[EICO] Eico 666 help - Update

[Percy Mistry]

The rectifier was shot. It was open. Replaced it with a 1N4005 (600PIV, 1A) 
that I had on hand. I havent tested any tubes yet but got past the first 
step of line adjustment and calibration.

While I was replacing the recitifier and going through the schematic I 
couldn't really understand how it is supplying DC to the plate of the tube 
being tested. Is it actually an AC riding over a DC offset ?
Because it can supply upto 180V for the plate but the largest capacitor is 
rated below that - 150V. nor could I really figure out a rectifier in that 
path. So I was wondering how does it supply a good DC to the plate ?

Thanks!



----Original Message Follows----
From: "ks1u" <ks1u at prodigy.net>
To: "Percy Mistry" <pfmistry at hotmail.com>,<eico at mailman.qth.net>
Subject: Re: [EICO] Eico 666 help
Date: Fri, 25 Jun 2004 19:50:15 -0400

Percy:
     Hello and welcome to this fairly quiet list.  It's been awhile since I
played with the 666 but there are a few things I recall.  firstly, the roll
chart had quite a few errors and went through 9 or 10 revisions.  The filter
caps can be increased, but be sure not to exceed the maximum ratings for the
specified rectifier tubes.  You should be safe with 100pf but there isn't
much advantage to increasing their values well beyond there initial numbers.
Of course I would definitely replace any filter caps that are that old.  The
rectifier diodes can also be beefed up without much concern.  I don't recall
what the values of the 1n34 versus 1n48, but I'd make sure the values are
very close if not identical.  I wouldn't leave the unit on for extended
periods because heat build up in those testers can get quite high.
      That's about all I remember, you can probably do a search engine
request for the 666 and get quite a lot of info. There are still tons
(literally) of them out there.  Good luck.

George
KS1U

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