I picked up a Used (non-working) NAD 216 last week. The guy said it was working fine in his H/T, but just went out one day. Figured I'd take a flyer on it and see - mainly because the case was in perfect condition.
Took it home and opened it up - well it didn't just quit, the Left channel had a catastrophic explosion inside. 2 small 100uf/100V caps (C309 and C333) were completely blown off the board. It looks like the electrolytic went everywhere and has caused some corroision (yellow/green coating) on a few resistor, diode and one transistors legs and took the coating off the heatsink in a small area. He had clipped all the wires from the PSU to amp board. I guess he was trying to get the other channel to work. Either way it's stuck in protection mode.
Looking a little deeper and found Q301 has the bottom half of its plastic blown off, obviously measures bad. Then there were a few (4-5) resistors that look burned, but only 3 measure out of spec. I assume the others gave up before all the resistors could burn completely. R327, R315, R331 are badly charred and measure out of spec.
I checked all the small transistors and it looks like 3 are bad (incl. Q301) and only one power Transistor gave any strange readings - but might change if I re-work and test out of circuit.
The power supply also looks like the mains power caps have leaked - but only just starting to seep. Voltages going into and out of the PSU are within the 48VAC & +/-67 Vdc specs in the service manual. Hoping it just needs some new caps all the way around and it will be good. Will probably change the relay for good measure, since I can't test it without a good amp channel.
On the Right channel - which looks ok/good for being 20+ years old. However, it might be the protection circuitry, because I tried to fire it up out of the case, with only +/-53Vdc to see if the offset was causing an issue, but I only get -0.001V at TP301 and TP303 and when I turn the "idle current" varistor very little change if any (goes from -0.001 to 0.000 - 0.001mV) No real noticeable heat on the heatsink (even after 5-10 minutes of idle), but doesn't draw current with DBT in series either.
Could the issue be that I unhooked all the wires (with JP204/JP304) connecting the amp board to the soft-clip, protection board? Seems reasonable, but still new to reading schematics.
Bottom line question - is it worth rebuilding back to stock form, possibly with some help to include a few modifications to make it a better version? Could you tell me how to possibly test the Right Channel outside of the case to verify its working? Or should I cut my investment and start planning a different PSU/Amp board combination using the toroidal and case as a base?
Tried to include enough info and pics for someone to comment. Pics include the PSU and Amp schematic. I also have the actual PSU with a close-up of the leaking. Then a few pictures of the bad channel board, after I cleaned it with a toothbrush and Alcohol.
Took it home and opened it up - well it didn't just quit, the Left channel had a catastrophic explosion inside. 2 small 100uf/100V caps (C309 and C333) were completely blown off the board. It looks like the electrolytic went everywhere and has caused some corroision (yellow/green coating) on a few resistor, diode and one transistors legs and took the coating off the heatsink in a small area. He had clipped all the wires from the PSU to amp board. I guess he was trying to get the other channel to work. Either way it's stuck in protection mode.
Looking a little deeper and found Q301 has the bottom half of its plastic blown off, obviously measures bad. Then there were a few (4-5) resistors that look burned, but only 3 measure out of spec. I assume the others gave up before all the resistors could burn completely. R327, R315, R331 are badly charred and measure out of spec.
I checked all the small transistors and it looks like 3 are bad (incl. Q301) and only one power Transistor gave any strange readings - but might change if I re-work and test out of circuit.
The power supply also looks like the mains power caps have leaked - but only just starting to seep. Voltages going into and out of the PSU are within the 48VAC & +/-67 Vdc specs in the service manual. Hoping it just needs some new caps all the way around and it will be good. Will probably change the relay for good measure, since I can't test it without a good amp channel.
