DM42 works with USB but not battery

If you're having problems with the hardware of a DM41X or DM42, post about them here.
dfnr2
Posts: 1
Joined: Mon Jun 12, 2017 11:55 pm

DM42 works with USB but not battery

Post by dfnr2 »

I got my DM42 in February, and it worked great. It's been in a box (off, of course) for March and April while I moved my office, and I just checked it out again. The calculator would not power up without USB attached. With USB, it operated just fine.

I removed the battery, which read near 0V. I placed a new good CR2032, which read 3.1V, but still no activity when I press ON. I tried resetting the calc via the reset button, but nothing. Again, the calc works when USB is attached.

Has anyone seen this before? Is there a simple fix?

Thanks,

Dave
lescook99@gmail.com
Posts: 1
Joined: Fri Jun 22, 2018 3:37 am

Re: DM42 works with USB but not battery

Post by lescook99@gmail.com »

Am having the same problems with batteries. Michael from Swiss Micros told me to update to firmware to 3.5. Did so but the battery voltage falls from 3v to low 2's within say a day. Wondering whether you found a solution to the problem? Thanks Les Cook (Australia).
AKS2346
Posts: 3
Joined: Wed Dec 18, 2019 9:25 pm

Re: DM42 works with USB but not battery

Post by AKS2346 »

I have this same problem now after running fine and well on batteries for some time. Did you ever resolve this? If so, can you post a reply to this chain?

Thank you,

Anil.
Dubbie
Posts: 3
Joined: Mon May 22, 2017 11:53 pm

Re: DM42 works with USB but not battery

Post by Dubbie »

I also have this problem.
I have to run on USB now.
AKS2346
Posts: 3
Joined: Wed Dec 18, 2019 9:25 pm

Re: DM42 works with USB but not battery

Post by AKS2346 »

Hi,

Any update on this issue. I am hardly an electronics engineer, but a simple check with continuity showed that no major connections are off.

However, even with a fresh battery, calculator doesn't turn on. However it works perfectly on USB power.

I did update firmware today to the latest and power setting was on 3.

Anil.
EM41
Posts: 162
Joined: Mon Mar 30, 2020 12:10 am
Location: Overijssel Netherlands

Re: DM42 works with USB but not battery

Post by EM41 »

I discovered that the Chinese 10 for a euro batteries don't work in the DM41X and DM42, they show 3,1 V but under load they are sometimes below 1,5 V. Try a good Duracell or similar if you didn't do this already.
HP41C (2x), HP41CV, HP41CX, DM41X β, DM41X, DM42, HP11C, HP48G, HP97
AKS2346
Posts: 3
Joined: Wed Dec 18, 2019 9:25 pm

Re: DM42 works with USB but not battery

Post by AKS2346 »

EM41,

You diagnosed the situation perfectly. You were completely correct.

I did check the output voltage of the battery under various loads and it dropped like crazy. Bought a new battery from a reputable name, and the calculator works perfectly.

Now what do I do with the ten other Chinese batteries I have?! Make blinky LEDs for the kids I guess.

I appreciate your taking time to help.

Anil.
DA74254
Posts: 79
Joined: Tue Oct 03, 2017 11:20 pm
Location: Norway/Latvia

Re: DM42 works with USB but not battery

Post by DA74254 »

AKS2346 wrote:
Wed Aug 12, 2020 9:52 pm
Now what do I do with the ten other Chinese batteries I have?! Make blinky LEDs for the kids I guess.
Look at it the positive way. With those batteries, you do not need a current limiting resistor on the LEDs :lol:
Esben
DM42 SN: 00245
EM41
Posts: 162
Joined: Mon Mar 30, 2020 12:10 am
Location: Overijssel Netherlands

Re: DM42 works with USB but not battery

Post by EM41 »

I had some of these laying around and had the same experience :D
And yes blinky lights is what they are developed for.
I stopped buying Chinese stuff completely, its (too) cheap but you never know for sure what you get, even electronic components contain different things than what is advertised on the outside.
And they copy and rob Dutch, and other countries, designs too much, don't want to support that any more.

Erik
HP41C (2x), HP41CV, HP41CX, DM41X β, DM41X, DM42, HP11C, HP48G, HP97
Geoff Quickfall
Posts: 326
Joined: Wed May 24, 2017 10:44 pm
Location: Vancouver Canada
Contact:

Re: DM42 works with USB but not battery

Post by Geoff Quickfall »

Look at it the positive way. With those batteries, you do not need a current limiting resistor on the LEDs :lol:
Sometimes I look at the Chinese batteries the negative way and sometimes the positive way. All depends how I pick them up. :shock:

Also, I NEVER use Duraleak (Duracell) batteries! Two many flashlights and transistor radios have been contaminated by them.

Geoff
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