Tektronix 2230 - no readout


oneenaht@...
 

Hi guys,

my first post here.

I have been given a Tektronix 2230 scope.
The previuos owner could remember het go it from somebody else, and there was something about a fuzzy readout.

I always find it a challenge to repair electronic equipment, but this time I am stuck.
The scope is very clean and probably not used very much, if it ever has been used. Or if it has even worked as it should be.
Inside there is no dust, and no repairs have been done previously.
The GPIB option board is present, as well as the memory option. The backup battery is OK.

(please take a look at the video) / https://www.youtube.com/watch?v=8YkXAwB-x4Y&feature=youtu.be

On startup, the analog function looks OK, all the controls are functional. Tested when rest jumper is set.
(Except for an issue with the attenuator which looks to be open in some positions, bad contact?).
After some time, after 40" in the video, the analog screen disappears completely.
When you push beamfind, there is some small rectangular image somewhere, this can be top or bottom, an left or right.
After some time, after 1:20" in the video, things start to change. While pushing beamfind, it looks like some diagnostic things are displayed, but you cannot recognize any text.
So, the fuzzy readout the previuos owner saw was this behaviour.
Pushing the select on the cursor pot or turning it has no effect.

I have a nice service manual (Artek Media).
I must admit it is not very clear to me.

I have tested and measured all sort of things, but there is nothing that looks not normal at first sight.
Voltages are OK, also the plus and minus 15V on the vector board. I have forgotten to measure the 5V ref.
There are no leaking or thick capacitors in the PSU (Why do they make is so difficult to remove te cover?)
Data- and addresslines do not show unlogical signals, ie. shorts between addressline or outputs behaving strange. Tested real-time, and in testmode.
Clock 40MHz and 7.66MHz are OK.
Changed the processor (recovered from a very old Epson XT PC), no change.
Checked the display controller socket, but nothing unusual. The controller heatsink itself is touchable, so no overheating.
The digital push buttons are electrically OK, also the cursor pot (checked with ather scope). No of them seems to be doing something.

From the video, and monitoring addresslines, it seems the processor is running, but maybe it encounters some sort of error.
I have no experience with (digital) Tek scopes. Perhaps I am overlooking something simple.
Anybody has a clue?

Thanks in advance, Harry from Belgium


Bert Haskins
 

On 3/3/2021 12:51 PM, oneenaht@gmail.com wrote:
Hi guys,

my first post here.

I have been given a Tektronix 2230 scope.
The previuos owner could remember het go it from somebody else, and there was something about a fuzzy readout.

I always find it a challenge to repair electronic equipment, but this time I am stuck.
The scope is very clean and probably not used very much, if it ever has been used. Or if it has even worked as it should be.
Inside there is no dust, and no repairs have been done previously.
The GPIB option board is present, as well as the memory option. The backup battery is OK.

(please take a look at the video) / https://www.youtube.com/watch?v=8YkXAwB-x4Y&feature=youtu.be

On startup, the analog function looks OK, all the controls are functional. Tested when rest jumper is set.
(Except for an issue with the attenuator which looks to be open in some positions, bad contact?).
After some time, after 40" in the video, the analog screen disappears completely.
When you push beamfind, there is some small rectangular image somewhere, this can be top or bottom, an left or right.
After some time, after 1:20" in the video, things start to change. While pushing beamfind, it looks like some diagnostic things are displayed, but you cannot recognize any text.
So, the fuzzy readout the previuos owner saw was this behaviour.
Pushing the select on the cursor pot or turning it has no effect.

I have a nice service manual (Artek Media).
I must admit it is not very clear to me.

I have tested and measured all sort of things, but there is nothing that looks not normal at first sight.
Voltages are OK, also the plus and minus 15V on the vector board. I have forgotten to measure the 5V ref.
There are no leaking or thick capacitors in the PSU (Why do they make is so difficult to remove te cover?)
Data- and addresslines do not show unlogical signals, ie. shorts between addressline or outputs behaving strange. Tested real-time, and in testmode.
Clock 40MHz and 7.66MHz are OK.
Changed the processor (recovered from a very old Epson XT PC), no change.
Checked the display controller socket, but nothing unusual. The controller heatsink itself is touchable, so no overheating.
The digital push buttons are electrically OK, also the cursor pot (checked with ather scope). No of them seems to be doing something.

From the video, and monitoring addresslines, it seems the processor is running, but maybe it encounters some sort of error.
I have no experience with (digital) Tek scopes. Perhaps I am overlooking something simple.
Anybody has a clue?

Thanks in advance, Harry from Belgium
A few quick points some of which you may already know.

The intensity pot when rotated fully CCW and back switches the readout on and off.

There are separate adjustments for the readout and trace intensity on the MB.

It pays to be very fussy about all of the connections between the MB and the CRT pins as several of these are "dry" circuits and need to be nearly perfect.


Several years ago I bought a "parts" 2230 scope from ebay and at first it didn't do much of anything.

