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Using the diode test method I found what I believed to be a bad Q552 transistor. At the same time F558 was blowing. I have replaced Q552. But F558 does indeed blow every time the power on switch is pulled. The low voltage readings, except the 95V, are good at this point. 32V reads 32V. -5V reads -5V. +5V reads +5V. 95V reads 7.5V. I have checked every component in the 95V circuitry. All were good or have been replaced. Could I be looking at a bad T550 transformer or a bad HV module (U550)? From the schematic I have it would appear HV module pins 3, 5, and 11 feed T550 pins 8, 9, and 10 respectively. What would be the expected voltages on T550 pins 8, 9, and 10? Harrison N1FAM

Monty: That 840 Error Message means the drive belt came off the rollers
and the tape is not moving. The tapes are not attached on either end as I
am sure you are well aware. There are a series of holes punched into the
magnetic tape, and if the LED optical system does not detect the holes,
then it gives the 840 error message. There is nothing wrong with your
lamp/sensor circuit. Please don't mess with the sensors or you will have
real problems to cope with.

I still would like to buy 1 more 4041 tape with all of the files on it.
Please let me know if you have the time to produce it. Thanx.

Gary

--
Gary Robert Bosworth
grbosworth@...
Tel: 310-317-2247

I have captured the four CPU board EPROMs and two SCSI Option 03 board EPROMs and posted them on my github repository:

• System ROMs were two 27512
• Option 10 ROMs were two 27256
• SCSI Option 03 board had two 27128 EPROMs

I just added a photo of the new 4041 CPU board that only has two System EPROMs and two Option 10 EPROMs to my 4041 TekScopes photo album

New 4041 CPU board with only four EPROMs

Is this the one that had an onion skin thermal printer and when you printed
the screen, a horizontal line when from top to bottom like it was scanning
the inside of the CRT? At Aerotech labs in the early 70's, one was used
to create Ultrasonic transducer certifications. The Scope Main Frame had a
spectrum analyzer module in it. The output on the Green Screen was set up,
I think, to look like a complete cert. There was options to have text and
calculations on that screen and the screen shot of the spectrum analyzer.

On Sun, Aug 30, 2020 at 11:17 AM Holger Lübben <
tekscopesinput@...> wrote:

Hi!

I've added an old picture of a Tektronix DPO/DEC PDP 11/05 combination on
a 202D cart to the photo section:

/g/TekScopes/photo/252847/0

Has one of these machines survived?
I'm looking for some detailed pictures of this combination.

Holger

I just received my EBAY purchase of another 4041 - this time with the DDU disk drive unit attached.

The auction indicated they were working at the time they were taken out of service - I'm not so sure of that, but both 4041 and DDU powered up during my test last night.

However, even though the 4041 powered up, showed v2.1 firmware and 512KB of memory, the LED display showed a prompt, so I suspected it did not load any AUTOLD file from the DDU.

There are SCSI DIP switches on the 4041 rear panel for SCSI Option 03, one of which changes the default storage from internal tape drive to DDU hard disk - and that switch was set to DDU hard disk.

Looking at the front of the DDU, I could see the hard drive LED blinking three times, repeatedly. The DDU service manual indicated in the Shugart hard drive section that this meant the spindle failed to come up to speed :(

I turned off both units and changed that switch to tape, powered up the 4041 by itself with one of my tapes, but got an error on the LED display indicating 840 Lamp/Servo failure.

The tape did not move, so it appears I need to troubleshoot the tape Lamp circuit.

In the meantime, I pulled off the right side cover and did my front panel board mod to allow my USB to TTL serial adapter to be used with the front panel keyboard connector.

• Power off the 4041.
• Remove the 4041 two rear plastic "corners" securing the right panel and slide off the right panel.
• I dipped my desolder braid in flux, place the braid on the pad and apply your hot soldering iron to the braid and resistor lead to suck the solder completely from the pad. Be sure to cut off the braid and apply fresh flux before desoldering the pad for each resistor.
• Unsolder and lift the 'left' side of the two resistors closest to the unused J86 connector as shown in my resistor mod photo: 4041 Resistor Mod
• Solder a 1K ohm resistor into the hole (I first cut the resistor lead down to .25 inch).
• Then solder the tomb-stoned 1K ohm resistor to the lower resistor and clip off any extra leads per my photo
• Replace the right side panel to ensure proper 4041 cooling.
• Connect your TTL Serial interface ground to the top left keyboard connector female contact.
• Connect your TTL Serial interface TX to the lower left keyboard connector male pin.
• Configure your TTL Serial interface for 4800N2 speed, parity, stop bits.
• Power on the 4041 and you should be able to type on your PC using the TTL Serial interface - and see your typed characters on the front panel LED

