3. Tek 577 Curve Tracer with 177 Test Fixture
​
If you don't know what a curve tracer is and how useful it is, here's a great site with an introduction to curve tracer basics: http://www.microwaves101.com/encyclopedias/curve-tracer-measurements
​
I saw a Tektronix 576 Curve Tracer in my 20s as a 'vacation student' when I worked in my first job as part of my OND Industry/Education sandwich course, and told myself when I had enough money I'd buy one.
Even now 576s are expensive even on eBay, probably because of the conveniently lit panel to the right of the CRT, that shows at a glance the main selected parameters. The panel itself is a work of art, constructed using a large number of fibre optic leads originating at individual lamp bulbs. The 577 variant lacks this panel and is generally cheaper. I got mine for $200.
​
Left below: Tek 576 curve tracer right below: Tek 577 curve tracer
The 577 arrived in bubble wrap in a large box full of polystyrene peanuts which naturally all moved out of the way when the 40lb beast rolled around inside. As a result, the top half loosened from the bottom half of the chassis, although mercifully still held together at the back by one nut and bolt. At least, I assume it happened in transit...but it was a very good 'AS-IS' price so I'm not complaining:
​
(a) Tightened that nut and replaced the missing one
​
(b) HV rheostat coupling snapped
The plastic coupling probably snapped due to (a). I found someone selling similar sized nylon replacements (eBay seller beeline3) and bought some. They aren't exactly the same size and Tek's 6mm dia aluminium rod was too long, so I replaced it with a clear acrylic one that I could bend into place. It's a little flimsy, but works. I may replace it with a custom length aluminium rod at a later date.
(c) Check ESR of all capacitors over 1µF
I found C731, 3500µF 25Vdc rating on the +9.5V supply line to the -12V regulator U732 was >20Ω, and replaced it with a 6800µF 25V measuring 7334µF 0.030Ω that I had in stock. All the other caps looked ok and I applied power - all low voltage supplies on the 577 in spec.
(d) No ±12V output on the 177 test fixture front panel and ±12V spindle loose (no knob).
Dismantling the 177 revealed the 5kΩ ±12V output adjustment pot front had come away from its body, probably due to receiving a heavy shunt at the knob front. The Tek 311-1368-00 aka Bourns pot is difficult to source. Glued back together with epoxy and checked pot functional.
​
(e) Still no ±12V output on the 177 test fixture front panel.
Resoldered all through board connections until ±12V output appeared on 177 front panel.
(f) Several grey plastic knobs were broken or missing. Usually Tek knobs fetch high prices even on eBay, typically $7 - $15 each. An alternative solution was to replace them with $10 Sugru quick set silicone moulding compound, mixing black and white to 'Tek grey'.
(g) The original cover defeat switch was removed by Tek on the grounds of safety, but I need it.
Bought a latching changeover SPDT, added it to the vacant hole, wired across cover microswitch and added a switch warning label to front panel.
​
(h) Safety cover missing at purchase. On the only occasion I've seen one of these on eBay, the seller wanted $200 for it, which is as much as I paid for the entire 577.
Constructed alternative safety cover using 100mm acrylic cube ($10) and added adjustable cut out safety switch plunger mechanism. Yet to find a reliable cover retention method.
(i) No component holder test fixtures at purchase.
Hex transistor / FET holders are usually expensive on eBay at around $70 to $100 and single transistor holders $30 - $40, yet they are completely passive and of simple construction.
Made a single transistor holder using a SIL socket I already had in stock.
The 577 now displays the expected V/I step waveforms, but needs calibration.
Furthermore the mechanical controls are worn and causing issues. More work required.
New text box
µ Ω ± ° ⌠⌡ ∫ │ ─ √ φ θ Θ ∂ δ ζ ξ ς λ ψ ω τ µ Ω âˆ† Δ ∑ ∏ π Ξ â—‹ ≠ ³ ² ±