[TenTec] Orion II A9 power board

[gunnerjuulnyholm at me.com]

Warning.

My O2 has been a little unstable lately. and today I decided to change the 470 µF capacitors on the A9 board. The old ones were not entirely flat on the top, so ??  They were somewhat difficult to get out, but by pulling the capacitor firmly the terminals came out of the capacitor body, so I could pull the leads out of the holes with a tong while applying some solder on the other side. I could suck nearly all the holes free of old solder, but a couple could not be cleaned. Besides, my new capacitors had leads 0,8 mm diameter, and could hardly go through. So I took my little drilling machine for PBs with a 1,0 mm diameter drill, and cleared the holes. The new capacitors had a diameter of 11 mm, so I had to bend the leads a little in order to make room for them. No sweat.

Everything was assembled again, and power on. - The radio didn’t work. No light whatever in the display.
A voltmeter revealed just a fraction of 5 Vdc on the connector. The can of C9 had a voltage of 10,3 V, and no point on the upper part of the board had a reasonable voltage. Hmm. Wonder if T-T still have A9 boards?

Well, I hadn’t done anything but changing the capacitors, so back to the performed handiwork. Control measurements revealed that the capacitor leads didn’t all have the same voltage as the lead on the board, so clearly there were missing connections. It turned out that by drilling the holes free I had also removed the plating through the holes, and removed the connection between the two sides of the board. Besides, the minus lead on C9 required a bigger iron to heat the copper plate on the board to make the solder flow properly.

Luckily I had had to bend the leads and therefore had 5-8 mm lead between the board and the capacitors. I could therefore solder the leads on both sides of the board and thus reestablish the connection through the holes again. - Now the O2  works fb again.

My warning is, that if you have to drill the holes then leave ample distance from the capacitor to the hole so that you can solder the leads on both sides of the board. Next time I will use at least 10 mm. It does not at all have to look neat, but makes the soldering easier.

73
Gunner
OZ6NF