Instructables

Multimeter DIY Repair?

I have a Radio Shack digital multimeter, Model 22-174. Since the 10 Amp measurement circuit is not fused I blew this circuit and that part of the meter does not work now. I like this meter and would like to know if I can DIY repair it and what I need to do. I have looked around the Internet and have not found any information including the Radio Shack site. Was looking for the wiring diagram only found a parts list. I hope that I can fix it. If I can fix it I will fuse the test leads (black lead) or work out an internal fuse for this circuit so I don't repeat my mistake. Any help would be nice. Thank you.

rick5245602 years ago
It's a good multimeter, and even though you can replace it quite easily with a cheaper one, I really don't want to. My problem is a bad 1 watt resistor that sits up off the pc board a bit. It's blackened so I can't tell the value of it. My guess is that it is rather low but I really don't know. In fact I don't exactly know what happened to it, as when I left it was fine, I came back the following day and it didn't work.
Tell me where exactly it is and I will give you the value off my meter.
ottorick10 months ago
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CC0QFjAA&url=http%3A%2F%2Fsupport.radioshack.com%2Fproductinfo%2FDocumentResults.asp...
http://support.radioshack.com/productinfo/DocumentResults.asp?sku_id=22-174&Name=Meters%20and%20Scopes&Reuse=N
above title and link for manual and part list.
My meter 22-174B is stuck in overrange (display) since I replaced a fuse. I can't get it to read anything. Looking for Ideas.
nty4 years ago
Found this on internet.  Credit to Electronics-diy.com. 
May be not exactly like yours meter.
Hope this schemetic diagram can help you to trace the faulty part
meter.jpg
USUALLY, these things have a fusible shunt on the PCB, which will have burned out. Its often WWWWWWW shaped,
phantom9 (author)  steveastrouk4 years ago
Shunt is intact. See my reply to Jack A Lopez  below. Thanks
Sometimes the current measuring shunt is a piece of wire (of some kind) that jumps off the board for a few cm, then jumps back.  Some pictures of this are attached.
centech98025-multimeter-shunt.jpgcentech35761-multimeter-shunt.jpg
phantom9 (author)  Jack A Lopez4 years ago
Thanks for the pictures, my shunt is intact. No burnt circuit paths, no odd smells. I really think I need a road map of the circuit to figure this one out. All surface tech parts and a main processor chip. If I don't get it fix no big deal.
framistan4 years ago
You likely blew the internal fuse usually located next to the battery.  New users of multimeters are unsure of where the probes go since there are 3 "holes" and only 2 probes.  NEVER place any probe in the AMPS jack unless you are VERY carefull and you know what you are doing.  Because...  if your probe is in the AMPS jack and you plug meter to anything, you will either damage your meter, or the device you are testing.  The AMPS- setting places a direct short across whatever you are testing.  If you keep your meter set to VOLTS or OHMS and keep probes out of the AMPS jack... then you will not have this problem.  If you cant fix your meter, consider going to harbor freight tools. You can buy a cheapy meter for about 2 or 3 dollars.  They are decent meters too!
Re-design4 years ago
You'll have to open it up and see if you can find out which part or parts have gone bad.

Look and smell for any burned parts.  If the meter still works on ohms of voltage then the meter is not burned out.  Look at the pcb traces, resistors, switch legs etc.

If it's digital then you're going to have to be really lucky if you're going to be able to repair it.

Use another meter on resistance to check that the resistors and diodes are still good.

Even if you can't fix it, it is still good experience to try.

Good luck.

phantom9 (author)  Re-design4 years ago
Thanks, I sure wish I had a wiring diagram, or know someone else that had to do the same repair and what they replaced.