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[Solved] Assessing and Repairing a Defective MacAllister Screwdriver Battery Charger

margosmat 15876 14
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  • #1 17237389
    margosmat
    Level 7  
    Hello,

    My MacAllister screwdriver battery charger broke recently. I have no experience in repairing this type of equipment, but I opened it, checked if there was voltage at the end (on the contacts where the "pins" of the battery go) and it is not. The diodes are off, the battery is not charging or heating up. The charger did not come into contact with moisture, it was not kept outside.

    Below are photos of the disassembled charger. I wanted to ask you, are you able to assess what could have broken in this charger and if I can repair it with your help? Thank you in advance for your help.

    Assessing and Repairing a Defective MacAllister Screwdriver Battery Charger Assessing and Repairing a Defective MacAllister Screwdriver Battery Charger Assessing and Repairing a Defective MacAllister Screwdriver Battery Charger
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  • #2 17237405
    bearq
    Level 39  
    No, you are not able to fix it yourself with home appliances :(
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  • Helpful post
    #3 17237572
    wojtek 9007
    Level 40  
    Hello - please check with a multimeter this element marked on the PCB as F1
    (it is a fuse).

    Added after 52 [seconds]:

    Assessing and Repairing a Defective MacAllister Screwdriver Battery Charger
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  • Helpful post
    #4 17238137
    automobilklub
    Level 17  
    Check the battery again. If there is no voltage on its contacts, the charger may not activate.
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  • #5 17238557
    margosmat
    Level 7  
    @jtek 9007 I checked the fuse and the voltage is approx. 10 V weaker than at the input (203-4V, at the input 213-214V).
    @automobilklub There is a voltage of 14.75V at the battery contacts, so probably approx.
  • #6 17238572
    robokop
    VIP Meritorious for electroda.pl  
    You are not even able to properly check the fuse. You know what kind of animal this is, that fuse or not?
  • Helpful post
    #7 17238577
    wojtek 9007
    Level 40  
    The fuse should be checked with a multimeter (diode, buzzer).
    If the fuse is good, please measure the voltage on the electrolyte
    maybe (320 V) - I noted in the photo.

    Added after 51 [seconds]:

    Assessing and Repairing a Defective MacAllister Screwdriver Battery Charger
  • #8 17238856
    margosmat
    Level 7  
    @jtek 9007 Ok thanks for your patience. I checked the fuse, it shows 1, it is not approaching 0 and there is no voltage on the electrolyte.
  • Helpful post
    #9 17238999
    bearq
    Level 39  
    margosmat wrote:
    @jtek 9007 Ok thanks for your patience. I checked the fuse, it shows 1, it is not approaching 0 and there is no voltage on the electrolyte.

    Because the converter does not start, did you check the power supply of the chip?
  • #10 17239423
    marian1981.02
    Unitra equipment specialist  
    margosmat wrote:
    1 is not approaching 0, and there is no voltage on the electrolyte.
    So what is the conclusion of this? Is this fuse good or not good?
  • #11 17260569
    margosmat
    Level 7  
    Forgive me for not answering for so long, but I waited for the fuses I ordered. So I replaced the defective fuse, the charger still doesn't start. I checked the voltage on the electrolyte and it is still gone.
    @bearq - could you explain how to check the power supply of the chip or this converter? As for whether the current goes to the plate then yes.
  • Helpful post
    #12 17261660
    bearq
    Level 39  
    margosmat wrote:
    Forgive me for not answering for so long, but I waited for the fuses I ordered. So I replaced the defective fuse, the charger still doesn't start. I checked the voltage on the electrolyte and it is still gone.
    @bearq - could you explain how to check the power supply of the chip or this converter? As for whether the current goes to the plate then yes.

    You check what the scalak is, look for its documentation on the internet from which you can find out which outputs are responsible for what. You check the power supply of the chip and if you do not have it, you are looking for a power problem by deduction. If the power supply is only an oscilloscope and measurements ...
  • #13 17261801
    marian1981.02
    Unitra equipment specialist  
    margosmat wrote:
    could you explain how to check the power supply of the chip,

    How do you want to check the power supply of a chip if you write that
    margosmat wrote:
    I checked the voltage on the electrolyte and it is still gone.

    bearq wrote:
    You check the power supply of the chip and if you do not have it, you are looking for a power problem by deduction. If the power supply is only an oscilloscope and measurements ...
    And you boy, finish the story because you can see that the author is green in the subject.
  • #14 17287746
    Anonymous
    Anonymous  
  • #15 17304740
    margosmat
    Level 7  
    Unfortunately, I could not find the scaler diagram, and on Castorama's website I got information that the charger can be purchased separately, so I close the topic. I would like to thank everyone who tried to help and devoted their time. For those who came to the forum "Beginners Repair" to mock and write that someone is "green in the subject", I suggest finding another hobby. I hear masturbation is a nice thing :D
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Topic summary

