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TDS30xx OMG.. Are these all broken ?
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So I have lots of anaog Tek stuff. Highly refurbished and upgraded 7904s and I think most every plug in. I have most all of the TM500/5000 stuff I will ever need. Mostly this stuff worked right away off ebay and then I would refurbish and make near new. Service manuals make this easy. Well,, except for the occasional custom IC,, everything I bought got fix and I have in my lab in use.
BUT I needed a digital scope.. No prob I thought.. Just grab a TDS3012B for fairly cheap off ebay. These are way newer and not much to fail. Wow was i wrong... You guys should let me know if my luck is just really bad or do these scopes have serious failure rates ? First scope looked great. Self test perfect. Calibration perfect. Everything worked except one knob had issues. I expected a knob issue after researching and knew how to fix it. So this was great.. UNTIL I let it run for 40 mins.. After warm up the front panel controls died and the LEDS all flashed.. It worked in every other way. I could control it via IEEE or e-scope. Just lost complete control from the front panel. After exaustive work, its something on the main board. Not power supply as all voltages on the main board at the chips involved are fine. I also swaped supplies. I swapped front panel boards. Nope. Its the main board and its complex as its something going on on the data lines to the front panel and these are hard to probe close to the CPU chip. It could be the CPU is wonky. So that main board is pretty much hopeless.. So I bought another one, they said fully tested. Indeed when i got it I fully tested and it was great.. In calibration... BUT THEN.. about 15 mins of on tine and dense positive going spikes appeared on the waveform with no input that were full scale that caused triggering and measured full scale even with no input. Both inputs. ONLY ON SCALES ABOVE 1V.. 500mv and down is perfect. Again its a thermal issue and easily missed with a quick check. Not the power supply. Its obviously a complex main board issue that might even be a ADC chip set issue. So I am batting 0 so far.. 2 junked main boards.. I was able to clean up 2 front boards tho. I got removing and cleaning the rotary encoders down great. So I now have a 3rd unit coming. This time from someone who knows these scopes I am talking to about these issues. So hopefully the 3rd is the charm.. So no schematics ? No one has come up with anything ? Are these things really that bad ? Are there lots of main boards in the trash ? Anyone have one they know works they might want to sell me ? Sorry for the rant.. |
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I had one I used for quite a while with no problems.? I wonder if something like capacitor issues?
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On 12/23/2023 11:41 PM, K7XYM via groups.io wrote:
So I have lots of anaog Tek stuff. Highly refurbished and upgraded 7904s and I think most every plug in. I have most all of the TM500/5000 stuff I will ever need. Mostly this stuff worked right away off ebay and then I would refurbish and make near new. Service manuals make this easy. Well,, except for the occasional custom IC,, everything I bought got fix and I have in my lab in use. |
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Yea I thought easy things the front panel going dead. Checked all the supplies on the main board, all perfect, no change in voltages, no change in the very low noise on the rails. I monitored the voltage supplied to the front panel board as well, stays the exact same and no increase in noise. I do not have a connector pinout for that front panel board and that would help. *think* there are I2C like data lines that go up and interface with the main CPU somehow. But this connector has a lot of pins considering there is a controller chip on the front panel board. You would think the whole board could communicate its data on one I2C bus of 2 lines and gnd.
