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Can anyone help identify these components please

dicky98

May 18, 2015
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Hi folks

I am trying to repair a SMPS that came from a Martin Ego x5 Disco light

From what evidence I can see this unit has had some sort of fluid get into it at some time. It is dead. No power.

Actually if you power it up you do have 350V DC on the mains bridge but that dissapears as soon as you turn it off, and there are no low voltage outputs

I think I have traced the problem down to two components on the PSU

These are marked as R3N and R46

I imagine they are drivers for the output stage which consists of two IRFP460A

At first I thought the IRFP460A were short circuit, but having removed one of them it checked OK on the Atlas DCA as a N Channel Enhancement MosFET

There are two pairs of these R3N/R46 devices and one pair seems to be short circuit

I lifted the legs on what appear to be the good pair and they test on myAtlas DCA as R3N = NPN Bipolar Transistor and R46 = PNP Bipolar Transistor

I lift the legs on the other pair and they are R3N short circut base-emitter and R46 short circuit collector-emitter

I can't see any other obviosuly (visibly) damaged components and with these legs lifted the short circuits around the second IRFP460 have gone away so it is probably good though i haven't pulled it to test on the DCA yet

Problem is I can't find any info/datasheet for the R3N and R46 devices???????

Can anyone please help - see pics attached

I powered up the light unit from my 5V/12V bench PSU (without the bulb fitted as it needs 24V 250W from the PSU) and the unit went through it's power on self check OK and appeared to start operating so I suspect everything else still works OK


Rich
PS - there is something very odd (to me) about this Switch Mode PSU - it doesn't have any large electrolytic(s) on the 350V DC rail coming out of the mains bridge rectifier!!- see last pic. Is that weird or what?
 

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hevans1944

Hop - AC8NS
Jun 21, 2012
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... it doesn't have any large electrolytic(s) on the 350V DC rail coming out of the mains bridge rectifier!!- see last pic. Is that weird or what?

The two blue components (one with a label stuck to it) look like high voltage capacitors, but it's not obvious whether they are electrolytic capacitors or plastic-dielectric capacitors. The one that I can almost see appears to have markings: 2μ2 K 250V whatever that means. Someone else here will have to help you find replacements for the two SMT-mount NPN and PNP transistors.
 

davenn

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Sep 5, 2009
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but it's not obvious whether they are electrolytic capacitors or plastic-dielectric capacitors.


definitely not electros

I only see 4 electros
in the last all board photo .... a large black one .. upper left corner .. a small silver one lower left
2 x small silver ones lower right beside bridge rectifier

what is the voltage and uF rating of that large black one ?

There is no large smoothing cap after the bridge rectif and I have no idea why not

Dave
 

dicky98

May 18, 2015
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Thanks for some replies :)

The two blue ones are 2u2 250V (removed the sticker) so thats like 2.2uF 250V and they are not even connected in parallel - if anything they are connected in series (one end of each is definitely connected together)

This is a three layer PCB which kmakes it more difficult to trace anything

Upper left - that is on the LV side - 4700uF 25V

Two small silver ones by the bridge are marked

441
100
16z

Like that in three lines of text


This to me is one rather weird PSU and I would really like to get it working. I have a lot of test gear and enogh experience to work on this safely but don't have an isolation transformer which makes it hard for me to work on the HT side (am looking for a good 240V:240V isolation xformer by the way - say 2000VA to match my variac - if I can find one cheap enough.....)

I really hope someone can help me with the SMT transistors - all I know about them at the moment is from what my Atlas DCA tells me from the good ones. They are a NPN-PNP pair that I assume are there to drive are PowerFETS - datasheet on output PowerFETS here http://www.irf.com/product-info/datasheets/data/irfp460a.pdf

However i am a bit puzzled why a FET would need anything much in the way of drive circuitry. The chip to the right of the two faulty bipolar transistors is a HEF4047 - single monostable/astable multivibrator - which I can only assume is the oscillator for the PSU. I honestly would have thought it could drive the MosFETS on it's own!!

