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Repaired my ATU
25 December 2015 | by Merry Christmas!
Not wishing to contend with an evening of dire XYL style Christmas TV (Strictly Come Dancing, Call the Midwife and Downton Abbey) I escaped into the shack and decided to repair my Vectronics VC300DLP Antenna Tuner. I got this ATU second hand last year and while it has been serviceable it had become temperamental of late. The units rotary inductor switch had become stiff and suddenly I was unable to match the OCFD on some bands so it had clearly broken.
I had a 12-position switch (rated at 5A) and knob, originally sourced for an abandoned project and hoped it would be suitable. The existing switch knob on the ATU wasn't an original, I'd assumed it had replaced one lost or broken. When I removed the cover it was clear that the whole switch had already been changed at sometime.
I also noticed a prominent burn mark inside the inductor coil, caused by a clear break in the insulation of the wire which was resting on the grounded bottom plate.
I know the previous owner of the ATU has a 300W RM BLA-350 linear amplifier, whereas I only normally operate around 30W maximum at my QTH, so not sure how much of this arcing I had caused but it needed sorting! A little over half an hour with the soldering iron and I had replaced the switch and slipped some heat shrink over the broken insulation and re-soldered the wire, lifting it off the ground plate.
The ATU seems to work well, now fitted with a new knob (just missing a cap at the moment) the switch turns nicely. I also cleaned up the SO-239 connectors on the back as they were tarnished and oxidised. I used a small bit of contact cleaner on some cotton buds to clean up the threads and the centre pins, removing a surprising amount of crud. The patch and antenna leads now screws on much better.
With the Mother--in-law staying with us over the festive period I suspect I may be in the shack quite a bit, I have plenty of jobs and half finished projects to keep me busy!
Andrew Garratt, MØNRD, is a regular contributor to AmateurRadio.com and writes from East Midlands, England. Contact him at [email protected].
Not wishing to contend with an evening of dire XYL style Christmas TV (Strictly Come Dancing, Call the Midwife and Downton Abbey) I escaped into the shack and decided to repair my Vectronics VC300DLP Antenna Tuner. I got this ATU second hand last year and while it has been serviceable it had become temperamental of late. The units rotary inductor switch had become stiff and suddenly I was unable to match the OCFD on some bands so it had clearly broken.
I had a 12-position switch (rated at 5A) and knob, originally sourced for an abandoned project and hoped it would be suitable. The existing switch knob on the ATU wasn't an original, I'd assumed it had replaced one lost or broken. When I removed the cover it was clear that the whole switch had already been changed at sometime.
I also noticed a prominent burn mark inside the inductor coil, caused by a clear break in the insulation of the wire which was resting on the grounded bottom plate.
I know the previous owner of the ATU has a 300W RM BLA-350 linear amplifier, whereas I only normally operate around 30W maximum at my QTH, so not sure how much of this arcing I had caused but it needed sorting! A little over half an hour with the soldering iron and I had replaced the switch and slipped some heat shrink over the broken insulation and re-soldered the wire, lifting it off the ground plate.
The ATU seems to work well, now fitted with a new knob (just missing a cap at the moment) the switch turns nicely. I also cleaned up the SO-239 connectors on the back as they were tarnished and oxidised. I used a small bit of contact cleaner on some cotton buds to clean up the threads and the centre pins, removing a surprising amount of crud. The patch and antenna leads now screws on much better.
With the Mother--in-law staying with us over the festive period I suspect I may be in the shack quite a bit, I have plenty of jobs and half finished projects to keep me busy!
2 Responses to “Repaired my ATU”
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I used to have one of those antenna tuners. Sadly it met it’s end when my G5RV suffered a near miss in a thunderstorm. A hole was blown in the side of the ATU and the FT101E was written off too. My ex-RAF morse key survived albeit with scorch marks. Two telephones were knocked out it the house and some electrical damage to the wiring. Not a pretty sight.
I have one of these tuners and I’ve been really happy with it. My unit dates from when Vectronics was part of Valor, long before MFJ acquired them. I don’t know if the construction in Ohio was any better than what MFJ does now. What I can say is that my tuner has been 100% reliable and all the switches are original. I suspect the previous owner of yours pushed the limits in terms of power with his amp. I definitely recommend the V3200DL for people who don’t run amps 🙂