Date   

Re: Tektronics Scopes

-
 

Alan,

If you are unwilling or unable to repair a scope then my first advice
would be that when it comes to E-bay, don't buy anything that isn't
classified as "New" or "Used". Under E-bay's rules, anything sold in those
categories must work, regardless of any disclaimer that the seller puts in
their description. If the item arrives and doesn't work or is damaged or
not as described, then per E-bay and PayPal's rules, you are entitled to
all of your purchase price back and any shipping and/or packing fees that
you paid. And the seller must pay for the return shipping if he wants the
item back. It's a pretty iron clad guarantee and E-bay and PayPal WILL
enforce it, but only as long as you buy an item that is "New" or "Used". It
helps to keep records and photos of everything. If I get a package that
looks beat up, I take pictures of it before I open it and more pictures as
I open the box and before I remove item, then more pictues as I take the
item out and then of the empty box and the packing material that was in it
and then all sides of the item. And more picture of the inside if I open
the item up. I bought a complete original BC-348 radio from E-bay a few
years ago and it was packed unbelievably poorly and smashed when I got it.
And I had very specifically asked the seller to pack it *well* and offered
to pay extra for that but he didn't do it. He just crammed it in an
undesize thinwall box with a single sheet bubble wrap. He and I went round
and round about it but I finally filed a claim with E-bay, sent them the
pictures and they *immidiately* refunded my money and paid me to ship the
item back to the seller. By the time that it was over with, the seller not
only didn't make a penny on the sale, he also paid almost $180 for the
shipping!

For tube type equiptment, you really shoud try to avoid shipping and
try to find something locally that you can go pickup in person. For big,
heavy or delicate items, when I search E-bay one of the things that I like
to do is to sort the results by distance from me. If I find something
nearby I then contact the seller and make sure that they allow local pickup
before I buy. I've bought dozens of big heavy items such as linear power
supplies and this has wrorked out well for me.

Post up your location and someone here might be able to help you out.

Joe

On Tue, Apr 27, 2021 at 1:39 AM Alan Young <agyoung@cox.net> wrote:

Hello All,
I am in a situation where I have been physically disabled. I am an
amateur radio operator and am looking for a scope for general purposes. My
partiality runs towards a 465 as that is what I used in the Coast Guard in
the mid 70's. It was state of the art and I always thought that we somehow
lucked out to get them. Most of our scopes were Dumont or Fairchild
surplus from the Navy. We almost never got new test equipment. I am
looking for a scope just to play with associated with hf stuff 50 MHz and
below. I see a lot of 465's on Ebay and would love to have one just for
nostalgia. I have put a bid in on a 2246 which was rather low so I doubt
that will happen.
I guess my question is would the 465 be a better bet than something like a
2246 for tinkering? I do notice that the electrolytic power supply caps
seem to be a problem with the switching power supply on the 22xx series and
I'm not sure I can physically replace then if needed.
Again, my use for a scope is tinkering. The 465 for nostalgia.
Any thoughts or help would be most appreciated.

There is a tremendous wealth of information on this site and I can read
posts for hours!

Thanks,

Alan Young
N5AGY






Re: Tek 1503C TDR

warren.stirling@...
 

Hi all,

As a first timer here, I thank you for your replies. The enquiry was on behalf of a friend who has a 1503c with a cracked screen, so replacement is his only option.

I'll follow up the links that have been posted, there may be a solution to be found...

For myself I've one point five 1503 with crts in them (one only half works and will be kept as spares if I can't resurrect it - it's been 'modified' shall we say...

Old technology never dies, the repairs just get newer


Re: Tektronics Scopes

 

Hi Alan,

The 2246 is quite a nice scope, but a big change from a 465, and maybe more than you need for the kind of work you want to do. In the 2200 series there are some very nice, lower priced scopes that will probably meet your needs; I would consider a 2215/2215A or 2235/2235A as common, full-featured scopes.

