The AM Forum

Hi All
I'm new to this fantastic forum and wondered if somebody might be able to offer some advice about my ART 13.
I aquired this rig a few months ago and initially it seemed to work fine. For some reason it seems to have started playing up with poor grid drive to the 813 and reduced power (10w) also it has now developed a short on the HT (400v) of 9 ohms when in the calibrate mode only. I ve done the usual things like change the tubes in the pa and multiplier and had a good look through it with all the panels off but cant see anything obvious. Any ideas?
73
Justin
Swansea UK

May I suggest following the wiring harness schematic in the tech manual? They are great with wire colours laid out and shows you how many wires are connected to just that component etc. With the 400v short only in "calibrate" you have a good starting point. The wiring diagram helped me a lot when I was working on my '13 which had lots of "loose ends". One possible thing with low grid drive might be the wafer switches in the multiplier section.
//Tommy, SA2CLC

J,

 You may find this site to be of interest.

http://bama.edebris.com/manuals/military/an-art13/

Keep us in the loop,

klc

Thanks for the replies. Yes, have a circuit diagram which I have been following, not the easiest I must say. The multiplier wafer switches appear OK but again with limited views. I did spray some dioxit on the contacts. Anyhow, will keep looking.

I'm sure you will find the culprit.
One thing that helps is to print the diagram on a large piece of paper and laminate it. Makes it durable and easier to follow. You can also use an erasable marker pen (cannot find the correct english word for it in my vocabulary) to track the progress.
//Tommy

Dry Erase Marker is what we call it on this side :-)

--Shane
KD6VXI

Well, I think I have traced the source of the problem...the dropping resistors that supply the HT for the audio amp and MCW unit. Talk about being in the most inaccessible and awkward part of the rig. It looked like the mounting screws for these resistors had become loose and the resistors wobbling around inside. I had to unpick a lot of the wire bundles and follow the offending wire down to the resistors; in order to get at them, I had to remove the frequency multiplier section which is a complete nightmare. Anyway, now to put it all back together again!!! ???

Justin

Suggestion: Go to hamfest and find some Jones plugs and sockets and make your own cable extenders with some hook up wire. You can check / test the modules outside the rig next time. Seth KC2WE

When I got mine, it had a harness short in the very tight area near the J108 main power connector U7/U. Wiggle and it would go away. So I jammed it so it did not short and sprayed it with some horrific stuff I got back in the 1980's from work that was used to conformally coat wires. Let it soak in and removed the jam and it has been happy since 1992.

Here is one of those home made jumpers. I was working on the audio module.