✨ The discussion revolves around troubleshooting a defective MacAllister screwdriver battery charger. The user reports that the charger is not providing voltage at the battery contacts, and initial checks indicate that the diodes are off and the battery is not charging. Various forum members suggest checking the fuse (marked as F1 on the PCB) with a multimeter, verifying the voltage at the battery contacts, and examining the power supply to the chip. After replacing the fuse, the user finds that the charger still does not operate, leading to further inquiries about checking the power supply of the chip and the absence of voltage on the electrolyte. Ultimately, the user decides to close the topic after learning that a replacement charger can be purchased separately.
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FAQ

TL;DR: Dead MacAllister charger? Expect ~320 V DC on the primary electrolytic; if zero, start at F1. "The fuse should be checked with a multimeter." Use continuity mode, then verify the bulk‑cap voltage before chasing the controller. [Elektroda, wojtek 9007, post #17238577]

Why it matters: This FAQ helps DIYers diagnose no‑LED/no‑charge SMPS chargers safely and decide when repair vs replacement makes sense.

Quick Facts

How do I quickly check if my MacAllister chargers primary is alive?

Start with two checks. 1) Test F1 with continuity (diode/buzzer) mode. 2) Measure DC across the large primary electrolytic. Expect about 320 V DC on 230 V mains. If the fuse is open or the capacitor reads 0 V, the input stage is down. Then trace input parts before suspecting the controller. [Elektroda, wojtek 9007, post #17238577]

Which part is F1 on this charger and how do I locate it?

Look for the silkscreen "F1" on the PCB near the AC input section. It’s designated as the fuse on this board. Visually inspect it and then confirm with a multimeter continuity test. Replace like‑for‑like after diagnosing what caused it to blow. [Elektroda, wojtek 9007, post #17237572]

What multimeter reading shows a good vs blown fuse?

Use continuity (buzzer) or diode test. A good fuse beeps and shows a low resistance path. An open fuse gives no beep and shows open circuit. Do not rely on measuring AC voltage across the fuse to decide its state. Always remove power before testing. [Elektroda, wojtek 9007, post #17238577]

My meter shows 1 on the fuse; is it blown?

Yes. On many meters, a steady "1" or "OL" indicates an open circuit. That reading on F1 means the fuse element is broken. Replace it only after checking the rest of the input stage for shorts, or it may fail again on power‑up. [Elektroda, margosmat, post #17238856]

What voltage should be on the big primary electrolytic capacitor?

Measure DC across its terminals with the unit powered. On 230 V AC, you should see about 320 V DC. If you read 0 V, the rectified HV bus is missing. Suspect the fuse, input resistor/thermistor, or bridge rectifier before the switching controller. [Elektroda, wojtek 9007, post #17238577]

Why wont the charger start when the battery is at 0 V?

Many chargers need to sense a nonzero pack voltage to enable charging. If the pack is collapsed to 0 V, the charger may not activate its output or LEDs. Pre‑charge the pack or test with a known good battery to rule this out. [Elektroda, automobilklub, post #17238137]

I replaced the fuse and the charger still doesnt start what next?

Recheck the new fuse; it may have blown instantly due to an unresolved fault. Inspect the input path and rectifier before powering again. Power up only after isolating shorts to avoid repeat failures and further damage. [Elektroda, Anonymous, post #17287746]

How do I check the controller IC (scalak) power safely?

Identify the IC and obtain its datasheet to locate the VCC/startup pins. Verify the supply with a multimeter; use an oscilloscope if needed for startup pulses. "You check what the scalak is, look for its documentation on the internet." [Elektroda, bearq, post #17261660]

Can I realistically repair this charger at home with basic tools?

It’s challenging without experience and proper instruments. Live‑mains SMPS work carries shock and fire risk. If you lack measurement skills and tools, replacement is safer and faster than trial‑and‑error repair. [Elektroda, bearq, post #17237405]

Do I need an oscilloscope to diagnose a nostart converter?

Often yes, once input faults are excluded. You may need to view startup behavior on the controller VCC and gate drive. That helps confirm whether the controller attempts to run or is latched off. [Elektroda, bearq, post #17261660]

Is measuring ~14.75 V at the battery contacts meaningful if LEDs are off?

Users reported ~14.75 V at the contacts with LEDs dark. Treat it as a clue, not a verdict. Continue by confirming the HV bus and fuse status to understand if the primary is alive or the indicator path failed. [Elektroda, margosmat, post #17238557]

When should I stop troubleshooting and just buy a replacement charger?

If the fuse reblows, there’s no 320 V on the bulk cap, and you lack an oscilloscope or datasheet, replacement is practical. The charger is available separately from the retailer for a quick fix. [Elektroda, margosmat, post #17304740]
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