help restoring a classic...

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help restoring a classic...

Post by QUINNQUIXOTE » Tue Mar 18, 2003 5:34 pm

Hi all,<p>I have a 1950's tube based BECKMAN/BERKLEY UNIVERSAL EPUT AND TIMER model 7350R counter. I am attempting to restore it to working order. This particular unit has two 4 amp, 125v fuses. They are littlefuse '313 3AG' type glass fuses. I am short one, plus a fuse holder cap. It would appear that this type is no longer made in this package by littlefuse. Does anyone know where I might find some of these fuses and a replacement fuse holder cap? I'd imagine I'll need more than one fuse, as I've foud that more often than not, when the fuse is missing, chances are your new one will blow due to another problem.... :) <p>Any help is appreciated!

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Re: help restoring a classic...

Post by russlk » Tue Mar 18, 2003 7:12 pm

How long is the "313 3AG" fuse? I have two 5 amp 3AG fuses if that is any help. I also have a replacement fuse holder. If the cap doesn't fit, you can replace the whole thing. If you want them, send me your address by email & I will send them, no charge.

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Re: help restoring a classic...

Post by Edd » Wed Mar 19, 2003 9:25 am

The 313 series of fuses shud be ~1/4 X ~1 1/4" size and are slow blo types and with as old of a unit as that, I would just as well suspect cannibilization as an equally viable reason for their being missing. Fuse Caps I usually run into are about 5/8" dia and about 1/2" depth and the majority are bayonet action but on Ur older unit you might see if it used the screw in threaded type of design with the milled bakelite knob tapering down to about ¼” in its end. I probably have some of both types in my collections if you want pristine restoration or do as Russ sez and just change out the complete unit(s). Those old tube designs were more forgiving in the stress factors on the power supply but I would certainly bring up the initial powerup very slowly on a Variac or if you don't have such , thru a 100/200 w incandescant in series with the AC in ( in place of the fuse). You have some mighty old electrolytic caps in that unit.
BTW doesn't that unit display its decades with vertically arrranged neon lamps for readout ?Or does it use special neon tubes with radially arranged and activated fingers for display. I believe it to be well before the first generation of numerical Nixies.<p>73's de Edd
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Re: help restoring a classic...

Post by rshayes » Wed Mar 19, 2003 11:50 pm

Some years ago, the fuse designation system was changed. I believe that the new designation for 3AG is AGC. The Mouser catalog still identifies some fuses by the old designation. They list a Littlefuse number 313.004, which is a 4 Amp slo-blo fuse. The equivalent Bussmann fuse seems to be a MDL-4. The fast acting Bussmann fuse is a AGC-4, so MDL apparently indicates a slo-blo fuse under the new designation system.<p>I have never seen the knob part of the fuseholder sold separately, so the best bet is to locate a duplicate of the old fuse post and swap the knob over.

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