Topics

Tek THS720 issues


 

I got one of these cuties on ebay (not expensive, it had bad batteries) and was amazed when I opened the tek travel bag it was in, everything was covered in sticky gray crumbled foam. what a total nightmare to clean...

I guess this is the deteriorated foam that once lined the bag, but wow, what a sticky, horrible mess it made. it also really added to the screen mess, which was scratched and marked. I managed to clean up the screen by carefully polishing it with Novus 1 and 2 plastic polish, rags and Q-tips. Eventually it was clean and readable. Novus is truly magical on plastic.

I tried to use the Tek wall wart power adaptor, but the cable was intermittent, and it was still sticky from the foam so I tossed it and used another generic 12V/1A adaptor (there is nothing special about it, just center positive barrel plug), and ta-da, we have lift-off. It wouldn't charge the batteries, so I opened the battery compartment and found somebody had soldered together 4 C nicads, and tacked on that weird outer ring Tek used as the bottom positive contact. Needless to say, all dead as door nails. I didn't have any C nicads around, so I ordered some and am waiting for them to show up, and I will try and re-create that goofy pack Tek had in there.

Incredibly, the scope and meter functions worked running from the wall wart. The meter was bang on, and the scope is working, but I am not sure I understand the control operation, changing timebase and vertical settings seems to work very poorly, and getting the trigger to work is REALLY difficult. Have to go through the manual again and see what I am doing wrong, but it really made me long for some knobs and regular controls, rather than on-screen nested menus. Am is being harsh, or this a really weak interface?

So at first blush, it looks to be workable, I just have to dig deeper into the user-hostile interface and see what's going on, and get the batteries up and running. Not unhappy for the small investment, although I am still finding crumbled sticky foam everywhere in the lab. I found lots of docs for it on line, which amazed me. Happy to hear from anybody with experience using this unit as to any tips and tricks.I am guessing genuine Tek batteries are no longer available...

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.


amirb
 

You're kinda harsh on her (him!?) all handhelds use keys and push buttons and menus to change settings
in fact I like its interface better than my Fluke 199C. If you know your way around Tek digital scopes (such as TD3000 for example)
you easily find out that this scopemeter is very similar in organizing the menus and buttons.

All these scopes have home made batteries these days and mine did and I had to change them
fortunately in my case the previous owner didnt solder batteries together. They were just tucked in the plastic
tube that contained the original batteries. The whole thing barely holds together when I take it out but why do I need to take it out.

w.r.t. issues, the major problem with these scopes is the unusual DC offset that they develop. The best remedy seems to be
changing the two optocouplers (on each channel that has offset) and then calibrating the scope. In my case just calibrating the scope
solved the issue though. Calibration is very very easy but you need to remove a jumper from the inside before going to cal mode
but equipment requires is found on every bench.

*** Before anything try the self test and also SPC and see if they run without issues

The power analysis option can be enabled by removing a resistor on the board !


 

On Tue, Aug 25, 2020 at 09:53 PM, walter shawlee wrote:


I tried to use the Tek wall wart power adaptor, but the cable was
intermittent, and it was still sticky from the foam so I tossed it and used
another generic 12V/1A adaptor (there is nothing special about it, just center
positive barrel plug), and ta-da, we have lift-off. It wouldn't charge the
batteries, so I opened the battery compartment and found somebody had soldered
together 4 C nicads, and tacked on that weird outer ring Tek used as the
bottom positive contact. Needless to say, all dead as door nails. I didn't
have any C nicads around, so I ordered some and am waiting for them to show
up, and I will try and re-create that goofy pack Tek had in there.
Hi Walter,
It takes a while getting used to these 'scopes.Do you make use of Auto Range for an initial set-up? I find the sluggishness of the user interface the main remaining annoyance.
When choosing a wall wart, choose a linear version, not a switching power supply. It's quite a bit heavier but it'll save you from looking for the source of that funny noise visible at high vertical sensitivities...
In my case, normal battery-like C-cells (the ones with the button on top) didn't fit; the result was too long. I decided to rebuild a battery using solder-together 3200 mAh NiMh cells. I re-used the original ring and used kapton tape and shrink tubing. Apart from the missing labeling, the result is a goofy Tek battery on steroids (much longer running time).

Raymond


John Gord
 

Walter,
If you make a battery tube with a side contact to match the scope battery contact, you can use 3 unprotected 18650 Li-ion cells or two protected cells plus a dummy spacer. The scope does not seem to mind the excess voltage, it just draws less current. If I recall correctly, the scope spots the higher voltage and does not attempt to charge the higher voltage cells. The protected cells should be safe even if the scope does attempt to charge.
--John Gord

On Tue, Aug 25, 2020 at 12:53 PM, walter shawlee wrote:


I got one of these cuties on ebay (not expensive, it had bad batteries) and
was amazed when I opened the tek travel bag it was in, everything was covered
in sticky gray crumbled foam. what a total nightmare to clean...

