Products > Test Equipment
Protek 608: Fried by a "69"
k1mgy:
30 years in electronics did not insulate me from this beauty - something you should NOT try at home. I determined that I should use my (once-functioning) Protek 608 handheld DMM to measure its own battery voltage. Why? Well, why not?? I simply wanted to know if it was time to replace it. Selecting VDC and attaching the probes across the 9V cell yielded a sput sound and a blank LCD display. Dead as the proverbial doornail. Doing a "69" with a multimeter is apparently not a good move.
It would be lovely to resurrect this meter, but a schematic is no where to be found. Anyone listening have access to it?
Or perhaps some tips on where to begin looking. Empty head calling for help.
No burn marks or odours to follow for this one. It's a mystery.
Nerull:
It's kind of amazing just how many stories there are of this exact sequence of events.
electr_peter:
Short answer - do not do it.
Such topic was discussed before on this forum dmm-reading-it's-own-battery-voltage-low-voltage-detection/
k1mgy:
I've taken it apart (in Dave Jones speak), found no issues, re-assembled and now the meter powers up. It's been quite a while since the initial damage and my memory of the event may be fogged in so perhaps it powered up before -- or maybe there was a mechanical issue. Anyhow, it has life, but is otherwise no good GOP.
Symptoms:
1. DC mode: 0.0000v indicated and does not move with input; 10.50 Megohm shown in secondary display and does not change when shorting leads
2. AC mode: 000.00 mv indicated and does not move with input; 1 Gigohm shown in secondary display and does not change when shorting leads
3. Ohms mode: 00.00 Ohms indicated; 2.5V shown on secondary display (1/2 of 5V vcc?); LCD display dims slightly when shorting leads with no other change shown
4. Capacitance mode: main display shows no digits and is constantly toggling between uF and nF; 2.5V shown on secondary display (1/2 of 5V vcc?); LCD display does not dim when shorting leads as it did in Ohms mode
5. Hz mode: display moves about in a range around 30Hz with 000.00 V on secondary display. The LCD display dims slightly every second, and just before the Hz display is updated. Holding the POSitive lead causes the display to read around 120Hz
6. Diode mode: 00.000 V indicated; 1ma on secondary display; Shorting leads dims LCD display slightly;
7. Microamp mode: 0000.0 uA indicated; 100 ohms on secondary display; Shorting leads has no effect
8: Milliamp mode: 0000.0 uA indicated; 100 ohms on secondary display; Shorting leads has no effect
9: Amp mode: 00.000 A indicated; 0.01 Ohms on secondary display; Shorting leads has no effect
The meter has a single A/D converter, a Cirrus Logic CS5508BSZ, which is a nice but expensive (around $20 usd) part. Might be a reasonable gamble to replace it, or perhaps (a bit tricky due to meter construction) lift the input and test the device independently. Although, given the symptoms being so widespread, it seems reasonable that the damage is in this part.
Anyone care to speculate along with me? Anyone have access to the schematic/service manual? How about a cheaper source for the A/D converter? Looks like Protek is out of business, which is unfortunate as this meter is a mid-range cost, high quality unit with a good set of specs and features.
Alex Eisenhut:
Is it your only meter? Because the paradox is you should measure power supplies first.
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