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View Full Version : drd420re that wont power up

12-12-2003, 02:28 AM
skinerd
12-12-2003, 03:05 AM
I think those are Q14101 and Q14102
Get the schematics and look, they are transistors, I don't think they are the same......
Be advised tho, those are in the high voltage side of the power supply, something on the low side made them go, so check that out before you replace anything on the high side and power back on.....otherwise they'll probably blow right back out.....


http://www.aros.net/~blaknite/roms/RCA/420_440_480/drd420.pdf
12-12-2003, 01:12 PM
12-12-2003, 07:07 PM
Rampage
12-12-2003, 08:12 PM
Gannon...
Q14101 - MPS8599 PNP Transistor.
Q14102 - MPSA06 or MPSA05 NPN Transistor(You can also use a 2N4401 for this one)

-Rampage
12-13-2003, 01:53 AM
skinerd
12-13-2003, 02:09 AM
Almost any of the diodes in the secondary section can short and cause an overload in the primary section......check them all
Rampage
12-13-2003, 03:20 AM
R14110 - 22 Ohm, 1/2W 5% Metal Film (flame resistant)
R14112 - 1K Ohm, 1/4W 5% Metal Film (flame resistant)
Q14100 - ST STP4NB50FP N-Channel Enhancement Power Mosfet.

I would start looking at Q14100. Component failure will send 150-160 volts to an area that uses 5 volts and will take out multiple components. This, as you have seen.... will do some nasty damage. Obtain the correct replacement part for Q14100 and NOT a substitute.

-Rampage
Killer-D
12-13-2003, 07:29 AM
I agree with Rampage 100%. Q14100 is the place to start for the exact reason he said. You should be able to test the part by taking it out and measuring it with a meter. You should NOT have continuity between the gate (G) and other pins. If so, that part is bad.

Once that part is working I would replace any resistors that look burnt. Also I would check ALL diodes and transistors with a meter to make sure none of them are hosed. Its important to check them all, if there is any doubt replace them.

If your able, I would also try to take out T14100 and connect it so that only the primary side is connecting to the board. This isolates any problems on the secondary side as the cause of failure. If things still blow, its in the primary side. Also while you have T14100 out you could measure the resistance on the secondary side where each of the ouputs of the transformer connect to. Anything less then say 10??? ohms would be bad. Not sure what it is normally.

Remember you are working with HIGH voltages on the primary side, handle with care.
12-13-2003, 02:04 PM
12-13-2003, 02:58 PM
Rampage
12-13-2003, 05:31 PM
Components Located on the Low Voltage Side of the Switcher.


U14103 - LM7905 - 5 volt 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 - 24V 500mw. This is a surface mount zener diode. It can be found either next to the LNB tuner circuit area, or inside of it.


Components Located on the High Voltage Side of the Switcher.


F14100 - 3 Amp 250V Axial Lead fuse.
R14102 - 3.3 Ohm, 1W 5% Metal film (flame resistant)
R14113 - 100 Ohm, 1/4W 5% Metal film (flame resistant)
R14110 - 22 Ohm, 1/2W 5% Metal film (flame resistant)
R14112 - 1K Ohm, 1/4W 5% Metal film (flame resistant)
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 surface mount diode.
12-18-2003, 12:42 AM
skinerd
12-18-2003, 02:27 AM
the metal film FR resistors are flame resistant, that will prevent a fire shoud they blow, which is not uncommon, seems like RCA went to great lengths to protect the fuse that is supposed to blow when a short occurs, I have yet to see a blown fuse in sevaral that I have seen with blown resistors and other components....