Yea, I was looking at the components in the list (specifically D117 / D317 , D118 / D318, D119 / D319) and discover these are SMD.
Kind of surprised.
I have a C325BEE that I repaired (parts-only, DOA special from ebay) that used SMD parts but only in the riser boards. I had to replace a couple e-caps that were SMD form-factor, not too bad, but I'd not want to deal with SMD transistors, diode nor resistors if at all possible.
No worries about the pictures. I saw the diagrams in the SM but wanted a "real" view of these on the board.
Kind of surprised.
I have a C325BEE that I repaired (parts-only, DOA special from ebay) that used SMD parts but only in the riser boards. I had to replace a couple e-caps that were SMD form-factor, not too bad, but I'd not want to deal with SMD transistors, diode nor resistors if at all possible.
No worries about the pictures. I saw the diagrams in the SM but wanted a "real" view of these on the board.
I forgot I already posted some pictures here:
https://www.diyaudio.com/community/threads/diagnose-of-my-amp-please.350167/
Its really SMD hell there
Wow, pretty busy on the foil side there.
But looking at those pictures I can see suspect solder joints from the top-mounted components. Some joints (red-circled-areas) have that bulls-eye ring look.
Also you can see the discoloration (yellow-circled) areas, these components producing lots of heat can weaken joints from the hot-cold cycle. Just some
areas I'd take a close look or just reflow (or remove and reapply fresh solder).
But looking at those pictures I can see suspect solder joints from the top-mounted components. Some joints (red-circled-areas) have that bulls-eye ring look.
Also you can see the discoloration (yellow-circled) areas, these components producing lots of heat can weaken joints from the hot-cold cycle. Just some
areas I'd take a close look or just reflow (or remove and reapply fresh solder).
Attachments
These yellow areas are around places where Q342, Q344, Q142, Q144 are installed.
They give a lot of heat.
Hope this issue will be fixed once I replaces zener, so current through these transistors will become normal (lower).
There are a lot of joints with bulls-eye ring look. In hot places and cold places too.
I think they come from factory like that.
Thanks for points.
They give a lot of heat.
Hope this issue will be fixed once I replaces zener, so current through these transistors will become normal (lower).
There are a lot of joints with bulls-eye ring look. In hot places and cold places too.
I think they come from factory like that.
Thanks for points.
Did you ever examine Q160 / Q360 as a previous poster mentioned? (he called it an amplified diode). The collector-base connection (short) does make the transistor act like a diode (the base+emitter is the PN junction).
Plus they are considered the BIAS transistors as labeled by NAD.
Plus they are considered the BIAS transistors as labeled by NAD.
Adding to my post, the previous poster mentioned Q148 / Q348 as bias control....but they are only a part, the Q160 / Q360 transistor-wired-as-diode devices are the other active part.
About the solder joints being factory, maybe. Probably a combo of poor QC and wear-n-tear on parts.
NAD didn't (still does not?) build in their own factories. They are a "design house only". So the actual physical creation/assembly of their products was contracted to companies in Asia. So QC has always been an issue, IMO. It was how to keep overall costs low making high-end equipment more affordable to the end consumer. All that being said, when the NAD designs are operating they are sounding great (proud owner of a 7125, 3155, 314, C325BEE and the mighty 310......and 5120 turntable).
About the solder joints being factory, maybe. Probably a combo of poor QC and wear-n-tear on parts.
NAD didn't (still does not?) build in their own factories. They are a "design house only". So the actual physical creation/assembly of their products was contracted to companies in Asia. So QC has always been an issue, IMO. It was how to keep overall costs low making high-end equipment more affordable to the end consumer. All that being said, when the NAD designs are operating they are sounding great (proud owner of a 7125, 3155, 314, C325BEE and the mighty 310......and 5120 turntable).
Thanks for the point.
I did not check/replace the Q160 / Q360. These are huge transistors that are mounted on big heat sink that stays cold most of time. So I think there is a very little chance that they became bad.
They are connected to main board with plugs, so I think its easy to get these plugs out and test these transistors.
Wow, you got some experience with NADs
I plan to do a recap of my c326bee. Maybe I will ask you some advice. But first I want to get into state when I am able to set idle currents properly.
I'd definitely look at these, especially the plugs and the connections. I'd go as far to remove the plugs and treat the metal with anti-oxide compound. I don't trust any NAD "factory" part....except maybe the power transformers.
Update.
As I wrote above I burned some resistor and one of Zener diodes too.
I replaced all 4 Zener diodes D322, D323, D122, D123 (MMSZ5231BT1) and now amp is fixed and also I have control on idle current (voltages)! They are going from very low 1mv and up when I turn the trim pot. So I guess what was significantly leaking is these diodes and not capacitors.
I measured all replaced capacitors and original capacitors have very decent specs (capacitance, ESR), almost as good as new capacitors that I installed (Nichicon stuff). I have very cheap ESR/capacitance meter though.
Transistors that were running hot (Q344, Q342, Q144, Q142) are still running hot, looks like this a separate problem to fix.
