Tektronix 2230 Scope - Vector Generator Cal Screen Frozen on Power Up (Fixed!!)

[fmashockie]

Hey y'all!  I recently acquired a Tektronix 2230 oscilloscope.  I bought it knowing that it was not working - I thought it would make for an interesting repair where I could learn more about how these analog scopes work! (yes I know this one is called a digital storage scope, but it still works very much like its analog brethren) But I think I am in a little too deep with this one.  First, someone had definitely attempted to repair it before.  Here's a list of what's wrong with it:

-wires and components left disconnected in multiple areas (too many to list)
-10x and 100x Attenautors missing on the A2 attenuator board (ordered replacements, just waiting for them to come in)
-several damaged knobs and connectors
-R4 on A2 attenuator board blown in half (replaced)
-C701B one leg cut or desoldered from board on A4 timing board (fixed)
-C4203 on A10 storage board removed (replaced)
-I am probably forgetting some things 

I have made some progress on this poor guy so far (if interested, I am documenting the repair on my YT channel.  Parts 1 and 2 I will put below for anyone interested), but I am stumped by this readout issue on the digital side.  When powering the unit up, this strange readout appears on the screen.  It looks like crosshairs with 4 triangles in each corner.  It reminds me of what someone might see when operating a stinger missile (I'm thinking Metal Gear Solid 2; screen grab below)!     So I have dubbed it the 'Stinger Missile Readout Fault'! (edit: this display has now been determined to be the Vector Generator Calibration Screen). I cannot find an example of this display in the service manual.  I cannot find any info on this fault either, although I did find an example of it online in a different forum somewhere.  Some poor sap like me also had this issue and no one was able to help him either.  Anyway, none of the buttons work when this readout appears, except the readout intensity, focus, and horizontal positioning (moves the crosshair side to side).  Nothing will make it disappear except isolating the analog circuitry from the digital. 

I've tried checking some of the waveforms in the service manual, but some of them are difficult to make out due to the poor resolution (I actually ordered a hardcopy of the 2230 service manual so I could see them better - just waiting for it to arrive).  I tried isolating the kernel to check the kernel timing and I have a few discrepancies with the waveforms, but it almost looks like it could be a mistake with the service manual (I posted a screen grab below of what I think they should be.  I know Tek service manuals are not without typos).  I've also ordered a NOS set of ROM chips just in case - again, just waiting for them to be delivered.

Anyway, I was wondering if anyone has seen this fault before?  If not, does anyone have any troubleshooting ideas/suggestions/comments?  I would greatly appreciate it! 

Thanks in advance and happy holidays!

-Frank

P.S. - I've already verified this does not appear to be a power supply issue.  All power supply voltage rails are within spec for accuracy and ripple.  Links to videos below if interested.

Part1


Part2

[bdunham7]

It appears to be a malfunctioning version of the vector graphics adjustment screen from the diagnostic menu.  Read this thread:

https://www.eevblog.com/forum/repair/tektronix-2230-new-to-me-some-questions-on-optimizing-it/msg5151516/#msg5151516

[BlownUpCapacitor]

Those "cross hairs" are the CRT calibration aid. I don't remember how to get out of it, but you can try pressing the move left button on the acquisition board.

This aid is accesed by going to the advanced funtions and going into calibration aids.

Seeing this is very good news! It also looks like the digital CRT alignment is in pretty good calibration too. You seeing this aid means the board mostly works. I have a fully functional 2230 myself, so if you need voltages or something just ask me.

https://w140.com/tekwiki/wiki/2230 I have added a picture of the 2230 menu reference guide in the pictures section of this w140 website.

[BlownUpCapacitor]

Video if my English is bad. https://youtu.be/ffE_GE4SpDU?si=qfYqukYmfknDzgTN

Edit: If this cal aid shows up on power up, something is still wrong with the digital board. It should not be there when you simple power on and press the menu select button.

