Identify display driver IC

[Unixon]

Hi!

Does anybody know what is this IC in SOIC-14 package with top marking ICN19032 YA2156 ?
Probably a voltmeter IC with built-in multiplexed 7-segment display driver, the display model is SMB310561K.
This board is from a front panel of a small Chinese welding machine.
A repair as such is not required (yet), but I'd like to reverse engineer this welder for future modifications.

However, the build quality of this unit is below average, when the machine just came in there was a small short on the back side of front panel board and displays/knobs were all mixed in a weird way. Thankfully there was only one issue and it cleared after removing this short.

[mikeselectricstuff]

most likely a cheap microcontroller

[retiredfeline]

Probably one of those ICs used in cheap 3-digit voltmeter modules. Problem is I can't find a picture of one of those showing the IC; they are under the 3-digit display or on the back side.

[Unixon]

most likely a cheap microcontroller

Probably one with pre-programmed OTP memory, yes.
In case of a failure this board is doomed, it would be impossible to find a drop-in replacement.
The hope is that this is a known ASIC just with random top marking.

[fzabkar]

The power pins appear to match a PIC micro.

For example, PIC16F1824 ...

https://www.microchip.com/ds40001419

[Unixon]

Probably one of those ICs used in cheap 3-digit voltmeter modules. Problem is I can't find a picture of one of those showing the IC; they are under the 3-digit display or on the back side.

That were exactly my thoughts when I saw front side of this board. I was curious to see if there is an MCU hidden on that front panel board that controls welder circuits, but it turned out that the device is simpler than I thought and all control circuits are purely analog. This is good since it doesn't depend on a secret firmware to perform its main functions.

I saw a few pictures of these 3-digit voltmeter modules with PCB and controller IC exposed, but none of them had any marking or sufficiently high resolution to read poorly visible marking on the IC. I wonder if anyone had dissolved one of these chips to make nice pictures of the die, that would clear a number of questions.

[fzabkar]

Compare the dimple at pin #1.

https://assets.rs-online.com/f_auto,q_auto/70414618.jpg
https://www.embedic.com/uploads/productFiles/PIC16F1824_I_SL/20190810170903_1719.jpg
https://lh3.googleusercontent.com/proxy/c1rSzatjyEEA2zYRDu1HQHFR2SXNJcuMhSmWWFi4KvFemIMv3H_DnbI_rdRPF-ujM-JKlx7NffuEtSmnedftH_6cIA
https://eldan.com.hr/2515_storage/Pic16f1824-sop-14-pic16f1824-i-sl-novi-original-1_cdn.jpeg
https://gcs.rimg.com.tw/g2/c/0f/8e/21513812364174_396.JPG


I guess this is the welder:

https://5.imimg.com/data5/DD/FG/MY-6948317/mig-welding-machine.pdf

I'm guessing that you set the welding current and voltage with the pots, and then the ICs convert the analogue voltages into digital.

[fzabkar]

Here is another possibility (but the dimple is different):

https://www.zl2pd.com/PeakReadDVM.html

[retiredfeline]

I did a bit of searching with "voltmeter ic" and one ID that turns up is "dsn-dvm-368", This is the ID of the module, and with that you can find online pages selling it, as well as some hackers who modified them to be ammeters. But in all the photos no markings on the chip can be seen. You could try asking those hackers for more info, but my suspicion is that it's a MCU chip commisioned by the module maker and manufactured in the millions. You could also take apart a module to check if the pinout matches.

But seeing as your welder circuit is analog, then there's no problem. If the display fails, then substitute one of those cheap voltmeter modules. Or make one from an off-the-shelf MCU.

[Unixon]

The power pins appear to match a PIC micro.
For example, PIC16F1824 ...

This might be a good thing because then it is only a small piece of firmware is needed.
I guess I will have to confirm this with a small amount of concentrated sulfuric acid and a decent microscope.
However, since I can't waste a welder for this experiment this has to be done with a cheap voltmeter module, but then there's no guarantee that ICs are the same.

[Unixon]

I guess this is the welder:
https://5.imimg.com/data5/DD/FG/MY-6948317/mig-welding-machine.pdf
I'm guessing that you set the welding current and voltage with the pots, and then the ICs convert the analogue voltages into digital.

Yes, pots are going directly to the main board and then to the riser board with PWM controller and other analog circuitry.
These chips in question are only there to put out a number on the display.

The welder is different, however, it's a very cheap (about $70-120) MMA machine with decent power components for such a low price.
It runs pretty well on high currents but since it's missing an output inductor the arc is not stable enough at small currents and rods with basic coating.
So I'm thinking of upgrading it a little bit, I guess even with all required mods it may stay below $120-150 mark.
The reason for getting this machine was to have a little but powerful enough welder with all arc settings on the physical knobs.
A professional MMA welder with same features is about 3 times heavier and 4-7 times more expensive, and cheaper welders rarely have all settings adjustable via the interface and out of them welders that have settings on separate designated knobs are even more rare.