Tektronix 465 Repair - Page 1
Forum section: electronics / testgear

author: nauseous
author_rank: Newbie
timestamp: October 14, 2015, 09:47:36 pm
content: Hi Guys,I have picked up a Tektronix 465. Turns on but nothing on screen. Pushing the beam finder button brings the trace up on screen.Downloaded the manual and started following the troubleshooting procedures. The 110 Volt rail is being pulled down to roughly 60V. All other voltages are within tolerance.The next step in the troubleshooting procedure is to isolate the Z-Axis amp and horizontal amp. To do this it looks like I would have to strip the unit down to get to the A9 board underneath so I can remove the ASTIG variable resistor. I really don't want to do this unless absolutely necessary. At the moment I assume the problem is somewhere in the Z-Axis circuitry.Should I bite the bullet and strip the unit down so I can isolate the 110V. Or am I better to spend the time troubleshooting the Z-Axis knowing that when pressing the beam finder button I can get the trace to appear on screen.Thanks All!

author: tautech
author_rank: Super Contributor
timestamp: October 14, 2015, 10:14:31 pm
content: Welcome to the forum.Tek trouble shooting guide:https://www.eevblog.com/forum/repair/repair-documents-and-links-sticky-me-please-mods/msg477909/#msg477909

author: PaulAm
author_rank: Frequent Contributor
timestamp: October 14, 2015, 10:48:29 pm
content: Have you checked the ripple on the supplies? If you've only checked the DC levels with a meter, you wouldn't have seen the massive ripple caused by an open filter cap.

author: nauseous
author_rank: Newbie
timestamp: October 15, 2015, 01:18:19 am
content: That manual is awesome, had no idea it even existed. Thanks!Will first check for ripple before going any further.Thanks!

author: nauseous
author_rank: Newbie
timestamp: October 27, 2015, 07:50:34 am
content: Checked for ripple on the power rails and in all honestly it looks A-OK.The repair manual says to isolate the 110v supply (for the CRT Circuit) unsolder 1 end of R1445, R1476 and CR1476.R1445 happens to be a variable resistor for astig settings. The only way I can see to unsolder this is to get to the bottom of the interface board. Which would require disassembling the complete unit.I don't think it's as easy as cutting a trace, but I'm hoping someone might be able to prove otherwise?? I really don't want to tear it down to isolate that one resistor...Thank you

author: tautech
author_rank: Super Contributor
timestamp: October 27, 2015, 08:17:02 am
content: Quote from: nauseous on October 15, 2015, 01:18:19 amYep, much of it applies to all CRO's.I linked it a week ago in the first reply.Quote from: tautech on October 14, 2015, 10:14:31 pmQuote from: nauseous on October 27, 2015, 07:50:34 amEver heard of the razor blade technique?It's a common troubleshooting technique.If you really need to, cut the trace.Solder hides a multitude of sins.

author: nauseous
author_rank: Newbie
timestamp: October 27, 2015, 08:41:40 am
content: I can't see bottom side of PCB to know if there are other traces that need to be isolated.... This is the real problem.From what I can see one trace leads to GND test point and the other a resistor. I can't isolate the GND side as it's only a test point. Trace 2 appears to go direct to resistor (R1282)....The manual doesn't say lift R1282. And the schematic indicates this won't work either.So unfortunately with a bit more research I don't think it's as easy as lifting a trace...

author: tautech
author_rank: Super Contributor
timestamp: October 27, 2015, 09:44:03 am
content: Can you provide a link to the manual you are using so we can all play along together.