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I have a nice 2465B that I bought as being fully restored and recapped (I’ve not opened it up yet but have no reason to doubt) that only has about 460 hours on it. I bought it back at the end of the summer but have only put maybe an hour and a half on it since; I turned it on a couple of days ago and it had a perfect display then suddenly everything disappeared to a diffuse glow off the right side of the screen (UL to photo album "2465B screen issue") After about 5 minutes it snapped back to being correct and stayed that way for another 30 minutes until I turned it off. I turned it on yesterday and it worked perfectly for about 15 minutes then went back to the fuzzies and has not returned to normal yet. Note there is no gradual transition between states, it is as far as I could tell instantaneous. When the display was working it had a perfect, sharp image and passed all self-tests. The problem is obviously (???) in the CRT/display circuitry, but I have not opened it up yet to check anything – I was hoping to find someone that might be more familiar with these units prior to starting.

Any hints and advice are very much welcome.

Harold,

It is likely that resistors on the high voltage board are bad. I did post the R numbers and other information for someone recently having focus problems.

Mark

My thoughts are not so much about a HV problem as the infamous U800 horizontal driving chip.

Raymond

That was the kind of thing that I was worried about. I do have a parts unit so maybe that could be used if needed. I'm not sure when I will get the chance to dig into it but I very much appreciate the ideas. I've not worked on these before so at least knowing where to start reading up is extremely helpful.

Thanks!

What SN? A5 SMD or TH ? Beware as hrs can be changes at CAL.

Have full serv man for the serial range?

Usual drill:

0/ IF A5 is SMD check for corroded SMD cap damages

1/ Check all PSU V/ripple at U119 header on A1 bd

2/ Probe CRT hor pins or HOR amp output for large DC bias.


Bon chance


Jon

Hey Harold,

I'm no expert on U800 failures, but the two videos I found show different
symptoms: . While the trace is
affected, the on-screen-display is not in both of those cases. Of course we
don't know whether you've turned the OSD off on your scope, and there is
likely more than one failure mode for U800, so YMMV.
Does the scope successfully complete power up? If it's failing
power-on-self-tests, it'll stop at some point with a single front-panel LED
lit, and when you press A/B TRIG, it'll continue to operating mode, which
will click some relays.
After that, the first thing to look at is the power supplies at J119.
There's a table in the service manual that specifies limits on voltage and
ripple. The next thing to look at IMHO are the -1.25V and +1.36V references
on the A5 board. If any of those are out, there's no point in looking at
anything else.

From there it's a process of elimination, I'd say, and if you haven't read
this document: , maybe
that's a good start. It's a fun read, if nothing else.
Some things to try:
- Does the beamfinder do anything?
- Does the OSD show?
- Does X/Y mode work?
- Does the B-sweep work?
- Does the 10X horizontal magnify do anything?

Since the symptom is so severe, you should be able to quickly figure out
what is bad in the horizontal or the HV.

Good luck,
Siggi

On Wed, Apr 2, 2025 at 9:18?AM Harold Foster via groups.io <halfoster=
[email protected]> wrote:

That was the kind of thing that I was worried about. I do have a parts
unit so maybe that could be used if needed. I'm not sure when I will get
the chance to dig into it but I very much appreciate the ideas. I've not
worked on these before so at least knowing where to start reading up is
extremely helpful.

Thanks!

SN is B058926. it powers up normally and passes all self tests. It will complete (assumedly from the light sequences) the boot sequence and power on tests even when the display is wonky. It seems to be the focus is lost and the display position is just past the right edge of the screen. At first it appeared to possibly be temperature related but now not so much... it does it from a cold (well, at least cool) boot now and it started working *after* warmup one time prior. When the screen is not correct it seems to respond to all button presses - the fuzzy blobs move in concert with the presses although it is only what could be described as the left quarter of a fuzzy blob that shows on the right side of the CRT. Running the self test while also seems to complete it's entire sequence.

Hal

How do you know which manual is appropriate to the SN? Am I missing the obvious? I have manuals with the PN of 070-6863-00 and 070-6863-01

'm no expert on U800 failures, but the two videos I found show different
symptoms

I was triggered by the frequent symptom of the complete screen info pulling to one side - and beyond. I hope it’s not that serious though.
Raymond

On Wed, Apr 2, 2025 at 12:41?PM Raymond Domp Frank via groups.io <hewpatek=
[email protected]> wrote:

'm no expert on U800 failures, but the two videos I found show different
symptoms

I was triggered by the frequent symptom of the complete screen info
pulling to one side - and beyond. I hope it’s not that serious though.

Yeah, you may well be right. Aside from the power supplies and U800, I
can't think of much that's common to the OSD and traces in the horizontal.
Personally I like to look for simple, inexpensive and fixable problems
first, I guess it's a case of streetlight effect (
).

On Wed, Apr 2, 2025 at 10:53?AM Harold Foster via groups.io <halfoster=
[email protected]> wrote:

How do you know which manual is appropriate to the SN? Am I missing the
obvious? I have manuals with the PN of 070-6863-00 and 070-6863-01

I'm not sure, and I'm not sure that it's going to matter until you're at
least elbows deep, at which point you'll know which SM you need. Note that
this scope may not correspond to a singular serial number, as individual
boards may have been moved from other scopes.

Also, something that nobody mentioned yet is whether the horizontal
connector to the CRT might have fallen off. I don't think that's likely, as
I think you'd have a trace and OSD on half the CRT, but again it's
something quick and easy to check.

Thanks to all that have posted - it looks like I'm just going to find the time to open it up and start diagnosing. My feeling, and that that seems to be the opinion here as well, is that the fault should be fairly easy to narrow down as all is working *except* for the display. Of course, finding the time is where the *real* work lies...

According to Findchips.com, Quest Components has VN1316