Tony G0MQG Tips

Here is another of Tonys tips taken from his experience of servicing and repairing radios over the years.

Repairs to a Yaesu ft290 P.A.

I've repaired several mark 1 FT290's with no transmit output over the years.

Some time ago i acquired a Yaesu FT290 mark 1 with no transmit output.

I opened the bottom cover and removed the battery tray and unsoldered it's connections to the radio to gain access to the pcb underside, then powered the radio from a PSU. A check on the base of the PA transistor (radio keyed up, FM selected and connected to a dummy load and wattmeter) with an RF millivoltmeter showed there was RF available at the PA transistor base so it looked as if the transistor had failed (a 2SC1947)

i removed the transistor and sure enough it was open circuit base – emitter. So i got a replacement (from ebay) this got the radio working again, a slight trim up to get it back on frequency (it was about 1.5 khz low)was all that was required.

It should be noted by anyone who owns an FT290 mark 1 that it's important that the internal telescopic aerial should be fitted even if you don't use it as when retracted into the radio it slides into a grounded metal tube (but is insulated from it) so has capacitance to ground. This means that, when retracted, it forms part of the PA tuned circuit so without it fitted the PA is out of tune and so failure of the PA transistor could result.

Tony g0mqg

Christmas 2017

2017party1