Eico 666 tube tester restoration - need grid control!

[jasonguitar]

Anybody have a lead on a grid bias control for a EICO 666 tube tester or know of a good replacement part? I read one article that says you cant get them but I'm sure there has to be some new part that can be used. I was given this unit years ago and finally cleaned it and fired it up yesterday. All other parts are good but when I opened up the grid control to clean it the fine wire inside was broken and all over the place. Thanks. J

[fyl]

Grid bias control? Do you mean R16, a 5K lin 4W WW pot with an SPST switch? If so you're out of luck: there no currently manufactured replacements. You may either fit a pot and an external switch; replace the pot with a multi position switch and resistors or wait for an elusive NOS part...

[jasonguitar]

I finally found the whole assembly manual with schematic and parts list. I had guessed 5k as when I measured the pot it is around 4k from the 1st lug to where the wire broke and there is just under 1k of wire from the break to the 3rd lug. In the replacement parts list the Pot is listed as a 5k - 4 watt pot with spst. Guess I'll have to do the new pot with a seperate switch. It will be a drag having to remember to flip the switch and drilling a hole in the panel. Any suggestions as to the best way to do this?

[fyl]

No specific suggestions, but maybe you could modify the new pot by isolating a very small portion of the winding, the wiper won't make contact, and presto you'd have a switch.

Or maybe the original can be reused by doing some surgery, like changing the windings/bobbin and keeping the rest. Or maybe you can have the pot rewound or repaired - some grumpy old men can work wonders with vintage stuff.

[JHow]

This may be a dumb question, but I'll ask anyway: Is it ever possible to repair wirewound pot with something like nichrome resistance wire and handwinding? I expect its not cost effective if you have replacements handy, but since you have a hard-to-find item, it makes me wonder if repair is a possibility?

It's not exactly the same thing, but I once saw my wife's uncle Stefan repair an old toaster with res wire, fixing a broken heating element back in the day in Warsaw. In that place and time a toaster was an oddity, unavailable, it was an ancient German one. Of course, I also saw him "repair" a fuse in an un-scientific manner by prying off the cap, dumping out the sand, and replacing the burnt link with a small guage wire, and then replacing the sand and cap. Uncle Stefan was a TV and radio repairman by trade in a land where labor was cheap (time was not money) but parts were expensive/unobtainable.

[JHow]

Oh, I see fyl posted while I was typing with a similar thought.

[jasonguitar]

Did some investigating and DIGIKEY has the CTS 026 series pots which are 5watt wirewound and they have a spst switch option. The CTS part number would be like this: 026T1253411 Waiting on a quote from DIGIKEY. The standard 026 pot is only $3.61!! Let's see what they come up with! Keeping my fingers crossed.

[jasonguitar]

Is it ever possible to repair wirewound pot with something like nichrome resistance wire and handwinding? I expect its not cost effective if you have replacements handy, but since you have a hard-to-find item, it makes me wonder if repair is a possibility?

Man, that would be so cool to restore the original part! Now you've got me thinking! If I could just find my michrometer to check the guage of the wire! Seems totally possible.

[JHow]

These guys carry nichrome wire in several gauges and sell by the foot. The resistance/foot varies by gauge. They mention pot repair as a possible use.

Antique Electronic Supply

[jasonguitar]

So the custom ordered pot from CTS would be like $100. For that I could buy a new unit. So I bought the correct value wire-wound unswitched pot for like $8 and added a mini toggle just below it. Works great. Now the only other issue is that the meter has been abused. The needle has been bent and re-straightened and the movement is finicky and not very reliable. So desiring to have a reliable tester and not willing to pay $150 for a new meter, I bought a beautiful 667 for $120 shipped. This thing is immaculate and functions perfectly! So I'm browsing the Eico tube tester listings today and to my amazement there is an original meter for a 666 with a buy it now price of $20 and $5 shipping! It looks very clean and the buyer claims it is in good functioning condition. I snatched it right away. Keeping my fingers crossed!

[Euthymia]

Good grab on the 666 meter. I need one, too. I was just going to take the route of getting any old 200uA 1000 ohm meter that fit and sticking on a new scale. Haven't gotten around to it.

Also, $120 shipped for a 667 is pretty sweet, too! I love my Eicos.

[jasonguitar]

Good grab on the 666 meter. I need one, too. I was just going to take the route of getting any old 200uA 1000 ohm meter that fit and sticking on a new scale. Haven't gotten around to it.

Also, $120 shipped for a 667 is pretty sweet, too! I love my Eicos.

I got the new meter today and its perfect! Dated 1959 on the back! Before removing the old meter however I was able to adjust it, calibrate it and it is actually working quite well. I decided to put it on ebay. Though it is in only fair condition I think someone who needs one will be stoked to have it. It does work and the graphic I have reproduced is beautiful. I have described it pretty thoroughly. Check it out.
EICO 666 TUBE TESTER PANEL METER - ORIG VINTAGE RARE!!! - eBay (item 260650100421 end time Sep-11-10 17:45:23 PDT)

[Rhodesplyr]

I've got an EICO 666 tester as well that's worked fine for years. Mine has developed one problem, though--a dead spot on the pot you use to adjust for heater current draw and line voltage. I've been wondering how hard it would be to fix since this is another special control--wirewound with multiple taps.

In any of these, I'd also check the inter-element leakage voltage supply for dried-out capacitors and/or a bad rectifier. If memory serves, they have selenium rectifiers for that supply. Then, of course, you have to recalibrate.