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

[walter.aranda]

I find a compatible display (320x240) 4.7inch

[walter.aranda]

check this ebay's photo about a firmware update card (TEKTRONIX 671-1701-01 ) , the connector is very similar to the one used in TEK THS7XXX series:

[TERRA Operative]

My turn to crack one of these things open.

I just got myself a THS720 STD with soft case and power supply for a bit under US$80.
It has the common burnt LCD polarizer (Not sure if I'll play with sourcing the correct polarizer to suit the STN/FSTN LCD or just throw a whole new LCD in, I'm not a fan of the yellowish on blue that you get with using standard polarizing filters..) and it also needs batteries so I'll be fixing this one up all good and proper.


So far, I have found a possible replacement for the DMM input jacks, they are marked as Mueller 3160X, and the closest I've found so far is the BU-31602-0 (Black) and BU-31602-2 (Red)
They aren't exactly the same as the pin is straight on the Mueller part, but the Tek part has a groove cut to help retain the clips on the jumper wires.
Testing will tell if friction is enough or if a dab of solder or a quick turn in a lathe to cut a groove is needed.

I'll leave that up to someone else to explore as my DMM jacks appear to be fine.


As for the BNC jacks (mine are useable but have a few chunks taken out) I am thinking of cutting the existing ones away and installing something like these from ebay.
[EDIT] Actually, even better... Part number 67.9766-21 (but it's for RG58 cable) or 67.9764-21 from Staubli look realllly good and aren't too expensive from RS Components..


I am planning to convert the top cap for the battery compartment into a battery contact using some tinned copper braid (leaving the side contact in place inside the scope) and use a set of 4000mAH GP brand Ni-MH C size batteries.
I just need to figure out the best way to reattach the metal piece to the plastic cap, as mine has also broken as usual, and solder to the stainless steel metal piece. I'm thinking either some silver braze, or copper plating then solder.


Then it's a firmware upgrade, recalibration and experimenting to see if it can be upgraded to a THS720P

[TERRA Operative]

Ok, I have reason to believe that the original designers had the idea to allow the use of standard C-size batteries, or at least a stick of batteries in a pack without that side ring arrangement, but it was scrapped for whatever reason...

I was thinking it was a bit odd that the metal piece was part of the battery cap when a plain plastic part would have been cheaper to produce and would work fine, unless there was a last minute design change...

Take a look at the attached image.. See the strange shape moulded into the top edge of the hole the battery passes through? I would bet money that a small metal contact was intended to go there so when the lid was installed, the metal part would contact both the top of the battery (or top cell) and the (missing) contact and allow for the use of standard cells.

I think it would be trivial to bend up a little bit of metal from some nickel or similar to clip in there and give the scope the option for either battery use case.

[TERRA Operative]

And here's the clip installed.
Just cut out of a sheet of 0.35mm thick nickel and bent with small pliers and finally filed to an interference fit.

The +ve lead will be extended from the existing side contact and soldered to the tab there.
All going well, when the lid is installed the metal part will make contact with the clip and the battery to complete the circuit.

[TERRA Operative]

And finally, it's all assembled.
A little tweaking is needed to ensure a firm contact between the battery door and the clip, but it works quite well.

For the battery door repair, I used a little bit of a pencil eraser carved to fit where the retainer strap locates and then held it in place as I filled the rest of the cavity with JBWeld.
Once it had hardened, I cut the eraser out and then filed the JBWeld flat. Be careful of the locating pin for the retainer strap! It sits higher than the edge of the cap so you have to file around it rather than just filing or sanding over the whole face at once.
I then drilled and tapped (not too deep!) four M2 holes where the broken pins were and drilled and countersunk the holes in the stainless steel plate (You can probably do a better countersinking job than me...).
Four M2 x 4mm countersunk screws and some superglue as threadlocker had it all assembled as solid as can be.

Reassemble the case and now you can use standard C-size cells in your THS700! 

[shakalnokturn]

I came to the same conclusions on the top cap:

https://www.eevblog.com/forum/testgear/tektronix-ths-7xx-battery-mods/

A couple of things that may not be obvious on the photos, there isn't quite enough length for standard cells, I cut away some of the scope's plastic under the negative contact spring, it was still a quite tight fit for the positive cap / lock so to not ruin the plastic I slightly bent and filed the edge that engages into the plastic so that it would enter without risk of wearing the edges.

[TERRA Operative]

Huh, we both did almost exactly the same thing, right down to the shape of the clip.

I didn't carve any plastic from the end yet as I didn't have a standard battery to compare to.

[1audio]

The pre-A version is more than a little different and the firmware to add the -p option may be not possible. The pre A does not have the ability to use the meter input as a trigger source. There may be other hardware level things that could bite.
The BNC's they used had a clever connection that is reminiscent of an F connector using the center conductor directly into the female socket. The outside of the BNC is insulated so they meet the safety standards. But the #$#&^% pins all break off so the connections are loose. . .
I converted to LED backlight which makes an enormous difference in utility. The hard part is power for the LED's The power on the connector swings a lot.

[TERRA Operative]

Well, I just bought a THS720P for equal to about US$120, working screen, no accessories.

I might take a couple high resolution photos of the PCB's of both the THS720STD and THS720P and compare them to see if there's any obvious differences.

