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spooney 21st February 2010 07:15 PM

Fisher AD-864/ AD-813 service manual
If anyone has a service manual for either the Fisher AD-864 or the Fisher AD-813 I would love to see it. Trying to get my fathers cd player back up and running for him. Just quit on him one day. No power or anything. There doesn't look to be any fuses inside to speak of and the power does appear to be making it past the switch into the transformer and onto the main circuit board. I'm having some trouble tracing it from there and I have very little knowledge of what makes a home audio cd player work. I'm more of a car amp guy myself.

gain wire 23rd February 2010 01:56 AM

Well, I don't have a service manual for that, actually I am looking for a couple of manuals myself. Anyway, without the manual I think I could help you get it working again. Depending on the age of this model ( I am guessing mid-eighties by a picture I saw on ebay) I would guess it has a fuse that looks like a resistor, it's probably gray, and it would be located on a pc board next to the transformer possibly on the same pcb that has the power switch. You need to backtrack to the last known point where you get AC voltage.
There is a possibility that there was a power spike and it might have killed the primary transformer winding, although that would be quite surprising, but not impossible.

Anyhow, that's it until you can provide us (OK, me) with some pictures of the inside! Come on gimme 'dem pictures! Women, or electronic innards, your choice...:D

spooney 24th February 2010 02:19 AM

It is a mid eighties model, 1986 to be exact. There is defintely ac voltage present on the primary and secondary side of the transformer. Primary is obviously 115-120 volts and if I remember correctly there was 9 volts on the secondary although I will have to measure to reconfirm that. There is a small pc board next to the transformer that holds the power switch but it only has a capacitor along with it. The transformer stands alone between the power switch pcb and the main pcb. I did see one gray resistor on the main board with none of the typical color bands. I pulled it from the board to check it out . It read 471 on the side of it. I'm not sure if this is the part you are speaking of or if it is just a precision resistor as the ohm reading is very close to that 471 labeled on the part. Anyways enough of my rambling. I have a few pics of the unit although they are not the greatest. Please let me know if you need better pics/closeups of any particular area and thank you for your help.

spooney 24th February 2010 02:23 AM

I just thought I might add while poking around in this thing last night I did notice that there is a voltage regulator directly to the left of the two larger capacitors(also in the middle of the three small capacitors) towards the bottom of the main pcb pic that ran very hot. Could be nothing but I'm not sure if those typically run warm or not.

gain wire 24th February 2010 04:27 AM

Hi spooney

Those are terrific pics! Very clear, and the components pictured are what we need to see. It's good that you've discovered that the transformer is actually functional, so the problem lies either in the power supplies of the main board, or... somewhere deeper.
Anyway, see that circular bridge rectifier with the four green cermaic caps around it? well probe the voltage there to see what you get. I am guessing it will be around +20V to 24V. Which in turn, should get divided into +12V and -12V. Those two big TO-220 transistors with the heatsinks, those should be the Pass transistors or voltage regulators. Check the numbers to see what they are. That little one you were talking about is either a voltage regulator or a transistor. You can always check the emitters of all those transistors (if they are transistors) and see what voltage you come up with. With any luck, you'll see somethign really strange like 4V or 8V, something that is not a common number. That means a zener diode has gone bad or maybe even the transistors have gone bad.

So check the DC voltage on the bridge, on the transistors (well first discover exactly what they are), and then tell us what you get.

More pictures aren't necessary but feel free to tell us where exactly you probe the voltages.

good work

spooney 25th February 2010 05:03 AM

Got a chance to play around a bit. All voltages are dc and I used the secondary ground of the transformer as my reference. bridge rectifier is outputting +11.6 volts and -12.7 volts(why are they different?) if i measure across the positive and negative outputs of the rectifier I get 24.4 volts. the heatsink mounted transistors are a 2sd612k and a 2sb632k. The 2sd612k has +11.6 volts on its collector and nothing on either other leg. the 2sb632k has -12.7 volts on its collector,nothing on the emitter,and varying voltage from 1 to 1.6 volts on its base. the small voltage regulator is a 78L06. It has +11.6 volts on its input terminal and nothing on the output or common terminals. Thats all i have for right now and I am too tired to even imagine what any of this info means for the moment.

spooney 26th February 2010 08:01 PM

I'm just guessing but I think something connected to the 78L06 is causing at least part if not all of the issue. When the part is in the board I am reading a short between the common and output terminals of the 78L06. When it is out of the board there isn't any short across the same two terminals. Is the circuit designed so that there should be a short between those two legs(i'm guessing no). Is there possibly a cap or something across those two terminals that has shorted and is causing the cd player to not power up? This is also the same part that runs very hot although that could be typical of it for all I know.

spooney 26th February 2010 10:16 PM

Found it! There indeed was a shorted capacitor across the output and common terminal of the voltage regulator. I just happened to have a cap of the same value but a higher voltage on hand to throw in there and it turns on and plays cds fine. Now I just have to address some issues with the loading mechanism. Doesn't seem to want to stay open when you try to load a cd. It pops open and goes right back in. More investigation to come.

gain wire 27th February 2010 05:42 AM

Hi Spooney!

Sorry, I kind of left you hanging there! Evidently, you made very good progress, the hunch that you had about the short on the output of the regulator was correct... No load should give that kind of short.

Anyway, that tray that doesn't stay open is probably a defective limit switch, or maybe it needs adjusting. You will need to take the player apart a bit more (I was afraid it would come to this) to search for it.

Also the fact that you have no voltage on either emitters of the two transistors is a bit of a concern... You should have approximately 0,6V less at their emitters than at their collectors. Maybe now that you've fixed the regulator problem, they are OK?


spooney 27th February 2010 06:28 AM

i'm afraid the disc mechanism may be unrepairable. I was disassembling it and I noticed a piece of broken plastic that apparently came from some kind of switch that appears to have been actuated by one of the gears for moving the disc tray. I tried glueing it but it would not hold. I don't imagine this part would be easy to come by.

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