Fluke 5440A repair

[Rax]

I decided to stop obsessing about unregulated supplies as long as the regulated side is in the ballpark. To that end, I enclose measurements from a couple of weeks ago, and then another set from this morning. In between, I've not only fixed the +-30V rails on A10, but also recapped and used 10A TO220 Schottkys on the high draw rail of A19.

In any case, a couple of questions to those that have similar units (and obviously, everyone else wanting to pitch in):

• Most voltages are close enough, though I will go ahead and adjust, as some seem to need to be dead on. For instance, could anyone confirm the TP1/TP2 measurement on A17 is supposed to be +5.15V +-0.00V? As the adjustment page (enclosed) calls it. This is a bit awkward, as the voltage there is labeled as "+5V" everywhere - on the schematic, PCB, etc. This seems pretty important to clarify before I dial that supply to 5.15V which is not a minor variation from 5.00V
• On board A5 I have a burnout spot around R102/R5/VR1. I pulled their legs and measured and the resistors seem fine. Also, VR1 drops 12V over itself. This seems to be confirmed by the SM part number, but not the description - the latter seems to indicate a "20.0V" zener. Can anyone confirm which one it is?

Thank you.

[Rax]

Unfortunately, this is part of path A - the launch of the digital part of the device. Further tuning uses a rich set of self-test tools for the instrument itself. And for this you need to be able to read messages from the display.

Working towards this goal. I don't feel I have clarity on what to do with the pulling of the cards process, but I'm taking it one step at a time and working towards hooking up my logic analyzer to the data lines.

Now, the interesting thing is I see no resemblance between my A2 PCB and the PCA in the wide circulation Service Manual. The Artek-sourced one has exactly what my board has (see attachments below). Megavolt - please let me know how you think that changes where I need to connect my logic analyzer to read those characters. For instance, I see D0 through D5 on U31 pins 9 through 4 - so that's six channels. Where does the seventh connect?

[Rax]

Due to size limitations, separate post with pics of my own A2 board.

[Rax]

BTW - unfortunately, the Artek Media SM doesn't have the 5440A specifications either.

[MegaVolt]

Thank you so much for these schematics!!! I didn't have them.

The point you need is on the u4 chip pin 4.

I have attached a small specification for the 5440a. But considering that all the circuitry completely coincides with the 5440b, I think you can safely take the specification from there.

The only difference is in the maximum output current.

[Rax]

Thank you so much for these schematics!!! I didn't have them.

Thank you for all the thinking on this with me!

The point you need is on the u4 chip pin 4.

You're a person of few words... I think you're saying this is the revised "letter writing signal" from your prior post (U4/pin4). Can you confirm? This would be one channel for the logic analyzer.

Can you also confirm the data lines are where I assumed them to be? (U31/pin9-pin4). Six more channels.

I also think there is a "0x20" to be read to better legibility - are we able to tell where to collect this data? One more channel to read here.
 
This would make eight channels to look at. If all of the above get confirmed, I should be able to read these shortly. I'd really be out of my mind happy to start registering some actual progress.

[MegaVolt]

I write through google translator, so I try to write briefly so that there are no mistakes ))

1. U4 pin 4 - write signal. The logic analyzer needs to be told that this is a rising edge clock signal.

2. Before starting work, you can check with an oscilloscope the presence of a signal on the U4 pin 4 line. This will indicate that the processor is trying to transmit data to the screen.

3. Data can be taken anywhere. It is possible on U31 pin 4-9. But better at the output of U31 pin11-16. It is also possible on any chip where there is D or D'. D is data from the processor. D' data after buffering. It is better to take the data after the buffer.

4. You will see data less by 0x20 i.e. the analizer will show 0x00 and this will mean 0x00+0x20 = 0x20 (Space ASCII).

4. I did not understand about the eighth channel. Seven should be enough.

[Rax]

I write through google translator, so I try to write briefly so that there are no mistakes ))

Thank you! All good and clarifying that is appreciated

[Rax]

2. Before starting work, you can check with an oscilloscope the presence of a signal on the U4 pin 4 line. This will indicate that the processor is trying to transmit data to the screen.

