I recently got this power amp from a friend. He told me a few resistors were burned out on the board, saying that the Channel 1 is not working, because if the problem. The following resistors are burned out: R218; R223; R224; R247 and R254. Any information on how to solve the problem would be much appreciated

You could be right the right channel audio amp but in my experience I have encouter that speakers do that too before they burn. To find that particular part just try the manufactor website & inquire a Q? now, you may find a web search engine that may take u to electronics surplus sites that may have what you looking for

Use the power of the internet my friend!!

Repaired a PMP5000. Several transistors, a chip, diodes and resistors all destroyed by arc-over in power amp area. Faillure burned the board and had to cut the cancer out and jumper around blown circuit traces. Lot of work and takes great care to restart to avoid blowing components due to bad ones that repair missed.

Resistors can fail from being turned up to hire, wires getting bumped together or against metal, speakers being wrong ohms, or just plainly overheating.

When replacing output transistors on amplifiers it is generally a good practice to replace the output capacitors as well as the biasing resistors. Just because one transistor is bad does not mean that that is the whole problem. Look for what caused the problem. Bad speakers,bad wires,defective traces on circuit board,poor soldering. Also when mounting the transistor make sure it is insulated and grease it with a dab of silicone heat sink compound. Whenever I service a board I examine all components for tolerance as well. A resistor marked at 1% tolerance,example 1k ohm + or - 1% should read no less than 990 ohms and no more than 1010 ohms. Anything else your asking for trouble. Another point is that some amplifiers use matching pairs. Pairs complement each other in an output stage and must be replaced in pairs. I repaired a Sansui Amplifier a while back and it looked as if a power output resistor was burned. Comparing the two channels I figured the matching value from the other side and replaced all of them and the system has worked flawlessly for years now. I am a retired electrical engineer and have worked in a few areas of electronics for over 35 years. Hope this information helps you.   

Check out the Bias resistors in the that channel then compare with the right. You might need an Ohm meter to do it, but the resistor(s) could look burned.

R403 would usually denote a resistor and not a capacitor.

Capacitors do fail but usually don't burn out in such a way but resistors do, usually because something has happened elsewhere in the circuit that overloads the resistance. I have never seen a burned capacitor but I have seen resistors glowing with heat and some white hot until they virtually evaporate blackening nearby components.

I suggest you take another closer look at the circuit board...

First, check which type of protect first.

Symptoms:
3 seconds (DC protect) OR immediately shut down (Over Current protect)

How to confirm?
1.Unplug the amp.
2.Remove the metal cover.
3.You will see a long vertically installed pre-amp board mounted next to those large power transistors fixed by 12 screws on a large aluminium heat sink.
4.Remove this long vertically installed board mounted by 2 screws.
5.With 2 screws removed, just pulling this board out and hold it with one hand.
6.Plug the amp and switch it on.
7.If your amp stays ON forever, the problem is from this long board.
8.If switch off at once, the problem is from power amp board.
Try the above- mentioned steps. If DC protect, write an email to me via searching you tube SR600 capacitor replacement. Don't be afraid.
So many people wrote to me.

If over-current protect do the
following steps
(O)unplug the amp.
(1)download DS-TX494 service manual.
(2)open the amp metal cover.
(3)measure 7 large white resistors resistance loacated next to power transistors mounted on a large heat sink with black probe touching the middle pin and red probe to first/left or third/right pin.
(4)If this 3 Pins large white colour 0.22ohm x 2 resistor is open with infinity ohms ,
(5)replace it and jot down this channel for example left surround faulty. Usually only 1 channel went faulty.
(5a)When the white resistor didn't burn, "2 channels" were damaged due to bad soldering joint of the large white resistor, however.
(5b)When this happened, time taken of shut-down due to over-current is 3 seconds NOT immediately.
(6)the two large power transistors next to this white resistor 0.22 ohms x2 should also be replaced.
(7)plug the amp
(8)switch it on
(9)if ok, troubleshooting get done
(10)if not ok
(11)replace ALL the components of this power amp channel.
(12)pre-amp section no need to check.
remember if not OK, the replaced 0.22ohm x 2 resistor and 2 power transistors maybe shorted again. Check them first. If OK, replace ALL Components in this channel except 0.22 ohm x 2 and 2 transistors. 0.22 ohm x 2 means left and middle pin 0.22 ohm as well as right and middle pin also 0.22 ohm that are 2 pieces of resistors with 0.22 ohm in a large white 3 pins resistor.
Remember sometimes the
0.22 ohm white resistor is normal. If so, use a digital multimeter to measure the be bias transistor voltage via multimeter diode test function. You can compare the normal value,580mV to 650mV with faulty one,3.2mV. And the CE resistance is 1.8ohms only instead of 3 Mega ohms.

I realize that this is an old problem, but folks are still finding it on searches, so here goes.

Here are the two pages of schematics from KLH. I wrote to their tech department and explicitly asked for permission to share them here.

Here's the lower board, which has the power supply:
KLH ASW 10-120 subwoofer schematic - lower board


Here's the upper board:

KLH ASW 10-120 subwoofer schematic - upper board

If the amp is not going into protect, the power supply FETs have probably failed. In the corner of the amp near the toriodal transformer, there are 4 FETs against the heatsink. When these fail, the 47 ohm resistors at the base of the transistors often fail. If the resistors are dark, it generally means the FETs have failed. If you disconnect the amp from power and measure the resistance from leg 1 to leg 2 of the power supply FETs, a reading of near 0 ohms indicates the FETs have failed.

This problem can be solved by either of the following:
1/ Modify the PCBA to prevent the auto shut off feature from working. This is done by adding a 20k ohm resistor across pins 1 & 2 on the timer IC6. This resistor will prevent the timer from turning off the amp. To do this, unplug the amp. Remove the 8 screws on the perimeter of the rear of the amp. Carefully remove the rear plate. Disconnect the speaker wires at the speaker and the front panel connection on the main board. Locate IC6 on the bottom of the main board. Solder a 20k ohm resistor (1/4W) across pins 1 & 2. Pin 1 and Pin 8 are noted on the board. Be sure to insulate the leads of the resistor to prevent contact with the board. See picture. Re-assemble in reverse order.
2/ Some 5.1 channel amps allow independent control of the volume for the subwoofer in their setup. Check your amp to see if you can raise the signal level going to the subwoofer to prevent the amp from shutting off. You can then dial back the volume of the subwoofer using the volume control on the front.