Tektronix 576 - broken CRT! - Page 1
Forum section: electronics / testgear

author: velik_kazakov
author_rank: Regular Contributor
timestamp: September 19, 2017, 01:16:11 pm
content: Long time looking to buy good tracer for my lab, but no success. Find one Tektronix 577 from UK and think to buy it. And at this time find this one on ebay and get it. The problem for finding curve tracer is with shipment to me. I'm in Bulgaria and the items that is shipped to here are some for one year. I'm looking for Tek 576 or 577, but they are very heavy for shipment.This oneis offered with international shipment and I pay it with shipment and import charges to here , because looking that this item is with working CRT and HV. All other think that can be repaired.The item come here with broken CRT (because was bad packing or it is cracked in shipment). It work for now but want to ask to do something with the screen or to keep it as is and to cross fingers.Have some other broken parts, but all other will be repaired w/o problems. Just for testing I clean some switches and all work fin for now (I'm happy - have a working part of Texas Instruments at home). Have a problem in step generator but this will do when have a time. Will check all inside when have a time for it, I just worry about the CRT.

author: MadTux
author_rank: Frequent Contributor
timestamp: September 19, 2017, 01:38:38 pm
content: I wouldn't worry too much about the CRT, vacuum begins where the phosphor ends. (since the phosphor is sedimented from watery suspension onto the front plate, as seen in the Tek "How to make CRTs" videos) And your CRT only has the edge of the glass chipped off, it didn't start a crack and is still quite far from the phosphor, so you were lucky this time. If there had been even a tiny leak, the CRT would be on air by now, so just keep it as it is.And keep in mind that the retards at ebay global shipping don't have a clue on how to ship sensitive items.

author: Testtech
author_rank: Regular Contributor
timestamp: September 20, 2017, 11:44:28 pm
content: This instrument was dropped either during shipping, or other handling. I have worked on many dozens of 576's, and have seen this before. The CRT impacted the top of the frame. The face plate has a chip out of it, but should not leak, just be careful with it!As for the collector supply isolated chassis, the same thing happened. An impact broke the insulators. Unfortunately, Tek used the same plastic for those, as for their knobs, an unfilled, weak styrenic, that breaks easily if placed in tension.These two chassis must remain electrically isolated, to about 2KV. The floating top half, if it moves too much, will break the coupling on the Looping control, and the Polarity switch coupling may disconnect. These are difficult to repair..Good luck with your 576, a truly great instrument!

author: velik_kazakov
author_rank: Regular Contributor
timestamp: October 06, 2017, 12:50:13 pm
content: Quote from: MadTux on September 19, 2017, 01:38:38 pmWill cross the fingers for CRT.Quote from: Testtech on September 20, 2017, 11:44:28 pmI'm sure - the tracer is dropped. About this insulators - I will order some PA6 (or PA66) and will try to make it in the next week and to exchange all of them (all 4 are broken).Other that I make for this item:Remove CRT and try to set straight the metal part over the CRT and all support items for it. Think all is good now. Find some bad caps and exchange all them. Now the tracer have no any ripples on the power rails and work very well. I'm very happy with it in my lab. Looking to find it very long time.

author: velik_kazakov
author_rank: Regular Contributor
timestamp: October 27, 2017, 06:27:55 am
content: Find a time to finish this repair and will post some pictures. I do the spare insulators from PA6 - 2 parts to keep using original screw (I can't find in Bulgaria the longer screw with the same thread). One insulator need to cut to can install inside - there have no enough place to fit it.Receive some spares bulbs at this time from USA (thanks to cycle_collector). Now all is ok with my tek576.