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Mystery Ebay amp purchase

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Pyre

Pyre

Member
Joined 2006
#1
I bought this amp on Ebay for 20 bucks as it looked pretty interesting and I figured it must have 20 bucks worth of useable parts in it. Does anyone have any idea what this thing was originally used for? I can not seem to find much info about it on the internet. The thing is built like a tank and is labeled:

Microvolt Indicating Amplifier
Leeds & Northrup Co.
Philadelphia Made In USA
Cat. 9835-B

It is obviously some sort of scientific instrument. It has a 6X4, 6L6gc, 12AX7 and a 6072 under some sort of thick shield. There are two big cylinders plugged into tube sockets, one is a modulator of some sort. Unfortunately it is not a Illudium Q-36 that I can use to blow up the earth.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.
 
#2
Sounds like a chopper stabilized DC amplifier/meter for uV LF signals. The mechanical vibrating chopper converts the signal to AC, where it is amplified by the tubes, then re-converted back to DC by another chopper contact set. This scheme avoids the DC drift problem of a DC coupled amplifier. Likely was used for amplifiying the weak LF signals from strain guages, biological probes, capacitance / electromagnetic sensors,... Could be used for a making a milli-Ohm meter if you add a current source to it. Or put a piezo sensor on it for an earthquake monitor.

Don
 
#4
The only markings on the chassis are just the same as what it says on the front.

There is a 2 prong input and the output is labeled recorder. I think Don is correct in thinking it amplified a signal from some sort of probes maybe for recording purposes on a graph paper or something.

I like the earthquake sensor idea. I do not think there are too many earthquakes in Ontario though. I was going to pull the power transformer off and test it. It may work out well for a preamp power supply given the tubes that it powered.

cheers
 
#6
Pyre said:
I bought this amp on Ebay for 20 bucks as it looked pretty interesting and I figured it must have 20 bucks worth of useable parts in it. Does anyone have any idea what this thing was originally used for? I can not seem to find much info about it on the internet. The thing is built like a tank and is labeled:

Microvolt Indicating Amplifier
Leeds & Northrup Co.
Philadelphia Made In USA
Cat. 9835-B

It is obviously some sort of scientific instrument. It has a 6X4, 6L6gc, 12AX7 and a 6072 under some sort of thick shield. There are two big cylinders plugged into tube sockets, one is a modulator of some sort. Unfortunately it is not a Illudium Q-36 that I can use to blow up the earth.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.
Click to expand...
None of these images opened to me.
 
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