The AM Forum

I have an old Motorola car radio that i want to try to get working again . It has a Motorola vibrator in it, model 48B522000. I did some research and it is the same as a Mallory G1601. It has a 4 pin base. Does anyone know how i  can test it to see if it is working.
shelby

Look at the output on a scope.
I think they vibrate and make square waves, they make solid state replacements now.

Brett

what i really need to  know is the pin assignments, because i remember seeing that if you apply dc to the right pins, then you should see the pulsed dc at the output.

Try the site  http://www.nostalgiaair.org/References/Manuals/
They have a lot of old car radio reference.
Norm

Try this: http://www.ax84.com/static/rdh4/chapte32.pdf

And the Bible: http://www.pmillett.com/Books/intro_mallory_vibe.pdf

Mike Wu2D

Why not just do this - - get a 40-60 watt conventional light bulb and wire it in series with a piece of zip cord going to the wall socket.  Put alligator clips on the ends of the zip cord and when you reach the right pin combinations, the vibrator will buzz.  Ones which sound raggety are dirty and/or worn out, and defective ones will never buzz, regardless of whatever the pin combinations are.  This is also a way to clean the contacts.

Placing DC voltage directly on the pins is one way to weld the points together.

Don't forget to change the buffer capacitor unless it's a ceramic disc already.  Most old Motorolas used wax paper 1 KV buffers and they usually fail a few minutes into operation.

ok i remembered seeing somewhere about using the light bulb in the line to limit the power to keep them from doing that but it wasnt quite clear on how big of a bulb or anything like that.

60 Watts is adequate.  If you get the pins wrong, nothing happens.

What seems to happen is that the sponge rubber "sock" which is supposed to act as a sound deadener out-gasses some chemical fumes which contaminate the points over the years.  I have a carton of new Motorola vibrators and none of them want to start until they have been fiddled with using the light bulb trick for 5 minutes or so.

In the worst cases, you may have to pry the base open and pull the innards out for cleaning and inspection.  Try to avoid filing the tungsten points as this seems to end badly.

I am under the impression that the transformer load has to be in place for the Vibrator to act properly. I could be wrong on that
Carl
/KPD

I had a girlfriend in college that would steal them off my workbench.... ;)

There are two common failure modes with vibrators.   THe contacts get hot and stick, or the contacts just get eaten away.  Both are caused by too many hours of operation, or a bad buffer cap.

I suggest you turn the radio on, if no buzzing, use the handle of a medium screw driver and give the vibrator a couple of hard raps, if no buzzing, extract and pitch.  They either work, or they don't work.

I suggest you go here to get a new solid state (http://www.radiosforoldcars.com/vibratorsF.htm)  replacement.  THese fully replicate the wave form from a mechanical vibrator, including dead time.  Not too expensive but they work very well.  Usual disclaimer, have simply used a few with no call backs.

Mike

Shelby,

Here is the schematic that you need. Most if not all 4-pin vibrators follow this pinout. Use a 4 pin tube socket and its pin numbers. A 6.3, 12.6VAC or even a 24 CVT CT fil transformer will be adequate to test it. You must hook up all of the leads to the transformer or no vibrate!

Mike WU2D

Many good vibrators (even NOS) wont start in a radio from long term storage due to contacts sticking.

Pull the vibrator and apply 6-12VAC to the 2 pins that wake it up and it will shortly settle in to that familiar vibrator sound. Ive used that method for decades and with all new paper caps and electrolytics they run for a decade or more according to customers and my own experience.

Carl