Yes, time for lunch <G>
Mr Moran recommended the unit be turned off when not in use to prolong life. The c375bee has a low power idle mode which the c372 does not, I believe.
Do you have any tips for pulling the Amp boards out? It looks the the large outboard heatsink may come off without having to even remove the channel amp board. Is that the case? I don't need to really rip mine fully apart as I only plan on reworking the channel amp boards.
cheers
Hmm, Left channel seems concerning to me. the 0.8Vdc on the right is close to what mine does.
Given the high Voltage across those resistors, that may be normal for them, after all they are speced at 3W.
Mr Moran recommended the unit be turned off when not in use to prolong life. The c375bee has a low power idle mode which the c372 does not, I believe.
Do you have any tips for pulling the Amp boards out? It looks the the large outboard heatsink may come off without having to even remove the channel amp board. Is that the case? I don't need to really rip mine fully apart as I only plan on reworking the channel amp boards.
cheers
Junie, I just noticed that the schematic differs much from our PCB for the TP TP303/TP304
TP403/TP404
the alignment talks about testing from IC301/401 pin 1 to ground which is actually how our units are wired. The schematic does NOT have these test points shown this way.
Try check the voltage from the IC pin and NOT the TP. I don't believe we should use the actual test point pins, but should directly measure from the IC pin 1 to ground.
I still think the right and left chanel difference is a problem in your unit that should be tracked down, but don't trust the schematic.
My work bench is almost cleaned up. so maybe this weekend I can get to my unit.
TP403/TP404
the alignment talks about testing from IC301/401 pin 1 to ground which is actually how our units are wired. The schematic does NOT have these test points shown this way.
Try check the voltage from the IC pin and NOT the TP. I don't believe we should use the actual test point pins, but should directly measure from the IC pin 1 to ground.
I still think the right and left chanel difference is a problem in your unit that should be tracked down, but don't trust the schematic.
My work bench is almost cleaned up. so maybe this weekend I can get to my unit.
I measured from pin 1 it's giving me the same results.
Btw, what type and brand of caps(big one) NAD has given to you? can you post a photo?
You can remove the Amp module by placing the unit on right side up while removing right channel. Pull the connectors first and hold the amp module while removing screws. remove first the screws underneath the plastic foots. same steps if you want to remove the left channel.
I'm suspecting the TL431.
Btw, what type and brand of caps(big one) NAD has given to you? can you post a photo?
You can remove the Amp module by placing the unit on right side up while removing right channel. Pull the connectors first and hold the amp module while removing screws. remove first the screws underneath the plastic foots. same steps if you want to remove the left channel.
I'm suspecting the TL431.
my Bad, the test points actually are wired to the pin 1 of IC 301 and ground as specified in the alignment procedure, but these are not on the schematic. This explains why no vr303/vr401
The 100V 10000uf are NAD brand, almost the height of the case and black. I will post pics when I have time to figure out how <G>.
The 100V 10000uf are NAD brand, almost the height of the case and black. I will post pics when I have time to figure out how <G>.
Hello AMGALITZ & JUNIE !
I am running the same adventure that you have run before.
I bought on eBay for 150 € this amp but I needed to change capacitors.
I have disassembled everything and cleaned, most of the soldering were sulphated and there were many clues from the PCB communicated.
I have solved all that, bought and installed the 10 largest capacitors, C724, C725, C727, C728, C748, C749, C734, C735, C306 and C406
Mouser Electronics
I have also soldered the cables under the PCB by connecting the 10000 uF capacitors in parallel with 18 gauge cable as suggested by the technical bulletin C372-H2005-01 since my unit is one of the first (V4 motherboard).
Login - HiFi Engine
Now it has a great sound, I had never heard anything with this quality, it is the amplifier that I had always dreamed and never could buy.
The problem is the alignment procedure, where I can not get any voltage measurement at the initial setting with no load connected
(V = 0.000 between pin 1 of IC301 and earth, the same in the other channel equals the position of the corresponding VR always is 0.000).
