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Mystery Ebay amp purchase
Mystery Ebay amp purchase
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Old 10th February 2008, 03:24 PM   #1
Pyre is offline Pyre  Canada
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Question Mystery Ebay amp purchase

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.

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Old 10th February 2008, 05:02 PM   #2
smoking-amp is offline smoking-amp  United States
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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
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Old 10th February 2008, 05:21 PM   #3
poynton is offline poynton  United Kingdom
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Default Must be worth the $20....

What does it say on the chassis?



http://www.l-n-metprod.com/interior_h2.html

http://www.nuclearmarket.com/Supplie...?IDcompany=571



You could be correct about a sensitive 'chopper' amplifier - see link


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Old 10th February 2008, 05:35 PM   #4
Pyre is offline Pyre  Canada
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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
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Old 1st June 2017, 06:55 PM   #5
garybleh is offline garybleh
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Default Value

Do you know how much that unit is worth? $20 is a great deal, but is that all its worth?
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Old 2nd June 2017, 03:45 PM   #6
FullRangeMan is offline FullRangeMan  Brazil
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Quote:
Originally Posted by Pyre View Post
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.

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Old 2nd June 2017, 04:26 PM   #7
RJM1 is offline RJM1  United States
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It's only a 9 year old post!
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Old 2nd June 2017, 06:17 PM   #8
kevinkr is offline kevinkr  United States
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Mystery Ebay amp purchase
This is what we call a necro thread...
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Old 2nd June 2017, 08:42 PM   #9
vinylkid58 is offline vinylkid58  Canada
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Quote:
Originally Posted by RJM1 View Post
It's only a 9 year old post!
Noobs don't bother to look at the date.

jeff
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