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Tektronix TDS1000B and TDS2000B series hacks

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braikin:
Last update... unless I find out more. I'm trying to measure rise times to confirm 200mhz. Generously, the best rise times i'm seeing are > 3ns implying < 100mhz.

Changing the Product ID doesn't seem to have increased bandwidth but did seem to enable 2GS/s. Maybe there's a small hardware difference in frontend, but that's beyond my skill to figure out. Also, the `factory` section of cal which contains stuff like: model id, serial number, etc, is about 2.5 kbytes. There may be other values that need manipulation. I'll poke around firmware a little more.

braikin:
According to the service manual models are required to be calibrated with a sine wave matching their respective bandwidth. Upgrading software doesn't change the fact the hardware is still calibrated to -3db @ 60mhz? Effectively cal data is limiting bandwidth? Seems like tinhead implied this early in the thread?

What the software change did do: my scope now expects a 200mhz signal during cal. So, I guess the next step is to recalibrate (if that were possible).

If I can get a crude signal source I may try out of curiosity. Calibration is reversible as long as my NVRAM survives another desoldering.


texaspyro:

--- Quote from: braikin on March 05, 2018, 02:51:22 am ---If I can get a crude signal source I may try out of curiosity. Calibration is reversible as long as my NVRAM survives another desoldering.

--- End quote ---

Geeeeeez, put it in a socket!

braikin:
Success!

I'm now seeing rise times ~2ns which is consistent with 200mhz.

Attached is an updated python script to patch more data in NVRAM cal section. This script should work correctly with 2 and 4 channel color models upgrading them to 200mhz 2GS/s. Upgrading non-color models is possible, but not all the way to 200mhz. See my previous post for instructions just use this script instead (and there's no need to edit it).

Basically some of the bytes in factory cal section are used to program a low pass filter of some sort. It looks like They're calibrated to get a consistent attenuation across all channels and vertical scales. Instead I just set the filter to max. So... I may get more inconsistency between channels and vert scales, but it works. I think a full cal would be better but after a couple days on ebay I can't find an affordable way to do that.

If you're interested; the function `cal_bwl_setup` is defined in FW at addr 0x437230. This function programs the LPF between 20mhz and full bandwidth. The values it writes to the LPF are stored in the factory cal section. Bigger values = more bandwidth. My patch sets them to 0x0f which is the largest allowed value for 200mhz. There's on value per channel and vert scale; and like a say above they vary slightly. My scope probably performs a little less consistent.

Good to bring some life back to my old scope! I hope I don't find anymore issues. Digging any further into what the calibration bytes to would be tough.

I feel like I'm talking to myself in an 5 year old thread. If you're interested in how this applies to non-color models, or you have some tests I should try... feel free to let me know.

Argiros:
I am glad that you made it! Maybe I give it a try later.
I want to say that I make a BW model to a color. I figure out the pinouts and after many search I finaly did it. I saw the red the cyan all the colors.
Unfortunately my color lcd had two  spots it came with that and I put again my b/w lcd. But I finaly did it. I ordered a new color lcd and finaly i will have a color model!

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