Nightpro EQ3D repair tips

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fazeka

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Hi all,

I have an old (ca. late '90s) Nightpro EQ3D that needs repair on one channel. I am yet to acquire it and am trying to do research on it while I wait for it. From the Nite EQ project here, it seems pretty straightforward. I am thinking at worst, it would be a bad IC? Otherwise, it's likely a cap and/or (less likely) a resistor. I mean, that's pretty much the only things it contains, it seems...  ;)

Any tips/things I should be on the lookout for, specifically?

Cheers!
 
be forewarned that portions of the circuit may be smd - the NitePro PreQ3 preamp I have from the same era is populated largely with surface mount devices - not sure if the EQ3D was done similarly.
 
fazeka said:
Hi all,

I have an old (ca. late '90s) Nightpro EQ3D that needs repair on one channel. I am yet to acquire it and am trying to do research on it while I wait for it. From the Nite EQ project here, it seems pretty straightforward. I am thinking at worst, it would be a bad IC? Otherwise, it's likely a cap and/or (less likely) a resistor. I mean, that's pretty much the only things it contains, it seems...  ;)

Any tips/things I should be on the lookout for, specifically?
Click to expand...

Before you start shotgunning parts, it's helpful to determine what's wrong. "Needs repair on one channel" is vague. And "late 90s" isn't exactly old, so I wouldn't expect electrolytic caps to have failed.
 
Thanks everyone on the feedback.

Yes, I will not shotgun parts.

Bummer if this unit is SMD...  :(
 
I've been doing traditional soldering with through-hole components for over 25 years now and consider myself pretty good. If this unit is SMD, how challenging is it should I need to replace SMD components? Should I invest in a hot-air pencil or reflow station?

Share yer tips and tricks with an "olde tymer"...  :eek:
 
Also has a switched power supply. Anyone can give some pointers on how to troubleshoot that?
 
fazeka said:
Also has a switched power supply. Anyone can give some pointers on how to troubleshoot that?
Click to expand...
If only one channel is faulty, this same psu will not be the reason of misbehaviour, considering the non-faulty operation of the other channel.
As Andy already said, "determine what's wrong".
Having a working channel, you can easily compare points of operation, following signal path, where signal splits to the seperate frequency bands and where signals recombine. Maybe it's only a broken XLR-cable, more likely a broken/oxydated pot or switch or a faulty electrolytic cap.
 
Harpo said:
If only one channel is faulty, this same psu will not be the reason of misbehaviour, considering the non-faulty operation of the other channel.
Click to expand...

Yup, you're right.

So, I traced a signal on channel 2 and get voltage on U4 pin 1. OK.

I go back to the dead channel and I get nothing on channel 1 U4 pin 1, no output. I go back to input (XLR pin 2), I get signal. I go to pin 3 of U4, no signal... then I look at the traces on the PCB... they look like they are... oxidizing... are my traces "rusting" before my eyes?
 
fazeka said:
I go back to the dead channel and I get nothing on channel 1 U4 pin 1, no output. I go back to input (XLR pin 2), I get signal. I go to pin 3 of U4, no signal... then I look at the traces on the PCB... they look like they are... oxidizing... ??? are my traces "rusting" before my eyes?
Click to expand...

They could look better thats for sure, but measure continuity in the traces, probably they are working fine,
you need to clean the PCB very well with ISO alcohol.
Then with a QTip I would apply a small portion of Deoxit D6 just on the traces to stop and prevent corrosion, probably that unit was kept in a really bad environment.

Start with measuring continuity and resistance in the traces, to be sure they're fine.

 
Hi all,

Life kinda got in the way recently so I haven't had a chance until the last week to get back to this and thus this update.

So I cleaned up the boards and went through the traces and there were a few that needed help and I think I have got everything sorted so far.

Now, channel 1 never had any sound whatsoever. I traced through the circuit and confirmed C14 on channel 1 went open at some point in the last 18 years (the unit is from 1999). I subbed a known good cap there (albeit temporarily as the lead spacing of this spare cap I had is way too big) and the channel is working just fine.  ;D Sounds pretty damn nice, actually. I can see why these are (somewhat?) coveted.  :)

Still working on channel 2 as (despite what the seller claimed) it is not working, either, though there is low output of sound available at output. I will be having to purchase a new cap for C14 so I may as well replace the other 470uF caps throughout.

Stay tuned for more.

Cheers,
Chris
 
fazeka said:
Hi all,

Life kinda got in the way recently so I haven't had a chance until the last week to get back to this and thus this update.

So I cleaned up the boards and went through the traces and there were a few that needed help and I think I have got everything sorted so far.

Now, channel 1 never had any sound whatsoever. I traced through the circuit and confirmed C14 on channel 1 went open at some point in the last 18 years (the unit is from 1999). I subbed a known good cap there (albeit temporarily as the lead spacing of this spare cap I had is way too big) and the channel is working just fine.  ;D Sounds pretty damn nice, actually. I can see why these are (somewhat?) coveted.  :)

Still working on channel 2 as (despite what the seller claimed) it is not working, either, though there is low output of sound available at output. I will be having to purchase a new cap for C14 so I may as well replace the other 470uF caps throughout.

Stay tuned for more.

Cheers,
Chris
Click to expand...
Hey hey hey c14 was an lytic..  ;)  Now that you have one channel working will make it easier to sort the other one...
 
Update: pin 4 on the ICs on channel 2 is measuring at ~1 VDC when it should be measuring -18VDC, so suspecting that channel's power supply. Will probably recap the whole power supply while I am there.
 
fazeka said:
Update: pin 4 on the ICs on channel 2 is measuring at ~1 VDC when it should be measuring -18VDC, so suspecting that channel's power supply. Will probably recap the whole power supply while I am there.
Click to expand...

Ummmm, both channels use the same power supply.  More likely there is a bad opamp or a power supply decoupling cap that has failed.  If the PSU was bad Channel 1 would be at -1VDC too.
 
Measure the -18V supply rail on the PSU and follow it to the Channel 2 IC's -V pins. Measure it along the way before and after each component.

I had to edit my previous post,
After cleaning the pcbs with Iso Alchool I would use a QTip to apply a small portion of Deoxit D6 on the pcb traces to stop and prevent corrosion.
 
On some old pcbs the vias (contact between top and bottom of pcb) liked to go bad, it might be something to look into. Also, is the pcb trace on the right hand side interrupted, close to the via? It is hard to see on the jpg, and maybe you spotted it already...

Cheers,

Michael
 
If the Ic measures funny,  pull the ic and see what you measure on those pins. If there is no socket,  then cut out the ic to make it easy as you would desolder one pin at a time vs 8. Then adds a socket... it's probably a tl072 or 5542/34 so they are pretty inexpensive to replace.
Without the ic if the voltage is low, look for a coupling cap and replace it. If voltage is what it should be, replace the chip as it has a fault
 
pucho812 said:
If the Ic measures funny,  pull the ic and see what you measure on those pins. If there is no socket,  then cut out the ic to make it easy as you would desolder one pin at a time vs 8. Then adds a socket... it's probably a tl072 or 5542/34 so they are pretty inexpensive to replace.
Without the ic if the voltage is low, look for a coupling cap and replace it. If voltage is what it should be, replace the chip as it has a fault
Click to expand...

It's not one IC that "measures funny".
The OP said all the IC's in channel 2 receive -1V from the negative rail. So if it's all the IC's, then it's probably something in the negative supply rail and not in the IC's themselves

 

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