Film-Tech Forum ARCHIVE: speco platter problem

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Posted by Bill Hall (Member # 10520) on 08-03-2018, 04:00 PM:

I Have a speco model 720 platter. It was working last night ok but then today as soon as I turn the power on it blows the breaker right away. Not fun as I just got the rectifier wired today and the lamp house working but now not able to run any film through the projector onto the screen for the first time . Does anyone out there have any suggestions on where to look for the problem. As soon as I turn the switch on the breaker cuts out so there must be a short of some sort . Any help would be appreciated.
Thank you
Bill Hall

Posted by Dave Macaulay (Member # 813) on 08-03-2018, 04:52 PM:

Speco platter... the words bring back feelings of dread.
Anyway, the schematics are a confusing mess. So is the wiring...
As I recall, it's possible to mash in multiple buttons and cause a short. But the thing has 3A fuses IIRC, how could it blow the breaker? Do you have GFI breakers? Even the slightest ground current will trip those.
If it's really blowing a 15A non-GFI breaker I would check for shorts in the power plug (if it's an add-on plug, not molded on) and in the internal wiring before the fuses. Maybe confirm that no PO has put 20A slo-blo fuses in place of the 3A ones wanted?

Posted by Steve Guttag (Member # 268) on 08-03-2018, 05:04 PM:

There should be a 3A fuse on the base of the platter that would go before tripping a breaker.

There is a bridge rectifier behind the button panel on the top (early ones were discrete components later ones used an octal tube plug with a 4-terminal device in it)...most often, when a fuse just blows, that is the culprit.

Posted by Monte L Fullmer (Member # 2797) on 08-03-2018, 06:04 PM:

Yea, the Drive-In Lp-270 platter.

Given that Model Number since 270 minutes was 4.5 hours of film those converted picnic tables held.

Ya, big issue was that plug-in Bridge diode module that was mounted behind the push button panel on the tower.

Don't know how many of those modules Ive changed out, but when we were popping fuses in the base of the tower, a changeout of this module cured the issue. Diodes would love to short out.

Posted by Bill Hall (Member # 10520) on 08-03-2018, 08:09 PM:

HI thanks for the information. I took the cover off and saw two long black things in there and if that is what has gone bad I wonder where one would find replacement ones or to try to find a EXtron platter istead I have a loop of film to see how the lamp house works on my temporary screen for tonight but really wanted to see the trailers I have on the platter.
The breaker is 15 amp and last night worked well and today after a lot of rain it just blows the breaker. I checked the wiring with a meter and found no problems there. The cord is in good shape as is the plug. I checked also the wiring at the base of the tower and saw no issues there so what ever is killing the power must be a direct short. I only wish it would have lasted a little longer to see and hear the film on the platter.
Many Thanks
Bill

Posted by John Eickhof (Member # 323) on 08-03-2018, 10:23 PM:

if it is an older lp-270 with three rows of colored pushbuttons, it could be the bridge rectifier that others mentioned, also if you had two buttons of the same color depressed for long it probably fried the small 12 volt transformer located in the button housing early lp-270s were not fused except for a 3amp fuse on the small black variac housing, it protected just the variac. i have the power transformers and replacent plug in bridge rectifiers in stock email me a picture of the button assembly without the cover so i can see if the rectifiers are soldered in or the later octal plug in module its an easy fix but remember to never have two of the same color buttons pushed in at the same time.other than that the lp-270 is a simple robust and smooth running unit i have sold and serviced several hundred of them through the years.

Posted by Richard B. Perrine (Member # 409) on 08-04-2018, 11:49 PM:

I found that just punching the buttons (from red to Green etc)..could cause a short in the switch assembly...frying the switch assembly and the diodes.
So after replacing a couple of the 4 button switches....punch any color button half way to release the lock on the previous one that was pressed in....then push the next one in.
this prevents 2 switches shorting as they travel in or out past the other switch contacts...
So if green(feed) is in...press yellow 1/2 way...then all 4 switches are released from any function....then press red(take-up) in.

The Diode are kind of simple...I think I replaced them with either 3 or 5 amp....400PIV.
if you've shorted a switch assembly...you might have to replace it...it could have created a permanent short.
Also found that some of the wiring was close to the cover screw for the function switch cover....and the screw for the cover actually caused a short (upper right one next to the diodes).

Posted by Bill Hall (Member # 10520) on 08-07-2018, 09:32 PM:

HI I looked up the manual for the speco 270 and found two part numbers the first one is 195-0251 59 a 250 ohm rectifier and then the diagram is a little confusing as I saw part number 195 -050-59 a 500 ohm bridge rectifier but I did not find that part number on the diagram that lists the part numbers etc but I did find part number 195 0501-59 so I wonder if the last number with four digits is the more correct part number .
Any suggestions
Thank You