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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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20th Feb 2012, 8:32 pm | #1 |
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What is a DG4N60?.....
.....is it bipolar, a mosfet, or a triac?? To explain, I was asked if I could repair a 'Reyed RYD 50' switchmode supply in which one of the above TO-220 case devices is totally s/c. Never having come across the type before, I don't know with what to replace it. The circuit is built around a UC3842AN PWM Controller, the o/p of which connects to the ?gate? or ?base? of the DG4N60
via a series 10 ohm/ shunt 5k resistor network, the ?drain? or ?collector? of which connects to the primary winding of the transformer, so it's function is to switch said transformer on & off. I can find no info. about the Reyed on the 'net, so can anyone shed any light on it, please? PS- to add to the confusion, according to a UTC Datasheet the 4N60 is a600v power mosfet, but a P24N60C3 from Cricklewood electronics checks out like an NPN transistor, although they describe it as 'an NMOS TO220 650v' Last edited by 'LIVEWIRE?'; 20th Feb 2012 at 8:48 pm. |
20th Feb 2012, 8:42 pm | #2 |
Nonode
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Re: What is a DG4N60?.....
It'll be a MOSFET. You will probably be able to replace it with more or less any similar device from, for example, a scrap PC power supply. If it's gone short-circuit, it's probably killed the UC3842 and the 10 ohm resistor, and if there's a current-sensing resistor in the source lead of the MOSFET that may have suffered too.
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20th Feb 2012, 8:44 pm | #3 |
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Re: What is a DG4N60?.....
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20th Feb 2012, 8:48 pm | #4 | |
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Re: What is a DG4N60?.....
Quote:
Yes typically one of those cases where just changing the obvious faulty part will result in it's immediate destruction when power is applied...... I'd also make a check to any diodes that may be in the area. Rich.
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20th Feb 2012, 9:05 pm | #5 |
Nonode
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Re: What is a DG4N60?.....
As others have said, it is Mosfet, rated at 4A, 600V, the clue is in the part number, it will be Identical to the common P4N60 so beloved of Vestal etc..
The way to work this out generally, The first couple of letters refer to the manufacturer (eg. ST = Signetics-Thomson, etc..etc) the first number is the rating in Amps, the second number you need to add a zero to, this then gives you the voltage, the last letter if any, refers to the packaging. eg. if ending in an F, this usually means it is fully encapsulated and insulated, this type usually has a lower Ptot, PD, or total power dissipation. There are other parameters to consider, but the above is a reasonable guide. Please see attached a data sheet for a 'similar' Fairchild device. Ps. this only works for for this series type of numbering, eg. it does not work with the IRF series nor the 2SK series
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20th Feb 2012, 10:25 pm | #6 |
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Re: What is a DG4N60?.....
Thanks, all for your assistance. CMJ, I have already replaced the UC3842 & the 10 ohm R.
There is a 2watt resistor from the 'HT' +ve line to pin 7 of the UC3842, which reads o/c on my Fluke 77, yet it's color code LOOKS like either 10 or 100 ohms, which can't be right. I gather from the data sheet that the UC3842 incorporates an internal 34v Zener. I'll check the 'HT' again, but, assuming it to be about 340v at the bridge rectifier o/p, I would guess 100k to be nearer the correct value. On the data sheet sample circuit the equivalent R is 56k, but this is for a circuit designed to run from 90-130vac. R to B, thanks for reminding me how to work out what type nos. mean. From this, the new device I have is indeed a 4Amp 600v type with a metal tab common to it's center terminal, though I'm still puzzled as to why it checks like a bipolar NPN transistor. Surely the gate of a mosfet should be o/c to both the other two terminals? |
20th Feb 2012, 10:54 pm | #7 |
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Re: What is a DG4N60?.....
Not if the gate has protection diodes and there's a parasitic substrate diode.....
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20th Feb 2012, 11:03 pm | #8 |
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Re: What is a DG4N60?.....
Check the sense resistor which tells the controller chip what the voltage is sitting on the capacitor. This frequently goes O/C and the controller goes full throttle, destroying the FET and subsequently everything connected to it.
Dave. |
21st Feb 2012, 1:21 pm | #9 |
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Re: What is a DG4N60?.....
Hi "Red to black", Just a small point: ST = SGS-Thomson.
