Gralab Model 300 timer internals?

Is anyone familiar with the internals on Gralab Model 300 timers?



Picked one up from a local shop recently, and I'm debating making a few minor changes. However it is a full riveted metal case version, and I haven't been able to find anything online to confirm what the internals are like to be sure the minor functionality changes I want to make are actually also minor physical changes.

Are these wired up with fairly open and easy to reroute soldered/crimped wires to obvious logic gates and relays? Mounted circuit boards? Or are they one of those 'lovely' fully potted/resin entombed messes on the inside?

Would really like to swap that buzzer for something a little more suited to a "Calm and Relaxing" hobby, and maybe a minor logic change to add a foot pedal for the timer start.

If it is a potted mess, then I'll use this as my session limit timer, and wire up a digital f-stop timer for the enlarger.

LOL. It's purely electromechanical motors, relays and switches. You'll not find a logic gate or printed circuit anywhere inside...

We are talking 1920's technology, but it is GOOD technology to have lasted this long!

Kino said:

LOL. It's purely electromechanical motors, relays and switches. You'll not find a logic gate or printed circuit anywhere inside...

We are talking 1920's technology, but it is GOOD technology to have lasted this long!

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A relay IS a logic gate, I'm looking to find out if the internal wiring is readily accessible after popping the rivets off, or if everything is gunked into truly inaccessible blocks.

Having not seen a photo of the insides posted anywhere I can't tell if the "No user serviceable parts inside" notes are "We want you to pay us to do it" lack of user serviceability, or "We've done everything in our power to ensure you're not doing anything even if you want to" lack of of user serviceability.

Ok, fair enough...

The only one I have ever had open (had to drill out the rivets) was not entombed in epoxy or such.

Just pulled apart a newer plastic housed version to verify, and it's 99% identical to a very old one metal cased one I remember cleaning up some years back. Point to point wiring, 2 switches, an ac buzzer, and a synchronous AC motor driving a gear train. The gear train has a relay on it for the receptacles/buzzer/turning the motor off at 0:00 The only difference I remember from the old one was the gear train has changed from brass to plastic, and the buzzer was on/off vs variable. The buzzer has 2 wires, so any AC buzzer will work. A footswitch would be pretty simple to tap off the focus/time switch, I would think. No ICs or 'fancy electronics'. Drill out the rivets and go to town.

Dirb9 said:

Just pulled apart a newer plastic housed version to verify, and it's 99% identical to a very old one metal cased one I remember cleaning up some years back. Point to point wiring, 2 switches, an ac buzzer, and a synchronous AC motor driving a gear train. The gear train has a relay on it for the receptacles/buzzer/turning the motor off at 0:00 The only difference I remember from the old one was the gear train has changed from brass to plastic, and the buzzer was on/off vs variable. The buzzer has 2 wires, so any AC buzzer will work. A footswitch would be pretty simple to tap off the focus/time switch, I would think. No ICs or 'fancy electronics'. Drill out the rivets and go to town.

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Excellent, thanks. That sounds like the insides are setup exactly as I was hoping for, and I can crack that open sometime with reasonable confidence. I'll hopefully return to this thread sometime soon with some photos for reference.

That photo of your timer is a marvel in itself. I've never, ever, seen one of those timers that looked like yours. Mine always looked like they'd been dropped a few times, but always worked fine.

momus said:

I've never, ever, seen one of those timers that looked like yours

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I thought the exact same thing! Wow that is clean!

Mine all look like they have been through the Nevada proving grounds. Of course I have like 6 of them sitting around all over the place, they breed like triffles...