The advantage of the 2215 and 2235 is that they are easy to work on and do not require much, if any, unobtainable parts to repair their most common failure modes. The 465, from the decade before the 2200-series, has more parts that are no longer obtainable, can only be obtained at significant cost, or must be salvaged from another scope. That is not say anything bad about the 465: it's a beautiful instrument, easy and fun to use, and built like a tank (both in durability and mass). The 2200-series were a cost-cutting effort by Tek in the 80s to compete with new foreign competition, and they feel like it. The 2200-series are still very good scopes, but they feel more flimsy (on the up-side, they are much lighter than a 465, which may be a concern for you, depending on your disability).

The features of a 2215 or 2235 are very similar to the 465, right down to having very similar controls for most functions. The 2246, being a much later entrant in the 2200-series (and actually looking a lot more like a 2400-series scope) has significantly different controls than the earlier scopes, so it will feel very different when you use it (it will also have features that the earlier 2200-series, and the 465 lack, like cursors, on-screen readout, and automatic measurements, so it's a trade off).

Any scope of this age, both 70s era 465s and 80s era 2200-series scopes are going to have dried out electrolytic capacitors. The problem gets a little worse with newer old scopes (late 80s/early 90s vintage) that have particularly destructive surface mount caps. The 2246 is right on the boundary for those specific bad caps, and the pictures I see of the insides on TekWiki don't seems to show any of them, so maybe that's not an issue for this model. Certainly the 2215/2215A or 2235/2235A do not have the bad surface mount caps.

That said, yes the switching power supplies have some specific failure modes that can apparently be challenging to diagnose, but the easy of servicing the 2200-series makes up for some of that, I think. I have worked on both the 475, which is almost identical to the 465, and a number of 2200-series scopes, and the 2200-series are arranged so that you can much more easily access both sides of the PCBs, even in the power supply section, while the 475 (and 465) can require significant disassembly to get to the power supply boards. Also, since the 2200-series are much lighter than the 400-series it is easier to move it around when working on or with a 2200-series scope (the 2215 weighs about 13 lbs, while the 465 weighs about 23 lbs).

Just my 2-cents.

-- Jeff Dutky


Re: New to Tek 465B operation

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!


Re: New to Tek 465B operation

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!




Tektronics Scopes

Alan Young <agyoung@...>
 

Hello All,
I am in a situation where I have been physically disabled. I am an amateur radio operator and am looking for a scope for general purposes. My partiality runs towards a 465 as that is what I used in the Coast Guard in the mid 70's. It was state of the art and I always thought that we somehow lucked out to get them. Most of our scopes were Dumont or Fairchild surplus from the Navy. We almost never got new test equipment. I am looking for a scope just to play with associated with hf stuff 50 MHz and below. I see a lot of 465's on Ebay and would love to have one just for nostalgia. I have put a bid in on a 2246 which was rather low so I doubt that will happen.
I guess my question is would the 465 be a better bet than something like a 2246 for tinkering? I do notice that the electrolytic power supply caps seem to be a problem with the switching power supply on the 22xx series and I'm not sure I can physically replace then if needed.
Again, my use for a scope is tinkering. The 465 for nostalgia.
Any thoughts or help would be most appreciated.

There is a tremendous wealth of information on this site and I can read posts for hours!

Thanks,

Alan Young
N5AGY


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!


Re: Tek 1503C TDR

romeo987
 

I had a problem with my display recently, and in my research gleaned that they are rare. However, I managed to repair mine - a relatively simple problem with an elastomeric connector. But your fault may be quite different from mine.
There is a long thread over on eevblog on this topic (in the repair section - if I was more savvy, or sitting at my desktop, I would add a link). A number of people have fabricated ‘modern’ replacements.
Happy to talk more if you think repair is an option for you...
Roman


Re: Tek 1503C TDR

 

On Tue, Apr 27, 2021 at 12:46 AM, Raymond Domp Frank wrote:


like in my 1502B and 1503C
That's 1502C and 1503B, FWIW...

Raymond


Re: Have some free 151-1001-01 FETs, and added piles of hard to find Tek 148 Relays

Dave Wise
 

151-1001 is also mentioned in the Circuit Concepts book, “Vertical Amplifier Circuits”, although they don’t say where it’s used.

https://www.davmar.org/TE/TekConcepts/TekVertAmpCircuits.pdf

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Wise via groups.io
Sent: Monday, April 26, 2021 3:47 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Have some free 151-1001-01 FETs, and added piles of hard to find Tek 148 Relays

Talon Electronics has one in stock: “Tektronix 050-0486-00 Modification kit for P6045 FET probes. Modifies probe to accept 151-1001-01 FET.”
So 151-1001 is used in late-production P6045, and upgrading was easy enough that Tek issued a kit.

