Can someone help me in finding replacement components for a 16-year old automotive (Mazda) diagnostic module ?
Diodes:
Using my Fluke 79 DMM set to the "diode" mode, all of the circled diodes are testing "open" in both directions, which supposedly means ALL of these diodes are "open" and need to be replaced.
The only markings I see are a "D" or "O" and a "4" (see attached pics for details).
Transistors:
NEC J143
NEC B1151
K105
Thanks, neil
BTW: input voltages are only 14.2-VDC, electrolytic caps are rated at 25-VDC, and have been replaced.
Do you know what those diodes do? It seems more than a little unusual that you'd lose 8 diodes like that. Have you tested the transistors to see if they need replacing or at least if they fail a diode test as well?
The diagnostic module is an airbag diagnostic module and is used to "fire" the airbag.
I have no schematic, and it seems ALL of the same diodes test "open" in both directions.
Attached is a narrative of the function of the module.
The module gives me a "3-blink" error, which means there's something wrong in the power-supply to the diagnostic module.
The flow-chart says to test all voltage inputs into the module. If they pass, then there's something wrong with the powersupply INSIDE the diagnostic module.
From the transistor id numbers, this is high-current transistor (NEC J153).
I'm thinking the transistors wend bad, and then they took out the diodes.
I am de-soldering one of the NEC J153 transistors, as both are testing open, to test out of circuit.
I seriously doubt all those diodes are bad, which makes me think they are all OK. Remove one and test it out of circuit, I bet it tests fine then (assuming your meter is OK).
I'm thinking that everything you test shows open. Are you sure the meter is good, your using it correctly or that the board isn't coated with something that's permitting contact with the leads.
I'm thinking that everything you test shows open. Are you sure the meter is good, your using it correctly or that the board isn't coated with something that's permitting contact with the leads.