I tried this and I see some sort of pulses - one every couple of seconds o so. May be a good sign, but maybe it's trying to start up and shuts down on a fault condition. I did this just as a general measurement with a 10x probe relative to the 5V GND, but I can apply a different protocol to looking at these - ECL or TTL on my 54522A scope.

[Rax]

Here's some data I just collected. This is with all cards present. I have no idea if my collection protocol produces legible data. Again, I'm new to this, so please feel free to comment, etc.

I am not sure whether I should see anything on Channel 0 (which goes to pin 4 of U4). Channel 1 through 6 goes to pins 11-16 of U31. With the Hantek, you can make Channel 0 the "source" of the vertical cursor, so that's what I did. I assume this makes it the trigger channel. I can't see much else in the software (rising edge etc. be darned).

[MegaVolt]

Synchronization doesn't seem to work I haven't used this logic analyzer and can't tell you how to set it up.

But something can be done.

1. Is the GND pin of the logic analyzer connected?
2. Can you increase the capture rate to 4M for example
3. Since we are writing all the data, we need to increase the recording time to 2-3s from switching on. Those. sample rate*3.
4. Does recording start when power is applied? Or is it data captured at a random moment in time?
5. How are the thresholds configured on the logic analyzer?

In the data that is, I do not see anything meaningful. There is one place where the zero channel drops to zero. But he is in it for a very long time and I do not see meaningful data there. It is possible that any of the above will correct the situation.

[Rax]

Synchronization doesn't seem to work I haven't used this logic analyzer and can't tell you how to set it up.

But something can be done.

1. Is the GND pin of the logic analyzer connected?
2. Can you increase the capture rate to 4M for example
3. Since we are writing all the data, we need to increase the recording time to 2-3s from switching on. Those. sample rate*3.
4. Does recording start when power is applied? Or is it data captured at a random moment in time?
5. How are the thresholds configured on the logic analyzer?

In the data that is, I do not see anything meaningful. There is one place where the zero channel drops to zero. But he is in it for a very long time and I do not see meaningful data there. It is possible that any of the above will correct the situation.

• I connected it to TP1 (5V GND).
• I enclose a couple of readings at 16M.
• I think this is covered by the above?... The only other thing I can change is the sample length, and I kept it at the maximum possible value of 1M.
• I can press on this "play" button and it collects at that time. Strangely, I seem to see it changing occasionally (?), so maybe it keeps collecting? I wonder if the readings changing at no prompt has to do with the cursor being triggered by Channel 0. But I never see any "1"s on Channel zero - always completely black.
• I don't seem to have any control over them. I assume it's in the software - some sort of auto-detect of the protocol - but overall, a very disappointing experience with this Hantek.

[Rax]

I am less and less convinced U4 passes anything - I see these faint pulses at random intervals (I really need to watch very closely and I may still miss it, and it may just be the triggering system on the scope trying to grab something that's not quite there), while I do see some noisy DC at the inputs of that U4 gate (in the order of about 100mV). I am not sure how regular/compliant conditions should look like, but I can persist with a bit of direction, including scope and/or logic analyzer setup.

[Rax]

• Most voltages are close enough, though I will go ahead and adjust, as some seem to need to be dead on. For instance, could anyone confirm the TP1/TP2 measurement on A17 is supposed to be +5.15V +-0.00V? As the adjustment page (enclosed) calls it. This is a bit awkward, as the voltage there is labeled as "+5V" everywhere - on the schematic, PCB, etc. This seems pretty important to clarify before I dial that supply to 5.15V which is not a minor variation from 5.00V
• On board A5 I have a burnout spot around R102/R5/VR1. I pulled their legs and measured and the resistors seem fine. Also, VR1 drops 12V over itself. This seems to be confirmed by the SM part number, but not the description - the latter seems to indicate a "20.0V" zener. Can anyone confirm which one it is?

Thank you.

Anyone having more info on this? (MegaVolt? essele?). Should the +5 rail be adjusted to 5.15V? Is that zener 12V or 20V? Not sure if either of you has adjusted the rails and/or may have easy access to measure that zener drop in a unit working optimally.