Another worrying thing is the extreme temperatures of Q709, Q712, IC703, IC704 and Q714 to such an extent I am afraid that I have decided to save the amplifier and not use it.
I also considered taking him to SAT to make the missing adjustments, but I do not have a lot of money and I am afraid they will crucify me.
I know that a long time ago of this conversation but perhaps they could finally solve these problems and continue to enjoy this great amplifier.
Any suggestion will be welcome.
I am running the same adventure that you have run before.
I bought on eBay for 150 € this amp but I needed to change capacitors.
I have disassembled everything and cleaned, most of the soldering were sulphated and there were many clues from the PCB communicated.
I have solved all that, bought and installed the 10 largest capacitors, C724, C725, C727, C728, C748, C749, C734, C735, C306 and C406
Mouser Electronics
I have also soldered the cables under the PCB by connecting the 10000 uF capacitors in parallel with 18 gauge cable as suggested by the technical bulletin C372-H2005-01 since my unit is one of the first (V4 motherboard).
Login - HiFi Engine
Now it has a great sound, I had never heard anything with this quality, it is the amplifier that I had always dreamed and never could buy.
The problem is the alignment procedure, where I can not get any voltage measurement at the initial setting with no load connected
(V = 0.000 between pin 1 of IC301 and earth, the same in the other channel equals the position of the corresponding VR always is 0.000).
Another worrying thing is the extreme temperatures of Q709, Q712, IC703, IC704 and Q714 to such an extent I am afraid that I have decided to save the amplifier and not use it.
I also considered taking him to SAT to make the missing adjustments, but I do not have a lot of money and I am afraid they will crucify me.
I know that a long time ago of this conversation but perhaps they could finally solve these problems and continue to enjoy this great amplifier.
Any suggestion will be welcome.
NAD C272 Restauration
I bought a C272 amplifier, because I do not know how old it would like to replace the (critical) capacitors, I would like to replace the 4 large power supply capacitors: I see there are still two free places for more capacitors (C719,C720). Is it possible and advisable to load 6 x 10000μF 80V 105 °?
second question: which condensers are in the signal path and are worthwhile to be replaced by better ones?
For suggestions I would be grateful, I think the power amp is very good and can be improved slightly.
I bought a C272 amplifier, because I do not know how old it would like to replace the (critical) capacitors, I would like to replace the 4 large power supply capacitors: I see there are still two free places for more capacitors (C719,C720). Is it possible and advisable to load 6 x 10000μF 80V 105 °?
second question: which condensers are in the signal path and are worthwhile to be replaced by better ones?
For suggestions I would be grateful, I think the power amp is very good and can be improved slightly.
Hello Boris!
I didin't saw your post until now.
I finished the rebuild of my C272 recently, but I'm improving some things right now.
The 68V rail has some factory "issues" and some parts run very hot.
But this can be fixed very easily. It can also be converted to a conventional zener referenced regulator.
NAD changed the 80V main PSU caps to 100V. But it's hard to find non fake caps with 35mm diameter.
Due to the fact that some units got new 80V caps as official replcement tells us that the statement from NAD tells not the whole story.
I belive that some of the cheap Jinghai caps was bad and blew.
And cheap 100V are probable cheaper as quality 80V versions.
I checked the temperature of the caps after a few hours and there are about 68V after rectifying without load.
There is no real reason to change to 100V caps. Just use good quality 80V caps.
I did some smal changes, to much to write right now.
If you are still interested please let me know.
I didin't saw your post until now.
I finished the rebuild of my C272 recently, but I'm improving some things right now.
The 68V rail has some factory "issues" and some parts run very hot.
But this can be fixed very easily. It can also be converted to a conventional zener referenced regulator.
NAD changed the 80V main PSU caps to 100V. But it's hard to find non fake caps with 35mm diameter.
Due to the fact that some units got new 80V caps as official replcement tells us that the statement from NAD tells not the whole story.
I belive that some of the cheap Jinghai caps was bad and blew.
