New to Tek 465B operation


Joe
 

I bought an 456B and mostly it seems to be in good working order. I have a couple questions and appreciate your time and help.
When using different sine wave inputs on both A & B channels pretty much match my Rigol1054. All of volts/div and time/div settings seem spot on. Nice sharp focused beam. Really very good for a scope sold as “for parts”.
Using the Source trigger NORM, LINE and CH 2 triggers fine, but it does not appear to trigger at all on CH 1. I can adjust the Holdoff to stop the scrolling, no TRIG light...

With 2 different sine waves on CH1 and CH2 1 get a blank screen with XY mode, the volts/div dials DO light. When pressing Beam Find I get a vertical line and a height I can adjust with volts/div but no horizontal deflection at all.
I will go through the calibration check list, this may be a problem somewhere on the horizontal board? Both problems may stem from the same place? I’d like to have more of an idea of possible problems before attempting any calibrations.

I realize that the volts/div maxes out at 5, but there are 10-20-50 V/Div on the dial. If I’ve read correctly these are for special probes (10x etc). Is there some sort of probe sense that lights up at the 1 o’clock position of the V/D dial? There doesn’t seem to be anything special on the BNC connectors on this scope...

Thanks I’m advance for any input!


Tom Lee
 

Hi Joe,

A 10:1 probe is actually the norm, because that's how you get to 100MHz bandwidth. A 1:1 passive probe is fundamentally limited to a small fraction of that (~5MHz for a 1m-long probe).

If you look more closely at the BNCs on the front panel, you'll see that they are not ordinary BNCs. There's an insulated ring that contacts a spring-loaded dingus that protrudes from a proper Tek probe to trigger the x10 LED.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 4/26/2021 05:34, Joe via groups.io wrote:
I bought an 456B and mostly it seems to be in good working order. I have a couple questions and appreciate your time and help.
When using different sine wave inputs on both A & B channels pretty much match my Rigol1054. All of volts/div and time/div settings seem spot on. Nice sharp focused beam. Really very good for a scope sold as “for parts”.
Using the Source trigger NORM, LINE and CH 2 triggers fine, but it does not appear to trigger at all on CH 1. I can adjust the Holdoff to stop the scrolling, no TRIG light...

With 2 different sine waves on CH1 and CH2 1 get a blank screen with XY mode, the volts/div dials DO light. When pressing Beam Find I get a vertical line and a height I can adjust with volts/div but no horizontal deflection at all.
I will go through the calibration check list, this may be a problem somewhere on the horizontal board? Both problems may stem from the same place? I’d like to have more of an idea of possible problems before attempting any calibrations.

I realize that the volts/div maxes out at 5, but there are 10-20-50 V/Div on the dial. If I’ve read correctly these are for special probes (10x etc). Is there some sort of probe sense that lights up at the 1 o’clock position of the V/D dial? There doesn’t seem to be anything special on the BNC connectors on this scope...

Thanks I’m advance for any input!




Dave Peterson
 

Welcome Joe!

Do you have the Service Manual hardcopy? Or have you downloaded it from the Tek Wiki page?

https://w140.com/tekwiki/wiki/465


There should be a fault tree in there (don't have a reference at hand at the moment), and it does sound like you might have a CH1 trigger issue. Or an issue with the sweep logic. Also on the Tek Wiki is an excellent document on "Troubleshooting Your Oscilloscope" in:

https://w140.com/tekwiki/wiki/465/Repairs


The Tek Wiki is a great resource.

Hope this helps.
Dave

On Monday, April 26, 2021, 10:39:25 PM PDT, Joe via groups.io <griscavage_j=yahoo.com@groups.io> wrote:

I bought an 456B and mostly it seems to be in good working order. I have a couple questions and appreciate your time and help.
When using different sine wave inputs on both A & B channels pretty much match my Rigol1054.  All of volts/div and time/div settings seem spot on. Nice sharp focused beam. Really very good for a scope sold as “for parts”.
Using the Source trigger NORM, LINE and CH 2 triggers fine, but it does not appear to trigger at all on CH 1. I can adjust the Holdoff to stop the scrolling, no TRIG light...

With 2 different sine waves on CH1 and CH2 1 get a blank screen with XY mode, the volts/div dials DO light. When pressing Beam Find I get a vertical line and a height I can adjust with volts/div but no horizontal deflection at all.
I will go through the calibration check list, this may be a problem somewhere on the horizontal board? Both problems may stem from the same place? I’d like to have more of an idea of possible problems before attempting any calibrations.

I realize that the volts/div maxes out at 5, but there are 10-20-50 V/Div on the dial. If I’ve read correctly these are for special probes (10x etc). Is there some sort of probe sense that lights up at the 1 o’clock position of the V/D dial? There doesn’t seem to be anything special on the BNC connectors on this scope...

Thanks I’m advance for any input!


jgiv510070@...
 

