drop-in LED meter bulb PCB for Auditronics (Beede, Modutec, Urei?) VU meters (open-source / gerbers included)

[zzzzz]

NOT FOR COMMERCIAL PURPOSES / NOT FOR RESALE / NOT FOR PROFIT.

I laid this out for my friend who has an original 8-bus Auditronics Grandson 110 console. All of his VU meter bulbs are blown out because they are powered by an unregulated 24V rail, and this is a known issue with those bulbs in that console. Made these drop-in replacement PCBs allowing you to use LEDs instead of incandescent bulbs. I realized it was cheaper and would take me the same amount of time to assemble a simple PCB and drop it in rather than take apart the existing one and replace the bulbs which will inevitably blow up.

This PCB specifically fits the top-lit “three bulb” Modutec and Beede meters, but I’ve also made a separate version for the plastic housing Weston meters that are backlit with two bulbs as found in other Auditronics consoles. More on that another time.

Obviously this doesn't only need to be used in Auditronics consoles, considering plenty of other equipment uses the same Modutec or Beede meters (3.69" W x 2.82" H ish) apparently including the original LA2A and maybe other Urei products. Use this to add nice lights to your otherwise non-illuminated meter! Seeing as both the Beede and Modutec meters Auditronics used are direct footprint compatible, I bet there are other meters out there with the same dimensions.

Remove your old meter bulb PCB, drop this one in, reassemble ring terminals as they were before. Done.

There are various optional pin-header jumpers on the back for configuring polarity/position of the ring terminal lugs, a brighter or more dim light option, etc. More on that in the build doc. I initially included these pin-header jumpers just for testing / configuration purposes of *one* meter with the intent of just using soldered wire jumpers for configuration once I got it all situated.

Here is a link to a fairly complete build guide with link to order your own PCBs (not assembled), download the Gerber files, and a bill of materials: https://docs.google.com/document/d/1XnkTOWzyiUlqTK5zi7hqMG6uh5VdrVWrgBty6MUNhkE/edit?usp=drive_link

As mentioned, I made another one of these boards to replace the 327 incandescent bulbs for the completely different style back-lit Weston meters found in other Auditronics consoles and will post here.

Photos are of the "prototype" so excuse any sloppy assembly.

 

[ruffrecords]

Now that is what I call engineering. An elegant solution to a known problem.

Edit: and very well documented too.

Well done.

Cheers

Ian

 

[zzzzz]

Thanks @ruffrecords -- really appreciate it, especially coming from you!

and as promised... here's the other one:

This board specifically fits the “two bulb” Weston 7532 meters with the white plastic housing. This PCB drops in to replace the existing metal bus bar where the incandescent bulbs are mounted. The assembly is not as simple as the 3-bulb Modutec/Beede bulb boards and does require some simple soldering and desoldering of wires, but it is still very straightforward.

Other console manufacturers of the era such used the same or similar Weston meters with different setups for backlighting them, so this board could likely be adapted for those as well. For example, Sphere used the exact same backlight setup as Auditronics on their Weston meters.

You can reuse the two wires coming from the voltage connections on the meter buffer PCB. On some variations of the buffer PCB, there is an old carbon comp resistor coming off the bulb “common” lead going to the 0V line – that can stay on and doesn't necessarily need to be removed, but the “red wire” going to the bulbs might need to be moved to a different pad depending on supply voltage. Much more on that in the Google Doc.

Here is a link to a fairly complete build guide with link to order your own PCBs (not assembled), download the Gerber files, and a bill of materials: https://docs.google.com/document/d/1FS0KaR-OHO-RjKvFlTQ33LGtHSqZfUb7XBg1HyFi3c8/edit?usp=sharing

Photos are of the "prototype" so excuse any sloppy assembly.