Resistor unknown

[DjKrish]

Guys, im confused about this resistor. Its fully burned. I cant check the colors as well. When i checked service manual, this is what i see

I check with parts vendor, even they dont know what value is this

[eccerr0r]

Re: Resistor unknown

post more of the schematic and the fried resistor, maybe someone can deduce the value from context and what it looks like now.

[budm]

Re: Resistor unknown

post more of the schematic and the fried resistor, maybe someone can deduce the value from context and what it looks like now.

+10

Also pictures of the board.

[DjKrish]

Re: Resistor unknown

Guys, heres the schematic diagram for HTS-3366 Phillips. The resistor part number is

[eccerr0r]

Re: Resistor unknown

First guess would be 15Ω (brown, green, black, gold?), which does seem to correlate with the resistor having few spirals. Depending on the tuning of the SMPS, it may dissipate more than the ¼W that the resistor looks like it was rated for...

[DjKrish]

Re: Resistor unknown

First guess would be 15Ω (brown, green, black, gold?), which does seem to correlate with the resistor having few spirals. Depending on the tuning of the SMPS, it may dissipate more than the ¼W that the resistor looks like it was rated for...

Yes it has 2 spirals. 2 spirals usually is 10 ohms? I can see the resistor legs goes to pin 12V

[Piotr07]

Re: Resistor unknown

It is 15Ohm 1/2W

[DjKrish]

Re: Resistor unknown

It is 15Ohm 1/2W

100% confirm bro? I dont wanna end up frying things there

[CapLeaker]

Re: Resistor unknown

When I look at that schematic, the value of the resistor has to be low, but it isn't that critical, as the blown resistor is used as a fuse. I guess the zener diode may have shortened, causing the resistor to blow. 15 Ohm sounds about right to me.

[DjKrish]

Re: Resistor unknown

Ok the thing is, the resistor burned, 2 caps shorted as per my checking using MM. All the voltage seems to be way higher than rated. The set is working but i dont wanna blow out the main board with excessive voltage by a faulty psu. I can see the display vfd is going at peak being over bright

So now ive replaced the caps and the IC, now need to figure out this resistor.

[budm]

Re: Resistor unknown

Ok the thing is, the resistor burned, 2 caps shorted as per my checking using MM. All the voltage seems to be way higher than rated. The set is working but i dont wanna blow out the main board with excessive voltage by a faulty psu. I can see the display vfd is going at peak being over bright

So now ive replaced the caps and the IC, now need to figure out this resistor.

How much higher Voltage? It has 12V zener on one side of the resistor so it should be within 12V on the Zener side.
What do you get on the 12V line feeding the resistor?

[eccerr0r]

Re: Resistor unknown

The voltage on the other side of the resistor can't be higher than 16V, and with good engineering practice wouldn't be much above 12V, even. I suspect that the zener was used for transient protection more than regulation.

Either way yes, a ¼W 15Ω maybe in the danger zone -- I only guessed this because of the physical appearance of the resistor with no ruler reference. A ½W resistor is probably safe for most uses, and a 1W resistor will give you enough leeway for other things to burn first before the resistor burns again, that is, if the zener or other downstream devices don't short out...

[momaka]

Re: Resistor unknown

What do you get on the 12V line feeding the resistor?

+1

Unless the IC in that schematic you posted is bad (or something is shorting its output) or the 12V line feeding the resistor is high (runaway power supply?), that resistor should not burn out like it does.

Also, as eccerr0r suggested, you may want to go with a 1/2 Watt or 1 Watt resistor.

Regarding the value... does the resistor show any resistance on your multimeter? Sometimes, resistors can get pretty cooked buy still read in spec. That's because most (quality) resistor can usually handle twice to 4 times their full rated power before burning out.

[petehall347]

Re: Resistor unknown

its a fuse .

[R_J]

Re: Resistor unknown

It's a 15Ω 1/4 watt resistor, you can use 1/2 watt, Philips schematics have always been strange.

[DjKrish]

Re: Resistor unknown

It's a 15Ω 1/4 watt resistor, you can use 1/2 watt, Philips schematics have always been strange.

Tell me about it , phillips service manual and their designs always been weird

[DjKrish]

Re: Resistor unknown

+1

Unless the IC in that schematic you posted is bad (or something is shorting its output) or the 12V line feeding the resistor is high (runaway power supply?), that resistor should not burn out like it does.

Also, as eccerr0r suggested, you may want to go with a 1/2 Watt or 1 Watt resistor.

Regarding the value... does the resistor show any resistance on your multimeter? Sometimes, resistors can get pretty cooked buy still read in spec. That's because most (quality) resistor can usually handle twice to 4 times their full rated power before burning out.

I suspect, 2 caps were shot, so that burned out the resistor due to high voltage. The resistor has no reading at all

[momaka]

Re: Resistor unknown

It's a 15Ω 1/4 watt resistor, you can use 1/2 watt, Philips schematics have always been strange.

Thanks for posting that info! Really interesting how they coded the specs on their schematics.
Learned something new today

I suspect, 2 caps were shot, so that burned out the resistor due to high voltage.

Yes, quite possible, especially if those caps were filtering that 12V rail.

I see it all the time with 2-transistor self-oscillating power supplies. O/P caps go bad and output goes wild.

[DjKrish]

Re: Resistor unknown

Ok manage to replace the 12v diode and resistor, so far nothing burned. Next i will measure the voltages.

I need to know, in the service manual it says KA7500C IC but on the board the IC is AZ7500BP-E1. I know its both 7500 but the letters seems diff. Any idea of they are the same?

[DjKrish]

Re: Resistor unknown

Ok managed to measure all the voltages after replacing the IC, resistor, capacitors and 12v zener diode.

12v - measures ranging 12.40v to 13v max
5v - 5.19v and down
-27v - -29v and below

standby 5v stands at 4.89v