FWIW,
Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of walter shawlee via groups.io
Sent: Monday, April 26, 2021 3:39 PM
To: TekScopes@groups.io
Subject: [TekScopes] Have some free 151-1001-01 FETs, and added piles of hard to find Tek 148 Relays

I have NO idea what these tiny gold flat-pack 151-1001-01 (FN1919 from Siliconix) FETs are used iin, the RPR only calls out an 050 kit, just not much help. anyway, I have 3, if anybody needs one, contact me off list, they can be yours for free.


Re: Have some free 151-1001-01 FETs, and added piles of hard to find Tek 148 Relays

Dave Wise
 

Talon Electronics has one in stock: “Tektronix 050-0486-00 Modification kit for P6045 FET probes. Modifies probe to accept 151-1001-01 FET.”
So 151-1001 is used in late-production P6045, and upgrading was easy enough that Tek issued a kit.

FWIW,
Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of walter shawlee via groups.io
Sent: Monday, April 26, 2021 3:39 PM
To: TekScopes@groups.io
Subject: [TekScopes] Have some free 151-1001-01 FETs, and added piles of hard to find Tek 148 Relays

I have NO idea what these tiny gold flat-pack 151-1001-01 (FN1919 from Siliconix) FETs are used iin, the RPR only calls out an 050 kit, just not much help. anyway, I have 3, if anybody needs one, contact me off list, they can be yours for free.

Many people have been searching for the tiny Tek made relays, and the larger P+B R10 148 series parts, I dug out a
lot of new 148 parts, and posted them to the stuff page in the tek section here:
https://www.sphere.bc.ca/test/stuffday.html#tekfans<https://www.sphere.bc.ca/test/stuffday.html#tekfans>

Also there are FREE 1/4 turn case cover latches I found, and two types of Tek handles, might be something there that will help you, have a look. Lots of cool goodies in the other categories too, have a look.

I have a HUGE pile of Tek mechanical new spares, not any help to me. Too much time and grief to photo and list everything individually, I was going to try and group like things together in piles, and toss them up on the page, any suggestions appreciated. There is a lot of hardware, odd trim and plastic stuff, covers, etc. There's some new FAN impellers for the tiny siemens motors too. If you have a specific request or idea, let me know.

Please contact me off list.
all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.
https://www.sphere.bc.ca/test/index.html<https://www.sphere.bc.ca/test/index.html>


Re: Tek 1503C TDR

 

On Mon, Apr 26, 2021 at 01:36 AM, <warren.stirling@bigpond.com> wrote:


Does anyone, by faint chance, have a replacement lcd assembly for a 1503C TDR?
If it's just failed backlights, like in my 1502B and 1503C: I replaced both electroluminescence foils with foils sold by some car accessory shops, intended to brighten up dashboard speed and RPM scales and the like.

Raymond


Have some free 151-1001-01 FETs, and added piles of hard to find Tek 148 Relays

 

I have NO idea what these tiny gold flat-pack 151-1001-01 (FN1919 from Siliconix) FETs are used iin, the RPR only calls out an 050 kit, just not much help. anyway, I have 3, if anybody needs one, contact me off list, they can be yours for free.

Many people have been searching for the tiny Tek made relays, and the larger P+B R10 148 series parts, I dug out a
lot of new 148 parts, and posted them to the stuff page in the tek section here:
https://www.sphere.bc.ca/test/stuffday.html#tekfans

Also there are FREE 1/4 turn case cover latches I found, and two types of Tek handles, might be something there that will help you, have a look. Lots of cool goodies in the other categories too, have a look.

I have a HUGE pile of Tek mechanical new spares, not any help to me. Too much time and grief to photo and list everything individually, I was going to try and group like things together in piles, and toss them up on the page, any suggestions appreciated. There is a lot of hardware, odd trim and plastic stuff, covers, etc. There's some new FAN impellers for the tiny siemens motors too. If you have a specific request or idea, let me know.

