Problem with my Tektronix 2465 - Page 1
Forum section: electronics / testgear

author: McBryce
author_rank: Super Contributor
timestamp: February 12, 2016, 02:30:16 pm
content: Hi all,after several months of non-use, I decided to check the accuracy of my trusty Tektronix 2465 scope (the original non A/B version with lever switches), to see whether it's doing what it should. Luckily, it seems to be still as accurate and reliable as always. All channels are still spot on as far as voltage and frequency are concerned, however I've found one minor problem that I'd like to sort out: On channel 2, when set to 2mV/Div, the DC offset is so far out that I can't even get the beam onto the visible screen area (with input shorted). Channel 1 isn't great either. I have to turn the Y-Pos all the way to the right to get CH1 beam into the centre of the screen, but I can get it there, whereas CH2 never makes it back onto the screen at all. I've browsed the Service Manual, but I can't find any internal pots to tweak this.Can any Texperts here point me to the right place?McBryce.

author: Orange
author_rank: Frequent Contributor
timestamp: February 12, 2016, 02:54:46 pm
content: Have you tried to run the auto balance routine ?You can invoke this by pushing up both input coupling levers at the same time.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: February 12, 2016, 02:55:25 pm
content: Here is what the user manual says:CheersAlex

author: Analogdevice
author_rank: Contributor
timestamp: February 14, 2016, 09:18:18 pm
content: Hello,I have Tektronix 2465B and during selftest or pressing the switches the LEDs and scale illumination flashes. Everything works fine besides that. Any reason or idea?I have SMD version of vertical board, caps are changed and power supply is in good condition.Thanks!

author: McBryce
author_rank: Super Contributor
timestamp: February 15, 2016, 09:29:03 am
content: Quote from: Alex Nikitin on February 12, 2016, 02:55:25 pmThanks, I wasn't aware of that feature, I'll give it a go tonight.McBryce.

author: McBryce
author_rank: Super Contributor
timestamp: February 17, 2016, 09:08:58 pm
content: Tonight I tried the Auto balance routine. It goes through the process and relays can be heard clicking while a dot jumps around the screen, but unfortunately when it's finished the situation is still the sameAny tips on where I should be looking inside the case?McBryce.

author: tautech
author_rank: Super Contributor
timestamp: February 17, 2016, 10:15:56 pm
content: Quote from: McBryce on February 17, 2016, 09:08:58 pmThe obvious?PSU to spec?

author: McBryce
author_rank: Super Contributor
timestamp: February 18, 2016, 09:39:14 am
content: I'll open it up and start checking things like that at the weekend. The fact that the problem is only on Channel 2 (Channel 1 works perfectly) makes me think that it's something that won't be common to all channels like the PSU.McBryce.

author: tautech
author_rank: Super Contributor
timestamp: February 18, 2016, 09:56:16 am
content: Quote from: McBryce on February 18, 2016, 09:39:14 amSure, but if local capacitance to Ch2 was sick as well as the PSU caps that might explain your symptoms.

author: McBryce
author_rank: Super Contributor
timestamp: February 18, 2016, 10:13:45 am
content: That was my thought too. The caps have never been changed in this scope, so it might be time to do a complete re-cap.McBryce.