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Tektronix THS7xxx Scope Hack/Teardown/Discussion - FW 1.16 found

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TERRA Operative:
Check out the tekwiki page for info on these units, including the pod needed for firmware upgrades. If someone were to emulate that with a raspberry pi or other suitable device, it would make for much easier firmware upgrades.
The motherboard looks simple to replicate from the schematics, but the Motorola M68332BCCDI 'DIBUG' debug module is unobtanium...
I haven't been able to find an exact match for the plug though, it appears to be a SCSI or similar type of thing.

https://w140.com/tekwiki/wiki/THS720

https://w140.com/tekwiki/wiki/067-1436-00


According to the schematics on Page 10 (Grid Ref A1) the 3-pin cal header is also some sort of test function, probably used during manufacture. I wonder if it spits something out over the serial cable?

For cal, I use some Advantest and Yokogawa AC and DC references, a bunch of Vishay precision resistors, and a HP 33120A Function Generator (Specified as <20ns, so juussstt good enough).


If you make the squarewave gen, share the design (Maybe in a new thread), I'd be interested in making one too. :)

HAHSM:

--- Quote from: TERRA Operative on October 14, 2024, 11:36:43 pm ---Check out the tekwiki page for info on these units, including the pod needed for firmware upgrades. If someone were to emulate that with a raspberry pi or other suitable device, it would make for much easier firmware upgrades.
The motherboard looks simple to replicate from the schematics, but the Motorola M68332BCCDI 'DIBUG' debug module is unobtanium...
I haven't been able to find an exact match for the plug though, it appears to be a SCSI or similar type of thing.

https://w140.com/tekwiki/wiki/THS720

https://w140.com/tekwiki/wiki/067-1436-00


According to the schematics on Page 10 (Grid Ref A1) the 3-pin cal header is also some sort of test function, probably used during manufacture. I wonder if it spits something out over the serial cable?

For cal, I use some Advantest and Yokogawa AC and DC references, a bunch of Vishay precision resistors, and a HP 33120A Function Generator (Specified as <20ns, so juussstt good enough).


If you make the squarewave gen, share the design (Maybe in a new thread), I'd be interested in making one too. :)

--- End quote ---

Hey thanks for the reply - in the Pod manual is a replacable parts list with the Tek part number for the adapter cable (with plug) to connect to the THS - part 671-3682-XX, doing a search for that 😎 ya good luck, right! haha.

I see that jumper in the schematics now - thanks for pointing to the location in the schematics, it seems to do some interesting things like (as you said) indicate some sort of diag mode, maybe the diag mode is the one in conjunction with the Pod?...

If I get my hands on a THS mainboard, or just a cheap parts only THS, I'll see if there is an AMP number on the that plug. Seems like there would be...

I'm waiting on some of the parts from Mouser for my diy cal circuits, if they work out & the square wave gen is nice and stable/no or low jitter then I'll (as you suggested) post a new thread with what I came up with - I'll also send you a msg with the new thread.

I've built my two battery packs, they work great, charge overnight, just get very mildly warm so not overcharged.

I made a RJ45 to DB9F serial cable and tested it as working with hardware flowcontrol.

So this THS720P that I bought as "For Parts/Not Working" is fully functional, only issues now are doing a firmware update and the DC offset in both channels issue (that I'm hoping the diy cal will fix).

More soon...

HAHSM:

--- Quote from: TERRA Operative on October 14, 2024, 11:36:43 pm ---According to the schematics on Page 10 (Grid Ref A1) the 3-pin cal header is also some sort of test function, probably used during manufacture. I wonder if it spits something out over the serial cable?

--- End quote ---

When I do my cal procedure (& have the scope opened up again) I'll try the jumper in the right/Diag location again & monitor the serial port (now that I have a serial cable) and see if it does in fact start spitting stuff out...

kblue:
Tried to get rid of the little but noticeable offset with a cal, but the step +7.000 VDC always fails, regardless what source i use and according to my bench-multimeters, which are connected during the cal, its 7.00012 +/- VDC and yes, the 50 Ohm feedthrough terminator is removed already. Bummer.

Well guess i need to live with the offset. The scope is running older firmware 1.11.

/edit: Nevermind, it was my fault! I had my Banana-to-BNC connector reversed so +7 was -7 for the scope. <self-slap>
/edit2: Kinda funny ... i did the cal with the original power supply connected. Back to batteries, there's some "tiniest of offset" back again and gone with power-supply connected (w/o batteries).

TERRA Operative:
There are four optoisolators that tend to drift. They can be directly replaced with Broadcom/Avago part number HCNR201 (any of the -300E, -500E, -350E, or -550E variants will work) which are still readily available.
I just bought 4 this week to keep on hand for my THS720P, just in case I need them.

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