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| Need Tektronix TDS220 firmware file |
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| Beerden:
--- Quote from: OH2LIY on February 27, 2018, 07:22:57 pm ---Success! Bend flash pins 1 and 31 up (can be done once). Then use narrow tape strips between flash and socket pins (I used capton, it worked nicely), and just solder flash pin 1 to U104 pin 4 and flash pin 31 to closest VCC (pin 32 is closest, just bridge them). Ramppa --- End quote --- Thanks! I can also confirm the modification I wrote up also works, I have the MM v1.00 working on what used to be a CM and now have FFT functions! I elected to jumper over pin 31 to pin 1 with a short tiny wire within the socket body. First though I had to remove the pin 1 pad (ground) from beneath the socket: desoldered the socket pin 1, lifted it up, applied heat to the pad until it separated from the PCB and pulled it out with tweezers. I put kapton tape under pin 1 in case the socket pin touched the original ground via. Then I soldered the wire from pin 1 to pin 31. This allows me to remove and re-insert the FLASH chip if needed (well, you never know!) I also replaced the 28-pin SRAM at U204 with a ISSI IS62C1024AL-35QLI which I found on Digi-Key as 706-1041-ND, and there are no problems with using this part. However, U204 SOP-32 footprint A17 (pin 31) is tied to 5V and A18 (pin 1) is floating. I left that unmodified and everything works fine, but I'm thinking I will experiment with actually connecting A17 and A18 to the signals. I'm anticipating either failure or no change in behavior. Apparently the software doesn't need more than A0-A16 (17 bits) anyway. But keeping A18 from floating is probably a good idea. |
| shakalnokturn:
Thanks to scopeman-Sam for sharing the files! I have just done the conversion myself using a M5M51008CFP-70 SRAM and SST28SF040A Flash, both from my scavenged parts stock. /WE (31) was kapton isolated and left floating (internal pull-up), A18 (1) was kapton isolated from the socket and wired to U104-(4) as seen on photos above. |
| Vorlon:
--- Quote from: Beerden on February 21, 2018, 09:34:26 pm ---There is a small pin difference between the 27C040 32-pin PLCC and the AM29F040B-90JC 32-pin PLCC: pin 1 is Vpp on the 27C040 OTP EPROM, but is A18 (address bit) on the 29F040B pin 3 is A18 on the 27C040 OTP EPROM, but is WE# on the 29F040B This pin difference needs to be corrected to work with the 29F040B; luckily the solution is already provided for by R306 and R307 resistor options for the U302 socket that connects pin 1 to pin 3: Remove the 39.2 Ohm 1206 size resistor at R306 Install a 1206 size shunt (0 Ohm, or short length of wire) at the empty pads for R307 Insert the 29F040B in the U302 socket --- End quote --- In my TDS220 that wasn't sufficient to run with a 29F040. I also had to isolate the WE# pin and pull it up. |
| Nprod:
--- Quote from: scopeman on December 26, 2017, 10:38:29 pm ---Also Nprod let us know how you make out! --- End quote --- Something a little strange happened, i used an Atmel 27C040 EPROM for the TDS2MM firmware and when i installed the module, the screen of the scope went blank. Looking at it up close i could make out the boot screen text saying all the self-checks passed - turns out the contrast had gone down by quite a bit. If i boot with the old 27C010 EPROM the contrast returns to its old setting, so it appears that the module is causing a change in the LCD's contrast voltage when running in "TDS2MM mode". The LCD itself is not factory original, i got it from some old stock warehouse on aliexpress and it requires a low contrast setting to look correct for some reason, which made the difference with the MM on more noticeable. |
| scopeman:
That's a new one on me. It has been at least 10 years ago when I converted my units and I would have to do a lot of digging to remember what I did then. All of my units were genuine Tek units with the Tek LCD so I have no clue as to what the problem could be and since schematics for these scopes have been closely guarded by Tek they have never been available AFAIK. So good luck with that and let me know if you find anything. Could it have anything to do with the speed of the rom or any configuration jumpers? I don't know. Sam W3OHM |
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