JUMA TRX500 half alive, no tx output

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JUMA TRX500 half alive, no tx output

Postby HB9FND » 19 Jan 2013 11:32

Electronic can be cruel sometimes... :x

Well, after finding a hiden solderspot (which should not be a solderspot and of course hidden on a stupid place "behind two pins of the processor"my juma trx was starting.

So far the trx seems to work abit, but there is no TX output.

Following things are tested so far.

Pin 18 of the processor generate the buffersignal while pushig the paddle.
This signal will be present at pin 13 of J3 on the control board.

On the main board J3 Pin 13 there is the buffersignal present and as well its present at following points on the mainboard: pin 5 of the IC5, Pin 14 at ic 4 Pin,

On the IC-6 Pin 4 the supply voltage is present.

Any suggestions?

regards HB9FND
Posts: 3
Joined: 15 Jan 2013 20:03
Location: Switzerland

Re: JUMA TRX500 half alive, no tx output

Postby VE3GSO » 25 Apr 2013 01:12

I've built and got working two TX500 Juma Kits. On the second unit there was an error in the IC shipped. Instead of the 74LS04, which is a buffer inverter, the chip was a 74S14, which is a Schmidt trigger. The chip oscillated at about 80kHz and took out the fuse. Replacing the chip with the correct part got it working. But before That error I went over both boards with a very careful examination and a very good magnifier. The slightest solder splash can take it out.

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Joined: 06 Jan 2013 19:38
Location: Canada

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