| Electronics > Repair |
| Fluke 89 IV - repair after input overload |
| (1/2) > >> |
| ve7xen:
I got what I thought was a good deal on a 'working' Fluke 89 on eBay. Turns out that many of the input protection devices have been blown (see attached photo). It doesn't look like this would be too hard to repair (there doesn't appear to be any damage to the traces or upstream parts), but I'm not sure what replacement parts would be suitable, or if it's just plain a bad idea. Any advice? |
| vtl:
Does it power on? Hopefully the overload didnt reach the processor. I suppose the most obvious thing to do is start desolding all the blown components and soldering in new ones. Just look at the component markings to find out what they are and you can decide to either desolder it and leave it (MOVs only short under HV) or replace it (input resistors). They don't have to be up to the same spec, you can just solder in anything functionally equivalent. You probably would rather verify the meter is working before ordering high quality replacements. |
| samgab:
I'd start with the two resistors that are either cracked or visibly discoloured... |
| ve7xen:
The meter does power up and seems to work otherwise. The current ranges seem to produce reasonable measurements as well, though I haven't tested it extensively. So far I've determined: The 10R resistor has gone open The 100K resistor measures OK, but I'd replace it anyway The 1K SMD resistor has also gone open What I'm not sure about: The part that has blown in half - I think this was a MOV? Thus the meter should work with it open, yes? The yellow part beside it - is this also an MOV? It appears to be damaged, but if it is open I think just replacing the resistors should restore operation. I didn't realize this was a 4-layer board and there is what looks like could be internal damage, but it's hard to tell at this point. A schematic would be helpful... Thanks for your advice! |
| vtl:
Service manual on the fluke website is pretty useless. Only has calibration procedures so no schematics unfortunately. The thing thats blown in half I think is a PTC resistor, I could be wrong. If its open, short it out with a piece of wire and see what happens. |
| Navigation |
| Message Index |
| Next page |