Heathkit TT-1 Leakage Test??
 

I restored the TT-1 four years ago. Lately the rotary switches have become stiffer, so I pulled the chassis to lubricate them. That worked well, BUT...then I decided to rerun all the calibration and verification procedures.

To get to the point, I get mixed results on the leakage test verification. The instructions are to verify the leakage detection on any one single tube socket but I went ahead with four sockets, hoping to find some pattern. These are the results:


https://farm5.staticflickr.com/4874/...6e5a3de3_z.jpg

I'm hoping that someone familiar with the circuitry can see a pattern in these results and give me some direction. I've spent several days trying to work this out, but I can't even see the tube sockets on the schematics. Last night I even tried changing my socks, but that didn't help.

So, please, if anyone can see a possible single fault that would explain the results, let me know. Otherwise I'll put the chassis back in the box and go ahead in blissful ignorance.

Thanks,
Henry

:) Hi Henry ,

My question here would be , what did you use for lubricant , and could it have become a conductive path for the leakage detection ?

I used an all-purpose spray, and that's the first thing I thought of when I got the unexpected testing results. I played with the ohmmeter and the lube, but couldn't detect any conductivity or insulation. Also, if the lube was the problem, I wouldn't expect the exact same results over three days. Nevertheless, I'll use paper strips to absorb as much as I can. Thanks

Conclusion is: I dunno.
Checked all the circuitry and connections with the assembly manual. Found no faults. Put the TT-1 back together and will use it with blissful ignorance. I usually check tubes with an emissions tester as well.

I have a TT-1 that I restored about 8 or so years ago. It had a wiring issue from assembly and therefore never worked. Unfortunately, I used contact cleaner spray on the "Grid Current" switch and often would show leakage with no tubes in any socket. So, as mentioned, that spring loaded switch may be the culprit. I have noticed that lately, especially with low humidity, it has been behaving itself and I can use it.

If you doused the switches, you may be able to carefully clean them with denatured alcohol to remove any residue.

Just a thought.

Actually, the potential problem would have been failure to identify leaky tubes. I've tested perhaps 300 used tubes and found maybe 5 leakers. Those results were always consistent with a second tester. Since Heathkit did make some changes during the production of this models, I might have operation and assembly manuals that are inconsistent with the TT-1 which I have. Thanks for your response.

My patented method of cleaning switches, and btw tube sockets on a tester such as the TT-1, is isopropyl alcohol spray followed by canned air to dry, then bake in the hot sun or a 110 degree oven for a while. THEN you can re-lube the switch detents, and apply a little dioxin with a q tip to the switch contacts if you want. My TT-1 is my go-to tester, even tho I've got several much "higher end" testers as part of the obsession ... er... collection.

Dioxin? Maybe you meant De-oxit. I bet that was a auto co wreck failure.

I refrained from making that comment! :D

Seriously, I made the bad mistake of spraying switches and not just cleaning them. DeOxIt can be applied with a toothpick. That stuff is expensive and you only need about ¼ drop of it.

The SPELL CHECKER did it, not me lol. Dioxin ... too funny

Naah, all the cool kids clean their controls with Dioxin....We also wrap our tubes in asbestos and tobacco to help keep them warm and give off a fresh scent and pump ailing transformers full of PCBs to revive them......It ain't much worse than some of the factory toxins. :D