I replaced two bad ribbon cables and in the course of further trouble shooting I was stunned to find a point where there was a signal on one of the eprom socket pins and no single on the eprom pin!

A simple cleaning of the chip and socket brought the scope back to life and it's been fine ever since.

Note that this was not even one of the POS Ti sockets, it was a Amp style socket.


FWIW Whenever I have a 2230/21/21A/32 scope open for service I replace the focus resisters and the input filter (line socket) just as a mater of course.


IMHO Any/all of the  2221A/30/32/35s are well worth restoring.


Have fun,

  Bert





oneenaht@...
 

Hi Bert,

thanks for reply.
strange coincidence: about a week before I got the 2230, I bought a digital scope (Hanmatek DOS1102, same as OWON) during an action at Ama***n, at almost half the normal price. I could not resist that bargain!
My purpose for it is to be able to see fast and slow things like I2C communication.
My workhorse is a 20MHz Hameg HM205 or so, but unsuited for that.

Now for the 2230:
I have removed the GPIB option (+memory) to take a look fot loose connectors hidden behind the mounting plate and under de CRT.
Without this option, the scope looks to be working analog only, do you need to jumper some cables?
Anyhow, I found nothing suspicious.
Also, I tried the Kernel isolation, and looking at the pins of U9112 and U9114.
All looks similar as in the service manual, except for pins 16/17/18/19 of U9114. There is a nice pulsetrain, but not as displayed on figure 6-3.
It looks they are all the same, but no pins are shorted.
A thing I have never came across before: Have you ever experienced bad EPROMS? Ans if so, where could I find hexdumps?


best greetings, Harry


Bert Haskins
 

On 3/5/2021 10:45 AM, oneenaht@gmail.com wrote:
Hi Bert,

thanks for reply.
strange coincidence: about a week before I got the 2230, I bought a digital scope (Hanmatek DOS1102,
I have a Hantek DSO5102P and several "pocket" scopes beyond my dozen+ Teks.
same as OWON) during an action at Ama***n, at almost half the normal price. I could not resist that bargain!
My purpose for it is to be able to see fast and slow things like I2C communication.
I use a saleae and/or one of it's ( many many ) clones for things like that.
My workhorse is a 20MHz Hameg HM205 or so, but unsuited for that.

Now for the 2230:
I have removed the GPIB option (+memory) to take a look fot loose connectors hidden behind the mounting plate and under de CRT.
Without this option, the scope looks to be working analog only, do you need to jumper some cables?
Anyhow, I found nothing suspicious.
Also, I tried the Kernel isolation, and looking at the pins of U9112 and U9114.
All looks similar as in the service manual, except for pins 16/17/18/19 of U9114. There is a nice pulsetrain, but not as displayed on figure 6-3.
It looks they are all the same, but no pins are shorted.
A thing I have never came across before: Have you ever experienced bad EPROMS
Not in any of my Tek scopes, but I have certainly improved my bank balance by restoring eproms in failed factory systems.

It's amazing how many things are still running on old vintage micros.

? Ans if so, where could I find hexdumps?
I checked for this in https://w140.com/tekwiki/wiki/2230 and didn't find any, maybe I should fix that.


best greetings, Harry
Where are you located?

I'm in west Michigan near the lake.

 Bert





oneenaht@...
 

Hi Bert,

I also have a Salae clone. Used it once to reverse engineer a display of a VHF radio, a Motorola MC Micro.
The story is on my blog (in Dutch): https://www.blogger.com/blog/post/edit/6705259174852751554/8643191421757783562
As there are not many countries where they speak Dutch: I live in Belgium, Flanders, not so far from the Northsea.
Aha Michigan, so Dr. Pol is one of you neighbours ;-) Your a bit to far away to visit...

I have been doing some more research today.
Sorry for all the Tek lovers, but this scope is not very service friendy. You have to unscrew several things, isolate the PCB's with cardboard and/or newspaper to be able to measure on certain boards and be lucky not to provoke shorts.
BTW:I found out you can test the scope without the GPIB option if you put P9107 (located 5B in schematic 10) in the other position, that way the reset from the GPIB board is inactive.
One thing I did not check previously: the 5V ref A and B, as well as the +5V on the vector and I/O board are OK.
Also checked point by point the flat cable between these boards, as well as the ribbon cable to the motherboard.
There is no activity on the X and Y vector pins going to the multiplexer 4053.
I am a bit running out of idea's. Do you have any more?

greetings, Harry


alastair.knights@...
 

Hi,

I've just had a similar issue with my 2230 - very faint and fuzzy image on the CRT, but Beam Find displays a solid rectangle. I found that R886 (180K) at the bottom of the Focus divider chain had gone open circuit for no obvious reason. You can check for this with simple resistance checks between the -8.6V rail and the -2KV Cathode supply rail. You can also check the focus voltage on pin4 of the CRT with a proper HV meter - around 1½KV is fine, but 2KV indicates a fault.

Hope this helps,

Alastair