What I will try to do is to replace diodes D324, D325, D326, D327, D124, D125, D126, D127 since they (as I understand) control the current that flows from my hot transistors. Probably they became tired too, same as it happened with 4 Zener diodes.
The main huge heatsink stays almost cold, even if I run the amp on high volume. The feeling is that
I guess I need a time now to run the amp, so all new capacitors will be settled and then I will try to adjust idle currents more preciesly.
As I understand idle currents should not drift too fast, right?
And if they will drift fast, this means that some components in circuit are not stable, correct?
As I wrote above I burned some resistor and one of Zener diodes too.
I replaced all 4 Zener diodes D322, D323, D122, D123 (MMSZ5231BT1) and now amp is fixed and also I have control on idle current (voltages)! They are going from very low 1mv and up when I turn the trim pot. So I guess what was significantly leaking is these diodes and not capacitors.
I measured all replaced capacitors and original capacitors have very decent specs (capacitance, ESR), almost as good as new capacitors that I installed (Nichicon stuff). I have very cheap ESR/capacitance meter though.
Transistors that were running hot (Q344, Q342, Q144, Q142) are still running hot, looks like this a separate problem to fix.
What I will try to do is to replace diodes D324, D325, D326, D327, D124, D125, D126, D127 since they (as I understand) control the current that flows from my hot transistors. Probably they became tired too, same as it happened with 4 Zener diodes.
The main huge heatsink stays almost cold, even if I run the amp on high volume. The feeling is that
I guess I need a time now to run the amp, so all new capacitors will be settled and then I will try to adjust idle currents more preciesly.
As I understand idle currents should not drift too fast, right?
And if they will drift fast, this means that some components in circuit are not stable, correct?
Hello,
I am a new member and I am not sure how to go about revisiting an old post or starting a new conversation so please advise me.
I was just reading the posts here as I own a NAD C160 which started misbehaving recently. My system includes one NAD C160 which feed two NAD C270 Power Amps, connected in turn to two Martin Logan SL3 electrostatic speakers.
The outputs from the C160 seem to have died (both PREOUT1 and 2). With earphones plugged in I hear sound from the test CD player. I have opened up the C160 and looked at the main board: Aside from glue around the large caps (it does not look like leakage from the caps) I don't see any obvious dmage to any component. The fact that neither the L nor the R channel have any output makes me think that the fault(s) may be with a section that addresses both channels at the same time: I am thinking of the earphones plug/board and/or the components which are used for Muting from the remote IR controller (see HeadphoneBoard and PREOUT1&2 images). I have started to measure some voltages at the earphones board: Pin 4 should read +26V (according to the schematic in the Service Manual) but it reads only +14V. I also measured the two spots marked with the Red and Green circles in the PowerSection image I include: Although at the Green spot I read about +27V, I read about +14V at the Red spot, which should read +26V.
I am not versed in amplifier electronics as I would like to be, any ideas or suggestions for where/what to measure are greatly appreciated!
I am a new member and I am not sure how to go about revisiting an old post or starting a new conversation so please advise me.
I was just reading the posts here as I own a NAD C160 which started misbehaving recently. My system includes one NAD C160 which feed two NAD C270 Power Amps, connected in turn to two Martin Logan SL3 electrostatic speakers.
The outputs from the C160 seem to have died (both PREOUT1 and 2). With earphones plugged in I hear sound from the test CD player. I have opened up the C160 and looked at the main board: Aside from glue around the large caps (it does not look like leakage from the caps) I don't see any obvious dmage to any component. The fact that neither the L nor the R channel have any output makes me think that the fault(s) may be with a section that addresses both channels at the same time: I am thinking of the earphones plug/board and/or the components which are used for Muting from the remote IR controller (see HeadphoneBoard and PREOUT1&2 images). I have started to measure some voltages at the earphones board: Pin 4 should read +26V (according to the schematic in the Service Manual) but it reads only +14V. I also measured the two spots marked with the Red and Green circles in the PowerSection image I include: Although at the Green spot I read about +27V, I read about +14V at the Red spot, which should read +26V.
I am not versed in amplifier electronics as I would like to be, any ideas or suggestions for where/what to measure are greatly appreciated!
Attachments
You should create a new post for this pre-amp.
Within the post you can reference some specific posts with hyper links (did you search diyaudio for references to C160 issues?).
Aside from this, being both channels are non-functional the power supply would be the best guess to be probing (which you are doing).
Additionally in the power supply circuits I would check for broken solder joints (from heat/cool cycles), possibly heat damaged resistors, small signal diode failures (1N4148). Many of these checks can be done with no power, just DMM resistance and diode checks.
But create a new post.
--Joe
Within the post you can reference some specific posts with hyper links (did you search diyaudio for references to C160 issues?).
Aside from this, being both channels are non-functional the power supply would be the best guess to be probing (which you are doing).
Additionally in the power supply circuits I would check for broken solder joints (from heat/cool cycles), possibly heat damaged resistors, small signal diode failures (1N4148). Many of these checks can be done with no power, just DMM resistance and diode checks.
But create a new post.
--Joe