I guess this is the deteriorated foam that once lined the bag, but wow, what a
sticky, horrible mess it made. it also really added to the screen mess, which
was scratched and marked. I managed to clean up the screen by carefully
polishing it with Novus 1 and 2 plastic polish, rags and Q-tips. Eventually
it was clean and readable. Novus is truly magical on plastic.

I tried to use the Tek wall wart power adaptor, but the cable was
intermittent, and it was still sticky from the foam so I tossed it and used
another generic 12V/1A adaptor (there is nothing special about it, just center
positive barrel plug), and ta-da, we have lift-off. It wouldn't charge the
batteries, so I opened the battery compartment and found somebody had soldered
together 4 C nicads, and tacked on that weird outer ring Tek used as the
bottom positive contact. Needless to say, all dead as door nails. I didn't
have any C nicads around, so I ordered some and am waiting for them to show
up, and I will try and re-create that goofy pack Tek had in there.

Incredibly, the scope and meter functions worked running from the wall wart.
The meter was bang on, and the scope is working, but I am not sure I
understand the control operation, changing timebase and vertical settings
seems to work very poorly, and getting the trigger to work is REALLY
difficult. Have to go through the manual again and see what I am doing wrong,
but it really made me long for some knobs and regular controls, rather than
on-screen nested menus. Am is being harsh, or this a really weak interface?

So at first blush, it looks to be workable, I just have to dig deeper into the
user-hostile interface and see what's going on, and get the batteries up and
running. Not unhappy for the small investment, although I am still finding
crumbled sticky foam everywhere in the lab. I found lots of docs for it on
line, which amazed me. Happy to hear from anybody with experience using this
unit as to any tips and tricks.I am guessing genuine Tek batteries are no
longer available...

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.








Carsten Bormann
 

On 2020-08-26, at 00:27, John Gord via groups.io <johngord=verizon.net@groups.io> wrote:

If you make a battery tube with a side contact to match the scope battery contact, you can use 3 unprotected 18650 Li-ion cells or two protected cells plus a dummy spacer. The scope does not seem to mind the excess voltage, it just draws less current. If I recall correctly, the scope spots the higher voltage and does not attempt to charge the higher voltage cells. The protected cells should be safe even if the scope does attempt to charge.
Neat! I’ve got to try that. Would go for 26650, though.

Grüße, Carsten


 

On Wed, Aug 26, 2020 at 12:31 AM, Carsten Bormann wrote:


If I recall correctly, the scope spots the higher voltage and does not attempt
to charge the higher voltage cells. The protected cells should be safe even if
the scope does attempt to charge.
Wouldn't using unprotected cells be risky, not just for the cells?

Raymond


Carsten Bormann
 

On 2020-08-26, at 00:48, Raymond Domp Frank <@Raymond> wrote:

On Wed, Aug 26, 2020 at 12:31 AM, Carsten Bormann wrote:


If I recall correctly, the scope spots the higher voltage and does not attempt
to charge the higher voltage cells. The protected cells should be safe even if
the scope does attempt to charge.
Well, I didn’t write that, but:

Wouldn't using unprotected cells be risky, not just for the cells?
Yes, don’t do that. Generally, unless you can install additional protection circuitry, any retrofit of this kind needs to be done with protected cells.

26650s are available at around 5 Ah, giving a 7.4 V dual-cell battery a nice 37 Wh.
Even with 3200 mAh C-size cells, NiMH gives you some 15 Wh.

You just don’t get a useful battery indicator...

Grüße, Carsten


John Gord
 

Raymond,
You are right, of course. Even if the THS720 does not charge the cells, unprotected cells might be over-discharged, causing possible safety problems which might not appear until they were charged later. Sometimes I try things that are not altogether safe.
--John Gord

On Tue, Aug 25, 2020 at 03:48 PM, Raymond Domp Frank wrote:


On Wed, Aug 26, 2020 at 12:31 AM, Carsten Bormann wrote:


If I recall correctly, the scope spots the higher voltage and does not
attempt
to charge the higher voltage cells. The protected cells should be safe even
if
the scope does attempt to charge.
Wouldn't using unprotected cells be risky, not just for the cells?

Raymond


 

On Tue, Aug 25, 2020 at 10:24 PM, amirb wrote:

the major problem with these scopes is the unusual DC offset that they develop. The best remedy seems to be
changing the two optocouplers (on each channel that has offset) and then calibrating the scope. In my case just calibrating the scope
solved the issue though.
This was a known issue on A and P models with firmware lower than 1.15.
See message 140959

/Håkan


amirb
 

On Wed, Aug 26, 2020 at 05:55 AM, zenith5106 wrote:


On Tue, Aug 25, 2020 at 10:24 PM, amirb wrote:

the major problem with these scopes is the unusual DC offset that they
develop. The best remedy seems to be
changing the two optocouplers (on each channel that has offset) and then
calibrating the scope. In my case just calibrating the scope
solved the issue though.
This was a known issue on A and P models with firmware lower than 1.15.
See message 140959

/Håkan
my firmware was 1.16