Testing Points

Some Pilot Production And testing points when building electronic Projects

Components

• Use 1% MFR 100 ppm resistors for all analog instrumentation.
• Use plastic or-and multilayer capacitors as ceramics are leaky.
• Product should have minimum number of fasteners.

Assembly

1. Nuts, Bolts and screws locked with adhesive so that they do not slip and the product falls apart.
2. Potentiometers should move smoothly and not get twisted, strained or locked due to cabinets.
3. Use Strain relief for wires and strip the wire and solder properly where required.
4. Strip with a stripper do not use your teeth., Twist all the strands Tin the tip of the wire.
5. After Tweaking and setting presets or trimpot lock it with paint or varnish.
6. Big Components should have large pads and separate mechanical fixing to PCB.
7. Acrylic and plastic can get blurred or deformed with some solvents.

Testing

Do assembly of the card with a tested assembled 3D reference. Even after all the care if the card does not work, then after full assembly do visual inspection in this order First keep both the cards one reference and the other manufactured under a bright light.

• Compare resistor color patterns one by one.
• Compare Electrolytic capacitors physical appearance and POLARITY.
• Verify values of plastic and ceramic capacitors.
• Cross-check Diode sizes and POLARITY. Verify Zener values.
• Check IC and Regulator POLARITY and Exact type number / brand
• Check Transistor, MOSFET, LED, POLARITY. and verify display type No. and Polarity .
• Check for connector patterns and polarity and switches etc.
• Reverse the card and Check for solder bridges between close pins .
• Reverse card and Check for hairline shorts and solder streaks due to bad PCB processing or Soldering.
• Reverse card and check for hairline cuts or pads lifted off card.
• Closely observe for dry solders on big electrical parts (L and TX) a dry solder will cover the pin and will be dull in shine.
• before calibration allow for product to warm up for 15 mts.

If all the components were subject to incoming inspection and testing. If still unit does not work remove power and do cold check comparison with reference unit in DMM 200K R range, if still problem persists continue with power on testing and solve by DMM or scope tests.

Danger ! when DMM is in Ohms Mode, Even if one probe touches 230 V, DMM is Gone, so take extra care while doing this. test probe.