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Hello I have a polaroid power supply that blows fuses here is the schematic The power correction fet Q1 is shorted and the zener. An ohm meter check finds no shorts in the immediate area. I am about to replace the fet and zener. Next?/ http://cabaret-karaoke.com/pol/Root_1.PDF Now you owe me one. None of the caps are poofed. What should I check ?

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Things to check for: Inductors ? These are really just coils of wire, sometimes wound around a metallic or ferrite core. These can take on a number of appearances such as a donut shape, a small cylinder with axial leads, or numerous other packages. Typically, you will find markings on the printed circuit board such as L1, L2, etc. where these components are mounted. For some photos of inductors, please check out: http://zeus.cedcc.psu.edu/, and click on Inductors. Inductors block higher frequency alternating currents while allowing DC to pass through unobstructed. Diodes ? These devices are usually long cylinders with leads sticking out of both ends axially. Usually, they are painted black and have a silver or white stripe on one end. Normally, there will be additional markings on the printed circuit board that identify these parts using symbols such as D1, D2, etc. Diodes allow current to pass in only one direction. You are most concerned about the diodes that will be used to rectify AC current into DC current. Transformer ? you will only be concerned with the power transformer that steps down the AC house current to a lower voltage. This component should look very much like the drawing on this page: http://zeus.cedcc.psu.edu/ind/ind.html. It should have an iron core and coils of wire wrapped around the core. The coils will have some kind of insulator coating around them. check all the above properly keepupdated,thanks. please do rate this solution positively.

Posted on Jun 18, 2009

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1 Answer

Polaroid 860-AZ0-GF371H Power Supply Unit. After replaceing all bad caps and and shorted fets Q102,103 I still need to know the value of smd zener ZK2 in Parallel with 3 low value smd resistors. I think...


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+48 volt in power supply is not working. All other voltages are present


Download the schematic at:

http://elektrotanya.com/mackie_1604-vlz_mixer.pdf/download.html

Scroll down to the link to download that says "Get Manual"

This is for the 1604 unit which is just a truncated version of yours. When downloaded, find the phantom power supply on page 18.

There are too many components to guess which one so best just to troubleshoot.

I would even suspect the phantom switch since they have POOR design with no inrush current limiting when charging the input capacitor. Since the 48 is not individually fused, if the inpout cap C3 shorts, it probably will take out the switch or the diodes.

Another user had the Zener D9 fail which would cause the problem. Meter the voltage across C3 (probably about 60 volts) and D9 and C4 (47 volts). First check C4 as that cap is run TOO close to the rating of 50 volts... poor design... C5 would also be suspect... or Q1 and Q2.

Then it gets dicey as there are UNDOUBTEDLY many bypass caps in the mixer portion of the board.

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Hello

There is some short circuit in the power retulator side of your TV. Never put a fuse and switch it ON, as it may damage more components in your system. A power voltage surge can damage the regulator side of your TV. There is a short [Direct short] occured inside it. Check the rectifier section first, with the help of a multimeter set to Ohms range. Measure the resistance accross the main filtler capacitor. if it seems to be very low, say less than 12 Ohms or so, resolder out the mains rectifier stalk, or diodes, whichever may used, and chck it for juction short. If shorted, replace it. Check out the switching regulator also. In most cases this regulator may get damaged due to power supply spikes. In some sets, there is a MOV [Metal oxide veristor], connected accross the main AC line, after the switching point. this component is used as a protection, and if there comes any overvoltage or voltage spikes, this veristor will get shorted, blowing off the fuse, and further damage is prevented. Check this also. This component will look like a disc capacitor, normally black or green in color. Check these, and further check most of the power regulator components, such as Zener diodes for short. Before switch on your TV. make sure you have tested all the componets in the power regulator side. OK.

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Hello,
All you need to do is to open the back cover of the television to check for dry soldering and bulged capacitor, if found replace with appropriate parts.
You need to check the output voltages of the power supply to see which one goes off. It may be due to short circuits some where.

Good luck in solving the problem.....

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1 Answer

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1 Answer

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Replace Q2 by 18N50, Q8 and Q9 by STP6NK60 and Z2 and Z4 by !n4739. I have the same problem and fix it.

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If the voltage is OK, the amp will likely need to be repaired. If that's the case, do you want to repair it yourself? This amp may not be easy to repair. If you are not interested in learning to do this type of work, you should pay to have it repaired. If you want to repair it yourself, I'll try to help you through it.

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1 Answer

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