Author Topic: Tektronix 11801 diagnostic and repair help [solved]  (Read 537 times)

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Offline rhb

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Tektronix 11801 diagnostic and repair help [solved]
« on: March 16, 2019, 07:10:02 am »
My 11801 arrived today.  On power up it makes two beeps and puts  up two lines of text on the screen:

Diagnostics in progress

Comm Test in progress

But does not go past that.  The seller sent a picture showing an E5622 error, "passed" below that and "????" for the timebase, main acq, mcu a-d acq entries and a picture of the screen with "Self test in progress". 

I have reseated all the boards and cables behind the CRT and the cables on the display board.  The display board was missing the 4 corner screws.  I have replaced those.

So does anyone recognize the issue?  While I was pulling the boards I checked the 4 lithium cells and all were over 3 V despite 1988 date codes.  That did not match the service manual for the 11801C which is a little disturbing.  Is this really just a CSA803 with 4 extra ADC channels?  Does anyone know of a manual for this unit?  I think all the ROMs are marked 1989, but was not meticulous about that detail as I expected reseating the connectors to have an effect.

Thanks,
Reg
« Last Edit: March 25, 2019, 11:55:21 am by rhb »
 

Offline pbarton

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Re: Tektronix 11801 diagnostic and repair help
« Reply #1 on: March 16, 2019, 08:03:55 am »
"Successful completion of the Kernal diagnostics is indicated by the start of the Self Test diagnostics."
single high/low beep and illuminated menu button indicators. = Executive Kernal failure.
Manuals available here http://w140.com/tekwiki/wiki/11801

« Last Edit: March 16, 2019, 08:21:22 am by pbarton »
 

Offline rhb

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Re: Tektronix 11801 diagnostic and repair help
« Reply #2 on: March 16, 2019, 08:17:12 am »
Do you have any more information?  I had worked out that the initial power on test was failing, but without any service data it's a little hard to proceed.

All the manuals I've found on line, despite other labeling have been for the 11801C which is very different.
 

Offline pbarton

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Re: Tektronix 11801 diagnostic and repair help
« Reply #3 on: March 16, 2019, 08:42:36 am »
Manuals available here http://w140.com/tekwiki/wiki/11801
Read the section on 'Diagnostic Troubleshooting'
"If the error message does not appear on the screen, the error index code can be obtained from the status LEDs and pins on the A15 Memory Management Unit board (see Fig 6-34)."
 

Offline rhb

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Re: Tektronix 11801 diagnostic and repair help
« Reply #4 on: March 16, 2019, 10:08:37 am »
Unfortunately, the 11801 link is actually  11801C documentation.  As is also the case at BAMA and a bunch of other sites. Having looked at the 11801C manual it's clear it's quite different from an 11801.

However,  after I pulled the boards a 2nd time to try to identify them it has come back to life!  But only 3 of the boards are labeled with anything intelligible to a human.  Just a number and two of them it's not clear it's even a Tek number!  One has a label "Property of and copyright Silicon Software".

I need replacements for the NVRAM which no one in the US has at the moment (and won't until June!!!), but a member of the tekscopes list in the UK has offered to get a couple and send them to me.

For $185 delivered a good score.  Now if the two SD-22s I got for $150 work....
 

Offline rhb

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Re: Tektronix 11801 diagnostic and repair help [solved]
« Reply #5 on: March 25, 2019, 12:24:21 pm »
After going around and around with it.  I finally got it working:

I set J710,711,712 & 713 to zero on the A14 I/O  board.  That still did not prevent it from getting stuck in the diagnostics at an E5622 error.  With the "exit diagnostics" button disabled on the touchscreen.

Then at the suggestion of a member of the TekScopes list I removed the battery backup sockets from U500 and U511.  In this case it had NEC D43256 - 10L CMOS static ram in sockets with two small lithium cells and small board with a DS1213 with a 1997 date code.  Removing the battery backup and directly seating the SRAM in the socket let it boot.

After resetting J710-713 back to one, it halts in the extended with a T1331 timebase error.  But pressing the "diagnostics exit" twice will allow the scope to  function.  With the calibrator connected to an SD-22 it reports a 30 ps rise time.

I still don't really know how to operate it, but everything seems OK.  It shows 44,000 hours of operating time and 2000 power ons.
 

Offline arw

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Re: Tektronix 11801 diagnostic and repair help [solved]
« Reply #6 on: June 16, 2019, 08:03:58 am »
Brilliant! Exact same fault, E5622, on my 11801, removed both battery backups on U500 and U511 and now works after exiting from diagnostic.
 

Offline rhb

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Re: Tektronix 11801 diagnostic and repair help [solved]
« Reply #7 on: June 25, 2019, 02:28:00 am »
It really is worth replacing the NVRAM chips.  STM makes a replacement.  Whether you install them now or later, don't wait to buy them.  They were almost unobtainium when I needed them.  I had to get a pair shipped from the UK and then I almost didn't get them as they sold some 36 pieces in about 10 days and RS claimed they were out of stock.  Conductive anti-static foam will discharge the internal batteries, so watch out for that.

While the UI is the worst ever, the performance with a fast head is quite a amazing.
 

Offline GreyWoolfe

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Re: Tektronix 11801 diagnostic and repair help [solved]
« Reply #8 on: June 25, 2019, 06:28:07 am »
While the UI is the worst ever, the performance with a fast head is quite a amazing.

I wonder of those engineers were having drunken conversations with HP engineers for the 54201D scope, truly a different UI.
That which doesn't kill you still requires a co-pay.
 


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