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How to open old Gralab 450 for repair?

LF_Alex

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Does anyone know the secret how to open old Gralab 450 darkroom timer for repair?

I have one with small slide switches (not membrane ones like in newer 450 and 451) and they are not working 100% of the time, requiring fiddling and switching them back and forth.

It seems to be an easy project to get them replaced, but I have no idea how to remove handles from rotary switches, they must have been glued on.

Hopefully I'm not the only one trying to fix things instead of throwing them out
 
cowanw said:
The feet on the bottom need to be peeled off.
Click to expand...

There is no problem with getting bottom part removed, it's the handle or rotary switch that I can't remove
 
If there is no set screw (and from pictures I see online, it looks like there is no set screw), then it would be a press-fit; try prying the knob up--you may need to use a flat-blade screwdriver to apply leverage. If you do that, put something under the blade so it doesn't scratch the faceplate.
 
I was able to gently pull those handles from rotational switches, there was no glue! 4 screws on the bottom - and I got it opened!

I'm going to spray/soak those switches in electronics contact cleaner and see if this fixes the issue. If not - will try to replace.
 

Let us know how it goes! Mine is starting to act up a bit on two of the switches.
 
I just got one from ebay; and the seller sent me a 2nd for free that was "not working".. I tested it and it worked as long as the start/stop bar was pressed.

Update1: This is an industrial timer, with 1980s technology. My neighbor is a retired electronic engineer and he looked at it.
There's only a few things that can go wrong with the insides, but mostly oxidation and end-of-life of capacitors (2) were his main concern, as well as a broken ribbon cable (3).
In my case the start/stop switch (1) was not working properly, contact cleaner worked after actuating it a few times, and everything else seemed OK. He applied contact cleaner in a few places and cleaned it anyways.
The Board uses 12V electricity, and there is a transformer in the back, which is the main weights of the timer.
There is a voltage regulator (4) and a large capacitor in the back; which must be used for big loads (400W or more) which this timer is rated for; but shouldn;t be a problem for a 100W enlarger bulb.
 
Last edited:
relistan said:
Let us know how it goes! Mine is starting to act up a bit on two of the switches.
Click to expand...

I got it disassembled and cleaned all small switches with Electronics Contact cleaner, while working switches back and forth.

It seems to fixed the issue
 
Update, I have been using a LED in the enlarger and it began flickering and never turning off.
LEDs flickr after the power should be off at about 5 Hz.

So now its time to replace the capacitors!

Or is there any there reason this might happen?
better buy a bulb?
 
Last edited:
PS. I had all the capacitors ready to ship from digikey (shipping was 4x the price of the caps)
but I read that non-dimmable LEDs flicker when placed in a dimmer, so I bought a dimmable bulb and presto!
 
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