Peter |
21st Feb 2012, 2:27 pm | #10 |
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Re: What is a DG4N60?.....
By this, if you mean the resistor to which I referred in my earlier post-that connects to pin 7 of the controller I.C., then, if I've done my sums correctly, I will fit a 100K, preferably 2 watt, replacement, since the original indeed reads O/C.
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21st Feb 2012, 7:57 pm | #11 |
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Re: What is a DG4N60?.....
Having carefully checked the components around the UC3842, I duly replaced this IC, together with the 4N60(using the P24N60C3 with a mica washer between it & the heatsink(The DG4N60 is a totally insulated plastic type), the 2W resistor-I used a 100k as explained above, and the 10 ohm resistor, replaced the 3.15A fuse in the mains 'live', switched on....the fuse blew, and upon checking again, the 4N60 is s/c, and the UC3842 has failed again!! I'm at a loss to know what is causing this, since no other components checked as faulty. Possibly the transformer could have shorted turns, but, if not that, then what else??
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21st Feb 2012, 8:31 pm | #12 |
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Re: What is a DG4N60?.....
See post 4, reference immediate destruction.
It's possible that one of the secondary rectifier diodes has failed - either short or open, the MOSFET will die. The way to run up this sort of thing is to apply 12V or so to the UC3842, so that this runs and supplies drive pulses to the MOSFET gate, 'scope the MOSFET drain, and then slowly wind up the mains with a Variac. You need to know what sort of waveforms to look for, but with this technique you can spot trouble before you blow things up. |
21st Feb 2012, 8:45 pm | #13 |
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Re: What is a DG4N60?.....
When powering up a repaired sm psu I always slowly advance the AC input via a variac, and if the input current starts rising suspiciously, quickly whip back the variac knob with a flick of the wrist. One possibility that could cause self destruction is a defective reservoir capacitor in the primary, an ESR meter comes in handy.
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21st Feb 2012, 9:30 pm | #14 |
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Re: What is a DG4N60?.....
Running up by a Variac alone may sometimes work. But, the UC3842 does nothing until it gets enough voltage to start up, by which time you may have sufficient voltage on the main reservoir capacitor to blow up the FET within the first few pulses of drive from the UC3842.
So, better to supply the UC3842 with 'housekeeping' power first. Then you can run the power stage up gradually from true zero. |
21st Feb 2012, 10:56 pm | #15 | |
Nonode
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Re: What is a DG4N60?.....
Hi Livewire,
Have you downloaded the datasheet for the UC3842 ?, these datasheets often have applications/circuit diagrams using typical values for components, and very often closely cross reference or resemble a PSU of unknown origin. I have found this to be of great help in the past. IIRC the UC3842 was made by several different manufacturers, and not all were direct substitutes (with each other), often requiring a resistor value or two be changed depending on which or whose IC was fitted. Another thing which can cause instant destruction (depending on the design of the Psu) is a short circuit on the secondary side, a rectifier for example. Iam not convinced the P24C60 is a similar spec to the orignal P4C60 device ( although willing to stand corrected!). And finally, dinkydi: Quote:
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21st Feb 2012, 11:35 pm | #16 |
Heptode
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Re: What is a DG4N60?.....
Check the Snubber circuit across the transformer primary, connected to the D (Drain) pin of the FET.
Occasionally the capacitor will go O/C, sometimes the resistor does too if you're unlucky. The diode usually gives not bother but don't rule that out either. One thing that hasn't been mentioned is the Opto-coupler, when the UC3842 gets a blast, sometimes some of the energy gets thrown into the opto. When this fails, it means that the PSU will run full throttle, and if the secondary (or the snubber) can't get rid of the excess energy, then the transformer saturates and the transistor goes bang. Dave. |
22nd Feb 2012, 10:50 am | #17 |
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Re: What is a DG4N60?.....
I thought, too late, about the optocoupler! Guess I'll have to change that, too. Fortunately, neither that nor the UC3842(for which, incidentally, I have downloaded a data sheet, R to B)cost very much, although the P24C60 was more than a few pennies!. It's more the frustration at doing all that, only for the ***thing to fail again!! From what I know, other than the DG4N60 being all plastic, and the P24C60 having a metal tab, their specifications are similar. I guess I'll have to check the rectifier, and other components and start again. Don't possess a variac, though!
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