| Electronics > Repair |
| W&G sna-20/23 spectrum analyzer repair |
| << < (12/20) > >> |
| Storm:
Gerhard and all others owning a SNA-20/23/30/33 Series A..E: I had the same problem with the zebra stripes with a C-Model after the Dallas RTC with SRAM and Li-Battery was completely empty. I did not yet modify the dallas chip with well-known external battery mod, but pressed DEL (or CLR on internal keyboard) on my external keyboard during bootup to enter the BIOS. Then I modified the Standard BIOS setting for HDD C: to „Disabled“ (from the default setting „8“). Hit ESC, and then ALSO enter the Advanced BIOS. Here I set the Shadowing to NONE or Disabled (default value BOTH is wrong!) Hit ESC, selected „Save to CMOS and exit“, confirmed with „Y“ and now it reboots..... DO NOT SWITCH OFF THE SNA! My SNA-23 now boots from C: (my orange Renata Battery is still working), starts the measurement SW, AND.... TADA... shows the spectrum! NO ZEBRA ANYMORE Looks like the Zebra-Effect comes from a memory conflict of BSK-3 with enabled BIOS shadowing. The service manual even mentions that shadowing must be disabled, otherwise conflicts will occur. So as a Conclusion: Whenever your Dallas Battery is empty and CMOS writes will not be stored anymore, remember to set HDD C: to disabled in Standard BIOS and Shadowing to disabled in Advanced BIOS, after installing a fresh battery. Hope this helps to get rid of lots of zebra cases out there. |
| Pude:
A HUGE thank you @Storm!!! That advanced bios setting was the thing. Finally got this SNA to signal screen. Still calibration data missing from B-drive, but I've seen that data there in place. Some more tweaking and I have properly working device. Thanks! |
| Gerhard_dk4xp:
Works for me, too. :-) But the behaviour of the sweeps is still somewhat special. Not like it used to be. I'll look into that tomorrow. BTW one of the differences between sna23 and 33 is the fundamental mixer. That must imply a different synthesizer. Cheers, Gerhard |
| Electro4lease:
Hello All, Just new on this forum... We're a french company specialized in the resale of used test & measurement equipments We have a W&G SNA-33 whose CPU board shows traces of corrosion and we don't have time to repair it. If someone in interested in this unit, please contact me before we sell it on ebay for parts. Br. Antoine |
| Pude:
About my SNA-33: I think, all thought the orange battery shows decent voltages(little bit over 3 V), some settings and data is lost quite frequently from my bios and drive. Time stays in the bios but year is 100 years off every time, but that is y2k. ;) And I have to set those hard drives all over again as described above. Also the unit doesn't start in many cases. I managed to reformat B-drive and I put the salvaged calibration data back there. Now my unit sweeps but shows bulky graph like in the pic here. Clearly it is curly because the calibration data but no actual signal there. I contacted @Electro4lease to buy a spare parts unit. And some day, some day my SNA-33 will be fully functional. :) |
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