full service manual NAD 7225 pe

Status
Not open for further replies.
Jump to Latest
#2
migouel said:
service manual NAD 7225 pe
draft.gif


Hi all. I have a NAD 7225 PE Amp that seems to not power up. Does anyone have a service manual for it or schematic? Where can I find info to help me fix the tuner? 4 Fuses Blown,Display,FM scan works ok.i suspect Q506.🙂

Thanks
Migouel
Click to expand...

Well I don't have a service manual but i can give you some basic amplifier troubleshooting.

If you replace the blown fuses, turn it on and the fuses immediately blow out again you can very well assume that you have some blown transistors (technically speaking shorted output transistors). This can be a good thing because it means that more than likely your amplifier does not have any other damaged parts. All you have to do is make sure that you have a digital multimeter that has a diode check or even a continuity test feature. Unsolder each output transistor and test the transistor by putting 1 test lead on the Base and put the other test lead on first the Collector and then Emitter. You should get a reading, possibly somewhere around 0.7 or such. Now reverse the test leads and measure again. If the transistor is good then it should show an open circuit, however if you get the same measurements as the first test then you have found your shorted transistor. You will need to replace both output transistors on that same channel with a matched complimentary pair set of output transistors.
 
#4
tanooki2003 said:
Well I don't have a service manual but i can give you some basic amplifier troubleshooting.

If you replace the blown fuses, turn it on and the fuses immediately blow out again you can very well assume that you have some blown transistors (technically speaking shorted output transistors). This can be a good thing because it means that more than likely your amplifier does not have any other damaged parts. All you have to do is make sure that you have a digital multimeter that has a diode check or even a continuity test feature. Unsolder each output transistor and test the transistor by putting 1 test lead on the Base and put the other test lead on first the Collector and then Emitter. You should get a reading, possibly somewhere around 0.7 or such. Now reverse the test leads and measure again. If the transistor is good then it should show an open circuit, however if you get the same measurements as the first test then you have found your shorted transistor. You will need to replace both output transistors on that same channel with a matched complimentary pair set of output transistors.
Click to expand...
He thank tanooki2003
i will try this out. Do you think that some other compoments would
be wise to verified...?capacitor,diode?
Thank again
migouel
 
#5
migouel said:
He thank tanooki2003
i will try this out. Do you think that some other compoments would
be wise to verified...?capacitor,diode?
Thank again
migouel
Click to expand...

Hi Migouel,

You probably may be lucky if the issue with your receiver is that it was blowing fuses, due to a shorted output transistor. You may not have to go any further after that.

Now if the issue is that you turn it on, all lights come on but no sound comes out then you will definitely have a much more difficult road. This means that the transistor has opened (not shorted) and other parts have possibly been damaged due to the main voltage supplied to the amplifier's power transistors (we'll say +/- 70V) has fed back into the basic amplifier stage taking out a lot of resistors, biasing transistors, and diodes. I am hoping that this is not the case as I have seen & repaired this kind of issue many times in the past. It was a total pain but you will almost need an oscilloscope to pull this kind of repair off.
 
Status
Not open for further replies.
Top Bottom