RCA Model DRD420RE Satellite Receiver burned SMPS

[Ron Novini]

Have a satellite receiver, RCA Model DRD420RE with burned components
in the primary side of the switch mode power supply. These parts are
badly burned and charred to the point of being unrecognizable. Need
part ids for the following:
Resistors R14109,R14110,R14113,R14112,R14103
Diodes CR14101,CR14102 and CR14103.
Transistor Q14100 (Can read P4NB50FP at bottom).
Any help is appreciated. Thanks in advance Ron.


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[ways]

"Ron Novini" <vcrguy@hotmail.com> wrote in message news:<4a0779109f39697ee43ce2bb31c36932.123933@mygate.mailgate.org>...

Have a satellite receiver, RCA Model DRD420RE with burned components
in the primary side of the switch mode power supply. These parts are
badly burned and charred to the point of being unrecognizable. Need
part ids for the following:
Resistors R14109,R14110,R14113,R14112,R14103
Diodes CR14101,CR14102 and CR14103.
Transistor Q14100 (Can read P4NB50FP at bottom).
Any help is appreciated. Thanks in advance Ron.

Hi Ron,

I'm trying to to do the same repair on the DRD420RE I found sum values
& part #'s . But still looking for the values or part #'s for
CR14101,CR14102

Here is what I have now if you find the values for CR14101,CR14102 or
part #'s
plz let me know...... Hope this helps.

-----

This is an attempt to list those parts that tend to fail in the RCA
DRD22x and DRD4x0 series IRD's. The PC board silk screen designations
were taken from a DRD420RE receiver, but should be the same for all
models in these series.

Abbreviations used:

S.M. --- Surface mount part was used.
F.R. --- Flame Resistant Resistor.
ST --- ST Electronics. www.st.com (maker of the STI5500)

---------------------------------------------


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. DRD22x used S.M. 33V 500mw, and DRD4x0 used
S.M. 24V 500mw. Any value from 24V to 35V at 400mw to 1W should work
fine.



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. -Blown Apart
R14110 - 22 Ohm, 1/2W 5% Metal Film F.R. -Blown Apart
R14112 - 1K Ohm, 1/4W 5% Metal Film F.R. -Blown Apart
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. -Blown Apart..Problem being not sure
which is the cathode end. Can anyone help?

The following three capacitors usually do not fail unless they are
literally burnt off the board by the flames from R14112 and R14110. I
will list them here in case you need them.
---------------------------------------------------------------------
C14100 - .033uf 50vdc S.M. ceramic capacitor.
C14104 - .001uf 50vdc S.M. ceramic capacitor.
C14105 - .22uf 63vdc mylar capacitor.


Notes:

DO NOT try to substitute for Q14100 ! I promise you will fail
miserably, I know I did. Save your money and buy this part from
RCA/Thomson, or from a ST rep. The Tr/Tf parameter for this part is
what makes it unique, not the Rds, Vdss or any other parameters. It's
how long it spends in that transition area. This part will be cool to
the touch when running, never hot. (unplug your IRD before you touch
it as 150vdc is present!) Just to prove this to myself I tried using a
IRF840, a BUZ80A, and a NTE2946 from my parts collection. They all
worked, for about 15 Seconds ! The parts become so hot after just that
short a time I pulled the plug quick.

Power Transistor Q24501 was of the plastic type on the DRD22x series,
and RCA switched to the type with the Metal Tab, plus the addition of
an insulating washer on later models like the DRD4x0 series. So if you
do use a TIP42A with the metal tab Do Not Forget to insulate it from
the heat sink with a mica or thermal pad. Also don't let the metal
retaining clip touch the tab and short it out to the heat sink either.
Use your ohmmeter when you are done replacing it to verify that there
is No Continuity between the metal tab of the transistor and the heat
sink.


Here are the measured inductance values for switching transformer
T14100 from a working DRD420RE. Part numbers on the side of this
transformer read 15440720 and SEH2516-04. You must remove the
transformer to obtain accurate readings. Most likely only 10% accurate
anyway, so unless you measure something like 50% different, don't
worry about it. I have never seen one of these transformers fail, but
I just had to put this information someplace.

......Pins...........Measured Inductance.
....3 to 5..........1.03 MH
....1 to 2..........9.8 uh
....6 to 7..........4.2 uh
....6 to 10........17.7 uh
....8 to 9...........2.2 uh