![]() ![]() In the event it will mess up the ADC settings (MAX134) and the common connection signal to RN1 (see the evaluation kit schematic).A description of a consumer’s right to a ”cooling-off” period is specified under the section ”Distance agreements - Consumers rights” under Terms of Service.įor all products from the standard product range, in their original packaging, still unopened (also applicable for CD/Software covers), the ISS Group accepts return and refund within fourteen (14) days from date of invoice. Rotary switchs are well known to fail over time! Thus trace it back to see who is responsible for that voltage switch.Īlso this evaluation kit schematic can shad some light. Likewise, pin 24 should not be alternating, it should remain in a stable value. Take RN1 out and check if it's the MAX134 that is (wrongly) pulling that pins to ground. If pin 25 measures 2.95V then pins 26 to 28 should not read 0V since they're connected thru RN1 to a common point. So, I am wondering if the problems I am experiencing are caused by a fault in the MAX134 A/D Converter IC (U2 on schematic diagram) or in the microcontroller (U1) that tells the ADC what to do, or some other componentry on the board? When there is no voltage to be tested at the probes, pins 24 to 28 should all be reading 0V. My limited understanding of this IC is that the ranges are determined via attenuator switches inside, which are linked to an external resistor network at pins 25-28 (RN1 on the DMM schematic diagram), and the voltage to be measured entering the IC at pin 24. I have attached the data sheet for the MAX134, the schematic diagram of the Protek 506, and a pin configuration diagram for the MQFP-44 version of the IC, because it is not shown on the datasheet. So it seems like the fault may lie within this A/D Converter IC. I've checked out the components leading up to the A/D Converter IC, which is a MAX314CMH, in a MQFP-44 case (Metric Quad Flat Pack 44 pins). It should be showing 3V or less, which is the voltage used to do the diode test with. The Diode Test Function is stuck on displaying the word "OPEN" and the accompanying voltage of "3.999V". So that indicates to me that the fault is with the 4V range. If I test a 9V battery, the display shows a steady 9V. If I test a 1.5V cell, the display alternates between 3.999V and 1.5V. ![]() When I select the DC voltage function on the rotary switch of this DMM, the display alternates between showing 3.999V and 0V. It seems that the Diode Test problem is linked with the 4V range Voltage Measuring problem, so I shall just focus on the 4VDC range to simplify things. I have posted this on three other forums, but have not been able to find out the source of the problem. I have a Protek 506 DMM which has a problem with the Diode Test Function and with the 4V range of the Voltage Measuring Function. ![]()
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