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Scodiddly wrote: ↑

Thu Feb 11, 2021 7:10 pm

If you followed my advice and bought more than one replacement, then put the extra into a little baggy and tape it to the side of the power supply.

Well, I've got a little container for studio spare parts like fuses, etc., but I did take your advice and get like 4, just in case!

20210211_155152_copy_514x906.jpg Fuck. Yeah. I replaced the lm317 voltage regulator. Not my cleanest solder job but I used a solder sucker for the first time ever (what an invention!). I started with the empty chassis and tested the power supply and the chassis' pinout, then put each preamp in one ...

Based on the remote diagnosis I can do through the tiny window presented, yeah, swap the regulator. Be sure to get the high voltage version. There's the risk that my analysis is incomplete...but a new regulator will be revealing. Of course, but I appreciate the energy you've put into helping me. I'...

I'll guess that the 10K is in parallel with the trimpot, combining for the 2.17 K. Adding 2.17K to the 15400, the calculator yields approx 48V. Your regulator is the prime suspect. 10 years of a slight overvoltage likely killed it. Would you say it's worth just replacing that voltage regulator firs...

Keep following the Adj pin: What's beyond the 15k4 resistor? It disappears under the PCB. Theres a resistor right next to it that COULD be in its path and that looks like it SHOULD be 10k, but is measuring at 2.17k. That one disappears under the PCB as well. And I was incorrect about my correction ...

Those are likely 1N400x, just basic power diodes, as shown in the datasheet. If the transformer gets disconnected, they discharge the output caps...as shown in Fig 15 of the datasheet. (No guarantee about what 1Nxxxx device is. They come in plain silicon, Schottky and Zener.) Can you trace the Adj ...

I sometimes use omni on something like percussion which i don't want to feel like it's RIGHT INSIDE MY EAR and then have to use eq or reverb to push further back... It's funny, I never think to do this. I do lots of percussion overdubs, and, like you, I want to give them a a certain amount of space...

I don't THINK I see any zener diodes. Do they ever look black like generic/schottkey diodes? There's a couple that look they're coming off of and bridging the outer legs on that voltage regulator, but I can't read the numbers to see what they are. They sometimes do look like that. Double check with...

I have 2 mics with switchable patterns. Akg 414 tlii - I use it on omni as a close-ish guitar amp mic. My favorite mic for this job unless I REALLY need the thump from the proximity affect. Otherwise, I'll use that mic usually in cardioid as a side-of-the-snare-drum mic. An inexpensive c12/251 imita...

The question in my mind is whether the regulator is standing on top of a zener diode, to boost it's operating range. If the zener failed short, the regulator would still regulate, just without the boost. I don't THINK I see any zener diodes. Do they ever look black like generic/schottkey diodes? Th...

(Edit) Ok this says that the right leg is input

So, here's what i got on that LM317:

Left Leg 15.78
Middle leg 16.2
Right leg 71.6

Wouldn't that be the opposite of how it should be?

And here's an overview of both sides.

The Scum wrote: ↑

Tue Feb 02, 2021 4:42 pm

In the top picture, center-left, there's a little black cylinder with a silver stripe on the end. Can you read any of it's markings?

Does he say "ZPY33"?

Can you measure voltage across him?

I measured all 4 large diodes

D1 and D2 give me 0.018
D3 and D4 give me 0.47

Testing 48v OUT gave me the same 15v DC But testing 48 PRE gave me 67v DC I'm hoping this means the problem is somewhere between these 2 points. I will have to unscrew the PCB (which will involve unscrewing a handful of other attached components) to see what's between those 2 points. Your gut feeli...