JYE Tech Forum

Posted: **Mon Feb 20, 2017 11:35 pm**

Interesting. Please do post back here with the details if you do end up replacing the ICL7660 with the LT1054 and the capacitors or anything else which can improve it!

About the power supply: how do I find a power supply which I can be sure is within 9V, is safe (I'm sceptical about buying electrical stuff from China -things have been known to cause fire or explosions) and won't cause any other problems for the DSO shell? Usually you just get the specs (i.e. output 9V/700 mA) and you just hope the circuitry inside actually does something good.

Posted: **Tue Feb 21, 2017 12:11 am**

One that is rated for 110 to 220 VAC, 50/60 Hz, will be a switching type power supply and have a regulated output. A simple non-regulating type will not be able to have that wide of a voltage input and still be able to claim to put out 9V.

Other than that just purchase one that has a lot of positive user reviews.

Posted: **Sun Mar 12, 2017 11:15 am**

I couldn't find any regulated 9V power supplies which weren't of the switching (100-240V) type, so I bought one of those instead of risking blowing up the DSO Shell with a non-regulated one.
I've already got several unregulated ones, and measuring one that claimed to output 9V would supply 19V!

Since I can only guess the voltage drop when actually connected there would be a fair chance the DSO Shell would get fried in the process.

I was suggested to build a filter to put in between the power adapter and the DSO shell to remove the switching noise. Is something like that available ready-made inside a box/enclosure?

Posted: **Sun Mar 12, 2017 4:18 pm**

I just killed my DSO when supplying it with 16.5 V from a non-regulated power supply. I should have read this thread before starting the assembly.

Lesson: always test; don't trust specs!

Posted: **Sun Mar 12, 2017 7:25 pm**

Sorry to hear that, Aldo.
I'm sure someone can answer this better than me, but perhaps you don't need to replace the entire DSO Shell, as maybe just some components have been fried and need replacing...

Posted: **Mon Apr 10, 2017 3:52 pm**

cdw2000 wrote:The ICL7660 negative voltage converter device on the analog board has an absolute maximum voltage limit of 10.5V and a spec'd limit of 10V.

I kind of wish they had used the LT1054, which is a better part, works up to 15V, runs at a higher frequency (25KHz), and with a couple resistors added can provide a regulated output. The ICL7660 runs at 10KHz and its output voltage is unregulated and load dependent.

Regarding the switch frequency - typically you don't want any power supply switching frequencies to be in the same area as the frequencies you are trying to measure (for noise immunity). At least at 25KHz, the LT1054 is outside the audio frequencies.

The LT1054 is pin compatible with the ICL7660, so I was actually thinking of upgrading my DSO Shell with the LT1054. I don't know if it will have any visible effect. The other improvement I was considering is to replace capacitors C12 and C13 with low ESR polymer aluminum types. This is supposed to improve the performance of the negative voltage converter by reducing ripple on the output voltage.

Hi cdw2000 have you replaced the parts? Can you give feedback?

Posted: **Mon Jul 10, 2017 2:16 am**

It seems that LT1054 does not have SOIC-8 variant, DIP-8 and SOIC-16 only. Both would be problematic in the current PCB.
On the other, more positive note, my recently purchased DSO Shell with PCB version "E" has 7660 AIBAZ-DN16WY chip installed.
This particular version supports up to 13V: http://www.intersil.com/content/dam/Int ... 660s-a.pdf
On a negative side, it seems there are a lot of fake 7660 AIBAZ chips around (http://www.quan-diy.com/misc/fake/icl7660.htm).
My DSO works fine so far from a 9V NIMH battery that gives 10.3V freshly charged.

Posted: **Fri Jul 21, 2017 9:13 am**

Tekmek wrote:...It's a pity about the missing battery, but I wasn't aware that a 9V battery wouldn't last that long with it. Still, I was hoping there would be a modification available for using a rechargeable battery. How about the DSO 138: does it have a battery option of some sort? What do you suggest the most convenient power source be for these scopes?...

There are several threads here about installing a battery, the mod I did is described here and here

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