Comments on: Drew A Small Circuit In Tina By Examining PCB Solderside

By: Harrie

Harrie — Sun, 27 Aug 2023 09:32:04 +0000

I have the same problem with a flashlight battery that does not charge
Checking R3 560k shows that it is OK
Transistor unsoldered and with tester indicates it is an NPN with hfe of 85 so I think that is good
Only capacitor C4 of 562K deviates very strongly, I measure 0.11nf
Replacement has no effect
The circuit does oscillate
However, the generated positive voltage is too low
Ordered a new transistor anyway and replaced it
And yes it works again
I replaced the old C4 for the test
This resulted in a sine wave voltage of more than 550V rms
And the frequency had almost doubled
Also, almost the entire mains voltage (224V) was on C1
I think that's why T1 has deteriorated
Now I measure a sine wave across T1 of about 400V rms and a frequency of 28kHz
So thanks Albert for sharing, saves a lot of research
Greetings from the Netherlands
Harrie v Z

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By: Henk-Jan

Henk-Jan — Fri, 13 Nov 2020 17:44:53 +0000

Dankjewel Albert, Thanks Albert,

Mine was broke to, didn't osscilate as well.
After i opened it up i thougth to myself: "I am not the only one in the world having this problem..." So, always when i think that i go to my best friend (Google) and i found your story.

In my case the transistor was broke (MPSA42), i had these in stock (?) because i bougth them to fix my Pinball machine 😉

Greetings from Zaltbommel, the Netherlands

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By: Idan

Idan — Fri, 10 Apr 2020 15:34:08 +0000

I'm going to attempt this exact same repair. Checking the board with my Fluke now - might need to find a resistor as I'm certain I don't have one.

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By: Albert van Bemmelen

Albert van Bemmelen — Sun, 26 Jan 2020 11:04:46 +0000

In reply to Beh.

You are right Beh. But these modern chargers of course are not completely transformerless because of the construction that in principle consists out of two separate coils forming a detachable transformer. And the second coil and the electronic charger controller circuit are placed in the interior of the flashlight around the battery compartment. As you know only the primary coil failed here to induce any energy to the second coil in the flashlight. Maybe in the near future our cars are charged this way with primary coils concealed in the road, and maybe we then at the same time are connected to the internet and to paying stations that control the energy to the charging unit of the car?

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By: Beh

Beh — Sat, 25 Jan 2020 11:05:19 +0000

In reply to Francisco Rica.

This diagram is a good example of transformerless power supply .good job and thanks

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By: Mark

Mark — Sat, 25 Jan 2020 00:24:31 +0000

In reply to Albert van Bemmelen.

Good explanation - thanks 🙂

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By: Albert van Bemmelen

Albert van Bemmelen — Fri, 24 Jan 2020 09:57:18 +0000

Indeed Robert. It was just one simple 560KB resistor to fix the problem for a big delicious Swiss milky chocolate bar! (LOL).

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By: Robert Calk Jr.

Robert Calk Jr. — Fri, 24 Jan 2020 07:01:55 +0000

Good job, Albert! Another device saved from the garbage!

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By: Albert van Bemmelen

Albert van Bemmelen — Thu, 23 Jan 2020 18:25:43 +0000

In reply to Albert van Bemmelen.

Of course I meant to write believe instead of beleave sadly editing to correct it is not yet possible.

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By: Albert van Bemmelen

Albert van Bemmelen — Thu, 23 Jan 2020 18:20:01 +0000

In reply to Parasuraman S.

It was an easy repair dear Parasuraman. It probably would have been a painful repair only if the flashlight had been defect too because it had a small pcb with a lot more small components on it. Including the electronic charger current regulator circuit.

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