Good day all.

I am trying to find the fault with a DC Motor Speed Control Unit.

I am thinking the fault is with the VHF 28-08io5 Half Controlled Single Phase Rectifier Bridge.

Can someone please advice how I can go about testing this part.

Thanks for your time.

Best Regards.

 

Try this from our E-book - http://www.allaboutcircuits.com/vol_3/chpt_3/2.html

Since the component you have is really five diodes, the tests must be done that many times, using the part schematic to identify the pins.

 

Thanks for your reply.

I know how to test standard diodes and standard bridge rectifiers, but this unit is a "Half Controlled Single Phase Rectifier Bridge"

I have never come across a unit like this before so I am unsure how to test.

I would guess that you need some kind of input on pin 1 and 3 for them diodes to work.

Can you please advice.

Best Regards.

 

For the non-controlled side I get the following test results.

Pin4 & Pin8 = No Reading.
Pin4 & Pin8 = 514.

Pin6 & Pin8 = No Reading.
Pin6 & Pin8 = 513.

Pin2 & Pin8 = No Reading.
Pin2 & Pin8 = 510.

 

The device connected to pin #1 and #3 is an SCR, so you need to find how to check it - http://www.allaboutcircuits.com/vol_3/chpt_7/5.html