Please contact me off list.
all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.
https://www.sphere.bc.ca/test/index.html


Re: Tek 1503C TDR

Paul Amaranth
 

Someone on eevblog replaced the lcd screen on a 1502B with an LCD panel:

https://www.eevblog.com/forum/repair/tek-1502b-tdr-restoration-project-and-more/msg3555459/#msg3555459

Some useful info there.

Paul

On Mon, Apr 26, 2021 at 01:08:05PM -0400, Harvey White wrote:
In one of the TM5000 series function generators with an LCD display, I was
able to replace the Tek display (with an EL backlight) with a standard 2
line x 16 character off the shelf LCD display.  The two displays looked
physically identical with the exception of the EL backlight, of course.

Harvey


On 4/26/2021 11:44 AM, Jeff Dutky wrote:
Judging by the pictures on TekWiki those LCD displays could use replacing even when they were "working."

It looks like the LCD is getting 8-bit parallel data from the CPU with 3 address lines and read and write strobes. The display modules are only referenced using Tek part numbers (672-1241-00 below SN B023854, 118-9050-01 after), but I wonder how hard it would be to decipher that protocol. At the very least you could read the Z-80 assembly that generates the video output straight out of the ROMs.

That would be a lot easier to read with a modern LCD and backlight, or a nice, old-school gas plasma or vacuum fluorescent display.

-- Jeff Dutky
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


FS: A-B pots; FFP: 515/515A manual

Brad Thompson
 

Hello--

FREE FOR POSTAGE plus a cuppa coffee: one only 515/515A manual in good condition
(plastic spiral binder chipped, front cover missing small piece). There's no serial number
inscribed on the front page).

FOR SALE: I'm offering one batch of 32 pieces each of used/removed from equipment
Allen-Bradley type J potentiometers. These feature screwdriver-adjustment locking-shaft bushings and
are an unsorted mix of 10Kohm and 20 Kohm pots. They were used in rheostat mode
(soldered connections to wiper and one end). The original applications were unknown,
but were likely used as set points in fearsome analog kludge.

(Note: my long-gone RM515 used a 20K A-B pot as the -150V adjustment.)

For a detailed description and a source of NOS type J pots, go here:

https://www.tedss.com/LearnMore/American-Made-Potentiometers

I'm asking $13.50 for this assortment of 32 pots (with some mounting hardware),
which includes $8.45 for USPS Priority-mail shipment.

Questions welcomed, PayPal honored.

Thanks, and 73--

Brad  AA1IP

FAQs:

Q: how long are the pots' shafts?
A: they're designed for screwdriver adjustment and hence have stubby shafts unsuitable for attaching knobs.

Q: what's the resistance taper?
A: random samples appear to be linear versus rotation resistance-tapered.

Q: are these all tested?
A: sorry, no. There's a limit to my patience.

Q:  what's the power rating?
A:  they're spec'ed  for 2.25 watts. Ohm's Law applies to the entire resistive element.

Q: what's with the weird part numbers (e.g., CBZ xxxxx) stamped in some of the pots' cases?
A: it's a military specification.

Q: what's a kludge?
A: an inelegant solution using available parts and poorly-suited tools
     to expeditiously solve  a problem at hand. You'll know one when you see one.
--
Sent from Postbox <https://www.postbox-inc.com>


Re: Cannot delay the B sweep on a 465B

Ozan
 

Hi! Thanks! In the end I found the problem: R7069 which lies between a
55VDC supply
and Q7074/Q7075 was cracked and open circuit....It's supposed to be 6.2
kOhm. After replacing it, my 465B works perfectly!
Great news, congratulations for the fix.
Ozan


