The Problem

One of the more common failures in the T-368 has to do with safety interlock design. The T-368 has 4 interlocks, one on each deck, and an additional one located in the center of the rear cover. These interlocks prevent HV being applied if a deck or cover is open. Over time these interlocks corrode  and cause all sorts of problems.

The fix often applied is to simply bypass the interlocks with a jumper. This does work well, and takes little time to implement, but leaves the unit in a potentially hazardous condition. Ott makes some suggestions here that may help with the problem…

Interlocks by Ott Kazott

With regard to intermittent interlocks. Boy, what a miserable design. While I have removed my locks I did leave the one on the HV deck. This was done as avoid “807” fatigue and possibly bringing up the HV with the drawer in the “out a bit” position and the spring loaded B+ shorting bar in the “bad” position.

I have found that if a person wants to continue to use the locks their reliability is improved somewhat by using aluminum/copper conduction grease employed by electricians in houses where aluminum and copper wire are joined.

I have been told that the grease is supposed to have sintered zinc dispersed in it and the sharp zinc particles actually cut into the metal when pressure is applied giving a better connection and the grease prevents further air contact and oxidation. Just a little goes a long way.

Unfortunately, the limiting factor here is that the lock’s springs are capable of at best, limited contact pressure.

(After the springs have been heated up by the high resistance in the contact they to lose a great deal of their temper/tension, compounding the problem. -KG2IC)

Most people pull yearly maintenance on bigger stuff so its a good time to service the interlocks.