DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

[Ali101]

Hello Folks,
i have one DC Power Supply (DF1730SB-5A), where power supplier is Programmable and i can adjust output voltage and it was working fine before one month, i had not use it for a while & last time when i power it on, it show on both LCD display VOLT/AMP (LO BAT -1.8:88) as show on attached pics, i can test out-put voltage with multi meter & it working fine, i can adjust volt, amp & put load and all working fine, seems like LCD display have some problem, both LCD show same error, i try to open power supply and check if any where short or any cap got shorten or burn but not found any thing with physical inspection,
not sure where need to start to find fault & fix it, any help shall highly appreciated,
Below DC Power Supply (DF1730SB-5A) link
https://www.elfa.se/en/bench-top-pow...-5a/p/16984742

Thanks.

[sam_sam_sam]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

Unless it has a power supply problem that powers the meter circuits and is locking the meter chip up or ( the meter chip is bad but for both of showing the same exact thing probably not )

I do have a question for what is the part number on the ic chip that is doing the voltage and current measurements

If it is a ICL 7106 or ICL 7107 or something similar then see if you unhook the input leads to the meter ic chip and see if it will show 00.00 volt or 00.00 amps with the wires shorted together

If it has this type of meter chip they can be powered two different ways either one power supply rail or a “ + “and “-“ power supply rails if has the last type of power supply and you do not have the “-“ power supply it might cause this problem

Unless this power supply is using some type of controller to do the voltage and current measurements and it has a chip something like this chip

https://www.ebay.com/itm/Eventide-H3...-/322273446880

If has something like this chip then you could have some problem getting this to work again unless you have have a way to get the parameters back into the controller

[Ali101]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

Thank Sam for reply & help, i am not sure which ic chip that is doing the voltage and current measurements, i had take few more pictures of power supply board, seems like IC is N7CC1LK (LM324N) (Pic-6 in attachment)
appreciated your further help to sort-out fault,
Thanks.

[R_J]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

I would think it is something that is common to both meter display boards, It looks like all segments are being turned on, including the LO BAT, Do the modules have numbers on them?

[Ali101]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

i try to unhook the input leads to the meter ic chip and display gone, so this trick not working,

@R-J yes but where is that LO BAT part? i mean is that some IC?
i have update high resolution pictures in this post

[R_J]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

The LO BAT is just part of the display, likely not used in this case. The modules seem to be DX61030A with ICL7106 ic's?
The power supply looks a bit water damaged (on controls) I suspect the display ic's may have some corrosion as well.

[stj]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

those chipsockets are a writeoff,
need a pair of machined-pin sockets and clean the chip legs with a small wire brush and some IPA

[sam_sam_sam]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

Thank Sam for reply & help, i am not sure which ic chip that is doing the voltage and current measurements, i had take few more pictures of power supply board, seems like IC is N7CC1LK (LM324N) (Pic-6 in attachment)
appreciated your further help to sort-out fault,
Thanks.

What is the ic chip part number for meter display board there are two of them but I can read the number

[Ali101]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

@R_J its not water damage, Taiwan is humidity place that's why it might looks like this but i had check all over the Power supply & it don't have any rust or corrosion included display section,

@stj i did clean all boards of power supply with IPA using brush but nothing seems working,

@sam enclosed close pic of meter display,

i suspect issue belong to 2nd enclosed pic since that board is connected to display section,

Display wire connected to second pic board as mark in red circle, if i disconnected any of those wires then display gone,

[stj]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

the chipsockets look like they are full of white stuff.

[Ali101]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

@sam IC Chip Part Number for meter display board is CS7106AGP (IBAD1K3232L) Semic

hope can get help from your side to sort-out issue,
Thanks.

[R_J]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

@R_J its not water damage, Taiwan is humidity place that's why it might looks like this but i had check all over the Power supply & it don't have any rust or corrosion included display section,

I was just looking at this white discoloration on the pots. does'nt look normal to me.
Did you ever check if you had proper voltage going to the lcd modules?

[Ali101]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

@R_J how much is proper voltages?

[R_J]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

@R_J how much is proper voltages?

I believe it is 9 volts, It should be marked on the module (+9V) and (-) Measure it where C3 would be.

[Ali101]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

on module it marked 7.5 V and i am getting around 7.6 V,

[R_J]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

on module it marked 7.5 V and i am getting around 7.6 V,

That voltage is on the input, There is a +9 Volt line that operates the ic

[Ali101]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

ah got it, let me check again & get back to you,

[sam_sam_sam]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

Icl7106

Look at section ( 5 )

Some how it is in the test mode or the ic chip is damaged from something kind-a voltage spike or static electricity

Look at the test pin ( 37 ) and see what it is hooked to this pin

https://cdn.badcaps-static.com/pdfs/...ab8c44713c.pdf

I have use these two meter module before ICL 7106 and the ICL 7107 both are covered in this data sheet

[sam_sam_sam]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

on module it marked 7.5 V and i am getting around 7.6 V,

No it has a 7.5 volt reference voltage for the ic chip

Look at the voltage on PIN number ( 1 ) and ( 26 ) you should have 9 volts
Is that Zener diode across the two pins if so then they doing it for a stable power supply

This might be the low battery warning reference if you were running of a battery or used for something else

( Look at both Figure 7-1 [ A and B ] to see which set you have for the reference voltage and check to see if you have that voltage if it has a Zener diode ) if not then your voltage reference will 100 mill-volt and is adjustable ve-a trim pot

[Ali101]

Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

Thank R_J & Sam, appreciated your help & support,

@R_J it given me 7.8 V on C3 because it getting same voltages from back board,

@Sam, i checked voltage on PIN number ( 1 ) and ( 26 ) and it given me same voltages, 7.8 V , Pin 35 (V Ref -) & Pin 36 (V red +) given me 0.98 V ,
look at attach pic,