Most of our service manuals will include disassembly instructions, schematic diagrams, parts lists, exploded views, troubleshooting, wiring diagrams and much, much more. Service Manual, Paper Manual. Related products. You will need a free Hifi Manuals account to be able to download our manuals for free.
Please use the form below to log in, or click the 'sign-up' tab to create a new account. We are glad to see you are using our service again. Please let us know if you have any questions or comment on how we run Hifi-Manuals. Below you will find the XRDS. The schematic is a technical drawing or diagram of your system, a perfect supplement to the Service Manual. The photo that you posted shows this board on the top with the shiny solder side facing up. If you look at the drawing and then the board, you should be able use the drawing as a road map to identify the real items on the board.
The board contains the power supply and output transistors for both of the channels. The two sides are more or less mirror imaged from the center out. Because the drawing is shown from the component side, you will have to mentally flop the image or use your computer to flop the image for you. Some people find it helpful to print out the drawing like a real map. The power supply diodes are located at either end of the board. They are mounted on end, in between the two large filter capacitors.
If you look at the drawing, there are schematic diode symbols printed to show the polarity or how the diodes should be mounted in the board. To test the diodes, turn off and unplug the amp. Let it sit for a few minutes to allow the filter caps to discharge. Set your meter to the diode test position or a low ohm range. Place one meter lead on each end of the diode and see what reading you get.
Now reverse the two leads and see what reading you get. A good diode will conduct in one direction only, so with the leads connected in one way you should get a low reading and with the leads reversed you should get a high reading. Because the diodes are connected to the filter caps, the low reading will be fairly immediate, let's say 0.
When you reverse the leads, if there is any charge on the filter cap that the diode is connected to, the meter may take a while to react. Hold the leads on the diode for a few seconds and see if the reading starts to rise. If the diode reads low in both directions then it may be shorted and then you will need to remove it from the board for a final test.
Or at least unsolder one lead from the board to isolate the diode from the circuit. Test all 4 diodes on the side that is blowing fuses. Edit: I see you already figured it out, so never mind.
I will leave the post here for future readers that may need the assistance. In regards to purchasing transistors. Any better sources? I also wonder if it is ok to just replace the two or is there any need to replace all six of them for matching purposes. The Then again, maybe not. In a perfect world, the other transistors may have taken a 'hit'. Under a microscope, it may be apparent.
Which is a destructive test. There is not really any 'on the bench' test that will prove that they will work. Short of testing them in circuit Most times the remaining good transistors will be fine.
There is no need to match them. That is what the ballast resistors do.
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