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Used test equipment opportunity
To: "'CRTech'" <crtech@crtech.org>
Subject: Used test equipment opportunity
From: "gcartercrt" <gcartercrt@gcarter.us>
Date: Thu, 21 Sep 2017 12:59:50 -0500
Content-language: en-us
Thread-index: AdMzAJexbT//DY5USQSfChK+jH8rYg==

Here is an opportunity for those of you who need some test equipment or like to collect vintage gear.  The price is right!


I am in the process of cleaning my basement.  I have several pieces of test equipment that I am no longer using.  Much of it belonged to WFMT.  When I retired I knew that a lot of the test equipment there would be scrapped, so I asked if I could have it.  They said yes, so it came home and has been living in my basement ever since.  All of this was working when last used except as noted.  I would like to find a good home for it.  Most of this stuff was new in the 1980’s.  It is not really portable and is better suited for a test bench.  None of it has been calibrated in years, but it was all stable and should be close.  There are calibration services still available if necessary.


I am willing to give it away, and am only asking that whoever wants it either pick it up in LaGrange, IL (west suburban Chicago)  or pay for UPS packing and shipping. 


Everything has full manuals included.  Here is the list.


1.       Clemens SG83C RF signal generator.   This was popular when I was a student.  I bought this one several years later.

2.       Sound Technology 1000A FM Alignment generator.  This creates a modulated FM signal.

3.       Amber 4400A audio test set.  This is a full audio test device with generator and analyzer.  There are some switch issues, probably some switch cleaner will take care of them.

4.       Altair T2DS tape transport diagnostic system.  Do not confuse this with the Altair computer (no connection).  It is a self-contained wow and flutter analyzer, and was the first available unit to measure scrape flutter.  One of its more useful features is an output of the flutter signal (minus the test signal) that can be fed to an FFT to see the flutter component frequencies.

5.       Audio Precision System One + DSP – this was the first generation of their test set.  It has stereo inputs and outputs.  It requires a computer and a special interface card (included).  The problem is that the card is ISA and the software requires Windows 3.1.  Later versions will not work due to software “hooks” that are different.  This unit cost about $10,000 new.  I would love to keep it as it has better audio specs than most stuff, plus it can be automated, but it is big and bulky especially with the computer.  I would love to see someone with more knowhow than I have create a new USB interface for the device along with software that would run on a modern OS.  This would be a killer system with a laptop.  Full package includes computer, printer, software, cables, and manual.  Manual includes interface information which would be a good start for the project.  If someone could “modernize” the interface and drivers, I suspect there would be a limited market for it, as there are still some out there.  However, most have been scrapped in favor of newer stuff.

6.       2 8 ohm 250 watt non-inductive resistors used for power amplifier testing.


All the rest of the equipment is from the Tektronix TM500 series.  Each piece of test equipment is a module and requires a power supply.  Most modules are 1 unit wide, but a few are 2 as noted.  A mainframe is required to operate the modules.  To maximize the usability of the equipment I would prefer to match the number of modules to the mainframes.

1.       PG505 high voltage pulse generator

2.       SC503 10mHz storage scope.  Storage is analog and does not work well.  Scope is otherwise fine.  2 units wide

3.       DC503 digital counter

4.       PS503A dual tracking power supply

5.       DM502 digital multimeter

6.       FG504 40mHz function generator.  Signal can be modulated. 2 units wide

7.       AA501 distortion analyzer.  2 units wide

8.       AA501 distortion analyzer with intermod option (second unit) 2 units wide

9.       TM503 3 wide mainframe with protective face cover

10.   TM504 4 wide mainframe

11.   TM506 6 wide mainframe

12.   TM506 6 wide mainframe with rack ears

13.   Storage module.  This is a 1 unit wide module with a lid.  You can plug it in to a mainframe to hold cables, tools, etc. if you go on the road.


These last two pieces are one of a kind.  One of the cool features of the TM500 series was that they had some really cool “do it yourself” modules.  The modules came in one or two unit sizes, complete with front panel (the panel was thin aluminum front with a plastic back and aluminum inner panel), PC board with proper edge connector and high quality perf board, and all necessary hardware.  The standard test gear mostly had unbalanced inputs and outputs (usually BNC connectors) and only a single connection.  Since we were mostly testing professional stereo equipment, true balanced connections were necessary as were stereo.  I built two add-ons to provide this and a few other capabilities.  When coupled with the other equipment it becomes very handy to perform stereo testing. The electronics were designed to be as good as the measuring equipment so they did not affect the readings.  The front panels were professionally done, but the inside is all hand-wired perf board.  Both of these units have been used as recently as 6 months ago.

1.       TS501 (my designation) input side audio test set.  2 units wide.  Takes a single input (BNC) or internal signal and converts it to stereo balanced outputs.  A front panel switch allows choice of external input, internal IM generator, internal TIM generator, and internal flutter generator.  Front panel switches allow either output to be balanced or unbalanced.  Each output can be independently terminated with either a lo impedance, 600 ohm, or 150 ohm precision resistor.  The phase of the right channel can be flipped relative to the left with another switch.  A precision attenuator allows up to 49.9 db of attenuation in .1 db steps.  A meter output is provided prior to the attenuator to insure a stable input   A precision 75 usec de-emphasis can be applied to the outputs for classic proof-of-performance measurements of FM.  The outputs are banana jacks with standard ” spacing so that they will accept a Pomona triple-banana plug.  This unit does not have a true manual, but I can provide schematics and an explanation of how it works.

2.       TS502  (my designation) output side audio test set.  1 unit wide.  Accepts stereo balanced signals on triple-banana jacks.  Both inputs can be switched to be balanced or unbalanced (one switch for both channels).  A switch selects which input is fed to the outputs.  Two outputs are provided – the main output and a “meter” output.  The meter output is not affected by any other switches.  The main output can have a precision 30 db attenuation applied.  The main output can be selected to be either flat, A weighted, or 15 kHz low-pass filter.  The 15 kHz low-pass is a commercial UTC filter.  One of the most unique features of this unit is a phase meter.  This is a 5 segment bar-graph display that shows the phase relationship between the two inputs.  Each segment is approximately 36 degrees, but the display also uses brightness to show approximate smaller amounts.  Two additional indicators show lead or lag (left relative to right).  This phase meter is something that I invented.  Unlike most phase meters it is easy to read, and is relatively intolerant of level differences between the two channels.  It is accurate with up to 40 db of difference between channels.  Its primary use was for aligning heads on a tape recorder.  We had some special alignment tapes (still available on special order) that were a 5 second sweep from 20 Hz to 20 kHz.  Playing this tape back through the phase meter allowed us to adjust alignment on a playback head in about 30 seconds.  Since it was a fast sweep and we were able to see it quickly, we could see the alignment at all frequencies, thus ensuring the absence of false peaks that you typically can get with spot frequency tapes (typical alignment tapes).  Again, this unit does not have a manual, but I can provide schematics and explanation of how it works.


That’s about it.  If you want more information about the Tektronix stuff, there is good info on the web.  The Audio Precision has limited information available on the internet, and the manufacturer won’t even talk to you about it.  I can provide some information on all of it, so feel free to ask.


Please respond off-list to equipment@gcarter.us.  First come-first served.  Questions will hold an item until released.  Responses to other email addresses including this list will be ignored.


Gordon Carter


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