Eico 666 No Line Cal

[Cyberdragon]

The line cal button just suddenly stopped working. The rest of the functions appear to work (it seems to test tubes) but it behaves a bit funky, like measuring reverse leakage on some leak tests. I've tested all the calibration resistors, they measure a bit high but not bad (it's always been like that, I never bothered to adjust the trimmers). The switches seem to have continuity to the meter when in line test and the selenum rectifier reads 70V output (is this correct?). Any ideas of what else I need to test?

[Andy Watson]

According to http://www.oldtubes.net/library/test_equipment/reeland_eico_scans/ the circuit for the line-cal is completed via the chassis - I would check the integrity of chassis connections at both ends of the circuit. Also, do you have means to test the capacitors - perhaps replacement might be easiest test. Either of these problems might also be the source of your "funky" readings.

[Cyberdragon]

It's not an open circuit, already checked that, it appears to be a short. I'm getting 60-70V across C1 and C1 is good. R8 is also OK but after it I get nothing. I'm getting 60 to ground between R7 and R8. Bad pot?

[Cyberdragon]

I pumped the pot full of cleaner (didn't move it) and it's gone now. Tin whisker? Let's see if it works now.

[bob91343]

Those selenium rectifiers are notorious.  I replaced the one in my 666 with silicon.  It works fine.

In addition, switches are a common problem.  Make sure the button actuation accomplishes the desired result.

This instrument is an example of minimalist design.  How they accomplished so much with so little is a wonder to me.  Some very sharp engineering, but I wonder how solid it really is.

In any case, I don't find the 666 a useful instrument and would love to see it find a more welcome home.  I have another tester which I find meets my needs better.

[Cyberdragon]

It's still working so I'm just keeping it untill it blows it's guts.

The spray in everything fixed the circuit being totally dead. But it still doesn't work due to the bad carbon resisitors. Unforunatly I don't have the right value at 1/2 watt (or are they 1/4?),  I only have1/8 watt of that value.

Will that work or will they burn out?

[Dacke]

Old tube testers generally have some special considerations to take into account with regards to cleaning,  so just keep that in mind and don't get too crazy with the DeOxit.   Selenium rectifiers at 70V relative to chassis ground is fine.  Also,  even high quality carbon comp resistors tend to drift upward in value over the years,  but they don't usually burn out and they can take a hell of a beating with regards to heat.   They can however develop cracks both internally and visible and these older ones are a bit more sensitive to mechanical stress on their leads than most other types of resistors.   And apparently the Eico 666 has both factory assembled models and kits that were built by hobbyists,  according to the article I linked below the difference is in the serial numbers.   If I had a kit version I would thoroughly inspect all the solder joints and make sure none of those carbon comps have been pulled tight by their leads and soldered.   Hobbyists sometimes get a little excited (who wouldn't) when building these things and their may even be some bad solder joints or even joints that they missed altogether. 

I have a lot of new old stock carbon comps in my storage bins,  1/2 watt to 3 watt.   What value(s) do you need?  I wouldn't charge anything as I barely paid anything for them.

Some more interesting info here about the Eico 666 - http://www.fourwater.com/files/restr666.txt