Group 1 Smoke Test

When I completed Group 1 assembly of the microprocessor, display and associated parts, it was time to run through the Group 1 smoke test routine. This called for a 9v battery to be connected, the on/off switch flicked to on, and the LED display should light up with four digit eights being displayed for a second or so. This is the display test.

Well, I did that but the display did not light up as it should. This is what mine did.

The Group 1 smoke test.

So I jumped onto the forum and posed the question as to why mine was behaving as it did. In no time at all I received a bunch of very useful pointers. First check to see if all the solder connections are OK and that the through holes are actually as they should be. Some PCBs I was told were defective in this respect. So it was out with my soldering iron and I resoldered all joints, this time on both sides of the board. I could not get the tip of the iron to C50 so I removed that little cap and replaced it. Still no joy.

The members of the forum then suggested U7 could be faulty as some chips seemed not to have been programmed in the past. I took voltage measurements on all 28 pins and compared the readings with another State-side builder who was also experiencing the same results as I was. An almost perfect match.

I then asked Ray, VK4ZW to cast his experienced eye over my rig as he is also building one and is at the same stage of the build as I am. His rig past this smoke test with flying colours. So he swapped U7s around and got the same result as I did with mine in his rig. So it seemed that U7 was the problem.

A quick email to Doug Hendricks and another was popped in the mail to me. At present it still has not arrived, but this is normal for the mail service between the US and Australia.

In the meantime, I busy myself trying to work DX on my FT-450.


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