>I have a Ohmite VT4-F varible voltage unit that was taken apart when I
>>got it. It is wired but just disassembled. It appears the fuse socket
>>is broken and had no continuity between the front of the fuse under
>>the cap and the terminal. The fuse has continuity. I would like to
>>know if someone can tell me how to test this thing to see if it is
>>good. TIA... J.P.
>
>
> The later models had a plastic fuseholder that would crack if its nut
> was overtorqued or if the fuseholder was dinged. Try wiggling the
> back of the fuseholder (with power off, of course). If you have to
> replace it, it's a standard size.
>
> Now, for troubleshooting, unplug, open the front panel, and have the
> whole front panel assembly laying on the bench. Just to begin with,
> look at the lapped surface of the windings (where it meets the brush)
> and look for burn marks or discontinuities. Now turn the control from
> 0 to 140 and back while feeling the dial and looking at the brush. See
> that the dial turns smoothly, and the brush does not catch throughout
> the range.
>
>
> Now use an ohmmeter to look for continuity through the circuit. Black
> from the line cord through the fuse and through the VT to L@ and to
> the output wire (power off, again).
>
>
> Having passed so far, get a clean lint-free cloth and some pure
> alcohol (NOT 70% rubbing alcohol). Moisten the cloth with the
> alcohol, and gently wipe the lapped wire mating surface. (This is a
> PM procedure that should be performed periodically -- carbon crumbs
> from brush wear are a major killer of VTs.) Let 'er dry.
>
>
> Now, replace the cover, and place the wiper at around the midpoint. I
> forget the wire numbers on the front panel of the VT itself, but you
> should be able to see there's an L1/Hot/black (from the fuse), and
> L2/Neutral/white from the line cord. You've also got a green ground,
> which is connected to the chassis, and the output, which goes to the
> L1
> connect on the front output outlet. You should put your meter across
> the outlet, and plug it in. You should see about 70V. When you dial
> the control from min to max, you should see around 0 to 140V (it will
> be a bit high with no load).
>
>
> If you don't see an output, and you are somewhat adept at working with
> line voltage, you can do the above with the case cover open. Just
> trace the voltage relative to the white wire/L2. Be careful, as line
> voltage is present on all parts inside the box. If the voltage isn't
> there, there's an open. Simple. Fixing it, though, can be a problem.
>
> I'd guess your VT winding wire has probably opened up somewhere along
> the lapped surface. That's not economical to repair, because you'd
> have to first remove the varnish, then strip off the wire, rewind,
> revarnish, and relap the windings. In days of yore, Ohmite used to
> rewind the larger units, but not any more. Less likely but possible
> is lack of contact between the brush and the lapped surface. This
> happens from wear, as well as the brush falling out.
>
>
> If you have a newer one, it's possible you have a Staco variable
> transformer inside the unit. If you want, you can still get the Staco
> replacement AFAIK -- I believe Staco still sells it. The brush itself
> is not replaceable.
>
>
> Remember, just trace continuity, then the voltage. Where continuity
> or the voltage disappears is where it's open. And do be careful --
> it's never a good day to dance the 60 hertz.
>
> Oh, yes -- would you like fries with that? ;-)
>
>
> Good luck
> Chris
>
>
Chris, I missed your reply somehow and just found it on Google.Thanks for the answer.The problem that I now have, since this was already partially disassembled, is that there was no wire from the fuse to the circuit board (and I do not know which terminal to attach one to), and there is no apparent conncetion between the dial and the circuit board (and I do not know what type of wire nor how it conncets to the dial).Any ideas here? Thanks again. J.P.