Is it worth purchasing a 7603 with modules for home use and historical interest? - Page 1
Forum section: electronics / testgear

author: ElizatronicWarfare
author_rank: Contributor
timestamp: September 28, 2021, 12:43:05 am
content: EDIT: Apparently there was a miscommunication - this scope is free, on the basis that I take care of it and get good use from it. I'm delighted!A coworker of mine who also shares a passion for older RF equipment has offered to sell me a Tektronix 7603 scope with 7A26, 7B53A, and 7L5 modules. I have been wanting to get a low-frequency oscilloscope for home use, and this seems like a great way to meet that need while also satisfying my desire for vintage gear. However, I don't have as much knowledge about Tektronix gear as I'd like - Is the 7603 a good secondhand purchase? So far it seems to be in good condition mechanically, and I plan to so some electrical verification before I make my decision to buy or not.Here are some photos as hyperlinks, since they are too large to upload to the forums:7603 with 7A26 and 7B53A installed:https://media.discordapp.net/attachments/815030662838353940/892209008264478791/IMG20210928103637.jpg7L5 in carrying case:https://media.discordapp.net/attachments/815030662838353940/892209009094959154/IMG20210928103716.jpgApologies if I missed previous threads like this in the search bar.

author: bob91343
author_rank: Super Contributor
timestamp: September 28, 2021, 12:45:50 am
content: Yes it's good stuff. But you should get it cheaply and realize that when you want to downsize you won't find many takers. The bottom has fallen out, more or less, for old gear even if high end.

author: ElizatronicWarfare
author_rank: Contributor
timestamp: September 28, 2021, 12:51:35 am
content: Thanks very much Bob, how cheap is cheaply? I see they are going for about two hundred dollars on eBay at the moment.EDIT: scratch that - apparently this is going to me free, on the basis that my coworker got it for free and it's going to a good home. I am over the moon.

author: David Hess
author_rank: Super Contributor
timestamp: September 28, 2021, 01:08:08 am
content: Be prepared to do some restoration. Replacing worn out aluminum electrolytic capacitors, replacing shorted dipped epoxy solid tantalum capacitors, and repairing mechanical issues are common. I would not recommend this type of instrument unless you are comfortable maintaining and repairing old test equipment.The 7603 is a little unusual because it has a larger CRT screen than commonly found in a 100 MHz instrument which some people will find desirable.Note that the 7603 has two vertical bays so with a pair of 7A26 dual trace amplifiers, it becomes a 4 trace oscilloscope. The 7B53A is the common dual delayed timebase for the 7603, however it supports mixed sweep instead of alternate sweep so you will not be displaying 8 traces with it; it was intended more for video applications where mixed sweep might be desired. If some of this means nothing to you, then a 7603 and 7B53A are a great way to learn it but I have never found a modern application for mixed sweep.The 7L5 is a nice bonus if it works. Some people could make good use of it even today.

author: ElizatronicWarfare
author_rank: Contributor
timestamp: September 28, 2021, 01:16:34 am
content: Thankyou David, I appreciate the assessment. I am not averse to fixing this up - it's already known to blow line fuses, but as this comes with original circuit diagrams and manuals, it will hopefully not be too much of a struggle to find the issue.

author: Johnny10
author_rank: Frequent Contributor
timestamp: September 28, 2021, 01:31:46 am
content: Yes 7L5 is cool !The 7000 series scopes are big and heavy and take up a lot of space.But hey, why not. It's FREEI use my 7A22 differential plug-in often.Don't forget to look up.http://www.barrytech.com/tektronix/tek7000/tek7000scopes.html

author: james_s
author_rank: Super Contributor
timestamp: September 28, 2021, 01:33:44 am
content: If you have the space to spare it's a fantastic classic instrument. If I had an infinitely expandable workshop I'd certainly have one or two in my collection.

author: reboots
author_rank: Regular Contributor
timestamp: September 28, 2021, 01:46:21 am
content: I have the bench-top version of the 7603. It's a serious, lab-grade scope, but getting quite long in the tooth. I wouldn't pay over $100 USD, and that's if I needed a 100MHz analog scope. But from the pictures, everything's clean and in good shape. A matching set of good probes would sweeten the deal considerably, because you'll need them anyway. (Although the deal doesn't get much sweeter than free!)The onscreen readout is a handy feature of the 7000-series scopes, and an advantage over portable scopes like the 465. The 7A26 (200MHz dual-trace amp) is a good complement to exploit the full bandwidth of the mainframe. Do note that the 7603 is physically massive for a transistorized scope; the bench-top version is 23" deep.The 7L5 spectrum analyzer is likely to be of very little use for RF, marginal even for the AM broadcast band, but it might be interesting for audio. I have a 7L12 (IIRC), and those analog spec-an plugins are incredibly complex and cranky: lots of shielded modules, lots of coax interconnects, lots to go wrong and inject spurious interference. The ancient digital storage makes things even more interesting. There will be a learning curve to interpreting a useful result from the captured signal.Congratulations!

author: David Hess
author_rank: Super Contributor
timestamp: September 28, 2021, 02:21:32 am
content: Quote from: reboots on September 28, 2021, 01:46:21 amThe reason the 200 MHz 7A26 dual trace vertical amplifier was commonly included with the 100 MHz 7603 was not to preserve the full bandwidth of the 7603, which only makes a trivial different in performance. The reason was that the 7A26 includes the 20 MHz bandwidth limit function and the 75 MHz 7A18/7A18A dual trace vertical amplifier does not. Earlier amplifiers did not include it either which makes me wonder why the 20 MHz bandwidth limit became a commonly desired feature between 1971 and 1974.Quote from: Johnny10 on September 28, 2021, 01:31:46 amThere are a lot of great plug-ins. I especially like the 7A13 100 MHz differential comparators although they are awfully noisy. Alternate dual delayed sweep for an 8 trace display can be added by replacing the 7B53A dual delayed timebase with a 7B92A dual delayed timebase.QuoteOr hit the 7603 entry at Tekwiki. Considerable information on all of the plug-ins and the entire 7000 series is available there.https://w140.com/tekwiki/wiki/7603Note that the 7603 was produced for a long time and there are several variations. Mine has a practically silent cooling fan for which documentation was difficult to find.

author: ElizatronicWarfare
author_rank: Contributor
timestamp: September 28, 2021, 11:00:48 am
content: Tekwiki is indeed one of the first places I went. It was a great resource for getting me started on the basics of just what I had in front of me and what it was capable of.

author: david77
author_rank: Frequent Contributor
timestamp: September 29, 2021, 01:30:37 pm
content: For free and if you've got the space - go for it!I love my 7603 even though it's been a problem child at first. Since I refurbished it over 10 years ago I had no trouble.I've even recently deleted Option 01 on mine. Went to the trouble of retrofitting a readout board. The readout and the big screen are sweet af.

author: PaulAm
author_rank: Frequent Contributor
timestamp: September 29, 2021, 02:02:39 pm
content: Now go find a 7ct1n curve tracer plugin. It works nicely with the larger screen on the 7603.