I am using a 115V variac for now. I could run it into a step up transformer if required but I only ran the AC input up to about 70 V RMS


I did run about 700 V of HV into the rf deck earlier this afternoon so there are no hard short circuits in there.


I have the power supply power supplying the low voltage into the amp right now. I will change the tubes tomorrow and power it all up I think. I suspect the old tubes of maybe being soft and arcing over inside on random occasions.


Mark N1UK

Can that damage the tubes?

Mark N1UK

Can I hook up the rf deck and just wind the variac on the psu a little to check for rf deck problems? Can I do this with with and without the tubes in place?

Mark N1UK

Sounds like the auto tuner would do better if it was installed between the antenna and the feed line up on the tower


Mark N1UK

I used the solder wick as a copper conductor, laid down on the board to repair a blown trace.

I much prefer my solder sucker when it comes to removing solder and components.

Update....The new board is built and wired in. I am applying approx 60 VAC in from the variac and have 600 VDC on the output of the board. I will let is soak for a while.

http://img829.imageshack.us/img829/8499/dscn8831a.jpg

http://imageshack.us/a/img59/1062/dscn8829.jpg



Mark N1UK

I like to have control of my station and all my tuners are manual. They generally have better power handling capabilities and are cheaper.

I will probably never have an auto tuner, they just don't meet my operating requirements. That said, auto tuners are useful if you are using them in a remote setting such as at the base of a non-resonant vertical.

Mark N1UK

I hooked up a variac to the transformer primary, bypassing the soft start circuit and on/off relay and I was able to apply approximately 25VAC and see 214 VAC on the HV winding. So so far so good. I will rebuild the HV bridge rectifier and smoothing board and wind up some voltage onto that next.

Here is the schematic for the PSU. Mine is slightly different to this. Soft start resistor is 10 ohms, and the combined rectifier smoothing pcb is different but the main details are the same.

http://www.mediafire.com/view/?d8117dib1zyjqt5

Mark N1UK

Amps is amps, so it shouldn't make any difference. Is it basically a current transformer?

However you never know..something to investigate


Mark N1UK

I have a Fluke 80K-6 6kV 1000:1 probe. It takes the guesswork  right out of it. Not for the untrained.


Mark N1UK

I am moving..hi hi . Fixed plumbing this morning and now I want to hook up the variac and wind it up a little to check everything before I replace the pcb.

I will repopulate the pc later today. and wire it back in and then variac test the psu assembly without the rf deck connected.

Maybe time to add a whole house surge protector as well. I have two 200 amp panels. So it will be two surge protectors. Any advice on a good one to fit?


Mark N1UK

Did you actually measure the HV line with something like a high voltage probe or are you relying on the internal metering?


The internal metering using 4 resistors to pot down the voltage. If the value of these resistors has drifted then your reading will be inaccurate. The original carbon resistors have most likely changed value over the years. One of mine was open circuit and the other two had changed values. I replaced them all.

As always be mega careful working around HV. You won't get a second chance.



Mark N1UK

Since I took that picture I l flowed some more solder down because I thought that it was a bit thin as well.

I used solder wick and maybe you are seeing the slightly serrated edge of the solder wick catching the light of the camera flash.  The solder wick on the top trace is really overkill because there was only a small area of trace burnt away but I wanted to make doubly sure.............................

OK I added more solder.  Here it is

http://img689.imageshack.us/img689/8674/dscn8804u.jpg


Mark N1UK

There seems to be a corner missing from the trace.  Probably not burnt but missing I think. It is where one of the electrolytic caps connect. I will make sure that there is enough meat there when I replace that particular capacitor.

Mark N1UK

I repaired the two traces this afternoon

http://imageshack.us/a/img822/2865/dscn8798j.jpg

http://img855.imageshack.us/img855/1133/dscn8797.jpg

Mark N1UK

Yes that is very possible. Anyway I have a complete set of new parts for the board. I like to get in there once, fix it properly and move on.

The capacitor bleeder resistors are two (150K 2 watt) I think in parallel. They all look good and test OK. Tentec now fits something 35K or 40K 2 watts but installs them in series. Most likely for the voltage rating on the resistors. Since mine are still good I am tempted to leave the parallel combination in service. What do you think?


73 Mark N1UK