[fmashockie]

It appears to be a malfunctioning version of the vector graphics adjustment screen from the diagnostic menu.  Read this thread:

https://www.eevblog.com/forum/repair/tektronix-2230-new-to-me-some-questions-on-optimizing-it/msg5151516/#msg5151516

Thank you so much! I had heard some people speculate it was a test mode like this!  You'd think the service manual would have an example figure of this diagnostics window... Not in the 2230!     But this is interesting... on the 2230, the Vector Generator has its own board... might be worth checking there for faults!  thanks!

Those "cross hairs" are the CRT calibration aid. I don't remember how to get out of it, but you can try pressing the move left button on the acquisition board.

Thanks BlownUpCapacitor!  But unfortunately, there is no way to leave this screen.  None of the buttons respond (except focus and readout intensity).  It is definitely a fault of some kind.  Just not sure if it is related to memory, microprocessor, or an issue on the Vector Generator board itself.  But both of you definitely gave me something us to check/consider so I really appreciate it! 

I will also change the title of the topic now that I know what this screen is 

[fmashockie]

Video if my English is bad. https://youtu.be/ffE_GE4SpDU?si=qfYqukYmfknDzgTN

Edit: If this cal aid shows up on power up, something is still wrong with the digital board. It should not be there when you simple power on and press the menu select button.

Yea see this much I know.  As I said this is definitely a fault of some kind.  On the digital side of the unit.  Sorry if my original post wasn't clear.  I am trying to ask for ways to diagnose/troubleshoot this issue.  But I appreciate your help!

-Frank

[BlownUpCapacitor]

Is the digital menu navigatable at all?

Sorry english is not my strong suit.

[fmashockie]

Again, I apologize for any confusion, just want to make sure I make the following clear for future comments:

-I am aware this is screen (now determined to be the Vector Generator Calibration window) is NOT suppose be displayed on initial power up
-There is no way to exit the screen.  It will not go away by pressing any buttons/knobs.  The only knobs that respond are the readout intensity, focus, and horizontal positioning knob (moves the square side to side)
-The window does go away by isolating the analog circuitry from the digital (procedure in service manual).  The unit also needs work on the analog side, but this thread pertains to this window being frozen and how to fix it
-Any suggestions for how to repair/troubleshoot/diagnose are greatly appreciated!

Thanks!

-Frank

[fmashockie]

Is the digital menu navigatable at all?

Sorry english is not my strong suit.

No you are fine! Your english is great.  I really appreciate you posting your video, too!   But to answer your question, no.  The digital menu is not accessible at all.  None of the digital buttons will work. 

[BlownUpCapacitor]

Since only really the digital part has the main problem, digital trouble shooting is diagnostic needed.

"If the instrument contains the RS-232C option, an ASCII version of all erroes found during power-up is sent to the option"

If your model has the RS-232 option, try connection to that and see if error codes come out of there.

Error codes will help you diagnose the faulty part on the digital board.

Edit: Quote directly from the service manual.

Edit 2: If your scope does not have RS-232 connections, U4119 displays the error codes too. Page 6-14 of the service manual

Edit 3: Also It would potentially be useful if you let us know what EPROM versions you have. My scope has the -15 version. I think it's the latest version.  You have the -12 version. What kind of NOS ROMs did you order? What versions are they? I belive there are 15 variations. w140 only has 2. The -01 version, and the -15.

[fmashockie]

Since only really the digital part has the main problem, digital trouble shooting is diagnostic needed.

"If the instrument contains the RS-232C option, an ASCII version of all erroes found during power-up is sent to the option"

If your model has the RS-232 option, try connection to that and see if error codes come out of there.

Error codes will help you diagnose the faulty part on the digital board.

Edit: Quote directly from the service manual.

Edit 2: If your scope does not have RS-232 connections, U4119 displays the error codes too. Page 6-14 of the service manual

Edit 3: Also It would potentially be useful if you let us know what EPROM versions you have. My scope has the -15 version. I think it's the latest version.  You have the -12 version. What kind of NOS ROMs did you order? What versions are they? I belive there are 15 variations. w140 only has 2. The -01 version, and the -15.

I believe this scope does have an RS-232 connection on the side.  Called the auxillary connector.  You're saying I can check diagnostics via the RS-232 connector? 