But given all that we do have some useful info - the DC rail (without any much smoothing) is 350V. The PSU supplies 24V AC at around 10A plus from powering the rest of the unit up of my bench sullpy it also gives 12V at an amp or so and 5V at not very much. We know the output device spec. I could probably power the oscillator up enough to figure out the operating frequencey. Given all that can anyone therefore work out the maximum likely ratings of R3N and R34 and come up with some decent replacements. I know the hFE of them is around 100-200

Rich
 

dicky98

May 18, 2015
14
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OK so I had another little poke around at this

The two blue 2u2 250V caps (with the white sticker on) are connected in series from the +'ve end of the bridge. These form a AC 'voltage dropper' and charge up the two little silver electrolytics to the right of them which are connected in parallel with each other.

This in turn supplies power to the HEF4047 multivibrator. There is probably a zener diode somewhere in this circuit as well as there are quite a few diodes in that area of the PCB

The large transistor just below the two silver electrolytics is a D2NB60 600V 2.6A N-Channel MosFET

http://pdf1.alldatasheet.com/datasheet-pdf/view/113256/STMICROELECTRONICS/STD2NB60-1.html

At the moment I can't imagine what this is supposed to be doing :( Any ideas?

There is also a relay which looks like is connects certian windings on the transformer together oe selects certain windings. I haven't figured what powers the relay coil yet due to internal pcb layer making it hard to trace and can't get my mind around what it is supposed to do unless it is some sort of soft-start mechanism?.

There is however an optoisolator between the LT and HT sides of the SMPS as you would expect on a more conventional design.

The small 8 pin IC to the left (see pic attached) is a L6384D High Voltage half Bridge Driver

http://pdf1.alldatasheet.com/datasheet-pdf/view/22575/STMICROELECTRONICS/L6384D.html

The HVG and LVG outputs from this go to the Base connections of the pairs of R3N/R46 transistors

The emitters of these NPN/PNP pairs are connected together and drive the Gate of the IRFP460A Power FETS

I connected a 16-0-16 transformer to the live and nuetral connections of the SMPS

This caused the two little silver electrolytics to charge up to around 1.5V (with about 0.2V of ripple on it)

The HEF4047 then actually had the audacity to oscillate with this low voltage supply!!! Period seems around 5uS so what's that, about 200KHz?

The HEF4047 output pin 13 was oscillating but I can't see any waveforms going on around the L6384 though it is not connected directly to pin 13 of the HEF4047 and I haven't tried to trace the circuit

I really need some data on this R3N/R46 transistor pair or could someone make a reasoned guess from the above info?

I know I have the faulty pair and possibly a faulty L6384D as this connects direct to those faulty transistors, one is s/c B-E and the other s/c C-E. But I think the rest could be OK. Your thoughts would be welcome

I really need a higher voltage isolation transformer to test this much further I think - or some other safe way of connecting my scope on the HT side. Can anyone help me here? I do have a Variac but it does not provide isolation.

Cheers
Rich
 

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dicky98

May 18, 2015
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Unfortunately I seem to have exhausted any suggestions here for replacements or datasheets for the transistors type R3N and R46, or should the request be re-posted in the Datasheets, Schematics, Manuals and Parts section here?

It seems bizarre that a fairly recent device (say 10 years old or so) would contain transistors I can't find datasheets for - are there any other places/forums/etc you could recommend that I should be looking for this info

Cheers
Rich
 

dicky98

May 18, 2015
14
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May 18, 2015
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Whilst working on something elseI had a bit of a breakthrough finding similar coded transistors to these via the package type - for example google: SOT23 + the code number eg 'SOT23 R43'. Could anyone one identify the package type of R46 and R3N from the above pics? They are around 7mm x 4mm This may help me find the datasheets

Thanks
 
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