Author Topic: DIP8 power supply IC, unknown  (Read 467 times)

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Offline najraoTopic starter

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DIP8 power supply IC, unknown
« on: November 27, 2024, 09:40:17 am »
Has no markings at all, this switcher converts 300V dc to 5V 6A, claimed.  Comparable to Power Integrations devices.

The traced pinout is:
1: GND, 300V Minus
2: Unknown, has 220R to Vcc cap Plus
3: Vcc, 10uF cap fed by a transformer sec, with 2×500k to 300V for startup
4: FB, from Opto LED
5: Source of switch, has 560mR 0.5W to power ground
6, 7 and 8: Drain, to transformer primary.

All 8 pins present, none deleted to extend hv drain clearance.

Problem is: it is kaput,  SHORT between 2 and 3. Vcc builds up to 17.5V nevertheless. No switching action though. Power mosfet tests OK, source to drain..

Claim of 30W output with not much heatsinking estate on PCB is suspect.

My Google and other searches have failed. Anybody can identify this IC?

Thanks in advance.

 
 

Online coromonadalix

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Re: DIP8 power supply IC, unknown
« Reply #1 on: November 27, 2024, 02:59:47 pm »
photos of it could help,  pcb markings  etc ...
 

Offline fzabkar

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Re: DIP8 power supply IC, unknown
« Reply #2 on: November 27, 2024, 08:03:18 pm »
 

Offline Kim Christensen

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Re: DIP8 power supply IC, unknown
« Reply #3 on: November 27, 2024, 08:38:44 pm »
3: Vcc, 10uF cap fed by a transformer sec, with 2×500k to 300V for startup

Have you checked the ESR of that 10uF? When they go high ESR, the chip cannot bootstrap itself and will appear to be faulty when it's really the capacitor.
 

Offline najraoTopic starter

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Re: DIP8 power supply IC, unknown
« Reply #4 on: November 28, 2024, 03:43:00 am »
Photo/s show nothing more.
I have already said Vcc cap starts up, reaches 17.5V without being fed by transformer. ESR check has no value.
Excellent 'resource' to ID by pinout but alas, no match in list. Thank you sir.
 

Offline fzabkar

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Re: DIP8 power supply IC, unknown
« Reply #5 on: November 28, 2024, 04:01:15 am »
I have already said Vcc cap starts up, reaches 17.5V without being fed by transformer.

This would suggest that Vcc is clamped by an internal zener, unless the capacitor is leaking.
 
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