On the Right channel - which looks ok/good for being 20+ years old. However, it might be the protection circuitry, because I tried to fire it up out of the case, with only +/-53Vdc to see if the offset was causing an issue, but I only get -0.001V at TP301 and TP303 and when I turn the "idle current" varistor very little change if any (goes from -0.001 to 0.000 - 0.001mV) No real noticeable heat on the heatsink (even after 5-10 minutes of idle), but doesn't draw current with DBT in series either.
Could the issue be that I unhooked all the wires (with JP204/JP304) connecting the amp board to the soft-clip, protection board? Seems reasonable, but still new to reading schematics.
Bottom line question - is it worth rebuilding back to stock form, possibly with some help to include a few modifications to make it a better version? Could you tell me how to possibly test the Right Channel outside of the case to verify its working? Or should I cut my investment and start planning a different PSU/Amp board combination using the toroidal and case as a base?
Tried to include enough info and pics for someone to comment. Pics include the PSU and Amp schematic. I also have the actual PSU with a close-up of the leaking. Then a few pictures of the bad channel board, after I cleaned it with a toothbrush and Alcohol.
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Hello .. worth a bash, if any thing will improve your restoration skills .. if not chuck it my way 🙂
I'm guided by two things when faced with something like that.
1/ Have I use for it when its done.
2/ It must be cosmetically near perfect.
Those boards would clean up like brand new (in the sink, hot water and detergent). Discrete circuitry should be a doddle to repair, no unobtainable special IC's and so on........
Its your choice 🙂
1/ Have I use for it when its done.
2/ It must be cosmetically near perfect.
Those boards would clean up like brand new (in the sink, hot water and detergent). Discrete circuitry should be a doddle to repair, no unobtainable special IC's and so on........
Its your choice 🙂
Surely;-)
Without me;-)
@ bullittstang:
Suggestion:
Restoring the NAD. On the side build a little quasi. Then compare;-)
And tell us;-)))
Without me;-)
@ bullittstang:
Suggestion:
Restoring the NAD. On the side build a little quasi. Then compare;-)
And tell us;-)))
Here are pics of the front and back and the sides are just as clean. I would consider it very clean, especially for 20-years old.
There is one solder track (highlighted in PIC) going to -V that is gone. It's missing 10-12mm (1/2") of solder track. Should be easy enough to patch back together.
There is one solder track (highlighted in PIC) going to -V that is gone. It's missing 10-12mm (1/2") of solder track. Should be easy enough to patch back together.
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Do you have a recommendation? I have the parts and plan to build "shaan's" PeeCeeBee with laterals in the near future.
I have also build MyRef LM3886 about 4 months ago.
Any little quasi. 5 transes, 10 resistors max. Possible without pcb. ONE psu/ONE "rail". Input and output caps.
honestly what are you going on about 😕 please explain yourself more clearly .. your text does not make sense .. well in English is doesn't 😉
regards from the UK
Build any little quasicomplementary-pp-power-amp.
With 5 transistors and 10 resistors maximal.
It is possible to build without a pcb/to build without a pcb it is possible.
Do construct/use just ONE psu (not a "complementary"-, "two-rails"-psu, + and -) Just ONE voltage. For both channels.
Ergo: with input- and output-caps.
Like this;-)
Like a Pioneer SA-500 power-amp. Without Q1;-!
With 5 transistors and 10 resistors maximal.
It is possible to build without a pcb/to build without a pcb it is possible.
Do construct/use just ONE psu (not a "complementary"-, "two-rails"-psu, + and -) Just ONE voltage. For both channels.
Ergo: with input- and output-caps.
Like this;-)
Like a Pioneer SA-500 power-amp. Without Q1;-!
Hi bullittstang,
I would rebuild it to almost stock. Once you have it working you can start changing things bit by bit. It will be a great learning experience for one,and you can be proud of what you accomplished. Then listen to it and decide if you need it to sound different.
A few Western-Union joints and heat shrink tubing will make those cut wires reliable. Yes, solder the actual connection.
