Comparison of multimeters PROFESSIONAL and MASTECH

Comparison of Master PROFESSIONAL and MASTECH multimeters made in Hong Kong. Support.
A lot electricians and radio amateurs use inexpensive digital multimeters M-830V, M-832 and the like. It is impossible to imagine the desktop of a repairman without a handy inexpensive digital multimeter. This article examines the 830 Series Digital Multiset, the most common malfunctions and their elimination methods.
M830 Series Digital Multimeters
The M830 series digital multimeters (M830B, M830, M832 and M838) are designed for use in laboratory, workshop, radio amateur and home environments. The M830 series is one of the most popular series. The multisets have LCD 31/2 digits (maximum number displayed 1999).

Multimeters designed to measure: DC and AC voltage, DC current, resistance, temperature (for model M838), diode test and transistors, continuity of connections (except for M830B), power supply to the tested meander circuits with a frequency of 50-60 Hz (for model M832). Provided indication discharge batteries «BAT» and overload input «1».The dimensions of the multimeters are 125x65x28 mm. Weight — 180 g. The multisets are designed according to the safety standard IEC-1010 category II.
If we compare printed circuit boards of multimeters of similar models MASTECH and Master PROFESSIONAL, you can see both well-known COBs (ADC with open frame). But, PROFESSIONAL master, unlike MASTECH, left printed lamellas for a standard 40-pin ADC 7106 or our analogue 572PV5A (V). As can be seen, replacing such an ADC, and according to experience, ADC failure often occurs, and is not a difficult problem, especially since there are now enough descriptions in the literature for repairing multimeters of this class.

Master PROFESSIONAL allows ADC replacement in all instrument models. And from the whole spectrum, ordinary MASTECH multimeters, unfortunately, can be repaired at 100%, only a few multimeters remain.
In addition to simplifying the ADC, MASTECH has unified some device series. For example, the M89 series (a very popular series due to its optimal price and features) became similar to the MY6 series *. Same indicator, same limits. They denied the M89 not only a convenient indicator, but also the automatic shutdown of the device.
Now compare with PROFESSIONAL Wizard. It has in the same popular M89 series, the old indicator with an indication of all operating modes and measurements (capacity, resistance, current, etc.) has been preserved. Two models have automatic power off.
For example, a mistake is made that leads to the failure of the multimeter: on the ohm stuck in high voltage - the ADC is on ...

When repairing the ADC device, replace the microcircuit with the KR572PV5 microcircuit (domestic production), it is completely suitable, only this (Chinese) is not in the form of a droplet, there are no known analogues for «droplets».
Comparing devices from the brand MASTECH and Master PROFESSIONAL is not unambiguous to claim which is better or better.

Both these and other models use the same electrical circuits. similar models, with standard protective elements of both MASTECH and Master PROFESSIONAL. Both manufacturers follow the path of simplification, and recently "droplets" are found in both.
And now for the case!!! The price difference is immediately apparent.
You can also add that the Master PROFESSIONAL multimeters (a brand later introduced to the market) due to their high quality and relatively low price, gained great popularity.
Below I will give a table (the information I agree with is taken from the website of the company Febras) in which some possible problems and their elimination are indicated:

Malfunction multimeter

Possible reason

Repair

Multimeter display during all limits show random numbers much greater than zero

Defective ADC multimeter

Replace the ADC

The device overestimates the readings

The battery is discharged

Replace the battery

The temperature is measured with a multimeter only with a thermocouple

Blown protection 200 mA

Replace the fuse

Individual segments are not displayed on the multimeter display

In older model testers, there were cases of the LCD display being poorly pressed against the tire under tension

LCD glass glue (under the clamping frame) a strip of electrical tape

Multicet series M830:

1.When measuring, the voltage tester overestimates the readings, goes off the scale, may not reset

1. Burnt R6 (100 ohms), most often;

2. Burnt R5 (900 ohms), this happens less often. Visually, the resistors may appear intact.

Replace. Check emergency resistors.

2. When measuring voltage with a multimeter in the upper limits, strong underestimation of the readings

Leakage seepage C6 — 0.1 mF

Check by replacing

3. When measuring resistance with a multimeter (ranges 200 Ohm, 2 kOhm) slow counting, gradual reduction of readings

Defect in C3 — 0.1 mF

Check by replacing

4. When measuring resistance with a multimeter (ranges 200 Ohm, 2 kOhm) slow counting, gradually increasing the readings

Defect in C5 — 0.1 mF

Check by replacing

5. When measuring, the readings float with an AC multimeter (20 — 40 units)

Capacitance loss C3 — 0.1 mF

Check by replacing

6. When measuring with a resistance multimeter, the display shows zeros

Broken transistor Q1 (9014)

Replace

7. Problems with measuring resistances, other modes work

Defective resistor R18 (2 ohms) — RTS

As a last resort, you can replace with the usual resistance of 2 kOhm.