TDS744 (NOT TDS744A) Option Resistors and Configuration
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The options are most easily enabled via GPIB as follows:
(Hopefully this formats correctly...) Send the GPIB commands over GPIB *after* switching the protection switch to unlock and sending the text string 'PASSWORD PITBULL' (without quotation marks) via GPIB. Option Label GPIB Command Description - 1M 4M acquisition length WORDCONSTANT:ATPUT 327686, 1 Extends standard acquisition length from 50,000 points per channel to 130,000 samples on three or four channels, 250,000 samples on two channels, and 500,000 samples on one channel. - 05 Video Trigger WORDCONSTANT:ATPUT 327687, 1 Oscilloscope comes with tools that allow investigation of a range of NTSC, PAL, SECAM, and high definition TV signals. - 13 RS-232C and Centronics interfaces WORDCONSTANT:ATPUT 327688, 1 Add RS-232-C and Centronics interface ports. - 2F Advanced DSP math WORDCONSTANT:ATPUT 327689, 1 Add advanced DSP math features such as FFT, integration, and differentiation. - 1F Floppy disk drive WORDCONSTANT:ATPUT 327690, 1 Add 3.5 inch, 1.44 MByte floppy disc drive. - 2C Communication Signal Analyzer WORDCONSTANT:ATPUT 327692, 1 Oscilloscope comes configured for communications signal triggering and mask testing. - 3C P6701B with system calibration WORDCONSTANT:ATPUT 327693, 1 Oscilloscope comes with a P6701B and calibrated short-wavelength optical reference receiver on channel 1. - 4C P6703B with system calibration WORDCONSTANT:ATPUT 327694, 1 Oscilloscope comes with a P6703B and calibrated long-wavelength optical reference receiver on channel 1. - 2M 8M acquisition length WORDCONSTANT:ATPUT 327695, 1 TDS 520D, 724D: To 2M samples on two channels and 4M on one channel. TDS 540D, 580D, 714L, 754D, 784D, 794D: To 2M samples on three or four channels, 4M on two channels, and 8M samples on one channel (Option includes a hard disk and is only available for the models listed above.) 1G 1 GS/S maximum Limit sample rate to 1 GS/s maximum. This option allows sales in export–controlled countries. (TDS 540B only). Note: Some options require additional hardware to be installed (05, 13, 1F, 3C, 4C, 2M). The option will simply not appear if the required hardware is not present. At the very least you'll have options 13 and 1F, and the manual says that 1M is an available option. You might also be able to unlock 2F and 2C if you are lucky (I never had a TDS744 to try), but I don't expect 2M to be available on such an early scope. I suggest trying anyway, if it doesn't show up on the boot screen, just disable the option (reapply the command, but put '0' instead of '1' at the end of the command) to prevent any errors. Incidentally, errors can be cleared by sending ERR CLEAR (no need for the 'pitbull' password or protection switch for this command). As for upgrading to 1GHz, you need to alter some resistors on the acquisition board, but I'm not sure if it is possible for the TDS744 or not. it would depend if there was an equivalent 1GHz model of that type (i.e. a TDS754C can be upgraded to a TDS784C etc.) You'll need to check the acquisition board for resistors R1061, R1062, R1063 and R1064. If present, let me know what configuration are jumpered (They may have some positions open, or may have a 1Meg or similar resistor for 'open') I'll check my spreadsheet to see if there is something likely to work (or run through all 16 combinations and see what gives you the desired results...) Do be aware though that if you are successful in the upgrade, that the scope will only be calibrated to 500MHz, so any input from just above 500MHz up to 1GHz will not be calibrated. To perform the calibration on these scopes requires a very specific collection of equipment and is a right pain in the bum and not for the faint of heart!.... Regards, Jared |
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Ah yes, the bandwidth limiting capacitors on the input lines also need to be removed too, I forgot about those.
