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 Post subject: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 12:57 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 4827
Location: Sunbury, Ohio 43074
Picked up one of these for almost nothing. It works, much to my surprise. Does anyone have one of these that would be willing to look underneath and see what is supposed to be in a spot that looks like something was removed?

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The missing component is underneath, near the. balanced output binding posts. Looks like it should have been a capacitor, or maybe an attenuator or filter. There's a stick on cable tie base with a cut cable tie ... looks like whatever was there was about 1" diameter. I am studying the schematic to try and guess what "was" ... I'm thinking perhaps a 1uf Mylar cap or something, but I don't see anything disturbed in the rest of the wiring there.

Thanks!

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Last edited by Barry H Bennett on Sep Thu 12, 2019 4:10 am, edited 1 time in total.

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 2:45 am 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: Norfolk, VA
Steam Powered Radio has the FREE PDF manual - does it give up anything?

https://www.google.com/url?sa=i&rct=j&q ... 9019214301

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 2:48 am 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: Norfolk, VA
BTW, DoD used those in field-level cal labs to calibrate audio oscillators and the like. Al the Navy ones had the blue "Meatball" metrology sticker indicating calibration standard status.

I've used one a time or two, but for most general purpose audio oscillator calibrations, a standard 334A was used.

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"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 3:32 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 4827
Location: Sunbury, Ohio 43074
Thanks Brian. That appears to be the same manual I've got here. It doesn't give any parts locations other than the PCB's themselves. I'll keep looking though, and post a photo of the missing item. It's tough to even make out where it was supposed to be connected. Maybe it was some mod along the way ...... I'll probably find out as I do some self testing on the thing.

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 4:11 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Philadelphia, PA
Barry,

I can take a look on mine.
I bought 4 of them a few years ago, have one left and have been meaning to get rid of it as I haven't used it in a long time. Will give me a reason to take it down off the shelf.

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 4:14 am 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
Thanks Chuck. See the amended photo in my original post.

much appreciated

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 4:26 am 
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Barry

Your guess was right a 1uF 400V cap

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 8:30 am 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
Chuck, thanks so much. I thought I'd figured it out from the schematic and this confirms it. Much appreciated! It appears to be in the grounding circuit for the internal coax shields, and an external fused ground. Don't recall seeing anything like it before. It looks to be pretty sophisticated in this instrument.

thanks again
Barry

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 12:03 pm 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: Norfolk, VA
Is your 1710A ex-DoD, perhaps? We (US) had a lot of gear with odd ground options, especially when it came to hull bonding as we had no "ground" aboard ship.

Our neutral (both 60Hz and 3-phase 400Hz) aboard ship wasn't bonded to the hull, so instruments truly floated (sorry for the pun), and phasing was "tres importante". Any connection to the hull could magnetize the hull, so there was a weekly check by the electricians to verify the isolation of neutral (and other phases) from the hull. Our degauss system aboard ship pulsed every 10 minutes or so. We'd have to manually degauss some CRT TVs after the ships degaussing system left them wonky.

We also used a lot of isolation transformers (within certain benches) to ensure any odd stuff that somehow bonded the neutral to the hull got isolated to prevent the bonding.

I was thinking that if a cap were between a neutral and chassis ground, it would've been removed for shipboard use, or possibly a local modification if otherwise.

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 12:13 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
There's no specific marking on the unit as to any DOD usage. Here's a photo the grounding schematic ... it's pretty involved compared to most.

The 1.0 cap in question is C10, lower left. There's also a fuse to chassis ground. This is in the Generator Output section showing the balanced output, GND, and CT. I haven't read enough of the manual to know what CT is. I'm just learning this unit, and liking it so far.

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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 9:28 pm 
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Joined: Jun Sun 23, 2013 9:03 pm
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Location: Canandaigua, NY
Those units are supposed to be very good, though prone to unobtainium photo-coupler problems. As soon as you try to measure very low distortion levels, you'll appreciate the attention they gave to grounding.


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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 10:56 pm 
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Joined: Jan Tue 10, 2012 8:39 am
Posts: 500
CT usually means center tap. The center between the balanced signal, often going to a trnsformer.


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 Post subject: Re: Sound Technologies 1710 Distortion Measurement System
PostPosted: Sep Thu 12, 2019 11:03 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 4827
Location: Sunbury, Ohio 43074
Bob, you get a gold star. It's more or less an electronic center tap on the balanced output, which in this case seems to be part of the floating grounding system. More involved than I really have energy to dig too deeply into. :). Just knowing what it's for is good enough this time. 8)

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