Without badgering you, Mr. Walton, but with your experience with regulators I am DYING TO KNOW did you find it (either one) to perform better, sonically, than the series version? Or is it more of a toss up?
Checked all resistor values. Lm329 to ground measures 3.59V. Boards are newly populated, cleanly soldered, and values appear and measure correct. Perhaps I do not have enough headroom. What is a safe value? Load resistor is 500R. I am truly baffled. The fact that I have had identical results from two different sets populated at different times adds to the fruustration. Transformer output seems low for 12V secondaries, being 15V. Dunno, that's why I came to the pros for help
Unless Mouser has a line on a bad set of parts, I would say no. I will try and see if more headroom on the input helps. Wouldn't expect it to. Like Jan says, the curiosity is the low reference voltage.
Pulled lm329dz and replaced. Same numbers. I am at a loss here. No broken traces. Correct values on all parts. Happening on both positive and negative regulators.
So, the voltage across the negative pin of the op amp matches the voltage drop across R6/r13 combo. Does this mean the opamp is failing to regulate the pass transistor? What else could cause the LM329dz to have only 3.6V across it. I don't think it is an issue of headroom. If regulating properly, the pass transistor would have close to 3V of headroom and most likely only need around 1V or less.
Although it is unlikely to get a fake from Mouser it is possible to get a bad part.
I have a new PIC straight out of the anti static bag that won't take a program.
Having the opamp the wrong way around would cause it...
What do you mean with 'across the neg pin'?
Jan
measure the voltage across the power pins.
This is a check I do BEFORE I install any opamp.
14V across pin 4 and 7. At this point I think I am going to order some ad817 and try them. Really can't come up with a reason why they are not working.
Starting simple and working back. What would cause a Vdrop of only 3.6V across the LM329dz? I have now tried two different parts from two different orders.
what would you try as opamp substitution between AD811 and AD604. These are the only two I have on hand.
OK, am at the PC now, looking at the circuit.
Let's take the easy stuff first. What is voltage on each side of R4 to ground?
Can you remove C9; could it be wrong way around?
Can you measure the voltages on the output connector, upper three pins against the 4th?
Since you build 4 regs all with the same issue (or so I understand), there must be some systematic issue.
Jan
Let's take the easy stuff first. What is voltage on each side of R4 to ground?
Can you remove C9; could it be wrong way around?
Can you measure the voltages on the output connector, upper three pins against the 4th?
Since you build 4 regs all with the same issue (or so I understand), there must be some systematic issue.
Jan
Let's do this methodologically. If you can't come up with a reason, why do you want to change the opamp??
Two possibilities: R5 is not really connected to the 14V - that's why I asked to measure at the resistor leads.
Second: current getting through R5 is shorted to ground by whatever is in // with D5. Like a very leaky C9 which will happen if C9 is the wrong way around. Can you remove C9 just to exclude that?
What is the voltage at the opamp pin 2 to gnd?
What are your R6, R7 values?
Jan
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Will have my hands on the circuit in about 10 minutes and will provide info you are asking for. I can remove C9 if that helps with diagnosis.
Either side of R4 to ground is 3.6v and 2.5v..
C9 is connected correctly according to documentation and silkscreen.
Output connector
14.34 for 1-4
14.34 for 1-3
0v for 1-2
Pin2 to G - 1.93V
R6 is 715
R7 is 1k
I can remove C9 if you like and remeasure.
C9 is connected correctly according to documentation and silkscreen.
Output connector
14.34 for 1-4
14.34 for 1-3
0v for 1-2
Pin2 to G - 1.93V
R6 is 715
R7 is 1k
I can remove C9 if you like and remeasure.
Nice. C9 seems leaky, only 2V across it. 1.5V across R4 (which is 10% of R4+R5 which are on 14V) gives the 3.5 you measure at D5. Please remove C9.
Jan