| Electronics > Repair |
| Metrix OX 2000 digital oscilloscope |
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| shakalnokturn:
I recently bought a couple of these DSO's plus spares, they are 4 channel full digital oscilloscopes with 150MHz bandwidth and 200MS/s (?) sample rate. Thy have GPIB and RS232 connectivity, internal monitor is a green CRT, there is also a VGA output with non-configurable color for the traces. I have: 1 repaired skynet PSU. 2 green VGA monitors, only one tested so far. 3 frontend boards, 2 are working with cal. errors, one is beyond repair due to something serious happening on the PSU. 3 CPU/Acq. mainboards, only one tested and appears to be working normally so far. 3 Front panel boards, only one tested so far. The first aim is to get one fully working scope out of all this before trying to throw a second one together, not an easy task as there is no service information out there. The F.E. boards are both failing the self test "randomly" mostly for bad offset on most channels but also for bad gain at times on some channels. I'm suspecting the relays could be the cause for the gain fails although all the N.C. contacts measured a decent resistance so far. Each channel has: Two RA12W-K, three A12W-K and one Hamlin (Littlefuse) HE3651A6490 reed relay. One AD711KR fast OP-AMP One TL084C Two SL3227 One SL2364C One MC14053B One ULN2003A (relay drive). There is some time sharing as CH1+CH2 are sent to one ADC (AD9002AJ), CH3+CH4 are sent to another ADC on the acquisition board, there are only 2 ADC's. I haven't identified where the switching happens yet, the last chunk on F.E. before the coax to the Acq. section is mainly discrete. Any clues on what to look for and how this could all tie together are welcome! Scans of the F.E. board here: https://photos.app.goo.gl/lsmE1pMSz0d0s6Sx2 https://photos.app.goo.gl/vJFXiwfXi71yETf73 |
| shakalnokturn:
BUMP Still playing around with these, it really looks like the person who sold them threw all the worst parts of a dozen identical scopes together, then threw the scopes on fleabay so I could have hours of fun for a moderate price. Getting in touche with Chauvin-Arnoux or Manumesure has not helped in any way so far. All the same I seem to be getting somewhere, although the one I've been working on so far was failing self-test randomly on all channels, it is starting to look like it was mainly out of calibration. The last cal. dating back to 2011. After many hours of trying to follow tracks around the F.E. board, I have a very slight better understanding of the machine. I have also dumped the two 27C4001 EPROMS, grouped them as a single 16bit image and found in the text strings that there was a hidden FULL 45" CALIBRATION (!) other than the FAST 5" CALIBRATION in the user menu. (Think SPC on the Tek scopes.) The point of leaving the 5" Cal. accessible to the user is that these bi*ches drift a helluvalot! Of DSO's of the same era I still find the LeCroy 9300's did best with their automatic re-cals freezing the UI for a few seconds. Also desoldered, dumped, socketed the M28C64C EEPROM holding the cal. data before finding the way to access the full cal. menu and fooling around with it. |
| shakalnokturn:
The only documentation I've found on this DSO is the attached commercial overview. It mentions a 200MS/s rate on CH1, and 100MS/s on the remaining three channels. I can understand how the acquisition system could be combined to reach 200MS/s when only one channel is used (two AD9002 ADC's are used in here) but no matter the setup the single shot acquisition remains the same. The brochure also states FFT in the math functions, nowhere in the scope's menu or even searching the ROM dump can I find FFT. Maybe this required another ROM version... I almost have two working scopes, all I'm missing now is a second PSU of course they are the main failure cause and pretty much unobtainium. Outputs on the original PSU are rated at: -16V / 0.7A -5.2V / 5A +5V / 3.5A +14.5V / 3.5A They all have OCP and possibly OVP. I have not yet measured actual current on each rail. I'm either thinking of using a cheap MeanWell 24V PSU (that I already have) followed by independent buck regulation for each rail or re-wiring (re-winding) an ATX PSU to suit the job. Given I have plenty of repair experience (including SMPS) but little design experience, which option would be more reasonable? (Unless anyone has a suitable PSU for sale of course...?) |
| shakalnokturn:
Here are the real life current requirements for whoever needs to know: -16V / 0.8A -5.2V / 4.6A +5V / 1.3A +14.5V / 3.12A Totalling around 90W, that's without PCMCIA card inserted and without using any ports. |
| shakalnokturn:
Still updating for the sake of documenting the instrument a little. The SkyNet AKE-9110 SMPS runs at 60kHz, the primary side PWM is a SK-6080, a custom design from Unitrode for SkyNet. (About the same era there were also similar PWM custom designed by Fuji-Electric with the same SK-xxxx part numbering) Auxiliary supply for housekeeping is +7.1V from a separate transformer. Main supplies come as -17.3V, -5.4V, +5.7V, +15,41V before LDO linear regulation using MOSFET's. Positive supplies share a common ground right from the main transformer, negative windings are independent allowing to use N-MOS pass transistors on the "high" sides of the negative rails before the regulated high side joins the common ground. Power rails do not appear to have any predefined startup sequencing. Line trigger output is built around a Sharp PC900V opto. |
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