Oops, followed the wrong line across the 3 pages. S1R18 goes to A3R3/V2.
Still think my analysis is correct. If so, an ohmmeter between A3R3 and S1R12 should read 400 ohms on the 1XX ranges, open circit on 3xx ranges, and various high resistances on the uV ranges.
The strange waveform may be the amplifier missing the feedback loop.
Have a similar problem on a Fluke 845, with 1XX ranges correct and 3XX
ranges 20% off. Decided it wasn't worth the difficultly of opening and the risk of introducing circuit board contamination, so live with it.
John
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On 1/23/2020 10:12 PM, John kolb wrote:
The meter pegging indicates that the feedback path back to Q8 is open on the failing ranges.? The switch contacts of the failing ranges are all tied together and connect to 400 ohm resistor S1R18 and a wire back to Q8 base. Almost impossible that the contacts of the 3mV, 30mV, ... 300V ranges are defective and only those ranges. So the connection between the connected contacts to S1R18 must be open for some reason.
John