While scratching my head over figuring out what's going on with the A2 board, I am also trying to make sure there's no weird behavior simply triggered by out-of-adjustment rails (which so often result in the most puzzling symptoms and behavior, isn't it?).

[MegaVolt]

1. Data must be taken immediately after power on. The instrument updates the screen only when parameters are changed. If this is an error message, it can only be one. And no repeats.

2. There was a failure with the logic analyzer.

3. 5.15V supply is within +/-10%. I don't think this is a problem. But you can probably adjust it more precisely.

4. You can try using an oscilloscope. By putting one channel on u4 pin 4 and see if there is a correct signal after turning on the power. You should observe a logic 1 most of the time and short pulses of a logic 0. (a few µs). If you find them, you can look at the rest of the oscilloscope channels on the data line, taking data one by one This is not convenient. But I don’t see other ways.

It may be possible to find information on using the logic analyzer on the net or on this forum. And it will turn out to get the desired mode of operation from it.

[Rax]

Thank you, MegaVolt, you've been very helpful through this saga and I really appreciate it.

There's obviously a "1" state on U4/pin4, and I've been trying to snapshot the state change to it when the unit it turned on. Somehow, the measly "half-a-buck" logic analyzer started to work, and I enclose a couple of readings at different settings. I am reviewing and trying to interpret this data myself, but if anyone is proficient at reading this and there's something useful in there, please do share.

[Rax]

One more data dump, this time with what I think is proper triggering ("high level" on U4/pin4), and with the channels named appropriately. I haven't used "sigrok session files" before, but I assume they embed all info picked during the data collection session. I did 5Ms @ 2MHz, so 3s collection.

Hopefully this is legible. I am doing this with PulseView, and I think it has some built in protocol decoders. What protocol is appropriate for this data? I assume a properly configured decoder would be able to interpret for me what exactly are the annunciations sent to the display.

[MegaVolt]

This data is still short.

I tried to display the correct data in the figure.

You can see it there.
1. Turn-on moment (all lines go from zero to 1)
2. RESET time.
3. Beginning of the processor. This is good.
4. Further, 1.7s after the start of the processor, the screen is accessed. I drew it.

Try to take them off like this.

The decoder can be set in parallel.

[Rax]

This data is still short.

Here's a 10 seconds read at 1M. What decoder is suitable for interpreting this? I've tried a few yesterday but only got gibberish out.

[Rax]

With the "7-segment display" decoder I see a repeating "bKH98" from a point on. Not sure if this is anything or as nonsensical as it seems.

[MegaVolt]

The data looks weird.  In the data that was before, the data was filled evenly.  In this data, one bit has large gaps.  This is weird.  Perhaps the sampling rate of 1M is not enough.  Or the processor has started badly

[Rax]

The data looks weird.  In the data that was before, the data was filled evenly.  In this data, one bit has large gaps.

Here's a couple other readings. Maybe let's assume worst case scenario - maybe the processor is bad. Are these unobtainium?

[Rax]

Attachment(s) were too large for a single post.

[Rax]

Are these unobtainium?

Both U5 and U16 seem pretty easily obtainable in the US, from some vendors I've used through the years and trust. I don't think I need to be swapping parts yet, not having narrowed down yet the issue(s), but just for reference.

[MegaVolt]

Maybe let's assume worst case scenario - maybe the processor is bad. Are these unobtainium?

1. The processor is the most common Z80, it is very common and it is not difficult to get it.

You can also swap chips between A2 and A16 boards. There is exactly the same processor. But from the data that I see the processor is working. It may have bad contact or wrong program.

2. You can check the data in the memory chips. If you have a programmer you can get them and check the data.

3. About the data.
I talk about how the data should look so that you can check it yourself. This will greatly speed up the check.

Below are two pictures. On one of them, as the data should look like. On the second there are places without data. It should not be. Files where there are gaps in the data are meaningless and of no interest. There is no point in posting them.

If there is no signal on u4.4, you can try to stand on u28.15 or u28.14.