My adcom gfa5500 .most of its output mosfets are shorted.
I m able to get the output mosfets. BUT,when i check other components,i found out the value of R 23 of the left channel is different from the rigt one.since i dont have the schematic.i neeeeed help!!!!
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Re: my adcom gfa5500 .most of its output mosfets are...
The colour code or the value it states on R23 should give you the reading you will see on a test meter on the Ohm setting. If the value doesn't match the colour code of the resistor then you should replace it. It's best to take any resistor out of the circuit to test as strange readings can be caused in circuit. The same applies to the left channel one. Ohm meters are not expensive if you don't have one and can be got from various places that sell electronics parts etc. Some car part dealers sell them. They are a worthwhile investment and can be used for many types of problem.
It's likely that it's a basis resistor and failed when the power jobs went.
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Check all the other component on board, associated with this MOSFET cirlcuit. Especially shorted zener diode, capacitor/s etc: Never replace an other FET, without check all the related component. It too will fail. Check and replace damaged component/s at its horizontal scan output section circuit. Check the LOT (Line Output Transformer) too for damage. Replace the horizontal scan output transistor. Check the input voltage to LOT. If the voltage is absent check the feeder resistor; if any. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. http://electronicshelponline.blogspot.com/
Type in this key phrase " my service table today " in the search box at the top right of the display window of the home page, to get gathered some pages which has the details of practical experiences to the author of that site.
The printer has the step down SMPS which supply the low voltage (generally 24V DC to the other component. It contains high voltage risk also the high frequency. Sound knowledge is required while repairing the SMPS also appropriate precaution. If somebody is present having electrical knowledge during repair is better.
First disconnect the electricity supply cable from the printer
open the smps, check visually for any physical abnormality of individual component, then check the fuse for open,if its open check the MOV,mosfet,capacitor,bridge/zener diodes for short if found replace with same value,
take a series lamp of 15W incandescent bulb, connect the smps, check the voltage at secondary output. utmost care should be taken with attention of co-worker while checking live circuit.
If there is no voltage, check primary component at area of PWM IC /replace PWM ic (smd).
Again FATAL ELECTRICAL SHOCK AND FIRE MAY HAPPEN IF CARE NOT TAKEN.
Did you checked balanced impedance?load speaker impedance vs PA output?or PA might over driven,causing a trouble on the pre-amp to power amp circuits and components damage,
need to recheck related components on the pre-driver up to main output section,
Note: That,blowing of fuses with the same rating is an indication of trouble/shorted in a circuits that driven on it,
That could be a problem on secondary side. Shorted rectifier diode.
Please do check start up resistor of uc3843, I think its on pin 7 with 110Kohms or 56Kohms value for 220VAC or 110VAC supply input respectively. Open or change value, it is a fusible resistor. If open do check other components for defects. Don't substitute a common resistor on this one. Datasheet could help you alot.
A word of warning, the voltage may bite and enough to kill. So take necessary precaution, if in doubt let the tech handle it. Or buy a new one.
That Mosfet is probably porprietory from Sports Art , But I would check the bridge rectifier I've had quite a few short out and make it appear that the Mosfet is shorted. Any of the Parts houses would carry that component.
Well it seems to me that the pictures of this amp show green ATC fuses which would be 30 amp fuses. What is your inline fuse from the battery? 40 amp fuses for the amp is too much current for the amps powersupply. If there was a short in the powersupply the max ammount of current that it could draw would be larger than designed to handle therefore damaging the amp.
The driver circuits should be just before the outputs in the circuitry. The easiest way to check this circuit is to remove the outputs and turn on the unit. Measure each of the transistor pads relativce to ground for DC voltage. You should see the following: B+,0.6V (or 1.1V), and 0V on one transistor and negative values on its compliment. If you have questions, measure the pads and post the measurements here. In some cases the output transistor needs to be in place to get the values above, so if yours don't measure that way, just post what you get and we'll continue from there.
I have had this problem in the Field with a Client.
I had fixed it by going into the ADCOM menu and Resetting ALL of the Inputs and output for the Devices.
You have to select everything you need, then exit out of the Menu, SHUT OFF the ADCOM, WAIT about 10 secs, then turn it back on.
Or Else it Does Not SAVE Properly! Weird.
If you can not see the Menu on the TV Screen then try to hook up a Composite (Yellow) cable from the ADCOM to the TV and select the TV input to make the Changes.
I really hope this helps out it sounds like an Evasive problem which is hard not being in front of the Equipment!
Remove the output transistors and measure each of the sets of 3 pads and report the voltage readings here. I suspect that you have either a blown driver circuit or output transistors. The voltage readings will give me an idea on where to start looking for specifics.