PSOM circuit help

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Hornnumb2

Joined Jan 17, 2013
22
I am trying to figure out where I am losing voltage, the center pin (c) on transistor should be giving me 9v but I am only getting 1.3. Which goes to pin 16 on IC1. B on transistor is outputting 11.8 but I only get 1.7 on pin 1 of IC1. Thanks Michael
Here is a diagram.
 

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ebeowulf17

Joined Aug 12, 2014
3,274
B on transistor is outputting 11.8 but I only get 1.7 on pin 1 of IC1.
Given that the schematic shows those two being directly connected, and you're reading very different voltages there, you obviously have a break somewhere, whether it's a bad solder joint, a chipped trace, a damaged via... who knows. But work your way back with a meter and find where that voltage disappears. Fix the break and maybe everything else works then. If not, you're one step closer.
 

ebeowulf17

Joined Aug 12, 2014
3,274
Trace was broke, now the only voltage I am missing is 4.3v on IC1 at pin 8, currently 277mv.
Interesting... I don't see IC1, pin 8's connections on the schematic you posted earlier (I see the outline of the chip with voltages for each pin, but not the connections between that pin and any other part of the circuit.)

Tracing it in the pics, it looks like it runs to a via under IC4, so presumably it connects directly to a pin on IC4. Is there more to the schematic? Does it show the connection I'm assuming must be there? If so, does it list the voltage for that pin (presumably the same 4.3V target.) You could check the pin there and see if voltages match. Maybe another bad connection? Could be a poorly soldered pin connection on IC4 breaking continuity there.
 

ebeowulf17

Joined Aug 12, 2014
3,274
Would you think IC4 is some type of controller?
Oh, I haven't the faintest idea what I'm looking at. Sorry! There are a few small sections of analog circuitry that I'd be able to analyze, but it looks like most of the action is in the ICs, and I have no idea what any of them are.

If I had to guess I'd say the brains were in IC4, just cause quite often the microcontroller that's running the show is the chip with the most pins, but that's a pretty flimsy line of reasoning.
 
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