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

[eKretz]

Hey can some of you guys take a peek here and let me know how your Tek handhelds behave as regards this issue I'm having with my handheld scope?

https://www.eevblog.com/forum/testgear/dc-offset-wander/

You could easily have some battery adapters machined from nylon for those Teks too. If there are a few of you who want them I could probably make up a batch for you guys.

[HighVoltage]

My Tek Handheld scopes do not show this behavior at all.

[eKretz]

I didn't think they would. My bench scope doesn't either. The seller is trying to downplay the issue though, telling me the trigger settings are wrong, lol. I took a couple videos of the handheld and my Tek bench scope being fed the exact same signal and will add them to the thread tomorrow. The Tek is rock solid with the same signal that has the handheld jumping all over the place.

[TurboTom]

What about connecting the inputs of the Micsig and another oscilloscope directly together with a BNC-BNC cable to check if the offset problem is really present as a voltage at the input of the Micsig? If it is, it should be the best answer to the seller's doubts. BTW, I've also got one of the Micsigs and despite the input is not the most noiseless one, it's by far not as bad as yours. I assume the 20mV/div input voltage range you're referring to are with the probe factor configured 1:10, so it's a true 2mV/div.

Cheers,
Thomas

[eKretz]

That's a good idea, but I don't have any hardware for that. I do have several BNC extensions though, I could probably cannibalize a couple of those and make one.

And yes, the probe factor is indeed set to 10:1 as my good probes are all 10:1, so in fact it's truly 2mV/div and 100mV/div that I'm looking at - but it's the same way on my Tek scope also.

[Zucca]

The C batteries wouldn't even last 40mins

Did you use 5000 mAh NiMH C Batteries?

Should I explore LED retrofit options?

YES PLEASE!!!!  Very good idea, my display is ok. When the backlight tubes will say goodbye I will definitely put some LED there. There is also a place for a LED driver board if you toss the HV Tube inverter one...

 

[1audio]

RE display lamps. I looked for LED solutions and there are many, but mostly for larger displays. I made a request to one outfit that seems promising for a more optimized solution. I would pay $35 for something that will just work over $15 and a lot of crude hacking to find it doesn't. If I hear back I'll post.

When the scope is unplugged and the battery is in it does it draw from the battery? Should I pull the battery when the scope will be sitting for a while?

For the deep cycle and repeated charging I have read the nicad is a better option. Nimh needs to be managed for max and min charge levels for long life. Toyota and Honda use 80% and 30% of max and min to get more life from the Nimh batteries.

[BMack]

The C batteries wouldn't even last 40mins

Did you use 5000 mAh NiMH C Batteries?

Yes I did. I was expecting longer life or else I would have done Eneloops to start. The biggest problem is the annoying "Low battery" warning that comes up every few mins, it literally takes less than 10 minutes to start popping up.

[Zucca]

The biggest problem is the annoying "Low battery" warning that comes up every few mins, it literally takes less than 10 minutes to start popping up.

I will investigate to reproduce this issue with my package, we are running with 5000mAh Bettery instead of the 2800mAh stock ones. It´s very surprising to me that this is happening. Surely the NiMH vs NiCd have different discharge ratings but jeeezzz...

I will perform a CSize 5Ah discharge test @1.2A (scope drain when on incl. Backlight) and report the results...

EDIT: Looking at the Spec. for Energized, Panasonic or other well know brand, a C Size NiMH is about 2500mAh-3200mAh... I am now thinking that 5000mAh are BS marketing....

Anyway

"Low Battery" warning appears at 4.6V. The power cuts off at 4.2V.

Interesting will be to know the power cut off time (@4.2V) comparison Csize 5000mAh vs 2000mAh Eneloop AA. Maybe you have already done this, 40min with Csize? CMIIW. In case the Csize will win... we could lower the low battery threshold by changing the R153 (close to U55) to a higher value (Low Battery when 4.3V or 4.4V).

To me it boils down to the following right now:

- 5000mAh C Size: no battery adapter required, compatible with internal scope charging circuit. Higher self discharging than eneloop. "LOW BATTERY" warning comes too soon (I 'll try to reproduce it)
- 2000mAh Eneloop AA: the opposite.

[Zucca]

When the scope is unplugged and the battery is in it does it draw from the battery? Should I pull the battery when the scope will be sitting for a while?

According to my investigation in standby (OFF with battery inside), the current drain is 176µA.

[BravoV]

Did you have an issue with the "Pro" cells fitting? I thought they were a little longer than the regular Eneloops.

Plain white Eneloop and the black Pro have identical dimension.

Its just Pro has "tad" higher self discharge rate than white one, no big deal imo, still much-much better than non LSD NiMh or NiCd.

If any of you have access to a 3D printer, that would be perfect for this. A C-sized tube with a AA-sized hole in the middle would work better than the C spacers...would also be great to fix my darn stand too

+1

[Zucca]

Thanks to ChippyZero we have a FW 1.16

not working...

This is an untested file that I pulled from a flaky THS720A.  I desoldered U1 using just enough heat to melt regular leaded solder and Chip Qwik low melt alloy.  Used self stick heatsinks and standard ESD prevention. Got a good read and verify using a TL866A.  When I copied the file to a new chip and installed it in the scope it would not initialize.  I reinstalled the original U1 and it acted the same way.  Don't know if the file is corrupt or if I somehow damaged the mainboard on the scope with my desoldering and soldering.  Use at your own risk!!

ftp://ftp.xdevs.com/Tektronix/THS7xxx_Portable_scope/FW/1.16/

[z01z]

Has anyone checked the contents of the file? The one I downloaded appears to be empty (0xff).