You can use an app loaded on a floppy disk to dump the NVRAM and edit using a hex editor to enable options, then reload it back in, but that requires a floppy disk and disk drive. The app (and others to backup the cal data) can be found on eevblog. If you are interested in this method, I'll post the relevant hex value info later. I prefer the GPIB way as it's simpler and faster IMO. The SPC doesn't affect the calibration, it mostly just corrects the input path offsets. The full calibration requires specific software on a PC with specific GPIB hardware and specific cal equipment unless you want to do it manually by hand, which is a tedious affair to say the least..... I'd love to reverse engineer the algorithms used in the Field Adjustment Software to make an open source implementation of the cal software that will work with modern hardware, but alas, it is completely out of my field of experience to do.... Jared. |
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Hi Jared ,
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I have been following this thread as I also have a TDS744 (non A) . When I first got it there were several faults but I managed to fix them all . After doing that I wondered about increasing the bandwidth and found the relevant resistors - I tried various combinations , perhaps not all , but nothing seemed to make any difference when re-booting the scope . Have you found the correct resistor pattern needed for this , and apart from removing the limiting caps is there anything else needed apart from the re-calibration ? . best regards Brian (UK) On Tuesday, 30 January 2024 at 06:01:37 GMT, Jared Cabot via groups.io <jaredcabot@...> wrote:
Ah yes, the bandwidth limiting capacitors on the input lines also need to be removed too, I forgot about those. You can use an app loaded on a floppy disk to dump the NVRAM and edit using a hex editor to enable options, then reload it back in, but that requires a floppy disk and disk drive. The app (and others to backup the cal data) can be found on eevblog. If you are interested in this method, I'll post the relevant hex value info later. I prefer the GPIB way as it's simpler and faster IMO. The SPC doesn't affect the calibration, it mostly just corrects the input path offsets. The full calibration requires specific software on a PC with specific GPIB hardware and specific cal equipment unless you want to do it manually by hand, which is a tedious affair to say the least..... I'd love to reverse engineer the algorithms used in the Field Adjustment Software to make an open source implementation of the cal software that will work with modern hardware, but alas, it is completely out of my field of experience to do.... Jared. |
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I've never played with a TDS744 myself, so I don't know any of the actual details as such.
Upgrading the bandwidth would depend on there being a corresponding model with the higher bandwidth to upgrade to. I'm not sure if this is the case with the TDS744? I don't think there was a non-letter TDS784, only A, C and D models? If the upgrade is successful, and the capacitors are removed, the scope will work, but all that is then needed is a calibration to effectively make the scope 100% identical to the higher model scope besides the front panel sticker. (I say 'all that is then needed', but it does require the acquisition of some decently specced and old/obsolete gear, but that's half the fun, right? :D ) |
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Hi, Jared
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Thank you for your comments regarding the 1GHz mod . My particular unit has the resistor pattern for determining the model of scope? but as it appeared to make little difference what the pattern was -- should I imagine that maybe the acquisition pcb was changed at some point in a repair possibly for a later version or could it just be that the first version of firmware did not know of future scope models . Thinking of that last case , have you heard of anyone upgrading the firmware to a later version on this scope model . regards Brian (UK) On Wednesday, 31 January 2024 at 09:57:12 GMT, Jared Cabot via groups.io <jaredcabot@...> wrote:
I've never played with a TDS744 myself, so I don't know any of the actual details as such. Upgrading the bandwidth would depend on there being a corresponding model with the higher bandwidth to upgrade to. I'm not sure if this is the case with the TDS744? I don't think there was a non-letter TDS784, only A, C and D models? If the upgrade is successful, and the capacitors are removed, the scope will work, but all that is then needed is a calibration to effectively make the scope 100% identical to the higher model scope besides the front panel sticker. (I say 'all that is then needed', but it does require the acquisition of some decently specced and old/obsolete gear, but that's half the fun, right? :D ) |
Jared Cabot
Brian