OT: Anyone familiar with Greibach Instruments Co equipment?

I know there are some folks here that restore "antique" electrical instruments.

I have a Greibach model 500 AC/DC true RMS voltmeter, having the bifilar suspension Emil Greibach patented (2,562,183), and a light-beam display. (light beam shows a line indicating the reading).

There is a problem with the suspension, and the suspension tube needs to come out to check it out further. The method for this is not quite obvious, although I probably can figure it out. However, if any of the folks who do instrument restoration happen to know anything about these, info would be welcome.

There is a fairly complete explanation of what looks like the correct, same, mechanism in the patent, but nothing of course on how to take the suspension assembly out of the unit. No doubt it was a "return to factory" situation even back in 1951 when the patent was issued.

Google etc provides ebay etc links but no further info. These things are fairly widespread, lots of "for sale" listings, and if the serial no is any guide, there were a fair number made.. IIRC, the serial no is around 8300.

BTW, yes I am crazy to fiddle with it.... Anyone who restores old stuff is probably by definition crazy.

Pictures of the item and innards

Beautiful piece!

Mike

I bought three of those instruments with different ranges from a McDonnell Douglas auction for next to nothing. Gave one to Jerry Friton, whom you may know. At one time Jack Scherrer could have told you all about them, but the last time I saw him, age was getting to his brain cells, as it is to us all. In the 60s he was the most impressive instrument man I have known, but time marches. His shop is still there, across from the Maplewood bus loop.

Bill

Yeah, I remember them, noticed the shop was still extant, but never had any work done there. Mr Scherrer must be very old indeed, now.

A friend, Bernie Feissle, was working there at the time, but formed his own cal lab later, and has since passed away. He did all the cal for both my last and current workplaces, until he passed. I am sure you knew him.

I am sure nobody at any of the other shops knows anything. Most of the ones I have tried for cal and repair work were not worth a hoot even on modern items, and wouldn't know anything about this.

I only have 2 bucks in this one, but I like fixing that sort of thing... strange, I know....

Yep, I knew Bernie. Jack Scherrer is actually a year younger than I am. His father started the business in a basement on Delmar so Jack had the advantage of growing up surrounded by things with switches with big open contacts and super accurate resistors. My favorite quote from him came when we bought a John Fluke power supply with accurate step outputs. I checked it against a drum resistor like Leeds & Northrup used on the K2 potentiometer and found non linearity. The Fluke rep's response was that my potentiometer had the non linearity. Jack's was "Bullshit- standards and violins improve with age. Damned little else does, but they do. Bring it over." That is when I learned about voltage coefficient in resistors, including the one I was using in the test circuit.

I don't know anyone who does movement work. I used to and have the various tools and parts, but I doubt that I an up to it anymore. When I worked for Greenleaf Mfg. in the mid 50s, there were no digital meters and I was in charge of the instrument room, so movement work was ordinary, but that was a long time ago. I think I have some galvanometer suspension ribbons if you need one. Anyway, I'll give you a tangent galvanometer for a free sample. I have a lot of old calibration equipment that I need to move on. Would you be interested in a Queen & Co. resistance bridge certified to accuracy of .2% in 1892?

When Bill Schallert, who was dean of Parks Air College, died unexpectedly, his wife had a dumpster brought to the yard and decreed that all his junk was going in it. We tried to explain that a lot of it was valuable and people needed it, but couldn't make a dent. A couple of us carried literally wagon loads of equipment out just to save it from the landfill.

Bill

I found this item (I can't help but wonder if it is the same one) and was wondering if anyone knows what the input voltage is? Google isn't showing much info on it but I saw in the description of an ammeter made by the same company said 6 VDC.

I also would like to find a set of the original or do a power cord and positive/negative leads that look like the originals.



My aim is to test it and perhaps fix it.

I expect it is the same unit.

It is a voltmeter, so the voltage is per the switch. You set the witch for the range and measure. Everything needed is inside the box. for the marked voltages.

