Author Topic: Identifying polarity.  (Read 246 times)

Derpinador

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Identifying polarity.
« on: June 02, 2022, 01:41:18 AM »
I'm fearing my inability to identify pin 1 of an SMD 4558 is to blame, but has anybody seen a puff of smoke waft out of their op-amp chip touching the wires to a 9v battery during preparation to use the DMM to check pin voltages? I went with polarity as marked on pcb and battery.
I've tried uploading a pic of the board but it's about as wonky as registering for the forum of who sold the board.... closest I have is a line from side to side that is to the left when you can read the writing normally and it's from texas instru I bought through mouser.
https://www.pedalpcb.com/product/pcb465/ bites even they have no documentation for building it, yet. The line as soldered is towards the mid electrolytic cap/ LED and away from the jack grounds/power wires. Can anybody assist with which way this thing is supposed to go? I think I may have already cooked the chip but I'll just tack a new 1 on to the order for the parts if it is fried when M'bean releases Tourbus ;)

Late edit, anybody have an idea which end was pin 1?
<a href="https://www.imagevenue.com/ME14WUTG" target="_blank"><img src="https://cdn-thumbs.imagevenue.com/a6/bc/bc/ME14WUTG_t.png" alt="SMD 1pjt.png"/></a><a href="https://www.imagevenue.com/ME14WUTH" target="_blank"><img src="https://cdn-thumbs.imagevenue.com/85/f9/60/ME14WUTH_t.jpg" alt="SMpjt.jpg"/></a>my apologies IF the thumbs aren't showing.
« Last Edit: June 03, 2022, 12:42:31 AM by Derpinador »

Derpinador

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Re: Identifying polarity.
« Reply #1 on: June 04, 2022, 01:24:49 AM »
Well... I need a new board now, went to try using a 30 watt weller iron to remove the old chip. Only applied for like 10~15 seconds and took the pads and couple traces with it >:( Have to see what I can save of all the other parts ><

oeslicoalfin

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Re: Identifying polarity.
« Reply #2 on: June 04, 2022, 12:44:01 PM »
A puff of smoke is never a good sign. In the close-up pic of your 4558 you can faintly see a solid line on the "south end" of the chip. This identifies the 1-8 pins on the 4558. The other indicator commonly seen is the dimple identifying pin 1. Once an SMD with more than 2 solder points in on your PCB, it's next to impossible to get them off without some mayhem occurring.

Derpinador

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Re: Identifying polarity.
« Reply #3 on: June 04, 2022, 01:11:25 PM »
thank you, ever thing I found online seemed to treat the SMD like the through hole in regards to identification, like notches, dimples or paint dots, but not that line.  I bet it could have been removed with 1 of those hot air stations but I'm a skin-flint, even at $50 for a 6 use china throwaway is to much ;D


only like $.70 max tacked on another order to replace it... I'll leave all the other parts on the old board until I get either a new pcb or a future project from B requires some smd parts.. is 2 basically brand new 3904 trans sitting there

mjg

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Re: Identifying polarity.
« Reply #4 on: June 04, 2022, 03:41:19 PM »
I find I have to use a magnifying glass to identify pin 1 on some of those tiny chips.  There may be a tiny little dimple that you canít see without magnification.

Once I identify it, I mark the pin with red pen, so I donít forget or get it backwards 20 seconds later.

alanp

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Re: Identifying polarity.
« Reply #5 on: June 05, 2022, 12:38:08 AM »
For SMD chips, the side with Pin 1 will have more of a slope to the black plastic-y body than the other side. This seems to be universal.

If you are massively, hugely lucky, then there will be a silkscreen line on that end, or a dot. Do not bet on it.
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Derpinador

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Re: Identifying polarity.
« Reply #6 on: June 05, 2022, 08:52:40 AM »
this thing has a consistent thickness. I'll get a Nisshi instead of another TI next time. I wonder if the ghost of SRV came to b-slap me because I paint my TS boxes in something other than green, my ts9 was red, this 1 the box was mid 60's Chevrolet blue.... :P