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TDS3032 does not boot. LCD backl-ight and fan working.
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Hi guys,
I have a TDS 3032 that does not start. When powered on, the fan spins, and the LCD shows a white screen (i.e., back-light only). There is no beep, no floppy seek sound, and no relay clicks - the scope simply stays this way and does not attempt to boot. All power supply voltages are within spec. Pressing the calibration button in the back during power on has no effect. Any ideas as to what may be the cause of this would be most welcome! Can it be a dead battery in the Dallas NVRAM chip? I know this can cause weird problems at startup, but I do not know if this is one of them. Thanks in advance, Benjamin |
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I would think if it is a dead NVRAM, holding in the B-TRIG button as you
power it up will cause a reset. See if that gets it booting. Dave On Mon, Dec 3, 2018 at 3:34 PM benj3867 via Groups.Io <benj3867= [email protected]> wrote: Hi guys, |
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" Unfortunately, holding the B-trig during power up makes no difference. "
My experience: When I replaced by NVRAM with a fake one I bought in China, the scope would light up, but would not boot. I then order a NVRAM from a place in Florida and replaced it again and then it worked fine (Have to hold the B-TRIG in as powering up to reset the new NVRAM. It worked great then. Its out to Spectrum now for re-certification (Calibration tables were NOT lost). Dave On Tue, Dec 4, 2018 at 5:01 AM benj3867 via Groups.Io <benj3867= [email protected]> wrote: Thanks David. |
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" @Dave, when you have had the bad NVRAM installed, how did the no-boot
situation look? I.e., was it also a white screen, no beeps and no relay clicks, or did it at least show the DPO splash screen? " Gosh, I'm afraid I am of no help then. I looked through old message threads I had on here from the last month and found my message concerning the fake NVRAM from China: ""After re-assembly, it will not boot past the "Digital Phoshor Oscilloscope" splash screen. During bootup, you do hear the hear the relays click, the splash screen flickers a bit and the floppy drive seeks. The splash screen never goes away. "" My TDS3032 did get to the splash screen and locked up with the fake Chinese i.c.. Sorry. The NVRAM is probably about the only thing you can fix on that main board. It cost about $38.00. You have to decide if it's worth a shot. I wonder if you removed it (lot of careful de-soldering - use a powered de-soldering pump (i.e. Hakko 808). Maybe if you removed it it would boot to the splash screen, then you know. If it is still totally dead, I doubt there is much you can fix. Look for a XTAL near the microprocessor and make sure it is good and not broken (if scope was dropped). I will be getting mine back with calibration seals, so I will not be able to open it to help do comparisons with you. Dave On Thu, Dec 6, 2018 at 5:42 AM benj3867 via Groups.Io <benj3867= [email protected]> wrote: @Dave, when you have had the bad NVRAM installed, how did the no-boot |
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I didn't see any other responses or follow ups in the Tek News Group.
Did you figure out your TDS3032 problem? The EEVBlog Forums might be another good resource to check out. Dave On Sat, Dec 8, 2018 at 10:46 AM benj3867 via Groups.Io <benj3867= [email protected]> wrote: Thanks Dave. |
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@David, thanks for the interest!
Unfortunately, nobody in the group had any feedback for me :( The good news is that after much probing and testing, I have managed to find the culprit IC, namely U100. After removing it from the board the scope boots fine except that, obviously, it complains about the missing chip... I will open a new thread to ask if anybody can help identify a source for a replacement. |
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Hello Ben,
I realize this is an old topic, but I have exactly the same issue you experienced. I have a Tek TDS3054B that just has the white screen, no boot activity at all. You mentioned removing a chip (U100), but didn't reference any other info. Any idea where I should start probing? I check the power supply board and I do indeed have 15V, so it's likely not the power supply. Any suggestions as to where to start looking? Cheers Paul. |
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Paul -
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There have been units in a similar state mentioned on the EEVBLOG that were due to a dead oscillator. Thread is called "TDS3014 adventures", and it's one of the top results when I search "tds oscillator site:eevblog.com". Look for a yellow-ish metallic 4-pin SMT package on the main board. Correct frequency will be marked on the case. Pinout is fairly standard to find the output. There are a couple different oscillators, so check them all. This is only one of many possible causes. I'm fighting a 3054 with power supply problems on the low voltage rails on the main board with the same kind of behavior though, so hopefully yours is just an oscillator. Do you hear any weird noises when the scope is on? If the clocks check good, the next thing would be to verify that all the voltages are good and the reset supervisor is letting the CPU run. 15V is only an intermediate step between the PSU/battery board and the main board; about 1/3 of the main board is more power supply stuff derived from that 15V. Dave Casey On Tue, Dec 6, 2022 at 4:16 AM Paul Carew <paul@...> wrote:
Hello Ben, |
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Hello Dave,
Thanks for replying. This scope used to work, but it has been powered off for ~3 years. I went to use it again the other day and came across the blank screen issue. When I power it on, the fan runs and the white back light lights on the screen. Other than that, there is no other signs of life. Thanks for pointing out the Oscillator issue. As it happens, I found the Oscillator reference soon after I entered my forum msg here. I checked the output and nothing from the 75.757. I also verified that the power supply is generating 15V. I guess, I need to next check the other voltages. Did you find a schematic or other reference as to what voltages should be present and where? I'm assuming that there is at lease a 3.3v regulator somewhere. Can you suggest any other test points to verify for the system voltages as a starting point? Thanks again. Paul. |
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Paul -
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If you have nothing from the oscillator, then you can easily check if it has power. If it has power but no output, then that's the likely culprit. As for the other voltages, look for four TO-220 packaged parts down by the transformers. Those account for some (but not all) of the lower voltages and are a good place to check for a sense of everything working right (both on the input and output side of those regulators). No, I do not have a schematic. Everything I know is from forum posts or time spent probing boards. Dave Casey On Tue, Dec 6, 2022 at 8:17 PM Paul Carew <paul@...> wrote:
Hello Dave, |
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Hello Dave,
Thanks, I verified that I have good voltages (+5,-5 and +3.3). i also realized that I really don't know the state of the oscillators. It was late last night and I wasn't thinking clearly. I checked the 48Mhz and 75Mhz oscillators with a 200Khz oscilloscope. Of course I didn't see any output :-). I'll have to get my hands on a 200Mhz scope and re-check. Paul |
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Paul -
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Have you tried holding the "B TRIG" button while powering on the scope? Dave Casey On Thu, Dec 8, 2022 at 8:50 PM Paul Carew <paul@...> wrote:
Sure enough the oscillators are both working. |
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Hello David,,,
I Tried the B-Trig reset with no effect unfortunately. While probing the main board with a scope, I determined that the power on reset circuitry is working (at least the 'MAX708R' generate the reset correctly), but there are *no* signs of life from the processor. Checking the A0 address line on various pins on the other chips, shows no activity whatsoever. I am now starting to suspect that the MPC860 processor is either dead or needs re-balling. Hmm, not the easiest of tasks to do. Paul. |
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