Not so long ago, for the repair of most equipment in home conditions, it was enough to use a traditional arrow tester. In the most difficult cases, an oscilloscope was used. Time passed and the arrow devices began to be replaced with digital ones. And today the digital tester has an intellectual competitor – a multifunctional tester of radio components, based on a microcontroller. So progress, development of the element base and IT technologies force us to acquire new devices.
Indeed, in testing more complex radioelements – MOSFET transistors and optocouplers, in determining the ESR parameters of capacitors and inductance of coils multimeter will not help. Of course, some of these parts can be checked by making additional special attachments for the multimeter, but today it is easier to purchase a relatively inexpensive universal radio component tester that will check these and many other parts in a few seconds. Moreover, it will do it automatically, with high accuracy and will give more information about the element.
In addition, yesterday and today, the radio amateurs' pantries are replenished with radio components extracted from discarded, but quite workable “obsolete” imported household appliances. The modern consumer society actively contributes to this.
Such details sometimes do not have marking or it is peculiar, each company has its own. The performance of parts is often unknown, and the functions and structure of some elements are at first glance incomprehensible. Therefore, before installation, all these parts must be checked, although today it does not hurt to perform this operation on new parts. In all these cases, a radio component tester can also help.
Advertising of the LCR meter tester mega328 (transistor tester, Markus tester, multitester, ESR tester, etc.), a successful Chinese clone of the German brand Karl-Heinz Kübbeler “transistor tester”, on specialized sites is extensive and attractive. There are also many positive reviews on this gadget on the Internet.
For the reasons listed above, I also had a desire to purchase such a device. On AliExpress I looked at a more or less modern model tester LCR meter mega328 М8 … However, the other day I went to a local radio store and saw this tester on the shelf. He reasoned that waiting a month for a parcel with a “pig in a poke” is inappropriate when the target is near, and the expected losses are small, no more than 200 rubles. The store checked the tester's performance and gave the traditional two-week warranty. In the evening of the same day I already used this tester.
Open-frame tester LCR-meter M8 made in China, made on the mega328 microcontroller. The tester has generic item inspection capabilities similar to earlier models, but there are advantages.
There are no problems with power supply from the Krona, since this tester from birth is powered by a 3.7V lithium rechargeable battery model 14500. At the same time, it can be powered and simultaneously charged its battery via a USB port (5V) from an external power supply (adapter) for a smartphone … The kit includes pluggable test leads that allow you to check parts on boards.
But there is also a traditional flaw in the design of the tester, its open-frame design. It is surprising that with such a scale of sales (tens of thousands on many models), they do not want to organize the production of a penny molded plastic case. And this is nowadays, given their capabilities and talents in copying, for example, similar products – plastic toys.
Of course, one can do without a case in measurement. But it is difficult to imagine on a desktop, an open tester board, with unprotected contacts and a fragile screen, surrounded by metal tools and parts. In this case, it is unlikely to save an open tester from breakage. Therefore, the case is still needed, and in order not to damage the device, we will make the case ourselves.
Making the case
To protect the tester from damage, we will install it in a plastic box of suitable dimensions. As a case for the tester, the case from the PNT-1 device was well suited for setting color TVs. Using this device, it was possible to control the linearity of the sweeps, check the convergence of the beams of masked tubes, control the color purity and check the white balance. But the age of CRT has passed, we are using the body of a device that is no longer needed for a new purpose. The overall dimensions of this case are 115 x 80 x 30 mm.
2. Modification of the body blank
The location of the mounting holes in the workpiece of the PNT-1 case is slightly different from the coordinates of the mounting holes in the tester board. Therefore, I had to slightly cut the mounting holes in the case and cut one mounting pad to accommodate the leads of the board elements.
Structurally, the tester board is complete plastic feet placed in the four mounting holes in the board. The height of the legs and pads in the case turned out to be close in size, so we remove three unnecessary legs from the board and install the board on the three existing pads of the case. The fourth leg-support in the board will perform its function.
Installing the tester board into the housing and pre-fix it with threaded spacer sleeves from old multi-position switches. It is also possible to mount with screws M3 x 30 mm.
One of the problems noted by many is the inconvenience of using the tester's control zone. Contact pads and connectors are located close and low in relation to the screen, which is very inconvenient for measurements. Even the newly introduced measuring probes, the protruding wires of which interfere with the use of adjacent contacts, do not help much. For this reason, in the manufactured structure of the case, we will move the control zone outside.
For ease of use, we will place the contact pads on top of the case, and the connectors for measuring probes on the side wall.
In accordance with the location of the elements of the installed board, we mark on the case the location of the window for the USB connector for connecting the power, as well as the position of the holes for the installation of three connectors for measuring probes.
Remove the tester board, process the marked holes in the case and install the board finally.
3. Processing the upper part of the case
Let's move on to processing the upper part of the case. In accordance with the actual position of the installed board, mark the location of the window under the screen on the case cover. At the corners of the marking rectangle, in relation to the lines, we drill holes with a diameter of 3 mm. Using a cutter, cut out a window for the tester screen. We will perform locksmithing and surface cleaning.
Using a cutter, focusing on the internal dimensions of the case, cut a rectangle of plastic from the transparent part of the DVD box to protect the screen. Alternatively, you can use plexiglass 1 … 2 mm thick.
Transfer to the housing cover, coordinates of the location of the power switch and the button for starting the test cycle, in relation to the dimensions of the case. Similarly, mark the location of the two signal LEDs (“Charging”, “TEST”). We mark the center of the holes with an awl.
We select multi-colored buttons. The power button 12 … 14 mm long must have a hole with a diameter of 3.0 … 3.2 mm at the bottom for fixing it on the switch.
The button for starting the test cycle consists of an M3 screw with a flat head and an upper decorative part of the button with an internal thread. Inside the case, the button is oriented by a weak (3… 5 g) spring.
Drill marked holes in accordance with the diameters of the prepared buttons.
Free top we use a part of the case to place the contact pads and a group of spring-loaded contacts.
The contact pad consists of three parts, made of foil-coated PCB and glued to the body with glue. It is designed to inspect SMD and other parts when testing by touch.
To install parts in the connectors, a shoe was used, previously intended for installing and replacing microcircuits in a DIP18 case without soldering.
The socket for microcircuits is installed on the case using drilled holes with a diameter of 1.5 mm.
4. Assembling the tester
Glue the protective glass on the case cover. Let's modify the glass in the area of the holes for the buttons.
Reinstall the three connectors for the test leads and solder the pieces of copper conductor with a diameter of 1.0 mm to them. Firmly insert the free ends of the wire into the small diameter sockets on the tester board.
Drill 1.0 mm holes in the corners of the contact pad. Through these holes, from the inside, we will bring out the conductors and solder them to the elements of the site.
On the inner side of the case, we divide the socket contacts in the socket for microcircuits into three groups (1, 2, 3). Contacts, in each of the groups, will be connected together. Let's connect each group to the corresponding elements (1, 2, 3) of the contact pad.
Install the buttons back and assemble the corpus completely.
5. Check in progress
We charge the battery through the adapter. In this case, the tester can work. The indicator stays on until the end of the charge or work.
We are testing the transistor.
Testing the LED.
The question/topic is automatically published in the social. site network – follow the answers there too: