Greetings All!
New user, with a small project I would like to sort out myself.
About a year ago, I bought a second hand NAD 3220PE, which was said to be tested and working. This was simply to play some old vinyls through an inherited Ariston QDeck. It took me a while to sort everything out, and earlier on this year i finally hooked everything up to test it out. When i initially turned it on, after a few minutes it started to smoke, and only one channel worked properly. idiotically i didnt turn it off straight away and after a short time the music stopped and all that came through the speakers was semi-rhythmic clicking. After this i diconnected everything, and sent it to the local Hi-Fi shop to ascertain what was wrong with it. they reported it was uneconmical repair, and that both channels were completely destroyed [as written on the job sheet].
After this I decided to have a look myself, and as such took the lid off the unit to investigate. It seems that the main four transistors were mismatched, and there was evidence of two being replaced. I sourced a pair of both, noted their location and replace them - although I'm yet to solder them back on the board. The heat sink was cleaned, and the contact surfaces were cleaned and recovered in heat paste [the silver stuff I used for my PS3 repair a few years back] on inspecting the main board I found a number of other problems. A total of 4 resistors were fried. I've located the manual, and have a print out of the board layout and wiring diagram too. From interrogating this and the board itself I have found that the following resistors are fried:
R438 - 68 or 80 on the diagram, the text is distorted.
R440 - 220
R452 - 33
R453 - 180
I cant see the colour codes on any of them, and i have scoured the internet for some pictures of other peoples to try and see if i can get the colours of the burnt out resistors to replace them.
What I would like to ask is the following:
How do I work out the type of resistor from the numbers stated on the schematic?
What would be prudent to replace while I've got the entire thing apart? I'm happy to spend the money on parts to rebuild this and make it right again. if that means buying long list of parts and replacing them out to freshen up then I'm happy to do that.
Fact is, most of my experience is in cars, model aircraft building, RC cars, road bikes, architecture and drawing etc and aside from a few projects electronically orientated this will be a new venture for me. I've re-floated my PS3 mainboard six years ago while modifying the fan circuit so it hasnt overheated again. car wise I've re-soldered multi-relays, rewired a throttle actuator motor and retrofitted electric windows, electric seats and other thing in various old mercs in the past.
While I am probably starting from a basic level of understanding on how this amplifier works, I would like to work it out and fix it myself. I'm sure that there are better amplifiers to just buy, or it might be easier to just buy another, but I would like to fix this one. I picked an 80s NAD because my dad bought a 3130 in the 1980s and still has it, and its in perfect order save for a little crackle on the volume. It will be running a turntable, and perhaps a CD player or auxiliary output in the future.
So where do I start?
New user, with a small project I would like to sort out myself.
About a year ago, I bought a second hand NAD 3220PE, which was said to be tested and working. This was simply to play some old vinyls through an inherited Ariston QDeck. It took me a while to sort everything out, and earlier on this year i finally hooked everything up to test it out. When i initially turned it on, after a few minutes it started to smoke, and only one channel worked properly. idiotically i didnt turn it off straight away and after a short time the music stopped and all that came through the speakers was semi-rhythmic clicking. After this i diconnected everything, and sent it to the local Hi-Fi shop to ascertain what was wrong with it. they reported it was uneconmical repair, and that both channels were completely destroyed [as written on the job sheet].
After this I decided to have a look myself, and as such took the lid off the unit to investigate. It seems that the main four transistors were mismatched, and there was evidence of two being replaced. I sourced a pair of both, noted their location and replace them - although I'm yet to solder them back on the board. The heat sink was cleaned, and the contact surfaces were cleaned and recovered in heat paste [the silver stuff I used for my PS3 repair a few years back] on inspecting the main board I found a number of other problems. A total of 4 resistors were fried. I've located the manual, and have a print out of the board layout and wiring diagram too. From interrogating this and the board itself I have found that the following resistors are fried:
R438 - 68 or 80 on the diagram, the text is distorted.
R440 - 220
R452 - 33
R453 - 180
I cant see the colour codes on any of them, and i have scoured the internet for some pictures of other peoples to try and see if i can get the colours of the burnt out resistors to replace them.
What I would like to ask is the following:
How do I work out the type of resistor from the numbers stated on the schematic?
What would be prudent to replace while I've got the entire thing apart? I'm happy to spend the money on parts to rebuild this and make it right again. if that means buying long list of parts and replacing them out to freshen up then I'm happy to do that.
Fact is, most of my experience is in cars, model aircraft building, RC cars, road bikes, architecture and drawing etc and aside from a few projects electronically orientated this will be a new venture for me. I've re-floated my PS3 mainboard six years ago while modifying the fan circuit so it hasnt overheated again. car wise I've re-soldered multi-relays, rewired a throttle actuator motor and retrofitted electric windows, electric seats and other thing in various old mercs in the past.
While I am probably starting from a basic level of understanding on how this amplifier works, I would like to work it out and fix it myself. I'm sure that there are better amplifiers to just buy, or it might be easier to just buy another, but I would like to fix this one. I picked an 80s NAD because my dad bought a 3130 in the 1980s and still has it, and its in perfect order save for a little crackle on the volume. It will be running a turntable, and perhaps a CD player or auxiliary output in the future.
So where do I start?