However, for any such device, you MUST BE CERTAIN TO SET FOR A RANGE THAT INCLUDES YOUR EXPECTED VOLTAGE. If you think it will be 500 volts, set for the 750V range. If you think it will be 275V, STILL set for 750V, and if it turns out to actually be less than 300V you are OK, and can switch to the 300V range.

If you think it will be 120V, then the 300V range is likely OK. With sensitive meters, I tend to set at a higher range just to be sure, and then reduce as needed. Safer.

If you tried to measure 100V and had the thing set for a low voltage, like 3 volts, the meter would be damaged. If you notice, almost allmeters, including that one, are set up so "off" is followed by the highest range. They knew what might happen.

The "off" position probably shorts the leads of the actual meter, to "damp" the motion of the needle (by generated current) and prevent damage due to handling. Leave it set there unless using it.

No idea what leads would have been used, these meters were simply hooked up as needed with standard wires used in the lab, as far as I know they were not supplied with "test leads".

Bill:

Missed your last post somehow....

1892 eh? I doubt my old L&N dividers and resistance bridges are that old, but I don't know, my last L&N catalog is from the 1950's, I think.

JST said:

I expect it is the same unit.

It is a voltmeter, so the voltage is per the switch. You set the witch for the range and measure. Everything needed is inside the box. for the marked voltages.

However, for any such device, you MUST BE CERTAIN TO SET FOR A RANGE THAT INCLUDES YOUR EXPECTED VOLTAGE. If you think it will be 500 volts, set for the 750V range. If you think it will be 275V, STILL set for 750V, and if it turns out to actually be less than 300V you are OK, and can switch to the 300V range.

If you think it will be 120V, then the 300V range is likely OK. With sensitive meters, I tend to set at a higher range just to be sure, and then reduce as needed. Safer.

If you tried to measure 100V and had the thing set for a low voltage, like 3 volts, the meter would be damaged. If you notice, almost allmeters, including that one, are set up so "off" is followed by the highest range. They knew what might happen.

The "off" position probably shorts the leads of the actual meter, to "damp" the motion of the needle (by generated current) and prevent damage due to handling. Leave it set there unless using it.

No idea what leads would have been used, these meters were simply hooked up as needed with standard wires used in the lab, as far as I know they were not supplied with "test leads".

Click to expand...

Thanks JST for the info. I'm wondering what the supply voltage is to power the unit. I'm just worried that I'll plug it into 120 VAC and get a puff of smoke and charred wires. I assume this pic is where the battery/power input goes. Thanks again.

The meter needs no power at all. The reading circuit is powered by the voltage it measures

That connector is for the light behind the scale, dunno what voltage, but may be 6V.

Okay, looks like I'm going to have to crack it open. It isn't responding to 6 volt anywhere I plug it in.

I'm thinking it could be 120 VAC but will do a lot more research and get it out of the wood box before i plug it in to the outlet.

Another persons that bought test gear from MAC TWENTY YERAS AGO , Paul Kersens

Another persons that bought test gear from MAC TWENTY YERAS AGO , Paul Kersens

JST said:

I know there are some folks here that restore "antique" electrical instruments.

I have a Greibach model 500 AC/DC true RMS voltmeter, having the bifilar suspension Emil Greibach patented (2,562,183), and a light-beam display. (light beam shows a line indicating the reading).

There is a problem with the suspension, and the suspension tube needs to come out to check it out further. The method for this is not quite obvious, although I probably can figure it out. However, if any of the folks who do instrument restoration happen to know anything about these, info would be welcome.

There is a fairly complete explanation of what looks like the correct, same, mechanism in the patent, but nothing of course on how to take the suspension assembly out of the unit. No doubt it was a "return to factory" situation even back in 1951 when the patent was issued.

Google etc provides ebay etc links but no further info. These things are fairly widespread, lots of "for sale" listings, and if the serial no is any guide, there were a fair number made.. IIRC, the serial no is around 8300.

BTW, yes I am crazy to fiddle with it.... Anyone who restores old stuff is probably by definition crazy.

Click to expand...