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Old 7th Sep 2020, 8:12 pm   #1
evingar
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Default Transistor markings 185 V / 26031

Hi,


I wonder if someone can help me source data for a transistor I haven't come across before and can find no Web reference ?

It's a TO220 type. Across the top is marked 185V and across the bottom is marked 26031. The transistors are the switching elements in an elderly switched mode power supply so are likely to be high voltage types. Both devices have all pins shorted, so I can't even tell if they are bipolar or MOSFET.



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Old 7th Sep 2020, 10:07 pm   #2
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Default Re: Transistor markings 185 V / 26031

Not the end of the world. Tracing the drive circuit will tell you if it's NPN or NMOS. Tracing out the power mesh will give an idea of the voltage ratings needed. Looking at the rated power will give you an idea of the current rating needed.

Putting a low voltage power supply onto the control circuits ought to get you an oscillator running to give you an idea of the speed needed.

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Old 8th Sep 2020, 11:01 pm   #3
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Default Re: Transistor markings 185 V / 26031

Hi David,

Thanks for the pointers. It's a repair for a 3rd party so it would have been nice to have the certainty of knowing what exactly is fitted but I suspect it may be a manufacture specific marked device .
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Old 9th Sep 2020, 3:06 am   #4
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Default Re: Transistor markings 185 V / 26031

BUT11 is the common bipolar SMPSU transistor of old.
I have even seen them with factory insulated tabs too.
https://datasheetspdf.com/pdf/709836...ctor/BUT11FI/1

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Old 9th Sep 2020, 4:17 am   #5
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Default Re: Transistor markings 185 V / 26031

Any maker's name on the PSU?

Any logo on the transistor?

Anything to date it?

What country was it made in?

What power level?

Any controller chip, or is it all general purpose parts? Many SMPS exist, but most didn't go too far from databook example circuits.

We need any info that might bring the size of the field down. The end stop is to trace the circuit, then the design can be analysed and a new device chosen with suitable ratings. Whether it's the original type or not then won't matter, it will be right for the job. In the eyes of the original designer, we are aliens from the future, with access to devices they never dreamed of.

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Old 11th Sep 2020, 9:31 pm   #6
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Default Re: Transistor markings 185 V / 26031

Refugee,
Thanks, that looks like a good general replacement bipolar device.


David,


The manufacture is LH Research. Model Number IM802-33/115A1.
There is no logo or maker on the transistors
The power supply was manufactured in Malaysia
Power out is 15V 6A / 15V 3A (135 Watts)

There is no power controller. The design uses comparators and op-amps.
The date on the electrolytic caps is 1988.
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Old 12th Sep 2020, 5:15 am   #7
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Default Re: Transistor markings 185 V / 26031

Ouch, that makes for a lot of circuitry to trace and no free ride from an applications note for a controller chip.

At the end of the eighties, far eastern SMPS were mostly bipolar based as a MOSFET's pricing ruled them out. 135W, TO-220. BUT11 sounds like a good possibility.
One concern remains. What is the input voltage? is it a single range 120v job, or 240v, or is it wide range or switched range?

I'm trying to guess the voltage on the reservoir capacitor(s) Some SMPS are simple bridge rectifier inputs, some hava a link or switch to go between rectify and voltage doubler modes. I'm assuming it's in the UK on 240v, so there will be 300-ish volts on the reservoir.

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Old 12th Sep 2020, 6:47 pm   #8
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Default Re: Transistor markings 185 V / 26031

I think it will be 115V mains as there is also a IM802-33/230A1 listed on the avantipowerrepairs site.
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Old 12th Sep 2020, 7:46 pm   #9
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Default Re: Transistor markings 185 V / 26031

Can you see if the rectifier is a doubler with split reservoir capacitors? Or a straight bridge into a single reservoir capacitor?

It'll tell us whether the chopper is powered from 170v or 340v

Also, is there a small 50Hz transformer for powering the control section? (Otherwise it's likely powered from its main chopper transformer, with some scheme for start-up)

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Old 13th Sep 2020, 8:46 pm   #10
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Default Re: Transistor markings 185 V / 26031

Quote:
Originally Posted by Radio Wrangler View Post
Can you see if the rectifier is a doubler with split reservoir capacitors? Or a straight bridge into a single reservoir capacitor?

It'll tell us whether the chopper is powered from 170v or 340v

Also, is there a small 50Hz transformer for powering the control section? (Otherwise it's likely powered from its main chopper transformer, with some scheme for start-up)

David



The control voltage comes up even though the main switcher in inoperative. The power supply rating plate states 115V but there is a dodgy looking arrangement that enables usage at 230V. There is no PFC. The reservoir cap voltage is 170 V.
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