu socket.
This mornings investigation into the issue lead me to discover that the resistance between the two above transistors was 0. I unscrewed them slightly from the PCB, magically the resistance was 60k ohm and the power returned to the socket.
This lead me further to discover that either the bolt or the tightness is the culprit. I removed both and just pressed the transistor down with the probe on the DMM and resistance was exactly where it was supposed to be.
I have no idea what chamfering is but I have a feeling im going to go grab a drill bit and carefully drill out the metal band in the hole that passes through the pcb for those two transistors. I think it hitting the heatsink and its grounding the transistors.
Last night I got done with my build, plugged it in, lights flickered for 10 seconds and died. I started to get really really upset and panicky, I said **** it and went to sleep pissed off. The only thing I discovered last night was that the battery or the adapter got very very hot and there was no power on the cpu socket.
This mornings investigation into the issue lead me to discover that the resistance between the two above transistors was 0. I unscrewed them slightly from the PCB, magically the resistance was 60k ohm and the power returned to the socket.
This lead me further to discover that either the bolt or the tightness is the culprit. I removed both and just pressed the transistor down with the probe on the DMM and resistance was exactly where it was supposed to be.
I have no idea what chamfering is but I have a feeling im going to go grab a drill bit and carefully drill out the metal band in the hole that passes through the pcb for those two transistors. I think it hitting the heatsink and its grounding the transistors.
#11
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Want the real reason?
They have metal bolts because that's what comes with the Mica kit. We didn't spec the contents of that kit out ourselves. Nylon would work just fine which is why we use it everywhere else, and on these two trany's the metal bolt will work just fine if it's properly insulated, but that can be a bit troublesome sometimes. Nylon would do the trick just fine and help prevent the issue...
EDIT:
Going forward (next batch of kits built), we're including a note to direct people to use the metal screws on Q3/Q11, and to use the nylon screws on Q9/Q12. We were going to just put extra nylon screws in the bags but then figured we'd still have to put a note in there to tell people what to do with them, and then decided just the note would do just fine....
![wink](https://www.miataturbo.net/images/smilies/wink.gif)
EDIT:
Going forward (next batch of kits built), we're including a note to direct people to use the metal screws on Q3/Q11, and to use the nylon screws on Q9/Q12. We were going to just put extra nylon screws in the bags but then figured we'd still have to put a note in there to tell people what to do with them, and then decided just the note would do just fine....
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Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Last edited by FoundSoul; 11-12-2007 at 04:43 PM.
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