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What is this component on a SIMM?

Muse

Muse

Lifer
I got a used Postscript SIMM off ebay for an HP Laserjet 4+ printer and it had a tiny part broken off when it arrived. The SIMM wasn't well protected, sent in a soft bag. The tiny part broken off was right there in the ziplock baggie and I told the seller I could try to solder it back on and see if it worked. I could see that it had been soldered on the SIMM, a bit of solder on both ends. He said he'd send me a replacement SIMM, regardless and he did. Meantime I did the solder job. I don't know what it was I soldered back on the SIMM. Below is a link to pictures of the SIMM before I soldered the part back on and the replacement SIMM, which shows the component. There are a couple of other components on this side of the SIMM that look just like this and 10 on the other side that also look the same. What could this be?

https://picasaweb.google.com/lh/sredir?uname=110090306825051457033&target=ALBUM&id=5698384189603506897&authkey=Gv1sRgCJqw-cT40aTPiQE&feat=email
 
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Pretty sure it's a capacitor. SMD resistors are usually black and the larger ones at least will have values printed on them, whereas caps will be that tan color and not have any values or markings.
 
frostedflakes said:
Pretty sure it's a capacitor. SMD resistors are usually black and the larger ones at least will have values printed on them, whereas caps will be that tan color and not have any values or markings.
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I suppose they are capacitors. I tried measuring resistance and it's apparently infinite. The multimeter acts as though it's measuring pure air. Is there any way I can test to see if it's a capacitor? Not that it matters at this point, I'm just curious and I guess I'd like some assurance that my fix worked. I suppose I'll sell one or the other on ebay, or try. I have no use for 2.
 
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RadiclDreamer said:
Oh wait, you mean the itty bitty one above it dont you 😀
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Yeah, it's itty bitty. About 1/8" long, if that. It was tricky soldering it back on the SIMM. What I did was first glue it in place with a couple of little drops of contact cement, one on the SIMM, the other on the part. Then I soldered the ends onto the SIMM.
 
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frostedflakes said:
Pretty sure it's a capacitor. SMD resistors are usually black and the larger ones at least will have values printed on them, whereas caps will be that tan color and not have any values or markings.
Click to expand...

I looked up the IC datasheet and it looks to be a bulk capacitor for the Vcc (power) pin, which smooths out the voltage spikes going to that power pin.

If that's correct, then it'll probably still work without it, although you might see some intermittent failures if there are ground loops or switching noise on that power rail.

EDIT: didn't read the part about you replacing it. that should do the trick, these COG / X7R caps aren't polarized. happy printing.
 
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It's a capacitor. 74FXXX Logic chips (821 is a flip flop) usually ask for a 0.1uF or 1uF capacitor across power and ground.
 
typically in these circuits its a 0.1uf or even smaller. Essentially it stabilizes the voltage at the chip its connected. When a chip turns on it draws a bunch of current and its possible that it can dip the supply voltage (load it down) below its own turn on voltage. It isn't "necessary", just a good design feature.
 
bobdole369 said:
typically in these circuits its a 0.1uf or even smaller. Essentially it stabilizes the voltage at the chip its connected. When a chip turns on it draws a bunch of current and its possible that it can dip the supply voltage (load it down) below its own turn on voltage. It isn't "necessary", just a good design feature.
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For most devices a cap of that size wouldn't provide much help against voltage dips. It's more for noise and stability.
 
chorb said:
I looked up the IC datasheet and it looks to be a bulk capacitor for the Vcc (power) pin, which smooths out the voltage spikes going to that power pin.

If that's correct, then it'll probably still work without it, although you might see some intermittent failures if there are ground loops or switching noise on that power rail.

EDIT: didn't read the part about you replacing it. that should do the trick, these COG / X7R caps aren't polarized. happy printing.
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Yeah, I was wondering if it mattered which end was which. Looking at it, it looked symmetrical, so I figured it was probably OK either way. I was concerned that too much heat from the solder iron (a typical ~25-30watt all purpose), would damage it, tried not to fry it.

Now I have to address the apparent reason I found this printer on the sidewalk: At first I thought it was OK because the test prints look perfect, but running the continuous test print item in the test menu had a succession same test prints issue and after a few the printer jammed with "accordion" prints. So, something's wrong. I have been told that this is easy to fix but I don't know how just now or how exactly to approach the problem.
 
NutBucket said:
Probably needs new rollers. Most common problem with HP laser printers.
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😀
That is basically our printer repair guy's main troubleshooting. Just replace the rollers. I finally convinced my boss to buy a few sets of rollers and now we save a ton of money.
 
Capacitor. You'll always find a nearby (eg as close to the chip leads as possible) capacitor bridging the power pins on every digital logic IC.
 
it's hard to tell, but the SMD caps are color coded
I never had a good enough eye to tell the difference between orange and almost orange
or tan and lighter tan ....

good luck
 
Soulkeeper said:
it's hard to tell, but the SMD caps are color coded
I never had a good enough eye to tell the difference between orange and almost orange
or tan and lighter tan ....

good luck
Click to expand...
Yeah, maybe you're color blind... I am, no doubt contributed to my not pursuing electronics. I built some kits when I was a kid-teenager-freshman_at_the_U, but reading a resistor's color code was beyond me. Instead I got into theoretical physics and math.
 
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