开云体育

First Post! Not seeing much by the way of editing tools for posts so I'll do my best.

Test equipment:
Hantek DSO2C15 oscilloscope
Tektronix 2465A oscilloscope
Fluke 87 V multimeter
DE-5000 LCR meter
Siglent Technologies SDG1032X - set to arrive later this week

Operator Level:
BSEET "engineer" trained in soldering and de soldering correctly. Familiar with schematics, P&IDs, pinning charts, flow diagrams, etc.
Have restored several pieces of vintage equipment (Tube amps, tube test equipment, Epson HX-20 laptops,etc)

Device Under Test:
Tektronix 465B #107437 with option 5 (TV Sync Separator). Boards have date of 1978

Last Calibrated:
6-30-1994
Last Used:
~20 years ago

Synopsis:
X-Y mode mostly works with extra signal anomalies present (rolling of signal on screen), Channel modes have some odd interactions with time base and cause lockup. Can sometimes get a signal to display properly.
+5VDC rail is low at 4.11V. All other supplies are within spec to the service manual including the high voltage.

So far:

Applied DeOxit D100L to push button switches only
Checked vertical attenuators with no signs of corrosion. Leaf switches look clean and functional, I didn't touch them as they appear very fragile
Gave all switches, knobs, buttons, levers a good workout.
Oscilloscope appears to be in good physical shape. Circuit boards appear to be visually OK, no signs of damage or leakage
Replaced all tantalum capacitors with aluminum electrolytic

Troubleshooting via ther service manual indicates possible faults in the Vertical Pre-Amp and A+B Sweep generator. I've tried getting a trace to appear but I've found many times the scope appears to "lock up". The trigger LED will light up and then basically everything stops functioning and I have to turn the scope off and back on.

Vertical Pre-Amp
+4.14V connected
+4.36 disconnected

Once I get the signal generator I'll start tracing the signal through the channel A vertical amp. In the meantime I pulled each transistor on the vertical pre-amp board and checked them for "go/no-go" with a arduino based component tester. They all tested "go", I did not pull the datasheets and compare the specs.

I did all the testing with the tantalum installed and then with the electrolytic. Replacing the capacitors did not fix the issue or introduce any new issues.

Are there any common failures that I should be checking for before going into the in-depth signal trace?

I've put some pictures up on my Google photos. These images show some of the anomalies when applying a sine wave and square wave using a cheap signal generator. The anomaly is not from the signal generator (verified with other scopes)

Always good to check the voltages rails first which I see you did. But I would still be interested in figuring out why that 5V rail is so out of spec (should be 5 +-0.075V). Also, I would check the ripple on those power rails as well. It should be very low (~2mV Vpp).

I really don't understand why people feel the need to replace all caps just because the unit is old. I'm glad it didn't cause any further issues because that can be one of the downsides to doing that.

Why do you suspect the issue being in the preamp section? Does the anomally appear in signals for both CH1 and CH2? Both channels have their own preamp circuitry so if the anomally is appearing on both channels, I would suspect the issue being further downstream of the inputs. Possibly the vertical output amplifer.

I would also be looking at the CRT circuitry. In some of the photos you show, the trace rotation is clearly off. It's possible you might have some issues with geometry of the display.

You have the right idea by injecting signal and following it thru the vertical amp circuitry to the CRT. If the issue is there, with the help of the service manual, you'll be likely to find it.

I've never owned or worked on a 465B, but I'm sure there are plenty of people in this group who have that will be able to give you more specific suggestions. Also, might be helpful to search through the forum to see if this issue has popped up before. Use the search box on the top right.

Good luck!

-Frank

On Sun, Feb 11, 2024 at 02:40 PM, Don - AC2EV wrote:

Device Under Test:
Tektronix 465B #107437 with option 5 (TV Sync Separator). Boards have date of 1978d

Nice scope, that option is what I'd hoped for, but didn't get, when I found my 465B. Not useful anymore, with digital TV. The rest of the scope is a great classic Tek portable.

First thing I'd suggest would be to turn down the beam Intensity. You don't want to burn the phosphor.

Next, take a close look at the +5 V rail. Yes, it's too low, and it can be difficult to figure out whether it's a power supply problem or too much load from a failed component somewhere down the line. I'd start by looking on that rail for the AC voltage. If things are good there, the AC component will be mV. With your DVM leads connected to the +5 and ground, switch the DVM from DC to AC. If there's lots of AC (ripple) then the PS is the more likely culprit. Look for an electrolytic cap that is no longer a capacitor. One way to test for this is to simply solder a similar capacitor across the Tek one (with the power OFF!) and see if the problem disappears.

Don,

You have bad condensers. That is the most likely problem. Being from '78, that is enough years to warrant replacing them. I have a B version I put new condensers in as well as increasing the wattage of some resistors. The tantalums are know to go bad. A good quality, i.e. Nichicon ULD 47mfd 25V, electrolytic will replace them. I would mine to have Option 5 like yours.

Mark

It's low likely because of a ton of ripple. More load ---》 more ripple.

Ripple is within spec.

Why did I replace the capacitors?
1. It's relatively simple and cheap to replace them
2. I've had capacitor issues in other equipment. The biggest offender being the Rifa caps in my other oscilloscope

I did suspect the CRT but given that the scope works in X-Y mode that lead me down that route.

Why the pre-amp and sweep? This is where the manual lead me through the troubleshooting so far. It may be the wrong path, but it's a path I can follow to see where it leads.

Since most of the replies are pointing to bad capacitors, I'll go back and double check the ripple, just to be sure. I didn't see in my notes where I recorded it, so I will do that.

Given that the scope "worked last time it was used", I'm leaning towards capacitors, vs an active component.