The ROM set on this scope has version 12.  I ordered a set that is version 15.

-Frank

[BlownUpCapacitor]

I believe this scope does have an RS-232 connection on the side.  Called the auxillary connector.  You're saying I can check diagnostics via the RS-232 connector? 

Is it a DB-9 connector? If so, that is not RS-232, but rather the plotter outputs. The 2230 utilizes the RS-232C, with the wide connector of DB-25, as shown in the image.

But if the scope does have a DB-25 connector, try to use that to check error codes.

Otherwise, as said, probe U4119 for possible error codes.

[fmashockie]

Nah its a DB-9 just for the plotter outputs like you said then.

So I'm having some trouble understanding the diagnostics section of the manual.  I see figure 6-5 which indicates the error code timing for U4119.  I also see table 6-10 which has U4119 error code display.  But I'm not sure I understand it (I attached a screen grab of both the figure and table so you don't have to dig thru the manual).  I probed pins 12-19 on U4119 and they all have the same waveform - each pin is exactly the same with respect to ground (waveform attached).  It looks very similar to figure 6-5.  A ~0.8s pulse with ~3.3sec in between each pulse.  Now the manual says it should be 0.7s, but since I'm measuring 0.8, there's roughly four 0.8s spaces between each pulse.  Does that mean there's 4 error codes?  If someone could explain this for me I would greatly appreciate it!!! 

[BlownUpCapacitor]

Yes. I am also having a little bit of a hard time understanding this.

But if I must make an educated guess, you have to probe all 8 pins at once, and the combinations of the pins being HI and LO, during each timing interval, will give you the error codes.

This is just a guess though, but it's my best guess. 

Edit: Perhaps the EPROMs are so corrupted that they can't even run the PU tests?

[fmashockie]

Well I wasn't able to figure out how to read the error codes on U4119, but I fixed it!!! No more squares and triangles!! 

So I decided to do a more detailed search the EEV blog to see if someone had this fault before.  And sure enough, someone posted about this exact fault in 2014 (also coincidentally, by someone else named Frank! We must have bad luck with this fault  ).  The thread is here https://www.eevblog.com/forum/testgear/tektronix-2230-display-problem/msg393111/#msg393111 So after reading that, I decided to check all the gang-style snap action switches - I buzzed them all out with my DMM.  Sure enough, Memory switch #2 is faulty!! They are DPDT switches and both poles were open circuit in both switch settings.  Which effectively is somewhat like the switch being depressed all the time!  So I just added some jumper wires to close both poles and then I powered it up - and it worked!!!

So I need to replace that switch (or possibly the whole bank of switches.  I'm not sure if they can be replaced separately).  But besides that, I am willing to bet that is all the digital side of the unit needs to be operational.  I still need the attenuators to get the analog circuitry up and running.  And then from there I will be able to do some thorough performance checks and possibly adjustments.  I really appreciate your help BlownUpCapacitor! 

Part 3 video

[BlownUpCapacitor]

Bravo!

I did some mild digging on the forum too but didn't get the thread you found.

But it looks like the acquisition board works now!

Out of curiosity, does the firmware version of your 2230 have the Tek wizard eater egg?

[fmashockie]

Out of curiosity, does the firmware version of your 2230 have the Tek wizard eater egg?

I'm not sure! Do you have the procedure to access it (if I do have it)? I might have to wait to try it until I have that button fixed because I can't toggle thru all the menus easily without it.

[BlownUpCapacitor]

My version, the -15 version does not have the wizard, so I'm simply guessing on how to acces it. But I know it is in the diagnostics menu. Open the menu, and go to advanced functions. Then go to diagnostics. You should see a "WIZARD" option if yours has the easter egg.

Follow my video until the "CAL_AIDS" part. Then go explore. It would be really awesome if your scope has this easter egg.

this is a video of a Tek 2232 with the wizard.

[BlownUpCapacitor]

Looks like the Wizard is more specifically located in the exercises part of the advanced functions.

I quite like how TEK put their easter egg in the actual service manual.