Notes on the Troubleshooting and Repair of Audio Equipment and Other Miscellaneous Stuff. Back to Audio and Misc Repair FAQ Table of Contents. Note troubleshooting of large audio amplifiers constructed with discrete. See. BIG Audio Power. The audio amplifiers found in small radios, Walkmen, portable cassette. Obtain a pin diagram, test inputs and outputs with. A dead output where inputs. Hairline Crack In Back Tooth Decay' title='Hairline Crack In Back Tooth Decay' />Question id 1827 I am a female 63 yo OAP, living in Scotland, and am NHS patient. Last week I had my lower left front tooth extracted, and a new replacement one. A page for describing Characters Monster High. This is the main page, or the page for characters not introduced in specials. For the ones that were, click. COMPLETE BANK OF TERMS USED BY NIGEL WISEMAN ALL YELLOW ITEMS ARE NOT FOUND IN OTHER TERM LISTS twelve impediments all all blood pain. Images/Patients/Treatments_and_Procedures/cracked-tooth-1.jpg?n=4264' alt='Hairline Crack In Back Tooth Decay' title='Hairline Crack In Back Tooth Decay' />Question id 1897 My lower left premolar has broken so that now the back and part of the side are missing. Ive been advised that I can should get root canal, a. IC as does one that. Larger audio amplifiers may use ICs up to 1. W or hybrid modules. W per channel and beyond. Purists may argue about the quality. Hybrids modules called blocks or bricks by some may be totally self. Failure of these bricks is quite common. Note that testing of these op amp designs whether discrete or brick. Intermediate signals in a working channel may look like power supply. Hairline Crack In Back Tooth Decay' title='Hairline Crack In Back Tooth Decay' />In a dead channel these same points may appear to be. In. addition, since extensive negative feedback is used, power supply ripple. One of the bricks may be shorted resulting in a blown fuse or overheating. It is usually safe to unsolder each of the hybrids. With stereo amplifiers, it is normally safe and most effective to. This is by far the. I would be a lot more reluctant. There can be all sorts of sources for low level noise or static including bad. These are usually hybrid circuits multiple devices mounted on a. Think. of them as entire subsystems encased in plastic. Thus, hybrid bricks may have problems with noise especially considering that. Thermal cycling can take its toll on this kind of device. If you have eliminated other likely causes, replacing the brick would be the. Of course, if there are separate bricks for each channel. This will be relatively low. A hot air gun used carefully on the final modules might. From Andy Cuffe baltimorapsu. If it has ICs for the audio output you can just remove one of them. If. the fuse still blows try removing the other one. If the fuse blows with. ICs out you know there are problems in an other part of the. If it uses transistors instead of ICs you just need to check them with. The bad ones almost always measure close to 0 ohms. Once you find the bad pair try. You should get normal sound from the. To determine if there is more damage. Before you remove anything WRITE DOWN where they go because. I strongly recommend that you dont. I have seen. a lot of repairable electronics ruined by this type of troubleshooting. From Dakuhajda dakuhajdaaol. Where one channel still works, on old amplifiers we commonly remove output. Then bring the power. With a. working channel it should be a simple matter of making DC measurements to find. From Wild Bill kwag. A lot of the diagnosis can be accomplished with a DMM. Either the diode check. Most of these. comments are related to units with through hole components with leads circuit. If you dont possess the skills, equipment and safe working habits required to. If. you read the rest, youll discover and maybe understand why technicians. For almost any bipolar transistor output type amplifier testing, its a. A good starting place is checking key components for. Bias resistors for open infinite ohms. Transistors for shorts with the diode test. Ohms checks for the power transformer, standby transformer windings, and. Diode check for rectifiers, full wave bridge rectifiers and transistors. Capacitor testing should also be part of the diagnosis stage, particularly. Make notes of defective components, you can offer some help to someone else. Before proceeding to the stage of disassembly, check for circuit board. When these get loose, this can cause a lot of weird symptoms. Its often necessary to start unsoldering parts since a 0. In most cases. where there is no output, or the protection circuits are preventing the amp. Since the unit isnt. This method is. also more economical since parts wont be repeatedly destroyed until. Many manufacturers utilize fusible andor flameproof small wattage resistors. They might. be blue, green or tan colored. When damaged output transistors are discovered, check the driver stage for. Some driver stages use linear ICs. After a thorough check of key components, and faulty devices have been. The lamp will. usually prevent destruction of components. Instead of attaching speakers to the outputs main or front L R, use dummy. The unit. should be powered with an isolated variac. VAC will probably be a good. You could also have an. If the lamp shows continuous light output at this low variac. In that. case, disconnect everything and resume ohmmeter tests. Check for components. If a dim glow is visible, dont rush to put a fuse in and attach speakers to. AC. transformer outputs and DC voltage checks full wave bridge rectifiers, plus. Check the individual supplies DC. AC at all of the amps outputs with a. If all appears to be normal at reduced line volts, turn the unit off and. If dummy loads havent been attached to the output terminals yet, turn. With the volume control set low, there should be little heat. For amps with rear and center channels, check the main channel L and R first. This seems like a lot of backing up and rechecking, but it is an economical. Before connecting a. The situation is that after finding and replacing output transistors and. From Mike Ross mike. Before you blow up any more parts insert some temporary current limiting. W is okay in series with each individual. If the transistors saturate then there. Blown diodes and resistors in the bias voltage reference circuit could. One common design problem is. Of course they should always be. This could be one cause. Good luck. If all else fails, hurl it across the room a few times From Dave gravmanidirect. Where one channel blows outputs, check the zobel network components. This is. a capacitor usually green mylar with values of. F connected in. series with a low ohm resistor 2. BETWEEN the speaker line and. I have seen a few amps with the same symptom and the cause was. OPEN Cranking up the treble full at very high volume. Even a nearby CB or HAM transmitter with lots. When that cap goes open circuit, the amp will oscillate at a high frequency. Ive scoped as high as 8. KHZ If those two components are OK, and you have definitely confirmed that all. OK, leave the output transistors out, install a 1. W speaker. load resistor and power up the amp with a DC voltmeter in place. You. should measure much less than. DC across that dummy load. If. the voltage is more, youve got a improperly installed transistor, bad bias. Check, double check, and re check your components. If the voltage is within proper range, connect a scope across the dummy load. If you see a extremely. F. value compensation capacitors in other parts of the circuit. You may have to. pull each one and checkreplace until you find the culprit. You may simply. have a leakyflaky transistor in there somewhere. You may also have a. Do these tests, and see what you find. ALWAYS CHECK YOUR OWN WORK THREE TIMES. BEFORE CURSING From Jerry Greenberg jerryg. The first step is to verify the voltages in the power supply for both the. Cessna Activity Center Wichita Ks Events Today. I would also start by changing the main filter caps in the power supply to. This is the only true way to test these. The best way to test for such a problem is to feed an audio generator into the. Use a scope and go through. Set the audio generator to a 4. Hz tone. The test for the output stage is to turn up the volume with the scope across. See and measure the amplitude of the waveform to. P P output. You should see where it is starting to. From that calculate the.