Thanks Dave. I have downloaded every manual I can find, and the Tek troubleshooting your oscilloscope guide as well. Spent the better part of yesterday going over it. I can get a trigger light on ch1 by adjusting the sensitivity of R7246, although it doesn’t stabilize the wave and it stays triggered with the probe detached. Also the trigger ADJ R7224 doesn’t help anything.
I’m very hesitant to reseat U375 or any of the socketed transistors because I understand replacements are difficult to get. In other manuals I’ve seen flowcharts of what to check with yes/no logic to narrow things down. I haven’t come across any like that yet. I’ll check out the Wiki today. Thanks again for any help or suggestions!


jgiv510070@...
 

Thank you Tom,
I see that now. I don’t have the original probes and have never looked at a set. Generic probes will work ok at 1x or are genuine Tek probes the way to go? Initially I thought that’s what the 10X button was to use the probe as 10X...


Tom Lee
 

If you don't need the bandwidth, and if it's acceptable to you to load the circuit under test with a very large capacitance, then a 1x probe is fine. Since a 1x probe is not much more than a piece of coax with a pointy tip, the manufacturer doesn't matter so much.

Some probes can act as 1x or 10x probes, depending on the position of a switch on the probe. But genuine Tek probes communicate their attenuation factor to the scope automatically through the spring-loaded thing I mentioned previously. No user action is needed. The correct scale light illuminates by itself. If you use an off-label probe, you have to do the math yourself. The scale light for 1x will always be on, so you'll just have to keep track of the decimal point in your head.

There are very inexpensive "P6100" probes available on eBay and other places. These are not nearly as good as Tek probes, but they're also a heck of a lot cheaper. We did a bulk buy of these for our undergraduate teaching labs, and we paid just under $4 each, including shipping. They are rated to 100MHz, and measurements show that they actually meet spec, although they are clearly inferior to true Tek probes (step response has worse aberrations, frequency response is not as flat). But they're a good value for what we need them to do. These have a switch that allows you to select 1x or 10x mode, so they're versatile. They claim a 600V rating, but a teardown shows that they just made up that number. I'd feel nervous about using them above 300V.

--Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 4/27/2021 05:18, jgiv510070@gmail.com wrote:
Thank you Tom,
I see that now. I don’t have the original probes and have never looked at a set. Generic probes will work ok at 1x or are genuine Tek probes the way to go? Initially I thought that’s what the 10X button was to use the probe as 10X...




Tom Lee
 

If you don't need the bandwidth, and if it's acceptable to you to load the circuit under test with a very large capacitance, then a 1x probe is fine. Since a 1x probe is not much more than a piece of coax with a pointy tip, the manufacturer doesn't matter so much.

Some probes can act as 1x or 10x probes, depending on the position of a switch on the probe. But genuine Tek probes communicate their attenuation factor to the scope automatically through the spring-loaded thing I mentioned previously. No user action is needed. The correct scale light illuminates by itself. If you use an off-label probe, you have to do the math yourself. The scale light for 1x will always be on, so you'll just have to keep track of the decimal point in your head.

There are very inexpensive "P6100" probes available on eBay and other places. These are not nearly as good as Tek probes, but they're also a heck of a lot cheaper. We did a bulk buy of these for our undergraduate teaching labs, and we paid just under $4 each, including shipping. They are rated to 100MHz, and measurements show that they actually meet spec, although they are clearly inferior to true Tek probes (step response has worse aberrations, frequency response is not as flat). But they're a good value for what we need them to do. These have a switch that allows you to select 1x or 10x mode, so they're versatile. They claim a 600V rating, but a teardown shows that they just made up that number. I'd feel nervous about using them above 300V.

--Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 4/27/2021 05:18, jgiv510070@gmail.com wrote:
Thank you Tom,
I see that now. I don’t have the original probes and have never looked at a set. Generic probes will work ok at 1x or are genuine Tek probes the way to go? Initially I thought that’s what the 10X button was to use the probe as 10X...




 

jgiv510070 wrote:

I’m very hesitant to reseat U375 or any of the socketed transistors because I understand replacements
are difficult to get.
You should not be hesitant to reseat the socketed parts, just be cautious and gentle about the task. Replacing the transistors, at least, is not really a huge problem: many parts are still manufactured, and those that aren't can be found NOS on eBay, or suitable replacements are available new and relatively cheap. Some of the ICs are more difficult to come by, but there are sources for such parts: Qservice in Greece is one good source (they list their parts on eBay) and Sphere Research in Canada is another (they post to this group). The prices are even reasonable.

I'm not sure that this is true of the 465B, but the higher bandwidth older sibling 475A has some transistors with a ferrite bead on one leg. You can see the beads if you look closely, then be careful extracting those transistors to avoid dropping (and losing) the bead. Specifically I have seen such beads on transistors in the vertical amplifier circuit.

You need to get comfortable with reseating these parts because oxidation at the contacts is a common problem, and the fix is to remove the affected parts, clean their leads with a bit of isopropyl alcohol, and re-install them. In some cases you can get away with simply reseating the affected part. I personally had a fault in a 475A where chop blanking was not working. I traced the problem to U340 (a quad NAND gate) that showed signals getting to the pad beneath the socket, but not to the legs of the IC itself. Removing the IC, cleaning the leads, and re-installing it fixed the problem.

