TEKTRONIX 570 Tube Characteristic-Curve Tracer

Extremely rare:one of only a handful of units ever built by Textronix with a
continously variable plate-sweep supply. In excellent shape and
one of the last few hundred units produced. Ser. no. 005372.

This Tektronix Model 570 Characteristic-Curve Tracer lived the first part of its working life at a medical school in Portland, Oregon, USA. From there, it was purchased by a long-time friend of mine, Jack Senecal who used it in the development of tube circuitry for Precision Fidelity, a small producer of pre- and power amps in the Portland area during the mid-'80s. I bought it from Jack about 1987.
Aside from its excellent overall physical and electrical condition, a number of features make this 570 unique:

  • it has been fitted with an original Tek' bezel that facilitates the use of a Tek' 'scope camera
  • A Tek C50 'scope camera is included in this sale, click here to view.
  • it was factory-fitted with a 3A Variac in the primary of the plate-sweep transformer
  • the original 3A unit has been upgraded to a 5A unit as I fritzed the original while doing the screen grid geometry redevelopment of the initially factory-defective Ei KT90 for David Manley back about 1991.
  • the 5A Variac has been connected to supply 140VAC to the primary of the plate-sweep transformer, providing thereby a continuous 0-to-650V range of plate sweep -- a very handy feature, click here to view.
  • it has been fitted with a switch that allows the placement of an external plate load such as a current source, click here to see this feature.
  • it has been fitted with another switch whereby the 50mA-div range of plate current can be increased to 100mA/div. Together with the 0-to-650V plate-sweep range this feature allows a 1A by 650V display of plate characteristics, click here to see this feature.

As well, two of each the socket adapters for octal, 7- and 9-pin tubes and a full complement of interconnecting leads are included.
Although it didn't really need it, I completely re-tubed this unit about 500 hours ago and just lately Irecalibrated it to easily meet the original, factory specification.

To see a large page of pictures of the inside of the unit, click here.

To download a 780K PDF of the first 11 pages of the manual and an ad from a 1956 issue of "Electronics,"
click here. Note however that the PDF has been made from scans of the manual for the first series of 570s, made in the mid-'50s. The manual supplied with the unit is nearly identical but is 8 1/2" x 11" format.

The unit will be properly crated in a braced and 1" Styrofoam lined solid plywood crate for which there will be a an additional $US75.00 charge. Short of an all-out disaster during shipment, we guarantee that the unit will arrive, intact, undamaged, in "plug and play" condition and meeting, as previously stated, the original, factory specification.

To see a page of pictures of the unit as it was being crated,
click here.

Over the last 15 years I have owned 8 Tek 570s and of these one was sold to Roger Modjeski of RAM Labs, two went to David Manley of Manley Labs who shipped one to Ei (Electronska Industrija) in what was then Yugoslavia. For lack of a 570 Ei fouled up the anode/screen geometry in the first of the now famous KT90s and, using one of my 570s, I sorted out that problem for David.
About a year ago another was sold on eBay to a very happy purchaser in Japan. Still another 570 went to Mr. Yeung, a reviewer for the Hong Kong publication "Audiophile" while yet another went, as I recall, to the folks at VAC in the USA.

Some Specifications and Features of the Tektronix 570 Characteristic-Curve Tracer
Vertical Deflection (click for a large page of close ups):
200uA to 50mA per div, 11 steps in a 1,2,5 sequence, with an additional range of 100mA/div being toggle switch selectable while in the 50mA/div setting.
Display of one of: plate, screen or control grid current is switch selectable.

Horizontal Deflection
(click for a large page of close ups):
100mV to 50V per div, 9 steps in a 1,2,5 sequence.
Display either: plate or control grid voltage is switch selectable.

Plate Sweep
(click for a large page of close ups):
continuously variable from 0 to: 6.5, 13, 26, 65, 130, 260, 390, 650V full wave AC @ 120Hz. and a max. current of 250mA avg. and 1A peak.

Grid Step Generator
(click for a large page of close ups):
The number of steps per family is selectable from 4 to 12 with grid voltage steps in a range from 100mV to 10V per step with 3% accuracy.
The maximum current is 50mA avg. and 100mA peak.
This generator's output may be offset in the positive direction by as many as 8 steps (+80V) thereby allowing the investigation of operation in the "grid current" region as long as the supply's current limitations are respected.

Positive DC Voltage
(click for a large page of close ups):
This regulated supply provides five calibrated steps from 0 to: 20, 50, 100, 200, 300VDC @ 3% accuracy.
Continuously variable, uncalibrated, from 10 to 300V.
Maximum current of 50mA avg. and 150mA peak.

Negative DC Voltage
(click for a large page of close ups):
This regulated supply provides a continuously variable output through the range of 0 to -100VDC and is used to set bias voltages i.e. to vary the voltage on suppresser grids in pentodes where the G3 connection is brought to a separate pin.

The Type 570 Characteristic-Curve Tracer presents a graphic analysis of vacuum-tube characteristics under a wide range of operating conditions.

Calibrated horizontal and vertical deflection make it possible to measure the characteristics directly or the curves may be compared with preselected tube characteristics that have been reproduced on a mask over the cathode-ray tube.

Front panel switching between two test sockets permits rapid comparisons between two tubes or between two sections of the same tube.

By means of various switch settings for the vertical and horizontal deflections the following displays are possible:

  • Plate current vs. plate voltage
  • Screen current vs. plate voltage
  • Grid current vs. plate voltage

  • Plate current vs. control grid voltage
  • Screen current vs. control grid voltage
  • Grid current vs. control grid voltage

The 570 can configured to provide displays of the characteristics of tubes connected in cascode, active plate load, compound connection such as the triode/tetrode operation of two output tubes or -- with an easily built additional sweep supply in series between the output of the +DC supply and the screen of a beam tetrode or pentode -- the characteristics of a tube with variable "percentages" of ultra-linear operation.

Additionally, the 570 can display the characteristics of solid state devices such as zener diodes, N-channel small-signal depletion-mode JFETS used in differential stages and high voltage, high power, enhancement mode MOSFETS.

Some FAQs:

  • Q: How much is your reserve?
  • A: $US4500.00

  • Q: Is the CRT OK?
  • A: As far as I know: yes, it's just fine and produces a MUCH sharper display than the pix would lead one to believe.

  • Q: Where can a replacement CRT be found?
  • A: While I do know where there is one new in the box, I suspect that the CRT from a 575 transistor curve tracer will sub in just fine and 575s are easily found. Perhaps more info can be had from the curator(s) of the virtual Tektronix Museum you can see here: http://www.geocities.com/r_corriveau/500/500series.html#tline

  • Q: Why are you selling this unit?
  • A: I'm building another, much higher voltage unit with dual CRT displays, automatic display switching, built-in ultra-linear display capability and so on. This is NOT an item I plan to produce for others

  • Q: How much will it cost to ship to me in (your location)
  • A: The crate is approx 30 x 20 x 24 inches and weighs 125 to 150 lbs. It travels as one piece with forklift cleats. With that info you can sort out what you need to know with the carrier of your choice. We will work with tem. Interenational shipment is easily handled.

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