IC identification

Thread Starter

tresguey

Joined Apr 22, 2013
55
Hi all,

I have an 8 dip IC I am trying to identify. I am assuming it is a dual op amp. It is in a 12 vdc circuit that fires two relays based on temperature one at a time at two temperatures. From what I have probed I am pretty sure pin 1 = out, 2 = VCC, 3 = out and 4 = ground. I am pretty sure pins 5 and 8 are noninverting inputs. This board does not have transistors to fire the coils of the relays it is just the IC itself which I find strange.

any help would be appreciated.
 

Thread Starter

tresguey

Joined Apr 22, 2013
55
top.JPG bottom.JPG

Here are pictures of what I have.

yellow wire powers the IC, Thicker black is ground, smaller black and purple are for the thermistor and the green over rides or triggers one relay only.
 

dl324

Joined Mar 30, 2015
9,626
It was sanded off, they didn't want anyone to know what it is I guess.
Treat the unknown IC as a black box and create a schematic of the rest of the circuit, giving part numbers and values for anything with markings.

The next time you ask for assistance, put yourself in the shoes of anyone who might respond. Do you think you gave anyone sufficient information to help you in your first post?
 

alfacliff

Joined Dec 13, 2013
2,458
the old "sand the markings off" trick? I have been fighting that since the 70's I found that sometimes they are marked on the bottom too. I havnt found any surface mount ones marked on the bottom yet. somewhere on ePanorama.net is info on identifying chips from the circuit they are in.
 

ian field

Joined Oct 27, 2012
6,539
the old "sand the markings off" trick? I have been fighting that since the 70's I found that sometimes they are marked on the bottom too. I havnt found any surface mount ones marked on the bottom yet. somewhere on ePanorama.net is info on identifying chips from the circuit they are in.
That's something I mentioned on another thread - they do occasionally slip up that way.

Given the overall nature of the equipment, I'd try an easy way out first - a wild guess that it could be an LM393 dual comparator. Even just starting on tracing out the circuit would give an indication whether it is or not - and by then a fair bit of the circuit is revealed anyway.
 

sailorjoe

Joined Jun 4, 2013
361
Based on the minimal information available, and from the photo of the circuit, my guess is that you have a dual comparator. The resistor network on the circuit board sets the threshold voltages for one input on each comparator, and the other probably comes from the thermistor. Of course, this is just a guess, but if it was me, that's the premise I would work on until proven differently. Look up an LM393 or LM2903. Good luck.
 

hp1729

Joined Nov 23, 2015
2,304
Hi all,

I have an 8 dip IC I am trying to identify. I am assuming it is a dual op amp. It is in a 12 vdc circuit that fires two relays based on temperature one at a time at two temperatures. From what I have probed I am pretty sure pin 1 = out, 2 = VCC, 3 = out and 4 = ground. I am pretty sure pins 5 and 8 are noninverting inputs. This board does not have transistors to fire the coils of the relays it is just the IC itself which I find strange.

any help would be appreciated.
Look at a data sheet for an LM56 and see if the function makes sense to you. Pinout isn't the same but you may get an idea of what you have. If they sanded off the numbers then it is probably a standard chip.

Can you identify the chip manufacturer by the body style alone? Seiko (SII) makes dual thermostat devices but not in a DIP package anymore (S-5842 for instance).
 
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Thread Starter

tresguey

Joined Apr 22, 2013
55
Thanks for all the help, I was pretty positive the pinout for 1 - 4 were good and never saw a VCC on 2 and ground on 4 before and figured someone might have some insight. I will work on making a schematic and post. I did give minimal info....sorry
 
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