Re: Cannot delay the B sweep on a 465B

Torquil Macdonald Sørensen
 

On 26/04/2021 07:17, Ozan wrote:
Hi Torquil,

I have a problem with my 465B where the delay time position 10-turn pot for
the B sweep has no effect. Everything else seems to work. Please see this
youtube video for a demonstration:

https://youtu.be/17ZGEw_jOmo

The intensified portion of the A sweep trace always starts on the leftmost
part of the display no matter how much I turn the delay time position knob.
However, the holdoff knob does make the B sweep duration/length vary, in a
periodic manner as I turn the holdoff knob slowly clockwise.
------
I don't have a 465B but B sweep delay circuit works similarly on several scopes. On sheet <7> Q7067 compares delay potentiometer voltage to "A ramp" voltage. Depending on where ramp crosses the delay pot voltage, B sweep starts with that delay. "A ramp" waveform (node 60) is not shown in the PDF I found but it is the same signal as node 82 which is in the manual. First check is whether the pot changes comparator threshold. Voltage on C7052 should change from 2.8V to 12.9V as you turn the delay pot.

If the delay pot voltage is OK next check is voltage at R7157 & R7152 junction. Looking at the schematic I expect it to be ~ -0.5V when "A ramp" is more that the delay pot voltage and should jump to ~ +1V when it goes below.

If you report back the observations there may be other suggestions.

Ozan
Hi! Thanks! In the end I found the problem: R7069 which lies between a
55VDC supply
and Q7074/Q7075 was cracked and open circuit....It's supposed to be 6.2
kOhm. After replacing it, my 465B works perfectly!

The fault with R7069 turned out to be intermittent. Since it was open
circuit on my first measurement, I just added on 6.2 kOhm in parallel.
However, measuring after that I found 3.1 kOhm across the parallel
combination... So I though perhaps it was a cold solder joint that I had
fixed when tacking on the second 6.2 kOhm. But on closer inspection, I
found the crack, and R7069 was back to being open circuit. So I clipped
it out and replaced it with a correct resistance.

Best regards,
Torquil Sørensen


Re: Tektronix 465B servixe manual containing waveforms 56-70

Torquil Macdonald Sørensen
 

Hi!

Thanks for the link. However, I found that the 468 was essentially the
same as a 465B when it comes to the analog parts. So I could find the
waveforms there, but numbered differently.

In the end I found the problem: R7069 which lies between a 55VDC supply
and Q7074/Q7075 was cracked and open circuit....It's supposed to be 6.2
kOhm. After replacing it, my 465B works perfectly!

The fault with R7069 turned out to be intermittent. Since it was open
circuit on my first measurement, I just added on 6.2 kOhm in parallel.
However, measuring after that I found 3.1 kOhm across the parallel
combination... So I though perhaps it was a cold solder joint that I had
fixed when tacking on the second 6.2 kOhm. But on closer inspection, I
found the crack, and R7069 was back to being open circuit.

Best regards,
Torquil Sørensen

On 26/04/2021 19:26, pdxareaid wrote:
i have a free manual i just checked and it has the same problem. i guess i never really used it.
i use a very good artek pdf manual purchased at http://artekmanuals.com/manuals/tektronix-manuals/
both hi and low serial number manuals available. just enter 465b into search box for options.





Re: Tektronix 465B servixe manual containing waveforms 56-70

pdxareaid
 

i have a free manual i just checked and it has the same problem. i guess i never really used it.
i use a very good artek pdf manual purchased at http://artekmanuals.com/manuals/tektronix-manuals/
both hi and low serial number manuals available. just enter 465b into search box for options.


Re: 485 super weak brightness control

Ozan
 

The node 1312/1318 is 0.0V in A and -0. 6V in B in the 521 mode
0.9V in A and -0. 6V outside of the 521
That looks suspect
I agree this needs to be investigated further. Easy explanation is N4 signal on <11> is wrong but we looked at it before.

--- copied from our earlier exchange --
In sheet <12> N4 is expected to
be -3V in B sweep and 5/2/1n mode. What voltage do you see at N4 when you
are in B sweep vs A sweep 5/2/1n?
I can see -3.6 when 521 is selected, -3. 7 when B is selected and -5.3
when there is A selected and outside of the 521 range
-- end copy ----------------------------------

Confirming again is a good idea.

How do waveforms look in the following points in 521n setting A vs B at:
"A sweep from Q888" left side of R1307
"B sweep from Q1236" left side of R1322

Again we expect no change.

Ozan

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