Gralab 300 buzzer repair

[juan]

I have three Gralab 300 timers and the buzzers have stopped working on all of them. I suppose to get inside, I need to drill out the rivets holding the front in place. Then replace them with small bolts and nuts.
However, what kinds of problems do the buzzers have? Do they simply get dirty and stop working so that a good spray with an electrical cleaner would get them going?
Or will the buzzers need replacement? If replacement, does anyone have a link to a replacement? I would suppose that any 120-volt (I'm in the US) buzzer, door bell, gong, etc. that would fit inside would work.

 

[MattKing]

I started to chuckle when I saw your thread, because my preference is to turn off the buzzers on Gralab 300's ASAP.
Do yours have an on-off switch for the buzzer, or a rotary dial to adjust the volume of the buzzer?

 

[darkroommike]

I've been inside a couple of 300's (and 168's) some are screwed together, others use rivets. Buzzers should be easy to fix or replace. You might also check the buzzer switch or knob for an "open". My riveted Gralab got new "Pop" rivets when I put it back together. Gralab will service them for about $200 (I think they would rather you bought a new one). I have not used but Rosy Products repairs a lot of kinds of darkroom equipment and took over making the Darkroom Products line of washers and sinks.
http://rosyproducts.com/repair.htm

 

[juan]

I started to chuckle when I saw your thread, because my preference is to turn off the buzzers on Gralab 300's ASAP.
Do yours have an on-off switch for the buzzer, or a rotary dial to adjust the volume of the buzzer?

I usually leave the buzzer off, but now I have a negative developing system that does not require my attention until the end of a cycle, so having a buzzer is a good backup to my potential inattention.
All of mine have the regular on off switch at the top, one has only that switch, one has what feels like a three position volume switch on the bottom right, and the third has what feels like a potentiometer controlling the volume. Turning these knobs has no effect.

 

[AgX]

Not knowing that timer I assume the buzzers are piezo-speakers. Not much to go wromg with such (though in theory they age), maybe it is the driver.

 

[rrusso]

I have three Gralab 300 timers and the buzzers have stopped working on all of them. I suppose to get inside, I need to drill out the rivets holding the front in place. Then replace them with small bolts and nuts.
However, what kinds of problems do the buzzers have? Do they simply get dirty and stop working so that a good spray with an electrical cleaner would get them going?
Or will the buzzers need replacement? If replacement, does anyone have a link to a replacement? I would suppose that any 120-volt (I'm in the US) buzzer, door bell, gong, etc. that would fit inside would work.

If you're electronically inclined, you can test it yourself if you have a multimeter.

When you get it open, the buzzer, or the board it's mounted on, should have a number on it. You could pull (de-solder, or cut) the buzzer out and check it by itself. But if the timer is working fine when the buzzer switch is in bypass, then the switch could be bad, or have dirty contacts, etc.

For starters, you can check mouser.com and see if there's a replacement or equivalent available. Shouldn't be very expensive.

 

[Fin]

<Service engineer>
The buzzer device in Gralab 300s (and also my very similar Berkey Omega, 240v 50hz) is a very simple device made up of a coil and a metal tab that vibrates when the coil is energised with AC electrickery to make the buzzing noise. You find similar devices in some 70s flip clock radios and old ovens and usually the volume control operates a screw which clamps down the metal tab to lessen and stop the vibrations of the metal tab.

If the buzzer isn't working the most likely cause is the microswitch in the timer mechanism. Inside it, there is a little spring between the contacts and they tend to loose springyness over time. The microswitch is a SPDT so it basically has 1 power in and 2 outputs. It is operated by a lever on the timer mechanism which releases the switch as you turn the hands off zero. When the switch button is out, the timer motor is powered and as it gets to zero the mechanism pushes the switch button in which cuts the power to the motor and sends it to the buzzer instead. When this little spring looses tension, the contacts won't make properly and then it doesn't work!

In the 90s, this particular type of microswitch used to be a fairly standard off the shelf size, now there's about a gazillion different types and sizes. I tried to find some replacements a few years ago for something and ended up opening each switch up and gently bending the spring back into the right shape.

HTH
</Service engineer>

 

[mgb74]

In the couple of gralab timers that I played with, I drilled out the rivets then replaced them with sheet metal screws.

 

[rrusso]

<Service engineer>
The buzzer device in Gralab 300s (and also my very similar Berkey Omega, 240v 50hz) is a very simple device made up of a coil and a metal tab that vibrates when the coil is energised with AC electrickery to make the buzzing noise. You find similar devices in some 70s flip clock radios and old ovens and usually the volume control operates a screw which clamps down the metal tab to lessen and stop the vibrations of the metal tab.

If the buzzer isn't working the most likely cause is the microswitch in the timer mechanism. Inside it, there is a little spring between the contacts and they tend to loose springyness over time. The microswitch is a SPDT so it basically has 1 power in and 2 outputs. It is operated by a lever on the timer mechanism which releases the switch as you turn the hands off zero. When the switch button is out, the timer motor is powered and as it gets to zero the mechanism pushes the switch button in which cuts the power to the motor and sends it to the buzzer instead. When this little spring looses tension, the contacts won't make properly and then it doesn't work!

In the 90s, this particular type of microswitch used to be a fairly standard off the shelf size, now there's about a gazillion different types and sizes. I tried to find some replacements a few years ago for something and ended up opening each switch up and gently bending the spring back into the right shape.

HTH
</Service engineer>

Well, there ya go...

 

[juan]

Thanks all. If the buzzer is bad, it looks like mouser has something. I would think the switches are a more likely source of the problem. I guess I'll deal with it after Irma passes.

 

[RalphLambrecht]

I have three Gralab 300 timers and the buzzers have stopped working on all of them. I suppose to get inside, I need to drill out the rivets holding the front in place. Then replace them with small bolts and nuts.
However, what kinds of problems do the buzzers have? Do they simply get dirty and stop working so that a good spray with an electrical cleaner would get them going?
Or will the buzzers need replacement? If replacement, does anyone have a link to a replacement? I would suppose that any 120-volt (I'm in the US) buzzer, door bell, gong, etc. that would fit inside would work.

I wish mine would stop working.one of these days one will give me a heart attack.

 

[Nodda Duma]

I fixed a bad buzzer in a Gralab by repositioning (slightly bending) the metal tab that Fin describes in his post above.

 

[David Brown]

Or for some patience and about $25, you could buy another old 300 ...

 

[Jarin Blaschke]

I just bought a brand new 300 a month ago. Is there no way to turn that damned buzzer off??

 

[rrusso]

I just bought a brand new 300 a month ago. Is there no way to turn that damned buzzer off??

Why don't you trade with Juan?

 

[RalphLambrecht]

I just bought a brand new 300 a month ago. Is there no way to turn that damned buzzer off??

of course; the new ones actually have an on/off switch for the buzzer.

 

[juan]

One of mine has an on/off switch at the top.

 

[Jarin Blaschke]

of course; the new ones actually have an on/off switch for the buzzer.

Actually, the one I bought two months ago has only POWER ON/OFF and TIME/FOCUS switches. That's it.

 

[Jon Shiu]

Crap, they down-graded it!