DRD420RE Flame out problems

[bigeee]

I have a DRD420re that is flaming out, the R14112 & R14103 resistors.
The below red highlighted components have been replaced and again flamed out.
Any idea what could be causing this.??????

Components on the Low Voltage Side of the Switcher.
--------------------------------------------------------------------

U14103 - LM7905 -5volt three terminal voltage regulator.
L14102 - 22uh 200ma choke.
CR14108 - ST BYW100-200 Fast Recovery Rectifier Diode.
CR14104 - ST BYW98-200 Fast Recovery Rectifier Diode.
Q24501 - TIP42A PNP Power Transistor (Must Use Insulator!).
Zener - This S.M. Zener diode is located either next to the LNB tuner
assembly, or inside of it.

Components on the High Voltage Side of the Switcher.
---------------------------------------------------------------------
F14100 - 3 Amp 250V Axial Lead (Pigtail) Fast or SlowBlow fuse.
R14102 - 3.3 Ohm, 1W 5% Metal Film F.R.
R14113 - 100 Ohm, 1/4W 5% Metal Film F.R.
R14110 - 22 Ohm, 1/2W 5% Metal Film F.R.
R14112 - 1K Ohm, 1/4W 5% Metal Film F.R.
R14103 - 2.4k Ohm, 1/8W 5% Carbon or Metal Film Resistor.
Q14102 - MPSA06 or MPSA05 NPN Transistor.
Q14101 - MPS8599 PNP Transistor.
Q14100 - ST STP4NB50FP N-Channel Enhancement Power Mosfet.
CR14103 - 1N4148 S.M. Diode.

:cool:

[skinerd]

Any of the following should be checked or changed as they can cause an overload in the high voltage side and blow those resistors.
cr14104 (22V supply),
cr14105 (5v supply)
cr14106 (3.3v supply)

[bigeee]

thanks skinerd, how do I test them, and when I find the bad one, what are the replacement chip info for ordering ???

[skinerd]

with an ohm meter, my have to remove from the circuit at least one end of the diode to get a good reading. If you have a bad one, get back and I'll get you the replacement number.

[bigeee]

cr14104 .003 tested with leads both ways
cr14106 .080 / 0.325 tested with leads both ways
cr14105 .040 tested with leads both ways
IRD was not pluged in when tested, all three were tested with out removeing an end from the circuit board

[skinerd]

based on those readings, I'd say, inconclusively, that the CR14104 and CR14105 are both bad, but that's INCONCLUSIVE, you need to read them out of circuit to be certain. Just unsolder one leg of each and read again.

[bigeee]

cr14104 .001 tested with leads both ways, one end removed from board cr14106 .000 / 0.079 tested with leads both ways, one end removed from board
cr14105 .000 / .511 tested with leads both ways, one end removed from board

I may have damaged them when bending them up, I should replace all three to be on the safe side. Could you give me the replacement part No.'s and where a good place to get them.
Thanks

[bigeee]

OK I have replaced the r14103 and r14112 resistors with new ones and the abovelisted cr14104, cr14105, cr14106 fast recovery doides from digikey and the same result, as soon as I plug in the resisters smoke up and turn black.
What else could I try or use it for parts ????

[babybear]

Try replacing the following also, just went through all of this and found the following to be the cause.

CR14104 - ST BYW98-200 Fast Recovery Rectifier Diode.
Q14100 - ST STP4NB50FP N-Channel Enhancement Power Mosfet.

Cheers and good luck.

[skinerd]

Never, NEVER change just those resistors, they don't fail unless the STP4NB50FP mosfet mentioned above fails, and that is usually overloaded by a diode failure in the secondaary like CR14104 as mentioned above.
If just those resistors are changed and not the mosfet, they will fail rapidly again, if the mosfet simply failed, just changing it with the resistors might fix the problem and might not. There are two small transistors that usually go also, I don't have any info with me for their numbers, but you can't miss them. They won't cause a flame out, but if bad they won't trigger the mosfet.
I always change the output diodes, all of them, because it's no fun to watch all that work go up in smoke again. Cheaper just to change them all.

[FreshManDTV]

Sorry that it's not related to this thread but how can I start a new thread? I've been looking for a good 5 minutes up & down and still can't find a place to post a new thread. Yeah, yeah, I must be blind or about to but please just tell me how. Thanks.

[skinerd]

Sorry that it's not related to this thread but how can I start a new thread? I've been looking for a good 5 minutes up & down and still can't find a place to post a new thread. Yeah, yeah, I must be blind or about to but please just tell me how. Thanks.

There is a "New Thread" button just above the anouncements for a particular forum, like DssReceivers and Hardware.

[bigeee]

skinerd, were can I get that mosfet, I've looked and a lot of suppliers don't carry it.
I'm not a electronics guy so I don't know what the transistors are, I would need the location No. on the bord and the replacement part description in order to get them.
I should probably find and read a book called "electronics for dummies"
Thanks for every ones patience.

[babybear]

Q14100 - ST STP4NB50FP N-Channel Enhancement Power Mosfet.
CR14104 - ST BYW98-200 Fast Recovery Rectifier Diode

go to mouser.com do a search for STP4NB50FP & BYW98-200 they are in stock

All the parts listed above ^^ in bigee's post have the board location numbers there for example Q14100 is the location number on the 420's board.

All the parts listed are probably available at mouser but did not check.

Also do a search for the 420 schematics they are around here some place.

Hope this helps..

Cheers

[skinerd]

The transistors are........

Q14101 MPS8599 or NTE159

Q14102 MPSA06 or MPSA05 or NTE287

[skinerd]

Can I use
NTE2946
For STP4NB50FP?

TYIA

I would not, that is a very critical component and the only substitute I have read of that works well is IFR830 or IFR820.

[axe3761]

try these.

[skinerd]

Can someone please post replacement part numbers for these.
preferably NTE parts as it seems many electronic stores where I live only offer NTE. Also is 2% better than 5% MF?
TYIA

U14103 - LM7905 -5volt three terminal voltage regulator.
L14102 - 22uh 200ma choke.
CR14108 - ST BYW100-200 Fast Recovery Rectifier Diode.
CR14104 - ST BYW98-200 Fast Recovery Rectifier Diode.
Q24501 - TIP42A PNP Power Transistor (Must Use Insulator!).
Zener - This S.M. Zener diode is located either next to the LNB tuner
assembly, or inside of it.

Components on the High Voltage Side of the Switcher.
---------------------------------------------------------------------
F14100 - 3 Amp 250V Axial Lead (Pigtail) Fast or SlowBlow fuse.
R14102 - 3.3 Ohm, 1W 5% Metal Film F.R.
R14113 - 100 Ohm, 1/4W 5% Metal Film F.R.
R14110 - 22 Ohm, 1/2W 5% Metal Film F.R.
R14112 - 1K Ohm, 1/4W 5% Metal Film F.R.
R14103 - 2.4k Ohm, 1/8W 5% Carbon or Metal Film Resistor.
Q14102 - MPSA06 or MPSA05 NPN Transistor.
Q14101 - MPS8599 PNP Transistor.
Q14100 - ST STP4NB50FP N-Channel Enhancement Power Mosfet.
CR14103 - 1N4148 S.M. Diode.

Most if not all of those pats have numbers posted for them, use the search feature for each.
Example: http://www.dssftp.com/forum/upload/editpost.php?do=editpost&p=70126