Tracing the lines on the board is no easy matter, they change sides a lot. They seem to terminate up below the CPU where there are a number of resistor/cap combos like pull up and filtering. So sure somethere there could go wrong, but none of that gets warmer. The only thing that gets warmer it the CPU and of course power supply stuff. On a really deep level std chips like logic arrays could get warmer and do weird things, I have never seen that, but, maybe. I am awaiting freeze spray next week. By using spraying and dropping little tiny drops of freeze liquid I should be able to locate better the issue. I did use a heat gun on that area. Like seriously. It caused it to work for 15 mins. Which was weird. I can't easily probe the area I need to. So its hard to see exactly what is going on. Thermal is almost always a cap power supply related or a solder joint. I have seen a few transistors get weird thermally. I just never remember seeing a chip get weird thermally like this. I really need to see the datalines on a scope. I may work out a way to better look at this. I have never done this, but, I think I can remove the whole power supply and maybe feed the main board directly from 15V ? If I dont need that ribbon cable from the power supply to the main board, I think its ethernet, then I think I can get the power supply away from the main board and still have it work. Its acting like the data-lines are somehow dropping in voltage getting sketchy and then gone completely. OR the CPU is less sensitive and cant see them well. If I had a schematic, this would be a 10 mins fix. But Nooooooooooooo....... And then this other board issue.. I have not even begun to think that thru yet. Only positive spikes away from zero. Random but low frequency.. However the spike seems infinatly short. Its a weird symptom. Its both channels evenly. The spikes occur on both ch1 and ch2 exactly the same in time. 500mv scale and below no issues and in calibration. There may also be a high noise floor on the 1V up scales. Not sure what would affect only the 1V up scale AND only on the positive side AND both channels. That seems deep enough to be some freakyness in the ADC chipsets. Might be something analog maybe but hard to explain the zero width pulses. Those look like data errors or something. Both problems are hard. For now I have the boards leaning towards scrap. |
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a lot of the weird issues that I have seen over the years in various models of Tektronix scopes from 2000 up to 2015 or so that had no other explanation
have ended up being due to RAM chips (or bad soldering of BGA chips to a lesser extent) from all the description given, I can say with 80-90% confidence it's a ram issue. one if the SDRAM chips is going haywire. I have seen cases that only a certain small range of addresses in a SDRAM IC had problem! very hard to find. and no, even if you had the schematics it wouldn't help you that much. Certainly it wouldn't be a 10 min job at all. Believe me perhaps that might have been true for old equipment with tons of transistor circuits and analog ICs and much simpler logic ICs... |
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On 12/24/2023 6:41 AM, amirb wrote:
Certainly it wouldn't be a 10 min job at all. Believe meAnd some people wonder why I like my '70s-'80's instruments. The reason why is simple - I can repair and calibrate them. -- Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA |
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Many of us, myself included, would say the same thing, Dale.
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Jim Ford Laguna Hills, California, USA "And we know that God causes all things to work together for the good of those who love God and are called according to his purpose for them." Romans 8:28 (NLT) ------ Original Message ------
From "Dale H. Cook" <bridgewaterma@...> To [email protected] Date 12/24/2023 6:19:09 AM Subject Re: [TekScopes] TDS30xx OMG.. Are these all broken ? On 12/24/2023 6:41 AM, amirb wrote:Certainly it wouldn't be a 10 min job at all. Believe meAnd some people wonder why I like my '70s-'80's instruments. The reason why is simple - I can repair and calibrate them. |
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Same here and it applies to my Automobiles too....pre - computer...although I do have 2004 VW TDI Diesel and I purchased the software and "dongle" when I bought the car.....
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Merry Christmas ( or however you celebrate) to all 搁别苍é别 On 12/24/23 9:17 AM, Jim Ford wrote:
Many of us, myself included, would say the same thing, Dale. |
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I will add a +1 to the Sram issue. I had some strangeness on my DSA602A that turned out to be an SRAM issue. Touching up the solder on all the pins of the SRAM chips has kept the issue away for a while now. Good news is nothing needed replacing.
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Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of 搁别苍é别 Sent: Sunday, December 24, 2023 2:46 PM To: [email protected] Subject: Re: [TekScopes] TDS30xx OMG.. Are these all broken ? Same here and it applies to my Automobiles too....pre - computer...although I do have 2004 VW TDI Diesel and I purchased the software and "dongle" when I bought the car..... Merry Christmas ( or however you celebrate) to all 搁别苍é别 On 12/24/23 9:17 AM, Jim Ford wrote: Many of us, myself included, would say the same thing, Dale. |
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And modular with the plug-ins, and repairable. Not as portable, though. IIRC, I used the TDS3052, 3054, and 3032 at work a few years ago. Very convenient and portable, but yeah, not repairable or modular. At some point, I will probably buy a portable DSO, but the only way I'd get a TDS would be if Raytheon (my employer) gave me one free of charge. GW Instek I probably will buy, 'cause it's made in Taiwan, not China. I love my 7904, 7104, and 5103N D10 pure analog scopes! But the other thing they lack is the ability to "stop time"; that is, look at slowly varying signals and get a stable image on the screen. HTH.
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Jim Ford Laguna Hills, California, USA "And we know that God causes all things to work together for the good of those who love God and are called according to his purpose for them." Romans 8:28 (NLT) ------ Original Message ------
From "David" <vexorg.calibra@...> To [email protected] Date 12/25/2023 2:46:10 AM Subject Re: [TekScopes] TDS30xx OMG.. Are these all broken ? Should've saved up and gone for the 5000 or 7000 series, much better and far more powerful. |
Dale H. Cook
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