Troubleshooting Obsolete Snap-On Motherboard (unidentifiable IC's)

[MtnMann]

Greetings,

I acquired an old Snap-On hand-spin wheel balancer machine (WB230/240) and am trying to figure out an issue with the motherboard (pics below). The machine is so old and obsolete that there is very little info out there. The balancer still works but the display will not show the initial settings when you change any one of the three potentiometers. These three pots set the variables for wheel diameter, width, and distance out from a point of reference on the machine. The display is normally just blacked out except the decimal point. When you adjust any of the three pots, it is supposed to show the corresponding numbers. Then, I'm not sure if those numbers are suppose to time out, or if they just stay lit until another dial is changed.

After those variables are set, you simply rotate the tire by hand bringing it up to a certain speed where the machine beeps. At that point, you let it spin until it calculates the weights needed at which point it stops the wheel spin with a brake. Then the display shows arrows indicating how far to rotate the wheel to find the point to attach the amount of weight shown on the display. Everything in this paragraph works fine. The display shows everything properly.

There is another setting that is for different modes (normal, aluminum rim, single plane, fine balance). This mode is changed by rotating the top pot to Zero and as soon as you rotate it off of zero, it changes to the next mode. You repeat this to toggle to the next mode. The modes are indicated by blank/AL/S/F on display. This all appears to work fine.

There is a black button on the back side that switches the machine from grams (no decimal on display) to ounces (decimal lit). That appears to work.

The white button on the back enters calibration mode. That, I believe is supposed to show CAL on the display. It just immediately goes into error mode ("EEE" on display).

Also, if you spin the wheel too fast or in the wrong direction, the display will go into "EEE" mode. When it does, nothing will return to normal mode other than reset by powering down.

Nothing appears to be blown on the board. I don't see any cracked solder joints, blown caps, or burns. J1 Input power can be either the 8.5 VAC adapter plug OR 12VDC battery. Both voltage regulators (lower left) work fine (9.96VDC in / 4.96VDC out). The lower one with heat sink gets quite warm. The largest IC near center gets slightly warm. All three pots get 5v and can properly adjust from 0-5v output.

I am not proficient enough to know what to replace at this point. I assume something senses a change in any of the three pots output voltage and activates the display to read the corresponding value. Would this be the main IC? Should it be getting warm? Or is this a function of another IC on the board? The main IC has a little block on its back that I'm not sure whether it is part of the chip or something epoxied on the back to cover numbers. Other unmarked IC's have sanding marks.

Any help would be greatly appreciated!

Thank you!

Other notes: J1 - power, J2 - unused, J3 (bottom) goes to brake (works), balance sensor unit (seems to work)

 

[kellys_eye]

Other than changing the electrolytics as a bog-standard 'old equipment fix procedure' you might be onto a losing streak if the main control IC is dud. Manufacturer specific etc and the sanding of IC's to remove identification is a nasty - but sometimes effective - way of telling you to 'eff off'. Nice people, aren't they????

Sure all the external sensors are supplying what they are supposed to?

 

[MtnMann]

Thanks for the reply...

No, I'm not sure but the external sensors I would think would be irrelevant to the setting/display problem as you should be able to set the parameters without moving the wheel at all. The calibration story might be a different scenario.

I'd like to get the display function working first...

The sensors appear to be working as it will actually display readings after cycling the wheel spin process. I have no way to tell if they are accurate until I get the settings to display.

 

[73's de Edd]

Sir MtnMann . . .

Have you got the WHOLE unit ?
Sort of looks like it interfaces thru a solenoid / pick up coil.
Read this, and see what you can further full us in on . . . .

http://www.icantclick.org/gallery2/d/91534-1/WB230_WB240+users+manual.pdf

73's de Edd
...

 

[MtnMann]

Yes, I do have the whole unit although I live in two places and presently only have the board and power supply with me. I do have a copy of that manual but it leaves a few things sort of ambiguous.

I may have assumed something that is not correct... I thought the display should read the settings based on the only video I found which was of the next model - WB250. But now I found a youtube video of an actual EB230/EB240 and it looks like the display does not reflect dial settings.

So I guess I was over thinking it. The only thing that appears to be malfunctioning at this point is the calibration mode. Snap-On says in the manual that it should not normally be necessary. It is supposed to say "CCC" on the display but mine just goes into the error mode ("EEE") immediately. Oh well, unless a Snap-On engineer sees this, I may just need to live with it as is...

 

[mr fixit]

I googled the brand name of the PCB and came up with "Balco" (link: http://www.agequipment.co.uk/johnbean/b9000.html). That's for their model B9400. Your snap on unit may be a rebadged model? Does yours look like the one in the picture?
maybe an email to them might shed some light?

 

[MtnMann]

Thanks for the input... The John Bean line is a line of Snap-On equipment but I believe it started after my machine was made. That one you found seems very similar to the WB250 which is the model after mine. Definitely more advanced with a dual display and that's the one where the display does actually read out the settings on the dials.

 

[MtnMann]

In case anyone needs this info in the future on a Snap-on WB230/WB240, I've learned the automated calibration procedure can only be entered from the "Fine" mode (after zeroing out a wheel). At that point a 3oz. weight (100g weight in gram mode) is added at 12 o'cock on the outer side of wheel (with both right arrows lit). Then with "000" lit, press calibration button (accessed through hole in back of panel). Spin a balance cycle as many times as "CCC" appears (at least 4x) until the 3.00 (or 100g) calibration weight value shows on outer with "000" on inner. So I guess my balancer is working. It was just a lack of available info on it that was making me question its working status.

 

[kellys_eye]

Thanks for taking the opportunity to update your progress. It might save someone else some hair-pulling!