# NAD 216 not coming out of protection mode

Alright so I've been just probing everything to do with that positive rail and here is some information that might help
the top of (metal top of capacitor)
C902 is measuring = -59.6V
C202 is measuring = 0.744V

I don't think its the bridge rectifier since its voltages are this
+ve =60.6V
the ac terminals = 44.5VAC
-ve =-60.6V

#### kaameelis

Power output supply is OK. What voltages are on R203 both ends and Q201, Q202 all pins?

R203:
-1.129V
-1.045V

Q201:
Emitter: -1.699V
Collector: -1.155V
Base: -1.142V
Q202
Emitter: 0V
Collector: -1.142V
Base: -8.9V

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#### kaameelis

Strange, seems voltage is missing from regulator input, so next voltages to test are D206, D202 and R201 ends.
On R201 is needed to measure AC voltage.

D206:
Negative side:-1.037V
Positive side:-0.525V

D202:
Negative side:-0.525V
Positive side:-3.04V

R201:
44.8VAC on left side of resistor
0VAC on right side of resistor

#### kaameelis

Yes, but it is also like fuse, will die when some other component in regulator is dead. Maybe C210?

Should I take out C210 and check for short?

#### kaameelis

Probably it must be possible to detect without taking it out, to burn 10 ohm R201 there must be proper short connection somewhere in regulator. But if it is OK, it depends with what meter you check it, some meters show short also on big capacitors because charge current.
As R203 is not shorted (voltages are not same on both ends), and it is 33 times bigger than R201, then short must be between them, D204 is also candidate.

C210-C213 not shorted
C208 not shorted
C206 not shorted
D204 was acting really weird with continuity measuring and resistance measuring,
Do you think it might be a good idea to just change all the 1N4003 diodes and recap the regulator?

#### kaameelis

I prefer not to change buy guessing but measuring and finding exactly what is dead.
What exactly was weird with D204? Had you any 100% working diode to compare measuring results?

Well i think the rest of the diodes are good, fx D205 since voltage is going through fine with that then there should be no problem with D205 as far as i understand and they are all of the same 1N4003 type.
So here's what I did to test it, i started to test for short so continuity test.
With black probe on negative side of cathode it should let current pass, an audible beep as far as I understand well with D204 this isn't the case, there is no beep.

Negative side of diode**

#### kaameelis

Something did not fit, D204 missing conductivity cannot burn R201. Usually multimeters have special position for measuring diodes, standard conductivity/resistance measuring did not give correct result because diode nearly constant forward voltage drop.
Is R201 burned or just broken?

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Ah ok, let me redo test on D204
D205 for reference as working diode:
Forward Bias:0.553V
Reverse bias:Ol
D204:
Forward bias:0.588V
Reverse bias:Ol

My bad then seems like D204 is all good.

R201 seems cosmetically fine but reads out 3.8Mohms

#### Vrystaat

Those ribbon cables from the power supply to the amp boards gives problems, better to solder the cables directly to the board and remove the plugs.

Might be a good idea in the future however, I want to figure out the problem with the power supply before I do that because it would be a real pain in the *** to have to desolder it everytime I need to check the bottom of the PS pcb

#### kaameelis

Maybe R201 just died without any short connection in +67 V regulator or had bad soldering?
Can you measure resistance from C212 and C210 plus terminals to the ground (wait longer time to charge capacitors), is it about same as from C213 and C211 minus terminals to the ground when mulitmeter leads are flipped and R202 disconnected from circuit? If about same, had you any 200-300 ohm resistor to replace R201 temporarily, with so big value because this help to avoid big short connection current if short still exist in regulator.

Notes:
Measure C212 and C210 resistance Both 4.4Mohms
Desolder R202 and measure C213 and C211 with leads flipped, black on minus terminals of capacitors and red on ground.
Both 4.35Mohms

I do not have a 200-300ohm Resistor i can change R201 out with the only one i have is a 5.6kohm resistor

#### kaameelis

It resistances on circuit are what you get, then is relatively big (maybe 80%) chance that +67V regulator is OK, only R201 is faulty.
5.6k can be too big, but possible you can still measure voltages on transistors Q201, Q201 and decide are they OK or not.

R201 changed out with 5.6kohm resistor, im assuming you meant Q201 and Q202,

Q201:
Emitter:8.1
Collector:8.6
Base: 8.75
Q202
Emitter: 0
Collector:8.7
Base:-8.88

Not really sure what to make out of this.

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