| Electronics > Repair |
| W&G sna-20/23 spectrum analyzer repair |
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| Gerhard_dk4xp:
The C series does not have a HDD. Instead it has a lithium-buffered CMOS RAM. The Lithium battery is the orange Renata thingy on the larger top board. There is also a Dallas 12887A realtime clock chip with some CMOS RAM that has an internal Lithium battery that may go empty. It is used to keep the bios settings in the usual PC AT way. Changing the CMOS RAM battery should be done with the SNA33 powered up, otherwise the content of b: is gone for good. (Supposed the Li Battery is not yet empty.) I have found the user manual, service manual and schematics somewhere as PDFs. |
| Gerhard_dk4xp:
There is more to the disks. (My serial number is D0029.) For those without a real harddisk, C: is an array of Flash eproms that can be written with an utility from the service disk. It is R/O to the normal user. B: is the lithium buffered cmos ram for user results and calibration factors. I also get the message that the HD controller is broken. But when I boot from floppy, I can see the contents of C: , so this seems to be more a driver issue. I cannot boot completely into the measurement program. All floppies must be dos6.22. Everything else seems to produce wrong_version errors. Some .com and .exe and .sys files are incompatible when taken from different dos versions. I replaced both the Renata Lithium battery and the Dallas Li buffered real time clock and managed to erase b: during that, should not do that in the night. I then tried to set the clock and disk type in the Dallas chip. I could find the required disk type nowhere in documentation. I finally restored the original Dallas chip, and it seem not to be completely empty. It contained HD type = 8, which is Cyl 995 heads 14 WPCOM 65535 LZONE 995 sect 17 Size 116 MB Funny enough, the old Dallas had the same time that I set with the new chip, but I think I must not understand everything. In NIKGEROS' case, the Dallas chip seems to be empty because it has forgotten the date/time. I could not get an original Renata battery in time, so I cracked the old one open and soldered wires to the leads of the carrier. Don't solder directly to a Lithium battery that does not have wires or tabs, that might result in a thermonuclear surprise. I used a 2/3 AA cell with wires, ugly but works. Sometimes, I also get the display with the zebra stripes from the first post, so this is not a hardware malfunction. Also, my reconstructed boot disk has a problem with the display window size. I cannot see the bottom line, so typing commands is a royal pain. The Wandel&Goltermann fan group on groups.io seems to be dead. I see there abt 3 posts, and my test post never showed up. cheers, Gerhard |
| alexturner:
Thanks for all the information and contribution in this thread - I bought a SNA-23 today with the same HDD controller issue. I opened the box up onto to not be able to find a HDD, so I'm assuming I have a flash model. I've bought a USB Flash to Floppy adaptor which is the same form factor as a floppy disk drive, so I might upgrade the box with some modern hardware, we'll see if it works... |
| Gerhard_dk4xp:
congratulations! Make backups of the software on it before you start playing with batteries, and also the bios settings. (I would appreciate a copy :-) it fits into an email nowadays.) Maybe we should have a repository somewhere of the essential disks and proms. I have paused the work on mine, tried to set up a different computer with DOS6.22 and a real hard disk, but it keeps power cycling. The kind of results you get when trying to revive hard & software from the early monolithicum. And don't think that "format" from 6.0 works with 6.22. It just says "wrong version" but not what version it is, let alone what it wants. cheers, Gerhard |
| Gerhard_dk4xp:
BTW I tried to contact the owner of the WG group on groups.io. No response yet. Gerhard |
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