Joe Meek OneQ

[bnwitt]

I'm looking for a schematic for a Joe Meek OneQ or at least the VU lamp specs as I have one in for repair that is burnt out. this lamp has 43.7VAC at it's pins. Thanks in advance. Ok, holding the unit upside down without the cover on dropped the second lamp glass body (which had broken off) onto the bench. Obviously these two lamps are meant to be wired in series via the PCB traces since neither lamp can connect to both sides of the supply without both of them in the circuit. Now I really need to know what type of lamps these are so I can replace them both. I'm assuming they would be 24 or 30V (half the supply voltage) and low wattage for a VU meter. Anyone have any ideas.
Barry

[bnwitt]

PCB photo

[vintagekiki]

https://www.gearslutz.com/board/low-end-theory/739813-needed-joe-meek-twinqcs-schematics.html
Joe Meek TwinQCS Schematics

http://web.archive.org/web/20040101204539/http://proaudio2.republika.pl/joemeek_1b.jpg

[bnwitt]

Thanks Vintagekiki. I saw those in my online search but they are for a different unit and I don't see a VU lamp called out anywhere. I appreciate the post.

[nevetslab]

PCB photo

I've attached some Chicago Minature data sheets, on their incandescent bulbs.

CML T-1 3-4 Incandescent.pdf
CML T-1 Incandescent.pdf
Incandescent Lamp Pages from CML Catalog.pdf

[bnwitt]

Thanks Nevetslab. That helps a lot.

[The Dude]

If I had it all apart anyway, I'd consider replacing the lamps with LED's and a dropping resistor.

[bnwitt]

The Dude, I'd like to do that but I have no idea how much wattage I need. I guess I could put something together from my LED bag and see what I can do to get an even lighting across the meter face with a potentiometer to determine resistor value..

[nevetslab]

The Dude, I'd like to do that but I have no idea how much wattage I need. I guess I could put something together from my LED bag and see what I can do to get an even lighting across the meter face with a potentiometer to determine resistor value..

A few years ago, I made a number of modifications to my second Amber 3501a Audio Analyzer, one mod being adding meter scale illumination. I used five WHT LED's in series with an 8.2k dropping resistor, and ran them off of +/- 15V from the generators power supply. I had looked around for light bars and light pipes, thought about trying to make one, but ended up using some white card stock, punched holes in it (0.188" dia) at 0.65" centers, glued them in place. Wired them up in series, and selected the resistor value empirically with a decade box. The array was taped into position, rather than gluing, using white artist tape. It's held up fine over the years, though I'm not crazy about the cold white light they give off. I've always liked the warmth of incandescent bulbs for meter scale illumination, personally.

[bnwitt]

Thanks for the post nevetslab. Very helpful. I'm going to give this a go today. I prefer a more amber back light as well so I'll try some yellow LEDs first and see what that looks like. PMI did send me a schematic (and an NDA), and it shows a 4k7 2 watt resistor in line with (3) LEDs coming off of the 17VDC power rail for the VU back light. My unit is an old one and as I said it uses (2) incandescent lamps in series off of the 48VAC supply. I'll probably keep the existing power tap and put in some diodes for the LED array. I've got lots of G10/FR4 board and with some turrets or eyelets I can make a plug in assembly. Thanks again for your help.
Barry