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 parameter. 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 of $200 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 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.