-Chris
I would rebuild it to almost stock. Once you have it working you can start changing things bit by bit. It will be a great learning experience for one,and you can be proud of what you accomplished. Then listen to it and decide if you need it to sound different.
A few Western-Union joints and heat shrink tubing will make those cut wires reliable. Yes, solder the actual connection.
-Chris
IMO NAD 216 is a well designed power amplifier.
Strong output stage with triple EF and 4 output pairs. NAD 214-218 (among many other NAD's) employs current feedback. See Stereophile review of the related NAD 218 (added cascode in VAS).
I'd rebuild it.
Strong output stage with triple EF and 4 output pairs. NAD 214-218 (among many other NAD's) employs current feedback. See Stereophile review of the related NAD 218 (added cascode in VAS).
I'd rebuild it.
I have the NAD214, the same as the 216 but with lower rails and less output trannies. It is a real old battle ax and has that usual Nad warm sounding character.
Fix it for sure !! 🙂
Fix it for sure !! 🙂
Ok guys - thanks for all the input. Sounds like a solid amp, I should attempt to rebuild, so here goes.
I started putting together a parts order list and have found a couple things hard to find or need a substitution. I'm was hoping to get everything from Digikey to save on some shipping.
1. 2SA970 PNP TO-92 transistor - I can find it on eBay, fairly local, but unsure if they are legit - know any trustworthy sellers on eBay? Or is there a suitable replacement?
I have seen mention of KSA992 (but on rated for 0.05A of current) also 2N5401 but I would need to swap the CB legs prior to installing. Any direct replacements?
2. 2SD600k - again I can find on eBay, but can't get both from same seller unless I go to Asia. Any reputable sources? Suitable replacement? I have searched and appears BD140, 2N4920G and maybe ZTX553 would be drop-in replacements.
Other suggestions are certainly welcome.
3. Suggestions on the 6-pin ribbon cable and 2-pin Input connectors? I would like to put a connector on the amp board, just to make it easier to assemble. They are both a standard size of 2.54mm spacing.
Found these - https://www.digikey.com/products/en?keywords=WM4828-ND
https://www.digikey.com/products/en?keywords=wm2904-ND
If these will work.
Prefer locking - but these are for 24AWG which seems too small to use for the Input?
Capacitors -
For the PSU - Rubycon for the main supply caps and Nichicon PS for all others.
For the amp boards - Nichicon FG since I can get all the voltages in that same cap.
I started putting together a parts order list and have found a couple things hard to find or need a substitution. I'm was hoping to get everything from Digikey to save on some shipping.
1. 2SA970 PNP TO-92 transistor - I can find it on eBay, fairly local, but unsure if they are legit - know any trustworthy sellers on eBay? Or is there a suitable replacement?
I have seen mention of KSA992 (but on rated for 0.05A of current) also 2N5401 but I would need to swap the CB legs prior to installing. Any direct replacements?
2. 2SD600k - again I can find on eBay, but can't get both from same seller unless I go to Asia. Any reputable sources? Suitable replacement? I have searched and appears BD140, 2N4920G and maybe ZTX553 would be drop-in replacements.
Other suggestions are certainly welcome.
3. Suggestions on the 6-pin ribbon cable and 2-pin Input connectors? I would like to put a connector on the amp board, just to make it easier to assemble. They are both a standard size of 2.54mm spacing.
Found these - https://www.digikey.com/products/en?keywords=WM4828-ND
https://www.digikey.com/products/en?keywords=wm2904-ND
If these will work.
Prefer locking - but these are for 24AWG which seems too small to use for the Input?
Capacitors -
For the PSU - Rubycon for the main supply caps and Nichicon PS for all others.
For the amp boards - Nichicon FG since I can get all the voltages in that same cap.
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I highly recommended avoiding eBay for components, unless the seller has a known good reputation outside of eBay. Way too many fakes of even dirt common currently made components, let alone discontinued components.
I have had some good luck with Bdent.com for some components with no reasonable equivalents.
