From ???@0x00001AB3 Mon May 12 10:37:19 2003 Path: pitt.edu!newsflash.concordia.ca!nntp.cs.ubc.ca!logbridge.uoregon.edu!feed2.news.rcn.net!feed1.news.rcn.net!rcn!not-for-mail From: Chuck Harris Newsgroups: sci.electronics.repair,sci.electronics.equipment,rec.audio.tubes,rec.audio.pro Subject: Re: Beginner looking for o-scope (Tektronix 465) Date: Mon, 12 May 2003 10:18:47 -0400 Lines: 114 Message-ID: References: <38bba.5$a73.84@news.aloha.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Trace: UmFuZG9tSVaZ+PEa7yr152aBL9hJPZr4jWz5pKFWnxzgnZiQLvAwc0QPq0HZiN1T X-Complaints-To: abuse@rcn.com NNTP-Posting-Date: 12 May 2003 14:21:27 GMT In-Reply-To: X-Accept-Language: en-us, en User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 Xref: pitt.edu sci.electronics.repair:333639 sci.electronics.equipment:66435 rec.audio.tubes:250859 rec.audio.pro:940177 Status: N Jim Yanik wrote: > YUk.I would never recommend an ancient tube scope (boat anchor)for a > beginner.Get a 2213/13,2235,465/475. > Or even a T922/932/935.The T922 and 932/35 are the simplest scopes,no TEK- > made ICs. > Spoken just like a man who ain't done it! The ancient tube scopes (545A/B, 547, 585A) are very easy to work on, work very well, are extremely rugged, and best of all are cheap! Very very cheap! Perfect for a newbie who wants to work on tube audio circuits. The single timebase versions of the above are also good, but these scopes are so cheap, you might as well aim for the best of the litter. Probably should avoid the 50x, 51x and 52x scopes. Tek was still learning what a lab scope ought to be back then. (Ny first scope was a Tek 513D. It still works, but it was a bitch to get working! The trigger is very unusual.) 465's are fragile, and can be easily ruined by an errant soldering iron on their lucite pc boards. Tek broke some new ground with 465s, being all solid state, using lots of custom cam switches, and IC's. The switches are getting old now, and the cams are breaking, and trashing the little gold leaf contacts. Pots break, and leave the shafts dangling. When they are in good repair, they are nice scopes. But they haven't aged well. The 475 has a very high anode voltage. 18KV, IIRC. Tektronix seems to have used the wrong kind of wire on the anode leads, and the HV leaks out all along the lead and around the anode terminal. When it does, it wrecks the HV section. The 475's high bandwidth (200MHz) is had by using an electrostatic magnifying lens to get a high deflection sensitivity. This reduces the slew rate required by the vertical amplifiers, but also results in a very fuzzy beam. It is still a great scope. But has most of the problems of the 465. I use one from time to time. But I wouldn't recommend one to a new user. They would be helpless if it broke. Lots of custom ICs. Lots of diddly little switches and contacts. The 22xx series runs with too low an anode voltage to get a respectable beam intensity at high sweep speeds. They were the very very cheap 60 to 100Mhz scopes. They were intended for hobbiests, and TV repair shops. The ruggedness was left out, so was the famous Tektronix high performance trigger, and the trademark snappy intensified beam. They are choc-a-bloc full of custom ICs, none of which are available today. The whole scope fits on a single circuit card. The 24xx is an extremely good series. A 2465 is my main scope. very long lasting....I bought mine new, and I suspect it is a keeper. My 2465 has been in continuous use for 20 years. I check it every couple of years, and it still is in calibration. But if you use it on tube circuits, and exceed the 400V vertical preamp limitation, you will burn out a terribly unavailable hybrid vertical preamplifier. You will most likely have to find a donor scope inorder to replace it. There are no non custom parts in this scope! 326s are reliable, except for a zener in the deflection circuit that is run at too low a current and will fail, causing the sweep to scrunch up. They are best run with bananna plugs and a wall wart instead of the battery pack and power supply. 323s are good too, but low bandwidth, and single trace. 5xxxs and 7xxxs are good scopes, but fragile in the user interface department. Ham handed users simply murder them. Most all parts are custom, and unavailable. 5000 series Trigger ICs seem to be especially prone to early death. Fortunately, plugins are quite plentiful, and fairly cheap. The T9xx series was used mostly in schools where they couldn't afford a good scope. The students always trashed them, and nobody I ever met liked to use them. They were very low bandwidth, had a low anode voltage, and hence a dim beam. Triggers were easily killed, and never worked very well to begin with. In an early EE lab where we used them, the students were always fighting over who got to use the instructor's 545B. Even though the support technicians tried to keep them running, there were always at least 2 that had serious problems on any given lab day. The 545B ALWAYS worked. It never needed to go to the shop for repair. The single biggest problem I have found in Tektronix 545s of any flavor has been in the horizontal output section. I have run into open circuited tapped 25K and 30K resistors a couple of times. With 585s, the vertical output tubes used to blow, and the relays used to fuse contacts before Tek put out a modification for the power supply. I haven't seen that problem since. I rarely find bad tubes in any of these scopes. Cathode interface shows up quite alot now days, but it is only a problem with maintaining perfect amplitude calibration from DC to max bandwidth. If you can stand the scope to be within 3%, it is not much of a problem. (Spec was 3% anyway.) MAKE SURE YOU ALWAYS USE SILVER SOLDER WHEN SOLDERING THE TERMINAL BLOCKS!!! ALWAYS! -Chuck, WA3UQV Note: I have been using and repairing Tektronix scopes for around 34 years. I am an EE, not a repair technician. My repair efforts have been in maintaining the scopes that I have had to use. I have repaired all of the scopes I have mentioned above, with the sole exception of my 2465. It has never needed any repair of any kind. I hope it remains that way! Very few scopes break when I use them. Very few probes break when I use them. I'm not sure what that means! But I have my suspicions ;-)