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Modded Velleman LAB1

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thobo:
Inspired by BitBastelei I modded my Velleman LAB1 having more handy voltages and a DMM without needing a 9V batterie, changed 3V to 3.3V and 4.5V to 5V on the PSU part.  Have not modded the Label for 3.3V but could paint over the "4." from the 4.5 setting with an Edding to get 5V Label.
The isolated DC DC converter is supplied by 9V AC used by the Backlight, rectified the voltage is high enough, because the DC DC converter is a 12V to 12V type. The 12V is then regulated to 9V by a 78L09 to get a clean Input voltage for the DMM.
For isolating it against other stuff inside the Device I putted the PCB into a plastig bag and used a zip tie for fixing it. Because the DMM consumes only a few mA's, heat is not a topic.
On the PCB of the Power supply, on the left bottom side are the R3 and R4 which needs to be replaced, they are the bottom part of the voltage divider used for the LM317. The top resistor of the voltage divider is fixed to 68 Ohms (R2). R3 is 96,3 and should be replaces with 111,52 and R4 is 176 and should be replaced by 204 Ohms.
The result is not that bad, especialy the 5V are spot on :)

BTW I would never recommend this Lab1, because its not its money worth, just a cheap 3,5 digit DMM, a poor PSU with discrete Voltages and a soldering iron which is ok, but not the reason to buy it.
I had it for several years and used only the iron, but with the modds its more handy for just fast setups on breadboards.

thobo:
Some more pics

thobo:
A little add on, a voltmeter shows real output voltage.

reseto:

--- Quote from: thobo on February 19, 2015, 03:57:18 pm ---Inspired by BitBastelei I modded my Velleman LAB1 having more handy voltages and a DMM without needing a 9V batterie, changed 3V to 3.3V and 4.5V to 5V on the PSU part.  Have not modded the Label for 3.3V but could paint over the "4." from the 4.5 setting with an Edding to get 5V Label.
The isolated DC DC converter is supplied by 9V AC used by the Backlight, rectified the voltage is high enough, because the DC DC converter is a 12V to 12V type. The 12V is then regulated to 9V by a 78L09 to get a clean Input voltage for the DMM.
For isolating it against other stuff inside the Device I putted the PCB into a plastig bag and used a zip tie for fixing it. Because the DMM consumes only a few mA's, heat is not a topic.
On the PCB of the Power supply, on the left bottom side are the R3 and R4 which needs to be replaced, they are the bottom part of the voltage divider used for the LM317. The top resistor of the voltage divider is fixed to 68 Ohms (R2). R3 is 96,3 and should be replaces with 111,52 and R4 is 176 and should be replaced by 204 Ohms.
The result is not that bad, especialy the 5V are spot on :)

BTW I would never recommend this Lab1, because its not its money worth, just a cheap 3,5 digit DMM, a poor PSU with discrete Voltages and a soldering iron which is ok, but not the reason to buy it.
I had it for several years and used only the iron, but with the modds its more handy for just fast setups on breadboards.

--- End quote ---

Hello @thobo,

Could you tell me the list of components you used...

In your images I see:
- 78L09
- B1212LS-1W
- Diodes: value?
- big electrolytic capacitor: value?
- small electrolytic capacitor: value?
- "orange" capacitor?: value?

Also, if is possible the circuit diagram, although maybe I can extract it from one of the images you published.

Thanks

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