I only use this TTL Serial interface to bootstrap to the rear panel COMM0 interface (if you have the Programmer ROMs installed in the ROM tray behind the front panel grill): 1. Type "SET DRIVER "COMM0(BAU=9600,FLA=BID,EDIT=STORAGE):" 2. Type "SET CONSOLE "COMM0(ECHO=YES):"

I find the EDIT=STORAGE parameter is easier to use when correcting PC typing errors, as the console will echo back each character you are deleting.

After the 4041 keyboard mod, I used my PC to type the command to format a DDU 5 1/4" floppy, and to run the DDU service manual program to do write and read performance tests on the floppy.

I got 1117 Bytes per second, which meets the 1000 bytes per second listed in the floppy spec.

So my DDU SCSI controller and floppy drive are working and I've ordered a Seagate 40MB ST-506 drive to replace the failed Shugart drive.

I also noticed my new 4041 has a newer CPU board which includes the memory on the CPU board and also only has four EPROMs!

The 4041 service manual indicates 4041 serial numbers B070100 and above have this CPU board.

The service manual also indicates two of the EPROMs contain 128KB of system ROMs - 28KB more than the earlier CPU boards. I believe the additional 28KB is the UTL2 ROM only available for these CPU boards.

The service manual indicates the Option 10 for this CPU board is the two additional 27256 EPROMs, which contain the R01 Graphics, R02 Plotting, R03 Signal Processing, R04 Utility1 option ROMs, which leaves room in the ROM drawer for developer ROMs to be installed.

I ran the ASK$("ROMPACKS") command and got the list of all those option ROMs and the UTL2.

I will capture the two Option EPROM images and post them on my 4041 github repository sometime this weekend.

There is a group [email protected], dedicated to HP equipments.

Warm Regards,

The digital board supply is only accessible if you remove all the logic boards - it hides away at the front of the 'scope to the left (as viewed from the front) of the logic boards.

You can't get at that board while the scope is running, so you have look at the schematics and board layouts to find places to check the -12V and +/-5V that it supplies to the logic boards.

Refer to pp 2-124 and 2-125 for a description of that supply and Schematic <38> for the A7 Auxiliary regulator board.

You really need extenders to work on this beast - Gerber files available - sorry I have NO SPARE edge connectors.

HI!

The P7001 digitizer is relatively rare, thats true. But I'm wondering more about the always missing minicomputers. I think 90% of the overall functionality of the DPO system sits in the computer - but nobody seems to have one...

Holger

Egge,
You're correct, of course; I wonder why so few of them are left?? I have the only one I've ever seen locally (core memory).
-Dave

Hi Dave,

You mean x010101 (the first of the production). I also have P7001 Manuals referring to B07xxxx and B09xxxx SN's.

Greetings,

Egge Siert

Alright, thanks for the info Dave. I checked everything in table 4-4 as well as any other areas that had a marked voltage test point that I could see (definitely could have missed some) on A22 (The LV regulator) But I only checked the 108 on A12 as everything else proved (at least for the time I had available to test things today) too difficult to do. I also couldn't figure out how I could leave it attached to the rest of the scope while removing the shield that separates A12 from the outside as to get any access to the front of the power supply I had to pull it out too far for the shortest cables to reach.

That 108 is the pre-regulator voltage. I don't think that ripple is of
great concern. There's not a lot of bulk capacitance on the 108 because it
is the feedback to the inverter controller (A12U75), so it's going to have
some ripple.
Did you check all the supplies coming off the A12 board, or just the
voltages listed in table 4-4?
You need to check all of the supplies for level and ripple.
The digital supply mentioned is generated by the auxiliary regulator,
assembly A7, schematic sheet <38>.
This is where the +5VD (D = digital), -5VD, and +12VD are generated; these
are the voltages that run the processor/digital half of the scope and thus
the most likely to cause your specific problems.
There are test points on A7, but you should also check the supplies from
the A12 and A22 boards, as they are the inputs to the auxiliary regulator,
which can only clean up a dirty input so much. Except for the -5VD rail,
most of the filtering for the digital supplies happens beforehand in the
analog supplies along with all the caps for localized filtering at the ICs.

