525 build thread

[benlindell]

I'm finishing up a pair of these that I bought from another user here and I'm having some troubles.

One is smoking up one of the resistors on the upright opamp. I check for shorts at the pins and there's none so I'm wondering what I should look at to fix it.

The second one isn't passing audio when engaged and the meter isn't showing anything except some jumps when turning the big knob. I did a quick once over with a probe and am getting sound off the upright opamp.

Any help on tweaking these to get them working would be great.

thanks

 

[peter purpose]

Ben,
Did you do the capacitor mod?
See page 3

 

[benlindell]

yes I did.

 

[peter purpose]

Check the transistors on the burny one. Check the wiring to the in/out switch on the other.

 

[benlindell]

Checked the switch, everything is wired fine.

I think I'm going to take this one at a time rather than trying to fix two things at once, so I'm starting with the non-burny one

I double checked the wiring of the switch and probed it and it's working fine.

I took the 3 DOAs from my working one (one I built myself and using your DOAs) and put them in, still nothing.

probed the upright opamp and it has signal in and out. This one is not burning but the transistors are significantly hotter than my working one, but like I said there is signal coming out of it's output.

Here are pictures of the upright opamp.

Where should I be looking next.

Thanks,

 

[peter purpose]

Grab the schematic and follow the signal through until it pops into the ether.

 

[benlindell]

any ideas on why the upright opamp would be running hot?

 

[peter purpose]

wrong components?

 

[ethervalve]

Hi,
I'm nearly done assembling my 525, but i'm a tad confused about r64. Does anyone know where it should be connected?
Thanks in advance.

 

[peter purpose]

On the rotary switch.

 

[ethervalve]

cheers good sir. this demon monday smote my wits and senses.
incidentally, fine work on the boards/layout.

 

[kazper]

http://www.apiaudio.com/nw_1090.html

It looks like something... just can't put my finger on it...

 

[benlindell]

Peter, I went through the upright opamp and it's all the correct components and I checked all the components around it as well and they all seem to be the correct values.

Took it off from the back again, I'm not seeing any bridges or non connections.

 

[peter purpose]

Troubleshooting is an art. I think we need someone who knows what they're talking about to pipe in.

 

[substitute]

I don't know why it took me so long to do this project but I finally have one channel up and running with just one issue.
My leds for the meter started smoking so I adjusted the PSU to +/-15v (from 18), they stopped smoking but no longer light up.  Any idea what might cause that?

Also I have a basic usage question, what happens when you have both limit and compress buttons engaged?

Thanks for the cool project Pete!  I really dig the limiter on acoustic guitar.

 

 

[kazper]

Too much current.... what resistor value did you use to limit the current to the LED/driver, and what driver IC did you use?

 

[substitute]

Too much current.... what resistor value did you use to limit the current to the LED/driver, and what driver IC did you use?

That would be RM1 correct?  It's 1k and I'm using the NTE 1549 meter driver.

I also noticed that if I turn the ceiling knob all the way up (position 20) I loose signal.  I assume it's shorting to ground, I'll double check my wiring but if any one has any ideas please let me know.

 

[emrr]

I've been pondering over the Attack issue since I'm in process of finally finishing up my 4 units.

I think peter originally designed this attack from Joe from JLM audio's post #18 on this thread http://www.groupdiy.com/index.php?topic=61.0

To add attack control just cut into the track or wire that joins to the join of R5 & C3 and add a pot wired as a variable resistor. A 10k pot will give the same attack range as a 1176 has.

Joe

It looks like Peter designed as Joe described with one exception:  I think the additional rheostat (whatever value, 10K, 50K, 100K) should not be between r5 and c3, but inserted ahead in the line feeding their junction.  C3 holds the bias to Q1, and we want to slow down it's ability to fill.  As drawn, I think it fills just as quickly, and we are affecting it's drain rate.  I may be wrong.    

 

[peter purpose]

Tried it both ways and with the wiper feeding the cap.... all NFG.

 

[peter purpose]

That would be RM1 correct? 

Jess my preng.