Fixing Stuff: First up – a TenTec 645 CW Keyer

Figure 1: The ball bearing assembly, extracted from the old keyer

The old TenTec Ultramatic keyer is still used today by many amateurs, including myself. Its Ultramatic keyer mode was born in 1953, and later overtaken by the Iambic A and B modes. I still use two of these keyers that I am lucky enough to own, but one recently needed a repair. In the video shown in figure 2, you can watch a 35 second walk-thru of the disassembly and repair.

Figure 2: A quick walk-thru of the TenTec 645 keyer fix.

The old 645 has two ball bearings – one for the dah paddle and one for the dit paddle. It was/is a well designed keyer. These were pretty good sized ball bearings that were used, and are usually found to be in good shape in spite of the age of the keyer.  Over time, the plastic housing that encases the ball bearings can develop small dimensional shifts, or a paddle endures excessive pressure at some point during usage.  The ball bearing attaches to a contact lever arm, which just barely misses the edge of the housing opening.

In the video, you can see me playing with the lever arm.  Occasionally, it can be seen to stick in the up postion.  This is bad because the only way to overcome the stickiness is to crank up the electomagnet’s power level via a control on the rear panel.  This makes the contact stick to the magnet itself, which makes more than one dit or dah impossible.

So, the lever arm must flop up and down with absolutely no resisance whatsoever.  Fortunately, there is a screw adjustment on the contact lever arm where it attaches to the bearing.  The arm can be moved ever so slightly away from the housing, and retightened, so that there is no longer any possiblity of sticking against the side of the housing.  Put it back together, and presto – the keyer runs like new.

The main logic board in the keyer pulls out as one piece, just like in all the other TenTec gear.  One caveat I should mention – the old tape on the electro-magnet coils sometimes sluffs off of the coils due to age (mine did).  Then – the coil wires are easily broken (yes – I did that).  Fortunately I was able to solder them back on – thanks to a lucky break (pun intended) that left me with enough coil wire without needing to fully unwrap the coils.