another 2465 300mhz to repair - Page 1
Forum section: electronics / repair

author: Daxxin
author_rank: Regular Contributor
timestamp: September 20, 2015, 09:27:20 am
content: bought this from ebay stock as is , display show everything correct and traces , knobs and buttons is working but miniature on displayany hints?

author: Isad
author_rank: Frequent Contributor
timestamp: September 20, 2015, 09:39:32 am
content: The coil on the back of the crt might have been moved back a bit or to much tryto push it a bit foward.If that doesnt work then probably a logic fault.

author: SeanB
author_rank: Super Contributor
timestamp: September 20, 2015, 09:53:00 am
content: Low supply rails for the CRT drive side. You have some CA 200VDC rails there, and if they are low then the trace will not fill the screen. Turn down the brightness otherwise you will burn the CRT with that permanently. The scope will probably need some replacement capacitors in the power supply as well.

author: mij59
author_rank: Frequent Contributor
timestamp: September 20, 2015, 10:12:15 am
content: Quote from: Isad on September 20, 2015, 09:39:32 amAn oscilloscope with a crt uses electrostatic defection, not magnetic like the old fashion tv.

author: Daxxin
author_rank: Regular Contributor
timestamp: September 20, 2015, 10:47:07 am
content: SeanB i am looking for the rail you mention on schematic but cannot find it , can you pls give more details? thanks

author: SeanB
author_rank: Super Contributor
timestamp: September 20, 2015, 11:35:34 am
content: Check power supply outputs. There are some 42 and 87 V rails provided by the PSU, which are used by the CRT alone. Also the 15V rails could be low, causing this. Otherwise there is a faulty IC, which can be replaced, there is a thread here about them and how to make a small board to replace it.

author: BravoV
author_rank: Super Contributor
timestamp: September 20, 2015, 12:03:48 pm
content: Quote from: Daxxin on September 20, 2015, 10:47:07 amAssuming 2465 has the same layout on the analog A1 board at 2465B, then check the J119 header, located at the photo below, the voltages specifications & tolerances at all rails required by the scope to work properly, quoted from Tektronix 2465B service manual.Make sure you check again at your 2465 service manual to confirm that it has the same voltage rails checking header like that.Side note, "ideally" there is a 2nd scope to trouble shoot, so you can check the ripple as well, not just using DMM which is quite limited.Make sure you have a huge fan blowing the "whole" board when without the case as there is no air circulation to cool off those unobtainium ICs, trust me, you don't want to them to overheat.

author: soren
author_rank: Regular Contributor
timestamp: September 20, 2015, 12:35:04 pm
content: Quote from: Daxxin on September 20, 2015, 09:27:20 amMake sure the beamfinder switch isn't stuck.

author: Daxxin
author_rank: Regular Contributor
timestamp: September 20, 2015, 12:42:32 pm
content: Hi BravoV here the measures:+10v --------- +9,98v+87v --------- +86.6v+42,4v --------- +42.4v+5v(D) ---------- +4.97v+5v(A) ---------- +4.96v-5v ---------- -4.97v-8v ---------- -8.01v-15v ---------- -14.94vchecked also the ripple with rigol scope seems very good , checked also the psu look reworked not so long time agoand checked also the rails -300v mentioned by SeanB and its ok just the -15v2 a bit lower than expected its 14,88vbut dont think its big deal.

author: Daxxin
author_rank: Regular Contributor
timestamp: September 20, 2015, 01:36:43 pm
content: Make sure the beamfinder switch isn't stuck.your right compliments it was button beam finder broken stuck in find position

author: AF6LJ
author_rank: Unknown
timestamp: September 20, 2015, 01:47:05 pm
content: Another fine piece of Tektronix gear back on the road to functionality.

author: Isad
author_rank: Frequent Contributor
timestamp: September 20, 2015, 01:47:23 pm
content: Quote from: mij59 on September 20, 2015, 10:12:15 amOh.Shame on me i have a crt for my self but havent touched it it ages XD.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: September 21, 2015, 04:13:33 am
content: If you are in to vintage Tek stuff you will almost definitely want to Jon the TekScopes Yahoo group. They are fantastically helpful folks, many with years of experience maintaining these things.I have a vanilla 2465, and most 2465(a/b) units need some love and care on the low voltage power supply. You definitely want to visually inspect it if nothing else. There are likely some leaking capacitors in there, damaging the board. The damage eventually eats through traces. Even if the scope seems to work right for the most part there is a good chance at least one is leaking or blown. Mine had two blown line caps and two leaking electrolytics, a blown in-rush resistor, and it generally worked fine. There was a small noise issue that led me to have a look inside.Most 2465 owners replace all the electrolytic and paper and wax capacitors on the LVPS. Anybody decent with a soldering iron can do it. A desoldering station helps immensely too. There are some other common issues as well.Great scopes, though. Fast, beautiful analog traces, with pretty decent cursors and readouts.Join the TekScope Yahoo group. You will be very glad you did.

author: BravoV
author_rank: Super Contributor
timestamp: September 21, 2015, 04:24:53 am
content: Here in this forum also has a teardown & discussion thread on 2465B ->HERE, may be not all applicable to 2465 model, but I believe the power supply part is identical, plenty of info and resources shared by other members in there, just take your time reading that gigantic thread.