@Don,

Fair enough. I am probably in the minority here when it comes to cap replacement. It doesn't make for a good preventative maintenance practice IMO. Because you really don't know how long those caps will last. No one can say for sure when they will fail. Usually parts that you can predict when they will fail can get placed on a scheduled replacement basis (ex. car analogy - your tires, your brakes, etc). Otherwise you risk overmaintenance and wasting money. I guess I take that approach because I work in the repair business as an in-house engineer for a biotech company.

As for the XY vert mode, you say the anomaly disappears when the scope is in that mode, but in one of the photos you shared (when you make a straight line), I can still see the anomaly at the top of the line. Looks kind of like a hook. So I don't think its safe to say it disappears in XY mode.

The reason I asked about the pre-amp is because each channel has its own pre-amp. So it would be unlikely that you'd have the same fault in both channels (though not impossible). That's why I'd be looking further downstream of the pre-amps (vert switching, output vert amp). And it is definitely still worth looking at the CRT circuit.

Granted, this could be from a switch with a dirty contact or something as well. In my experience, 9/10 times this complex issues tend to be from something stupid like that. Still worth going through the schematics and following an injected signal thru the vert amps to see what you get.

-Frank

Hey Don,

Great first post, I'm sure you'll get the old girl up to snuff in no time.
Oscilloscopes are kind of unique in that it's often possible to diagnose
problems to a functional block by "milking" the front panel. If you haven't
already, I suggest you read through the "Troubleshooting Your Oscilloscope"
document ().
Regarding the 5V supply, you probably need to sort that out before you can
expect anything else to make sense. I can't pull the service manual right
now, but generally the LV supplies in these scopes are current limited, and
will have a dropper resistor somewhere in line with the main supply. By
measuring the voltage over the dropper resistor, you can see how much
current is going through, and whether the supply is in current limiting.

... time passes ...

The dropper resistor is R4325, a 1.2Ohm. It is supposed to drop 0.4V, so
the service manual expects 333mA out of the +5V supply. If the supply is in
current limiting, it may be hard to trace it to a cause, depending on how
easy it is to isolate blocks of the 465B - I've never worked on one.

Good luck,
Siggi

Thank you.
I have a copy of the troubleshooting guide and went through it partially before switching to the ‘failed’ assessment of the power supplies (see oopsy). I need to finish reading it. It’s well worth the read even if you don’t have a scope. It’s a nice methodology to troubleshooting.

::Insert::
assume is an abbreviation not a (transitive) verb.

Checking R4325 the drop is
0.41 volts
4.539v
4.127v

Looks like that should be 5.4v according to the schematic.

::oopsy::
I rechecked my notes and missed that the ripple on the 5v supply is I thought I wrote 9mv not 0.9v. The others appear to be in spec. Got some work to do.

If you don’t make mistakes you’ll never learn anything.

::off topic::
If anyone has purchased the electronic manuals from Q-service. Is the PDF searchable and does it have a populated table of contents? I emailed them a few weeks ago with no response.

I have access to a plotter and 11x17 printer so I’d like to print out some high quality schematics.


::even farther off topic::
I bought a GBC c800pro binding machine on eBay last year for $40USD and free shipping. I print and bind everything now.

You can try Artekmanuals.com! They have an extensive library of Tektronix manuals

They are reasonably priced and they get them to you usually within 24 hrs of purchase via email in a compressed zip folder.

How does one tell if the scope is a low serial number or a high serial number?

My unit is #107437 as indicated on the front face. There’s no letter indicator.

On Tue, Feb 13, 2024 at 04:19 AM, Don - AC2EV wrote: "How does one tell if the scope is a low serial number or a high serial number? My unit is #107437 as indicated on the front face. There’s no letter indicator."
The "high" serial numbers for the 465B are S/N B0600000 and up. That's how it is stated on the cover of the high S/N version of the 465B service manual.
The 465B high S/N manual is marked copyright 1982. The previous version was marked copyright 1979.
The leading alpha character designates the manufacturing location and I am not sure how Tek controlled the assigned numeric characters with respect to the alpha characters. Hopefully, someone can clarify that.

Note that the High/Low break point is different for the 465 Model.

On Tue, Feb 13, 2024 at 07:59 AM, Tom Phillips wrote:
"...The "high" serial numbers for the 465B are S/N B0600000 and up..."
That should read "B060000 and up."
Apologies for the typo. I sure wish we were allowed to edit our own posts.
Cheers,
Tom

The 107437 is a Tektronix Guernsey numbering - unrelated the Bxxxxxx number from Beaverton - I imagine there's a correspondence but I doubt it was documented.

You best bet is to compare the board level revisions against those the low/high Bxxxxxx manuals.

David

The boards say (c)1978 so I’m thinking 1979 low serial is probably closer.

Nope. The low serial number has a different layout of the front panel. The calibration bar is shifted to the right. On mine, it is dead center in the middle.

Hopefully that helps someone in the future.

On Wed, Feb 14, 2024 at 02:44 AM, Don - AC2EV wrote: "Nope. The low serial number has a different layout of the front panel. The calibration bar is shifted to the right. On mine, it is dead center in the middle..."

Don,
Could it be that you are comparing the 465 to the 465B?
I have both high and low serial number 456Bs and the calibration bar on both is under the center of the CRT.
However, the 465 front panel layout places the cal bar to the right of the CRT under the horizontal display push buttons.
Cheers,
Tom

Yes the Artek manuals were labeled as 465B but both were actually for the 465.

I have a B.

The site openweb.de has a nice quality copy with full-size schematics 24x11 size

The title is
罢别办迟谤辞苍颈虫—465叠—蝉别谤惫颈肠别—滨顿1310.辫诲蹿

Don,What is the serial number. I have manuals for the 465 early, late, b, mil, etc.Dan G.Sent from my T-Mobile 5G Device