I've been eyeing this backlight mod, might make a PCB order soon...
https://www.eevblog.com/forum/testgear/tektronix-ths7xxx-scope-ccfl-controller-drop-in-replacement-for-led-conversion/msg4775420/#msg4775420

[1audio]

That power supply board is a much better solution than the 2 board kludge I used. Maybe someone will make a run of those through JLBPCB or other cheap source.

[eliocor]

Attached you will find the printable .STL file of the THS720 battery holder.
You will also find the Fusion 360 / STEP of the project + drawing/dimensions of the battery contact.
The O-ring type is OR2100 (25.12x1.78mm)

[zyxel13]

Hello to all,
some time ago I uploaded on the forum my 1:1 Drop-in LED Backlight Controller for the THS7xx Series of Tektronix Isolated Scopes.
In case of any interest, I just uploaded my Design of an replacement External Charger for the THS7xx Series Battery Pack:
https://www.eevblog.com/forum/testgear/tektronix-ths710-ths720-ths730-external-battery-charger-build/msg4840787/#msg4840787

Cheers,
Konstantin

[vishaldotgupta]

hi,

i got a led backlighted blue type LCD for this scope from china.  its a custom design.  will not need conventional ccfl driver.  original sharp displays are difficult to get.  fitting this one needs some modifications as its height is 1 mm more than the sharp.  but prices are good.  new display with backlight is just USD 60. 

[TERRA Operative]

So, with a heap of help from Hakan (Zenith) I have been able to dig up some info on the official firmware update process for these units.

I think someone smarter than me could possibly reverse engineer the software side of the process to create something possibly with a modern bit of hardware, maybe a Raspberry Pi type thing?

I uploaded the info so far to Tekwiki, including the user manual with schematics of the Communications Pod, the RomBurn PC software and the THD700 and TDS300 firmware files:
https://w140.com/tekwiki/wiki/067-1436-00

The real trick in reproducing the Pod is in finding the Motorola Dev Board, and getting a copy of the EPROM on the Pod mainboard, the rest looks pretty straightforward in terms of parts.

[seqvenzer]

The safety BNC Input Connectors:

Tektronix Part No.: 131-6263-00, "CONN, RF JACK; PLASTIC BNC, ADAPTER; FEMALE, STR, FRONT PNL/PELTOLA JACK, 0.501 MLG X 0.485 TAIL, PUSH-IN"

Inner Body: Brass
Center Conductor: Beryllium Copper
Insulator: Teflon
Outer Body: 66 Nylon

Manufacturer Part No.:
Mueller Electric - BU-X90132 (this was the last one)
Unknown Mfr. - MP1592381 (maybe the one prior to Mueller?)

Not sure if anyone has had luck replacing these. One of mine is cracked and I would like to replace it. Would appreciate reccos for which replacement parts gave you the least grief.

[TERRA Operative]

I replaced some using the Stabuli 67.9764-21 connectors.

Basic instructions:
- Cut off the plastic outer from the BNC in the scope
- Press out the metallic center leaving the plastic outer section of the BNC still in the scope housing
- Tap out the resulting hole with a 1/8-28 straight BSP thread tap
- Drill the center hole in the center contact of the BNC deeper, but not all the way and cut the contact shorter.
- Solder an SMB connector and insulate with glue heatshrink. (I would make it shorter than in my photos if I did it again).
- Install BNC into scope
- Desolder existing Peltola flyleads from motherboard and remove metal crimped piece from PCB end of cable.
- Crimp/solder the crimped metal bits to some SMB flyleads
- Attach the flyleads to motherboard
- Reassemble the scope.

You'll need to massage the angle of the SMB connector on the BNC for clearance, but the metal is soft so it will bend a few degrees no problems.
Also, the flylead will need to do a loop at the top of the motherboard then pass through the cutout to the bottom side for another loop before it attaches to the BNC assembly, to prevent sharp kinks in the cable.

I've attached a couple photos that might help show things.
I haven't tested how it affects bandwidth yet, once I get the LCD working, that is next on the list. I don't expect it to make much difference at all though.

[seqvenzer]

Super clear description and photos TERRA.

Do you recommend a mild application of Loctite or anything of the sort on the threads to keep the shell in place? I'm guessing the original was pressure-fit from both ends so it wasn't going to go anywhere.

This is a significant departure from having the Peltola connectors sadly. Oh well 

[TERRA Operative]

I wouldn't use thread locker as it tends to destroy certain plastics (and I think chemically needs the metal to initiate the curing process anyway?), but some superglue might be a good idea. However, the threads are relatively fine and can be torqued pretty well regardless.

It is too bad about losing the Peltola connectors, they are nice and compact and I do like them. SMB is the best I found that were readily available and allowed for simple disconnection to remove the motherboard if needed.
As I mentioned, cutting the center contact shorter than I did would probably help fitment though.

In the end it does look nice from the outside and is functional with the isolation etc. Better than a broken scope anyway.

Let us know how you go if you give it a try!

[coromonadalix]

can't recall the number   but loctite as one glue who will not damage plastics

[TERRA Operative]

I use Loctite 401 superglue which is really good, but I have never looked for a plastic safe thread locker so I'm no help there.