-- Jeff Dutky


 

I just want to second Tom suggestion to get some good, cheap modern probes. I have both original Tek probes, and a few sets of cheap Chinese probes from Amazon. The cheap probes work perfectly well, with the exception of not having the readout pin, so you need to do the math in your head, and they're so inexpensive that you don't need to worry about damaging them.

I specifically ordered probes from AST Labs and AUTOUTLET and have been very happy with them. I use them any time I'm doing something that I know might damage my probes. The AUTOUTLET probes are rated to 100 MHz and cost $20 for a pair. The AST Labs probes are rated to 200 MHz and cost $21 for one probe. AST labs also sells a pair of 100 MHz probes for $14. There are also 100 MHz and 200 MHz probes from Hantek, at similar prices, that I would trust as they make a pretty good line of hobby level digital oscilloscopes.

You can also buy original Tek probes on eBay that would match your scope and have readout pins (either P6065 or P6105 are what would have shipped with your scope, but there's also the P6062 that is a switchable 1X/10X probe and should also work with your scope). You should be wary of any seller that tightly wraps or folds the cables, however, as that is a sure way to damage them. Look for the cable to be coiled in a loose circle and not secured too tightly. A good price for such probes is under $40 (before shipping); anything more than that and you could just buy brand new probes (with readout pins) from Cal Test or ProbeMaster.

-- Jeff Dutky


Roy Thistle
 

On Tue, Apr 27, 2021 at 03:20 PM, Jeff Dutky wrote:


You should be wary of any seller that tightly wraps or folds the cables,
For an example of that... and of a probe9s) not to buy... see
https://www.ebay.com/itm/173844545432?epid=1401424527&hash=item2879f13f98:g:6xkAAOSwlAZaZ8LW
The fairly hardy P6109 coax pictured there could probably survive that bending and tying abuse... but these guys... probably not
https://www.ebay.com/itm/392472078481?hash=item5b6128a891:g:kesAAOSw-uddnfkU
Those are tight plastic cable ties around that delicate coax... and the coax is being over bent.
--
Roy Thistle


 

Roy Thistle wrote:

For an example of ... a probe not to buy see ...
and here is an example of a probe that is being properly handled: https://www.ebay.com/itm/333969631283

the price is okay, but the probe looks to be in fine shape (disclaimer: I've bought from that seller and got a good probe from the transaction)

-- Jeff Dutky


jgiv510070@...
 

Thanks everyone for the great advice! I’m looking into that probe now...

I found a complete service manual, it says for serials below 30,000. I have a newer 465B with SN:B045757, is there much difference in the manuals? I’d guess the procedures are the same and the schematics are different? (Should I find and print a new one, or just reprint the schematics). I was looking for particular sections discussed on other forums and became lost. There are many out there. The 465 and 465B are similar, and the 465B has 2 or more revisions. If I had a newer eye prescription I would have seen that before printing, LOL!

Probes: I have pair of cheap Chinese 1-10X probes and the set that came with my Rigol. Is the auto-set on the probes important to doing the calibration? It calls for 10X probes. The manual is pretty specific with other items; cable length, impedance, T connectors, BNC terminators etc... I have a Chinese DDS sig gen/counter that supposedly is good to 60mHz. What must have equipment needed to do things properly?

So as not to mix up this thread too badly, after I go through the checks in the correct manual I’ll start another. At the moment I’d like to just get this unit fully functional.

Again, I’m new to all of this and really appreciate everyone’s help. This is a great group!


pdxareaid
 

As you learned, some scopes have 1x/10x indicator lights on the dial.
ex. 465M does not. 465M you just have to remember (no direction is better than misdirection.)
ex. 465B it is selected by the contact pin on the probe and ring around the BNC.

If you are using a probe without the contact pin on a 465B, the dial will mislead by having the 1x lit on the dial regardless of the probe 1x/10x switch. You can force the 10x indicator by emulating the ring/pin by switching in <10K ohms to ground (1x is >10K to ground) in the indicator circuit. I did this for my 465B's channels (switch mounted on back - blasphemy, I know) with positions "Normal" and "Force 10x Indicator"). I just have to set things up once when connecting the non-pinned probe rather than remembering to ignore the INCORRECT indicator for each reading. That misdirection bit me a few times before I did this.

Something to consider if the misdirection bites you too and you are looking for something to do.

ps. there are other resistance values for 100x and 1000x but not useful for 465B dial indicator.


Torch
 

These are decent probes, good bandwidth, reasonably priced and have the Tek readout pin. 10x only though:

https://www.ebay.com/p/1762967673


Jim Adney
 

On Fri, Apr 30, 2021 at 12:41 PM, Torch wrote:

These are decent probes, good bandwidth, reasonably priced and have the Tek readout pin. 10x only though:

https://www.ebay.com/p/1762967673
Note that this particular example has a broken cable jacket at each end, which would seem to indicate that the cable had been stressed at those points. That might be okay, or it might be a sign of a problem. The probe tip also appears to be bent; those usually break off when you try to straighten them.


Torch
 

Good catch. I missed that that particular one was used. Buy new.