Gold

Light Beam Meters - Neumann PTMV
« on: February 21, 2018, 03:54:07 PM »
I have a set of light beam PPM meters in a Neumann SP66 mastering console. I had another set in previous MT66 which is almost the same as an SP66. I could never get them calibrated where I trusted them. 

I recently discovered a Neumann factory calibration procedure for the PTMV amplifiers. I also found a calibration procedure for the meter unit. I’m having someone restore them. The PTMV has nuvistors and that is out of my wheelhouse.

I can’t wait to see a properly calibrated light beam meter. I’ve never seen one before. I don’t imagine anyone under say 60 years old has ever seen a properly calibrated one.


[silent:arts]

Re: Light Beam Meters - Neumann PTMV
« Reply #1 on: February 22, 2018, 12:07:19 AM »
We called them "Lichtfinger"  8)

ruffrecords

Re: Light Beam Meters - Neumann PTMV
« Reply #2 on: February 22, 2018, 03:04:21 AM »
The first time I saw anything like that was in the physics lab at secondary school in the 60s. We had a couple of light beam galvanometers for measuring tiny current. They were about the size of a dinner plate. Saw one or two Neumanns  in studios around London in the 70s but they disappeared soon after.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Light Beam Meters - Neumann PTMV
« Reply #3 on: February 22, 2018, 11:07:32 AM »
I'm naive - what's a lightbeam meter?

ruffrecords

Re: Light Beam Meters - Neumann PTMV
« Reply #4 on: February 22, 2018, 11:12:04 AM »
I'm naive - what's a lightbeam meter?

It is like a regular edgewise meter except the needle is replaced by a small mirror. You shine a beam of light at the mirror and shine the reflection on the meter dial. As the meter operates, the mirror is deflected and with it the beam of light. And you get a 2 times optical amplification for free.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #5 on: February 22, 2018, 03:50:44 PM »
Here are some photos.


You can see the front panel calibration. Set 0% then set 100%. Then move into operation mode.



These are the PTMV amplifiers. You can see four trimmers in there. Mysterious.



This is the rear. You can see the nuvistors on the bottom PTMV.  You can see the festoon lamps on the rear of the meter unit. Apparently there are tweak point in the unit. I've never opened it up.

beatnik

Re: Light Beam Meters - Neumann PTMV
« Reply #6 on: April 05, 2018, 09:20:04 AM »
I am restoring a Neumann mixing desk that uses a similar meter and one of the two PTMV units is defective.

I haven't been able to find schematics for it, does anybody have a copy ?


Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #7 on: April 05, 2018, 12:36:34 PM »
I sent my documentation to the  guy restoring mine. When he’s done with it I can scan it.

beatnik

Re: Light Beam Meters - Neumann PTMV
« Reply #8 on: April 05, 2018, 01:05:49 PM »
Thank you. I have looked everywhere and couldn't find schematics for this module.

If you could also share the calibration procedure that would be great.

Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #9 on: April 05, 2018, 01:12:00 PM »
Thank you. I have looked everywhere and couldn't find schematics for this module.

If you could also share the calibration procedure that would be great.

Sure, I'll scan what I have when I get it back. I'd like to see more working light beam meters.

I just got an email saying he located a NOS Nuvistor to replace the missing one. The sticky thing is at some point the thermistor was replaced with a cap. Apparently the thermistor looks like a tantalum cap. He has to figure out a suitable thermistor to instal. 

He's also just finished a Waveforms 520-A VTVM. I'm excited to get that back. It's very compact and has a large meter with a mirrored scale. I like it better than an HP400.
« Last Edit: April 05, 2018, 01:16:57 PM by Gold »


leadbreath

Re: Light Beam Meters - Neumann PTMV
« Reply #10 on: April 05, 2018, 07:24:40 PM »
Yeah man love these old meters!! Buddy of mines got one on this old Ge Neumann desk that doesnt work so would love to get it back to life...
f**k marlbro's and weed ill stick to smoking germanium and silicon

guy_4

Re: Light Beam Meters - Neumann PTMV
« Reply #11 on: April 30, 2018, 06:58:18 PM »
We had this type of meters on the EMI TG12345 ( 16  )  and on the  EMI-NEVE ( 24  ) at  the EMI studios, in Paris.

When a bulb was blowing during a recording session, you had to wear sun glasses before opening the back panel of the Vumeters enclosure, because the light of all the bulbs was so intense   !     >:(
Under the instructions of the recording eng. the new bulb had to be slowly rotated until the filament was not making a " shadow "  over the vumeter scale....
Add two fans to blow the hot air out...
What a crazy design it was  ! ::)
"If you think it is expensive to hire a professional, wait until you hire an amateur ! "   Red ADAIR

beatnik

Re: Light Beam Meters - Neumann PTMV
« Reply #12 on: August 29, 2018, 04:31:46 AM »
HI Paul,

any chance I can get the documentation regarding the PTMV amps ?

I am coming to a good stage with my mixer refurbishment and would love to get the meters properly calibrated.


Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #13 on: August 29, 2018, 01:28:23 PM »
I sent the documentation with the unit and I don't have it back yet. I know the work is complete. I'm not sure when I'm going to get it back because I have him working on a pair of UE100's for me. They are about 200 miles away so I'm going to wait until the UE100's are done to pick up the PTMV.

beatnik

Re: Light Beam Meters - Neumann PTMV
« Reply #14 on: August 29, 2018, 02:25:56 PM »
Thanks, I will keep in touch

gyraf

Re: Light Beam Meters - Neumann PTMV
« Reply #15 on: August 30, 2018, 03:51:01 AM »
Can I come in on CC when this turns up?

Jakob E.
..note to self: don't let Harman run your company..

Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #16 on: August 30, 2018, 01:02:07 PM »
Can I come in on CC when this turns up?

Jakob E.


Sure, no problem.

DerEber

Re: Light Beam Meters - Neumann PTMV
« Reply #17 on: August 30, 2018, 05:04:39 PM »
Light Beam Meters are so cool!

10 Years ago I still worked in rooms at the government radio station equipped with similar NTP meters.
I got myself one, but failed very hard in replacing the murky mirror.
After spending a long time finding someone recoating the tiny mirrors I completely failed in reglueing the replacement.
This was one of my most unsuccessful repairs ever. 
;D







I still have everything ready to install one like this in front of my desk.
If anyone knows a source, please let me know.

Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #18 on: November 07, 2018, 02:21:44 PM »
I have all the documentation back. I will scan everything. I don't have the ability to stitch together the schematic scans. Does someone want to stitch together the schematics and then post the files in the Technical Documents section?

beatnik

Re: Light Beam Meters - Neumann PTMV
« Reply #19 on: November 07, 2018, 02:32:41 PM »
Excellent. I could do that