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Philips DFR-9000 blowing fuses

Hi im having a problem with my Philips Dfr-9000 blowing fuses, it clicks once then blows the fuses on the second click ( talking about relays turning on ) im not a big electronics guy and would love if anyone is able to help me either by locating where the problem is or finding the part i need to replace. the device is not grounded which is in my head the reason why it blows the fuse

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1 Answer

Chosen Solution

Hi,

When you say “fuses” is there more than one fuse blowing?

If it is only the one fuse, which one? The fuse on the Standby Power Supply board or the one on the Power Supply board.

Are you replacing it (or them) with the correct type of fuse i.e. a slow blow fuse? The designated value for both is T3 15A 250V.

A standard fuse may not be able to handle the current inrush surge when the device is first switched on, that is why a slow blow fuse is stipulated.

Not certain but the click once and then the second click may mean that the first click is when the Standby Power Board relay operates to connect the mains power to the Power Board and the second click is the protection relay operating to protect the receiver.

Have you checked that there are no short circuits between the wires going to the speakers, at the receiver end as well as the speaker end?

Here’s a link to the service manual.

It has full schematic diagrams which are a great help in finding the problem.

Fuses blow because the current flowing through them exceeds their current rating.

The receiver doesn’t have (or need to have) a chassis “earth” connection tied to the main household power supply earth. This is to prevent a “hum” being heard in the speakers due to a possible difference in voltage potential between the two.

Update (03/27/2019)

Hi,

If it blows in standby then the problem most likely is in the Standby power board as the relay doesn’t switch the active wire through to the power board until you turn on the receiver, unless the relay contacts have fused together

here’s the circuit to the Standby Power board

Block Image

(click on image to enlarge for better viewing)

The red box is the relay that switches the power through to the Power board, when the On button is pressed

The green box just shows the connections to the Power board and the black arrow is the 5V standby power into the Power board

The orange circles are just there just to show you the “symbol” for the earth connection in the circuit.

The green arrow is where you should start testing from using an Ohmmeter - totally disconnect the power from the receiver when using an Ohmmeter.

The purple arrow indicates the current path for the supply when in the Standby mode to produce the 5V standby power.

You need to put the Ohmmeter between the green arrow point and earth (the chassis metal should be earthed) and check the resistance.

Before you start testing, after removing the power from the receiver, operate or hold the On button for about 30 seconds to dissipate any residual power left in any capacitors, just to prevent any “sparks” or nasty “bites” if you accidentally touch something ;-)

Given that the current flows through either a 2M Ohm (2 million Ohms) (left purple arrow path) or a 10 M Ohm resistor (right purple arrow path) before it gets anywhere near an earth there should be at least a reading of 1.66M Ohms approx on the meter.

To blow the fuse the Ohmmeter reading should be a lot less than this.

If you do get a low reading you may have to start disconnecting components from the board until the low resistance reading disappears. Unplug the Power board and check if the reading is still there on the Standby power board

Apologies if you know how to read a circuit.

It’s a bit hard to explain to someone else what to do when trying to find a fault at component level in a circuit. I’m just writing down how I’d go about.

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Comments:

Hi, sorry if I was confusing but it blows the fused on the standby psu board, and I tried replacing the fuse with a t 3.15a 250v slow blow fuse same as the one that I found in the amp originally.

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It also blows the fuse without anything connected, no speakers no audio-video signal cables. The power indicator led turn red for a sec or 2 then it blows the fuse and trips the upstairs breaker, the amp isn't grounded which I can't understand but from what I can see it's never been grounded from the factory

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Hi,

Does it blow when in standby mode (power just connected to receiver) or when you go to turn it on?

Do you have a DMM (digital multimeter) and know how to use it? ;-)

See the end of my answer regarding earth connection

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I blows in standby mode, and yes I have a multimeter and I know how to use it. What happened when it originally blew was I was watching a show on Netflix and I heard a hum from the amp then boom, blown internal fuse and tripped house fuse

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Okay, sorry for late respons but after measuring between green arrow and +5V3_ever i get no reading, after measuring the left path i get a reading of 1.7M Ω and after measuring the right path i get 0 before the resistor and nothing after it. so heres the dumb question could it be that resistor messing it up?

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