8mm Forum: Help with Elmo ST800

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Posted by Jiyuan Sun (Member # 7174) on November 06, 2019, 04:17 PM:

Hi guys

Just bought a Elmo ST800 Projector from Ebay, a guys selling his grandfather's legacy, and he didn't know how to use and check them. When it came to my flat and got plugged, the machine worked in the first 5 seconds and bulb didn't light. And then the machine also stopped.

The level meter is always in the -10v. And I've already changed the new bulb and it still didn't work. Would you guys mind giving some advice to me? Should I change the belt? The longer one is white, old fashioned with gear and sticky by grease. Or should I change the fuse also? Totally confused about it.

Or do you guys know any person could fix it around London or UK?

Thanks a lot!

Posted by Steve Klare (Member # 12) on November 06, 2019, 09:47 PM:

Hi Jiyuan,

I have two of these set up right now, and the Vu meter starts out at -10 with no power.

I think step #1 for you is to check your fuse. If it's blown then you have other issues to solve before thinking about bulbs and belts. (The fuse pops out from the rear panel near where the power cord plugs in.)

Are you good with a multi-meter and have access to one?

Posted by Maurice Leakey (Member # 916) on November 07, 2019, 05:09 AM:

Jiyuan
John White in Stanmore, Middlesex, might be able to help.
http://www.the8mmshedshop.co.uk/

Posted by Jiyuan Sun (Member # 7174) on November 07, 2019, 05:33 AM:

Thanks Steve

I've try to changed the fuse. But it's fixed so tough, and didn't "pop out" even I try to twisted with the arrowhead. Still confused. Should I open the back shell of the machine?

Thanks Maurice My friend also just recommended he to me today!

Posted by Steve Klare (Member # 12) on November 07, 2019, 06:55 AM:

You should be able to twist the cap following the direction of the arrow and have the cap and the fuse pop out.

If you can measure any internal voltage in the machine greater than zero, your fuse has to be good (Please be careful! Some of them can kill you!)

Posted by Paul Browning (Member # 2715) on November 07, 2019, 07:25 AM:

My st800 had the same problem with the fuse holder, after some gentle persuasion it did unscrew. It had been stored somewhere damp like a basement or garden shed, the fuse holder was corroded with some white powder through moister/damp and had welded the metal holder shut. Disconnect from mains, and spray some wd40 just around that fuse holder and let it soak in, then try and undo.

Posted by Jiyuan Sun (Member # 7174) on November 08, 2019, 11:45 AM:

Hi guys

Finally I opened up the fuse cap and change 2 fuses which are not 3A but 3.15A. When I plugged the projector, both of them blew out immediately. I'll buy the 3A one and try it tomorrow.

Posted by Steve Klare (Member # 12) on November 08, 2019, 01:00 PM:

No need!

The value on a fuse is the amount of current it takes to cause it to blow. If you had enough current to blow the 3.15 Amp fuse, you also had enough to blow a 3 Amp fuse.

-so it's probably not a fuse problem. They are doing their thing! (Rest in Peace!)

BTW: At UK domestic voltages, I would expect this machine to draw less than 1 Amp if everything is OK. Because my voltage is half yours I should draw twice as much current as you do, and I've never blown a fuse.

Did you blow the fuses one after another, or does your machine have two fuses?

When you blew the fuses, what were the controls set to? Was the sound turned on or off? Was the motor control set for Forward, Reverse or Stop?

Anything that was "off" at the time becomes less of a suspect.

Posted by Dominique De Bast (Member # 3798) on November 08, 2019, 01:40 PM:

Jiyuan. Just to be sure, did you check your projector is a 240 volts one ? I have a GS 800 which is a 100 volts machine (for the Japanese market, obviousely), which I didn't notice immediately (and in the 90's there was no Internet to help no specialists, remember ?).

Posted by Steve Klare (Member # 12) on November 08, 2019, 02:21 PM:

Good Point!

Posted by Jiyuan Sun (Member # 7174) on November 08, 2019, 03:36 PM:

Thanks guys I checked it before. There is something written on the back is 240V. When I said 2 fuses, I mean I tried first one and it blew out immediately. And I replaced other one. And all the set is on the stop actually when I plugged it on.

Posted by Steve Klare (Member # 12) on November 08, 2019, 04:01 PM:

It sounds like you have a short: somewhere!

What's nasty about that is it could be before the transformer, within the transformer or after the transformer.

-not easy to trace down sometimes.

Let's start simple:

(After you unplug the machine!!!)

Grab a flashlight ("torch!") and look inside the machine looking for evidence of something burned up.

[ November 08, 2019, 05:07 PM: Message edited by: Steve Klare ]

Posted by Jiyuan Sun (Member # 7174) on November 08, 2019, 07:07 PM:

Checked them again. Didn't find any place looks like unusual. Should I need a multi-meter?

Posted by Nantawat Kittiwarakul (Member # 6050) on November 08, 2019, 09:49 PM:

A step-by-step investigation would be viable in this case.

First start by disconnecting everything else from the transformer, reconnect, and let's see if that still eats fuses. Then gradually reconnect each component on-by-one to isolate the cause.

Posted by Steve Klare (Member # 12) on November 10, 2019, 06:06 PM:

An interesting thing to try with something like this is inject power limited voltage into the transformer and troubleshoot at low power.

Transformers have a winding we call a primary where the power flows in, and one or more called secondaries where the power flows out. You can also plug one the secondaries into an AC voltage source of the correct voltage and all the other windings will light up at theirs too. The transformer doesn't know the difference.

If you have something like a model train transformer with a 12V AC output that has a circuit breaker you could connect it into the winding that powers the lamp and troubleshoot at low power.

As Nantawat says: disconnect all the various circuits and restore them one at a time until the short circuit returns. You could also disconnect them one at a time and see when the short disappears on the chance you find it before you get to the last one.

-bearing in mind that that 240V primary can still give you a nip!

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