Dave Casey

Alright I've checked all the power supply test points I knew the location of (A12,A22,A17) Except I didn't get that digital supply David mentioned, which I'm not sure where the test points are, how to reach them, or what the specs are for that.

Of the stuff I checked though everything came out relatively normal from what I could measure with my less than great instruments, well all but one thing, TP126 for the +108 volts that read 108.5 volts which is barely in spec but had some funky ripple pictured here on my auxiliary scope: /g/TekScopes/photo/252782/0?p=Created,,,20,2,0,0 . That was the only thing I saw that was out of the ordinary so far.

But don't the Tek part numbers sequences typically start at x100001?? To me, that means 772 were sold before the update, and I doubt they sold many P7001s after 1980; they were getting fairly old at that point.?
-Dave

Martin -
I'm no 7854 expert, but I've been poking around in a few lately, and the manual has been my bedtime reading material, so I know just enough to be dangerous. That being said, a few thoughts:

From experience, the CPU can look like it's running, but be running through garbage, a problem I'm still trying to troubleshoot on a comatose 7854.

Do the button lights change when you press them?

Does it start working again after powering down & powering back up, or does it need time to cool down?

Being able to send a debounced _RESET is a handy trouble-shooting tool. I think I just brought TP1200-1 to ground.

The mode select buttons are read to the data bus through buffer U61 whenever the _FPR signal is active. This is triggered by the CPU's DBIN line OR'd with some address decoding logic.

Ya got a hard-copy of the manual? I can't imagine trying to troubleshoot these without one (or two!). There's a few folks on here that /really/ know their way around the 7854 - hopefully you can tease out enough details to pique their interest!
cheers,
Paul

The Op manual p 9-43 only considers "premature termination" by the STOP
command.
After normal termination missing data are filled by linear interpolation.
(Though I think I also read filling with the last previous valid data value.)
After premature termination:
- AQR filles whole waveform with zeros
- AVR filles by interpolation (unless there were no valid data points at all).
Using AVR and nearly immediate a STOP I could generate a waveform with
interpolated sections.

Right - I don't think it knows if it's good data or bad data, only that it got filled up. I'm haven't figured out how yet, still making my way through the manual. I know it's also counting sweeps, but since it's sampling randomly, that wouldn't tell it if it was done or not. Is the CPU watching the address bus and keeping a tally of all the used locations?

I still suspect that given the predictable spacing in the gaps of data he's getting, the issue is manifesting as an addressing problem during the DMA writes from the digitizer to the RAM.

Hi Tim,

I have a P7001 Manual with dated MCI (06-17-80) for SN B100773 and above. Thus it seems thousands are sold.

Greetings,

Egge Siert

On Fri, Sep 4, 2020 at 09:28 PM, Albert Otten wrote:

The Op manual p 9-43 only considers "premature termination" by the STOP
command.
After normal termination missing data are filled by linear interpolation.
(Though I think I also read filling with the last previous valid data value.)
After premature termination:
- AQR filles whole waveform with zeros
- AVR filles by interpolation (unless there were no valid data points at all).
Using AVR and nearly immediate a STOP I could generate a waveform with
interpolated sections.

Hi Albert,
That's when the 'scope is healthy. In the video, it seems that acquisition proceeds to a certain stage, then sort of repeats, as can be seen in the periodicity of the pseudo-random garbling of the readout characters. This goes on for two minutes, when finally the AQR terminates.
I really think PS voltages should be checked so we know whether we're chasing real ghosts.

Raymond

On Fri, Sep 4, 2020 at 06:00 PM, Raymond Domp Frank wrote:

@Raymond -
The scope decides the Acquisition is complete when 99% of of the memory is full.

Thanks for that, Paul. Moving what I wrote earlier into this criterion: What
if the comparison is corrupted, IOW the acquisition thinks it's >= 99% done
but in reality, it isn't?

Raymond

Hi Raymond,

The Op manual p 9-43 only considers "premature termination" by the STOP command.
After normal termination missing data are filled by linear interpolation. (Though I think I also read filling with the last previous valid data value.)
After premature termination:
- AQR filles whole waveform with zeros
- AVR filles by interpolation (unless there were no valid data points at all).
Using AVR and nearly immediate a STOP I could generate a waveform with interpolated sections.

Albert