Looking for Tek 2445B schematics - Page 1
Forum section: electronics / testgear

author: deephaven
author_rank: Frequent Contributor
timestamp: January 31, 2014, 04:35:00 pm
content: My Tek 2445B was working quite happily, then it suddenly stopped while I was using it. It appears to power up in as much as it still flashes some of the LED indicators on power-up, just like it used to, but there is no trace on the CRT. I think the high voltage circuitry must be at OK because, if I turn it off and on again, I get a brief flash of something on the screen before it goes blank.So I'm looking for schematics plus any ideas from any Tek experts, just in case this might be a stock fault.

author: W7NGA
author_rank: Regular Contributor
timestamp: January 31, 2014, 04:41:38 pm
content: Google Tektronix 2445B and you will find a few links to downloadable service manuals. When you get farther along I would be glad to help if I can. I used to work for Tektronix and have half-dozen 2445B and 2465B's in my lab.daniel

author: deephaven
author_rank: Frequent Contributor
timestamp: January 31, 2014, 04:54:57 pm
content: Quote from: W7NGA on January 31, 2014, 04:41:38 pmThanks for the quick reply, daniel. I did quite a bit of searching for manuals and I could find a service manual, but the only schematics I could find seemed to necessitate me installing some sort of browser add-on which I didn't really want to do. It sounds like you would be very useful once I start probing. Thanks.

author: Kibi
author_rank: Unknown
timestamp: January 31, 2014, 04:56:11 pm
content: Any error code which would normally be displayed on on the CRT can also be displayed via the certain LED's being on.Once settled, can you change you coupling settings? If not, then the control panel is locked out and is displaying an error code. You'll have to get hold of the manual to figure out what the code is.If you coupling (and other controls) are available then there is no error code and you'll have to do some trouble shooting.Is your fan still turning. A failed fan often goes un-noticed and then U800 (horizontal driver) is usually the first to fail. I have a 'scope with a dead U800.

author: deephaven
author_rank: Frequent Contributor
timestamp: January 31, 2014, 05:09:49 pm
content: Quote from: Kibi on January 31, 2014, 04:56:11 pmThanks for the comments, Kibi. The fan is running, I will look for error codes on the LEDs when I get chance to run it up again. I have now found the full manual complete with schematics and it is very comprehensive. Just in case it helps anyone else reading this topic, I found it athttp://bama.edebris.com/manuals/tek/2445/

author: W7NGA
author_rank: Regular Contributor
timestamp: January 31, 2014, 05:12:34 pm
content: there is a Tektronix Yahoo! Group ... mostly ex-Tek employees that really know the older products and can help getting parts.

author: deephaven
author_rank: Frequent Contributor
timestamp: January 31, 2014, 05:15:28 pm
content: Quote from: W7NGA on January 31, 2014, 05:12:34 pmThanks, daniel. Is there an appreciable difference between the 2445 and 2445B? The full manual I have now is for the 2445

author: z01z
author_rank: Regular Contributor
timestamp: January 31, 2014, 07:40:34 pm
content: Yes, they are quite different. You'd be better off with a 2465b manual, search for "070-6873-00_2465bSvc_Sep89.pdf" and download that.

author: deephaven
author_rank: Frequent Contributor
timestamp: January 31, 2014, 09:16:23 pm
content: Quote from: z01z on January 31, 2014, 07:40:34 pmThanks z01z

author: deephaven
author_rank: Frequent Contributor
timestamp: January 31, 2014, 10:17:10 pm
content: Well, some progress. I followed the troubleshooting flow chart to the point where I tweaked up the Grid Bias preset. This got me a display with the timebase and vertical sections appearing to work. However, the Intensity front panel control does nothing, and rotating the Readout Intensity control seems to make the readout (alphanumeric display) intermittently come and go. When the readout is in it's off state, there is a dot in a random position on the screen instead, so it looks like the readout generator grinds to a halt at a couple of different positions of the Readout Intensity pot.I wonder if this rings any bells with anyone?

author: deephaven
author_rank: Frequent Contributor
timestamp: February 01, 2014, 09:13:20 pm
content: Can another 2445B owner do a test for me? When I go into diagnostics and invoke EXER.01 to get the pot values and rotate the intensity knob, it only goes from 80 at the anticlockwise end to FF at the clockwise end. Is this right? I say this because all the other pots I try go close to FF to 00 in their range.Any help would be appreciated.

author: z01z
author_rank: Regular Contributor
timestamp: February 01, 2014, 10:19:43 pm
content: Yes, that behaviour is correct. If you check table 6-9 on page 6-16 of the 2465b service manual, it's described there.Just to be sure, I've also checked the intensity pot on my 2465a and it works like that.

author: deephaven
author_rank: Frequent Contributor
timestamp: February 01, 2014, 11:06:11 pm
content: Quote from: z01z on February 01, 2014, 10:19:43 pmI didn't notice that entry and I had been looking right at it! Thanks. Will have to look elsewhere for the problem,.

author: deephaven
author_rank: Frequent Contributor
timestamp: February 02, 2014, 05:48:54 pm
content: If anyone has any experience on the insides of this scope, I would be interested to hear. If I look at U650 pin 25 (which I believe is a serial control data input), there is no data when I operate the main intensity pot, but there is data if I operate the readout intensity pot. This is strange because the main intensity pot appears to give the right data when in diagnostic mode.