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#1
10-22-2014, 11:58 PM
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Eico 368 Mods
I have read there is a mod for the Eico 368 to improve the marker side of things. Does anyone have the information and would you be willing to share? I am in the middle of restoring mine and would like to make it as good as it can be.
 Thanks Gregb 
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#2
10-23-2014, 08:17 AM
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From reading the thread linked below, it appears you need to be asking for a copy of the post-marker upgrade in Service Magazine from April 1969.
http://www.antiqueradios.com/forums/...=85146&start=0 .
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#3
10-24-2014, 09:17 AM
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I have the 368, like it fine. Did you use it before the restore? just wondering if you have used as is.
http://www.youtube.com/watch?v=MOnXt...CVtyRrqXVtll-g Post marker is nice (I have a BK 415 for late IF freq), but I found the 368 fine, you just get a little attenuation of the markers in the traps. Having a good freq counter really helps since the dial calibration is not that great (I did try to dial it in but with a good digital freq counter you don't really need it). If you do make the mods I would like to hear back how it went.
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#4
10-24-2014, 10:44 AM
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I have recapped it and sadly I don't really know how to use it and am still in experiment mode. I changed the old RF connectors to BNC to be compatible with my existing leads and will make one that has the 50 ohm termination as well.
I have watched your video before Dave and that is what gave me the idea to fix this up and give it a try. I have tried to get the wave forms that are described in the manual but so far no luck. I do get a wave form and can run the pip up and down it but it looks nothing like the one in the manual. Gregb
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#5
10-24-2014, 12:20 PM
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I had a lot of problems initially. Correct hookup to test points with correct leads, bias settings,contrast or AGC, then amplitude from the generator setup, lots of stuff to get to where that video was.
If you just want to look at the output from the generator (with out a TV receiver) you can just look a the output with a scope, you should be able to see the sweep width adj from a single sine wave (shape will not be perfect and amplitude will very with freq center point) with zero sweep then as you begin to sweep it fuzz up. I can't recall the exact look but I know I did try this (no tv receiver) and the do recall the amplitude and sine shape being less that perfect. Best thing would be to hook to a known working receiver and try hooking it up to see if you can get a decent looking band pass. again its VERY dependent on how you have the setup and hook up. I found even just changing a tube had a very noticable change on the curve shape (but not noticeble on the receiver CRT). Just moving your hands around the IF will cause variations. My best advise is to just play with it. This is where OJT would be invaluable.
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#6
10-25-2014, 11:03 AM
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#9
10-25-2014, 02:42 PM
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I have one of these 368s, which I have modified to make it post-marker,
using a dual trace scope however. The main problem is that the sweep out has harmonic content that varies across the band. This means that the leveler circuit levels the sum of the harmonics (or at least the lower ones) rather than just the fundamental. Its not a problem with 42 MHz IFs but is with 23 MHZ ones, and you just have to watch the waveform carefully as its not a really great effect (at worst 2 dB). I should add that this is with properly terminated cables. Doug McDonald
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