And cheap 100V are probable cheaper as quality 80V versions.
I checked the temperature of the caps after a few hours and there are about 68V after rectifying without load.
There is no real reason to change to 100V caps. Just use good quality 80V caps.
I did some smal changes, to much to write right now.
If you are still interested please let me know.
Hi guys.
I try to adjust my NAD C372 according to service manual.
There it is said:
IDLING CURRENT is OK - L-5.5mv, R-5.5mv
The problem is setup "ISC SENSITIVITY"
Manual says "adjust VR701 (47kohms) between –50mV to -100mV.", but I measure 70.5V between TP701 and TP702, not millivolts.
I measured with two multimeters and both show the same.
I try to adjust my NAD C372 according to service manual.
There it is said:
OUTPUT OFFSET is OK - L-4.8mv, R-2.3mv
IDLING CURRENT is OK - L-5.5mv, R-5.5mv
The problem is setup "ISC SENSITIVITY"
Manual says "adjust VR701 (47kohms) between –50mV to -100mV.", but I measure 70.5V between TP701 and TP702, not millivolts.
I measured with two multimeters and both show the same.
Hi guys.
I try to adjust my NAD C372 according to service manual.
There it is said:
IDLING CURRENT is OK - L-5.5mv, R-5.5mv
The problem is setup "ISC SENSITIVITY"
Manual says "adjust VR701 (47kohms) between –50mV to -100mV.", but I measure 70.5V between TP701 and TP702, not millivolts.
I measured with two multimeters and both show the same.
I try to adjust my NAD C372 according to service manual.
There it is said:
OUTPUT OFFSET is OK - L-4.8mv, R-2.3mv
IDLING CURRENT is OK - L-5.5mv, R-5.5mv
The problem is setup "ISC SENSITIVITY"
Manual says "adjust VR701 (47kohms) between –50mV to -100mV.", but I measure 70.5V between TP701 and TP702, not millivolts.
I measured with two multimeters and both show the same.
I have just finished a full recap of my C372 and I am having this exact issue. Were you ever able to figure out what was causing this?
These vintage NAD amps are a challenge to repair because they have so many components. I am impressed by anyone who does it.
I have NAD C320 which had intermittent volume fluctuations. I fixed it by installing a pre-regulator, to spread excessive heat, for the 18v supply. I also installed a small fan which stirs the internal air to reduce hot spots.
I have a NAD D 3045 for which is supposed to work in the horizontal orientation or the vertical. However, horizontal was so hot that I stung my fingers on the NAD logo which is a metal thing in the middle of a plastic cover over the Hypex module. I used it for a while with a fan behind the unit. Now I just leave it vertical without the fan.
Most of the new NAD designs now are class-D. They are made with a main-board computer and a Hypex module.
I have NAD C320 which had intermittent volume fluctuations. I fixed it by installing a pre-regulator, to spread excessive heat, for the 18v supply. I also installed a small fan which stirs the internal air to reduce hot spots.
I have a NAD D 3045 for which is supposed to work in the horizontal orientation or the vertical. However, horizontal was so hot that I stung my fingers on the NAD logo which is a metal thing in the middle of a plastic cover over the Hypex module. I used it for a while with a fan behind the unit. Now I just leave it vertical without the fan.
Most of the new NAD designs now are class-D. They are made with a main-board computer and a Hypex module.
I agree, Nads machine have been overly complicated and since about 20 yrs back just chinese parts don’t make it reliable at all..
I believe the C270/C272 and similar years NAD machines are the absolulely last machines i would like to upgrade/ repair etc…
Nad 215/216 was probably the easiest. Thanks to that Chris Evans from Now Myyryad UK designed them. Most Björn Erik Edvardsen machines very complex
I believe the C270/C272 and similar years NAD machines are the absolulely last machines i would like to upgrade/ repair etc…
Nad 215/216 was probably the easiest. Thanks to that Chris Evans from Now Myyryad UK designed them. Most Björn Erik Edvardsen machines very complex