[Zucca]

Has anyone checked the contents of the file? The one I downloaded appears to be empty (0xff).

same to me... 

[Zucca]

I will perform a CSize 5Ah discharge test @1.2A (scope drain when on incl. Backlight) and report the results...

So here we go. My batteries are these ones:

http://www.ebay.de/itm/291785752982?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

@CC 1.2A Discharge Test, I got the following:

4,6V Battery Low after 2 hours and 34 min
4,2 Cut off  after 2 hours and 58 min

Battery was charged 24 hours inside the Tek scope by 12VDC ext., left inside for more than 2 weeks. I turned on the scope 2 or 3 times for one minutes... just to see if I was already in battery low state, and I wasn't.I then took out the battery and performed the test this morning. At the beginning the battery voltage was 5,23V.

Attached the raw data.

So far no problem... now 'I'm recharging the batteries.

[texaspyro]

I have a THS730A.  Several years ago I made a replacement pack using 4500 mAh AccuEvolution LSD NiMh C cells.  These are high quality cells and not some over-spec'd Chinese junk.  It is still going strong.

I made the pack by taping a sleeve made of mylar around the cells.  For the positive contact I used some thin brass sheet from a hobby shop.  I cut it into a "L" shape.  The vertical part of the "L" is around 0.2" wide.  The end of the strip folds over the "+" of the top cell.  The bottom of the "L" is around an inch wide and wraps around the cells where the original battery contact is.

I taped the strip down and insulated it with Kapton tape.  The cells just slide into the mylar sleeve.  They are not tabbed together  and the springs in the scope press the cells together.  I do have a VERY nice CD welder that I built and intended to weld them together, but have never had a need or reason to do so.

I have always charged it in the scope without any problems.  I try not to leave it on charge for extended periods of time, but have occasionally left it charging for over a week...  the cells get pleasantly warm doing that but they don't seem to mind.

BTW,  I snagged the scope for less than $200 off of Ebay...

[BMack]

I will perform a CSize 5Ah discharge test @1.2A (scope drain when on incl. Backlight) and report the results...

So here we go. My batteries are these ones:

http://www.ebay.de/itm/291785752982?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

@CC 1.2A Discharge Test, I got the following:

4,6V Battery Low after 2 hours and 34 min beginning
4,2 Cut off  after 2 hours and 58 min from beginning

Battery was charged 24 hours inside the Tek scope by 12VDC ext., left inside for more than 2 weeks. I turned on the scope 2 or 3 times for one minutes... just to see if I was already in bettery low state, and I wasn't.I then took out the battery and performed the test this morning. At the beginning the battery voltage was 5,23V.

Attached the raw data.

So far no problem... now 'I'm recharging the batteries.

Wow, nice! So I guess we have a solution, buy Eneloops or other batteries that aren't these: https://www.amazon.com/gp/product/B00FHVM7GC/

[Zucca]

4500 mAh AccuEvolution LSD NiMh C cells.  These are high quality cells and not some over-spec'd Chinese junk.  It is still going strong.

Amen Brother!

Lesson learned: never trust the mAh on cheap no name battery. I am lucky than mines are roughly 3600mAh instead of 5000mAh, my BS detector had old firmare when I bought mines. Now I got the new FW on it...  it will never happen again.   

[HighVoltage]

So here we go. My batteries are these ones:

http://www.ebay.de/itm/291785752982?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Those batteries look nice, I will try a set in one of my Tek scopes.

[1audio]

Update on LED's for the LCD-
I got in a kit from China for "universal" LED update. Fitting it into the LCD is pretty easy BUT I found an issue in the manual (or in my scope). The manual says the supply voltage is 12V. It also references an incorrect pinout. Fortunately the schematics are correct once I found the connector in them. However its actually 5V. All the retrofit kits need 12V so that's an issue. There is a higher voltage available in the scope but I'm not sure where to get it and its -20V with limited current so not a great idea. Next step a 5V to 12V boost converter from China ($.99 w/ free shipping).  I'll need to find a cable since I don't want to destroy the existing cable.

So I'm reverting and installing a new FL lamp in the meantime.

[Zucca]

...and of course you can't just replace some R in der LED module to accomodate the 5V input...

Thanks for the info! ... appreciate that.

Z

[1audio]

Drat- even the new FL lamp doesn't fit. Its 3mm too long to fit properly. I spent an hour troubleshooting the orientation of the cable for the display. Not on top of things tonight. Probably the heat here. Even my battery got flakey.

[little_grey]

Hi all,

New to the forum, but been playing with scopes for work for years but recently acquired a THS710 all my very own.

mostly wanted to say thanks for all the tips and tricks, and i'll be sure to share my progress as and when i make some of the alterations.

[Zucca]

Welcome little_grey,

I have everything now to desolder the U1 and trying to readout my FW 1.14 with a TL866A, but no time to attack the beast.
Do you thing I should try it? I hope the the FW is not locked down in the U1.

[little_grey]

with all the hassle you have gone through so far to get connectors and alike.
you are so close.

that said, what would you want to achive once you have dumped the chip?

going to be using it primarily in the automotive world with hobbies along side, though used one when calibrating old equipment at Rolls-Royce.