I have successfully used ksa992 to replace 2sa970 in the past, but I’m sure there may be cases where ksa992 isn’t the correct substitute. I recommend changing any complimentary 2sc2240 to better maintain balance.
After quickly looking over the data sheet for 2sd600, it looks like ksc2690a would be another reasonable substitute. However, after a quick glance at the NAD schematic I believe it is in the bias circuit, and not too critical on specs anyway.
I have had some good luck with Bdent.com for some components with no reasonable equivalents.
I have successfully used ksa992 to replace 2sa970 in the past, but I’m sure there may be cases where ksa992 isn’t the correct substitute. I recommend changing any complimentary 2sc2240 to better maintain balance.
After quickly looking over the data sheet for 2sd600, it looks like ksc2690a would be another reasonable substitute. However, after a quick glance at the NAD schematic I believe it is in the bias circuit, and not too critical on specs anyway.
Hi bullittstang,
You can replace the capacitors using higher voltage ones. This would be better for you as the higher voltage capacitors generally perform better. Keep the voltage rise reasonable, like a 63 volt instead of a 35 volt. Try and keep the capacitance the same.
The bias transistor will only see the voltage between the bases, so probably around ~ 2.4 VDC. A 35 V transistor would work here. Current gain is more important, so try to use one that has roughly the same gain, or beta. Your input transistors are complimentary. See if you can use proper compliments and ones that are as close to the same beta as possible. If you do all these things, your repaired channel may outperform the other one from a distortion viewpoint.
-Chris
You can replace the capacitors using higher voltage ones. This would be better for you as the higher voltage capacitors generally perform better. Keep the voltage rise reasonable, like a 63 volt instead of a 35 volt. Try and keep the capacitance the same.
The bias transistor will only see the voltage between the bases, so probably around ~ 2.4 VDC. A 35 V transistor would work here. Current gain is more important, so try to use one that has roughly the same gain, or beta. Your input transistors are complimentary. See if you can use proper compliments and ones that are as close to the same beta as possible. If you do all these things, your repaired channel may outperform the other one from a distortion viewpoint.
-Chris
Ok - tried to test and get a list together of "bad" parts to make one order. I have tested every resistor to verify within spec., I have also tested each transistor with a DMM (by itself, but also comparing to the other channel)
I have attached a marked up schematic and I'm hoping you could verify if I'm on the right track, as far as replacing all the transistors that could be shorted as evidenced by the resistor and capacitor failures notated.
Case in point - R379, would that take out Q337? This is one that tests ok on one test, but the next day I tested it as bad?
Q301, Q305, Q307, Q311, Q321, Q325 all test as bad with a DMM - granted a couple others test good one day and then I do it again to verify and it tests bad. I am ordering complementary pairs and will replace both NPN/PNP.
Is this many transistors going bad typical? In past on much smaller repairs I've done, it was only 1-2 transistors that were damaged?
Additionally - the power transitors Q901, 905, Q329 and Q333 all 2sc3519 are all testing bad with DMM. They are showing 0.016 drop voltage compared to 0.593 on the compementary transistors.
I have attached a marked up schematic and I'm hoping you could verify if I'm on the right track, as far as replacing all the transistors that could be shorted as evidenced by the resistor and capacitor failures notated.
Case in point - R379, would that take out Q337? This is one that tests ok on one test, but the next day I tested it as bad?
Q301, Q305, Q307, Q311, Q321, Q325 all test as bad with a DMM - granted a couple others test good one day and then I do it again to verify and it tests bad. I am ordering complementary pairs and will replace both NPN/PNP.
Is this many transistors going bad typical? In past on much smaller repairs I've done, it was only 1-2 transistors that were damaged?
Additionally - the power transitors Q901, 905, Q329 and Q333 all 2sc3519 are all testing bad with DMM. They are showing 0.016 drop voltage compared to 0.593 on the compementary transistors.
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