Hickok Tester Help needed

[shaun]

Heyo,
I bought a Hickok 600A tube tester on ebay, and it arrived damaged. So it has sat under my workbench for a year, but now is the time.
I can repair most of the damage, but two wafers were broken when the transformer came loose internally during shipping. The wafers are part of two different switches; both are labelled "Filament" on the control panel - the two on the far left on the front panel. I have some UV epoxy that might work, but it seems likely they might simply come apart again fairly shortly, because there's not much for the glue to grip to. Plus, the tension on the switch contacts would have to be juuuust right, or it would be a waste of time - in fact, that might be an impossible task. I'd like to replace the wafers if possible. Or, if anyone knows a good trick for repairing wafers, I'd be much obliged.
Thanks.

[shooter]

as you figured, glue on a double break like you have, won't get you there.


trace out the wires, or post a schematic, probably a reasonable "new switch fix"

[shaun]

Thanks Shooter. I didn't know parts were available for these old beasts. I haven't been able to find replacement switches, so if anyone knows where I can get them....

Here's the schematic.

[DummyLoad]

schematic that's a somewhat more legible attached.

i have a 605 i'm working on. owner left it on for over a week by mistake & it quit working. powers up but the fuse lamp glows dimly. pulled the 83 rectifier and there's no getter material left at all. suspect that's the culprit for now. if it's not, i'll flip it on ebay for $125 as a parts donor. switches look to same as on your 600A. 


--pete

[Latole]

You can fix wafer with good epoxy glue.

Do you know how to use epoxy and how to prepare the parts to receive the glue ?  Parts must be clean, sand finish to remove brightness

Put a big drop of  good 5 minutes epoxy ; stay away from contacts.

[shaun]

Thanks, Dummyload. Nice schematic.

As for the epoxy, one of the wafers is difficult to get at - I will have to dis-assemble half the unit. I didn't think epoxy would stand up to such a tenuous contact - I certainly wouldn't sand anything, as the break itself is quite clean and would assist bonding if left as is.

Has anyone here ever actually epoxied a wafer back together with any success?

Thanks.

[shooter]

a million years ago I did a couple that were only cracked, not broke.  I explained it was NOT a fix, never heard back, both were on multi-layer PITA, forgot the "glue" I used.


trace it out, figure out the "on/off" logic, possibly use a standard multi throw switch, rotary switch, wire nuts, get creative until you find a proper fix 

[DummyLoad]

Thanks, Dummyload. Nice schematic.

As for the epoxy, one of the wafers is difficult to get at - I will have to dis-assemble half the unit. I didn't think epoxy would stand up to such a tenuous contact - I certainly wouldn't sand anything, as the break itself is quite clean and would assist bonding if left as is.

Has anyone here ever actually epoxied a wafer back together with any success?

Thanks.

i have grafted phenolic PCB patches and the epoxy itself is usually stronger than the phenolic. the problem you face is keeping the tension of the contacts in check as well as contact alignment proper as the patch resin sets. with the limited working space. perhaps documenting the connections to both switches (e.g., lots of pics) and removal of the switches for repair out of the chassis would be the best approach, since you're going to need to use some interesting clamps to keep tension and alignment of the contacts. 

IMO, you'll be time ahead looking for replacement parts, or flipping yours as salvage to fund the purchase of another. 

-pete

[shaun]

Yes indeed. I was thinking along those lines myself. I bought some UV epoxy which sets up in a few seconds when exposed to UV light. I'd have to take the switches out and try and hold the wafers together while the glue set. Then rebuild the whole thing, And, after a week, if the switches gave out again, I'd go stark raving  .

Maybe I'll try and find some spares. I do wonder whether this model is worth all the effort. I sit upon the fence of indecision.

[Latole]

Has anyone here ever actually epoxied a wafer back together with any success?

Thanks.

I did it on similar parts.
Obviously only you know if it can apply here, you who have the wafer in front of your eyes.

[Sonny ReVerb]

I would recommend limiting the options. Look at the types of tubes you will be testing, realistically. If you stick with 'common' guitar amp tubes, you can get by with relatively few pinouts. Probably 5V, 6.3V, and 12.6V filaments. Wire up a switching arrangement to get those voltages on the pins you need and forget the wafers. Or you could try, as an alternative, to wire up the filament pinouts you need on the remaining wafer positions that still work. You might need to make a custom tube chart...

[shaun]

That's a great idea, SR. Although the idea of redrawing the schematic is a little daunting....:)