TEK 465 - Page 1
Forum section: electronics / testgear

author: andy3055
author_rank: Super Contributor
timestamp: November 24, 2020, 05:40:04 pm
content: I am looking at a 465 (low serial) that I got a few months back which has the typical CH2 issues with those flimsy switch contacts. Managed to clean the 2 contacts towards the front of the scope which are operated by the AC/GND/DC selector. For those members who had done this before me, how did you do the rest operated by the knob that are hard to get in to? inserting a strip with IPA is very hard and I don't want to bend them in the process.The second question is about the tantalum caps. Which ones to replace and which ones to leave alone? I see a whole lot of them all over the place and was planning to replace what is on the interface board. Definitely those on the power supplies.Any ideas are much appreciated.Thanks.

author: tautech
author_rank: Super Contributor
timestamp: November 24, 2020, 07:05:46 pm
content: Jump on this recent post and quote it so the chaps in the TEA thread can give you the full run down on their experience with 465's:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg3339050/#msg3339050

author: andy3055
author_rank: Super Contributor
timestamp: November 25, 2020, 01:46:30 am
content: Thanks Tautech. I found the exact same thing Med has addressed and I have posted asking him how he removed those "blocks" to expose the switch contacts. I am waiting hopefully!Regards.

author: helius
author_rank: Super Contributor
timestamp: November 25, 2020, 01:50:15 am
content: Does the 465 have any non-hermetic wet tantalum caps? There is one in the 475 timebase circuit that likes to leak.

author: tautech
author_rank: Super Contributor
timestamp: November 25, 2020, 01:58:59 am
content: Quote from: andy3055 on November 25, 2020, 01:46:30 amActually I was a bit surprised Med hadn't already spotted this thread but knowing his lady cop friend was coming for thanksgiving I think we can excuse him for the oversight.I have been tempted to get a 4*5 or 2465 but seeing some of the headaches they can give I gave them a mis and splashed out for a 500 MHz Siglent instead. Sure a Tek would have been far less outlay but time is money if you need to fix it. Been there, done that and burnt the Tee shirt !

author: 0culus
author_rank: Super Contributor
timestamp: November 25, 2020, 02:21:21 am
content: Quote from: tautech on November 25, 2020, 01:58:59 amTEA Heresy!!!!

author: tautech
author_rank: Super Contributor
timestamp: November 25, 2020, 02:35:18 am
content: Quote from: 0culus on November 25, 2020, 02:21:21 amback at ya !Actually had to put some old TEA in the recycling just last week as time to fix it was more than its value.Er indoors had been going on at me about it and she was right for once so it had to go to free up space for new stock for the TEA enabler.

author: med6753
author_rank: Super Contributor
timestamp: November 25, 2020, 03:07:44 am
content: Quote from: tautech on November 25, 2020, 01:58:59 amI spotted this thread after I responded to OP in the TEA thread.The question of beaded tantalums came up. They areALLpotential time bombs but unfortunately the 465/465B has dozens of them. It can be a very time consuming and expensive undertaking to change them all. My experience is some values are more prone to magic smoke than others. Mainly 22uf, 33uf, 47uf, and above. ThoseHAVEto go.

author: james_s
author_rank: Super Contributor
timestamp: November 25, 2020, 05:13:07 am
content: I've had a 465B for about 20 years, I've never replaced any capacitors in it and it still works perfectly, or did the last time I used it about 6 months ago. I generally don't do shotgun capacitor replacements anymore, if there's one where failure causes damage then go for it but otherwise I'd just keep an eye out for issues.

author: andy3055
author_rank: Super Contributor
timestamp: November 25, 2020, 06:20:29 am
content: My plan is to replace only those critical tantalum caps on the power rails as the next person getting this must have something to do as well!

author: tautech
author_rank: Super Contributor
timestamp: November 25, 2020, 07:22:39 am
content: Quote from: andy3055 on November 25, 2020, 06:20:29 amYep, why the Tek designers didn't derate them just a little more IDK.Using 15V tants on a 12V rail was always gunna get ugly.

author: med6753
author_rank: Super Contributor
timestamp: November 25, 2020, 10:02:22 am
content: Quote from: tautech on November 25, 2020, 07:22:39 amI don't think Tek did this in a vacuum. It would not surprise me if this was a recommendation from the capacitor manufacturers. And within the normal 10 year use window that the instrument was expected to be used the derating curve worked just fine. But we're now talking 40+ years later plus total power on hours and the derating curve no longer fits and things can get ugly.

author: med6753
author_rank: Super Contributor
timestamp: November 25, 2020, 10:17:44 am
content: Quote from: james_s on November 25, 2020, 05:13:07 amI'm not surprised. I think it's highly dependent on total power on hours in addition to 40+ years old. The 465B that I referred to here I believe has many, many hours on it. It's not only blown several tants but also needed the PSU caps changed out due to excessive ripple. In addition some heavy handed tech damaged beyond repair the Channel 2 attenuator switch deck which required a complete change out. And just last week I was getting HV oscillator noise on the trace due to bonding issues between the HV cage to case to chassis.I have another 465B which I believe has fewer hours and if I recall correctly had perhaps one tant blow but as insurance I replaced many of what I determine to be high risk. But that scope also needed a CRT change due to a focus issue. I suspect the scope was dropped and the CRT gun assembly knocked slightly out of alignment.And then I have a darling 475A which I believe got little use and was a shelf queen. Did a cleaning and a check of the cal and it's good to go. But as insurance I did change out some (but not all) of the high value tants to avoid future issues.

author: andy3055
author_rank: Super Contributor
timestamp: November 25, 2020, 05:58:20 pm
content: Quote from: helius on November 25, 2020, 01:50:15 amSorry for the late reply. After seeing this, I remember noticing at least one of those on the interface board somewhere close to the back center (C1534). I did notice some leakage where the +ve lead is soldered in and was wondering why it showed the flaky stuff near the pin going in to the board but not near the cap itself-where the case is sealed to the +ve end. Now that I saw it, I plan to look for more of them damn things.

author: james_s
author_rank: Super Contributor
timestamp: November 25, 2020, 07:05:05 pm
content: I don't know how many hours are on mine, it's in great shape cosmetically but I also had to change the CRT when I got it due to a focus issue. I rarely use it anymore but it was my only scope for many years before I got a DSO. I keep it partly for nostalgia and partly because when I want to use XY mode to check a vector game board my DSO doesn't even come close.