Epic fail (L4 kaputt)

mybud

mybud

Well-known member
So after the L5 clean and L5 legacy builds, I was looking forward to building the L4 bass version. It's quite a bear of a build with some specialised parts, as below.

IMG_1821.jpeg

All seemed to be going according to plan but no dice when I fired it up. I had checked the voltages beforehand and they looked kind of off but I thought that this would come right in the wash.

Silly hubristic me. It didn't.

I haven't the chops (or the heart TBH) to try to troubleshoot this but it seems clear from the really silly voltages (0.678 on IC1 for starters) that I've somehow managed to bork the voltage converter. The rest is (a resounding) silence.

I'm trying to be philosophical and not yield to disappointment and self-blame for a change. This hobby is a learning curve after all.

This goes into the box of shame and I'll try again with a fresh board later, I think.

So the real question is how does the hive mind deal with abject failure if and when such occurs? I'd really like to hear from others on how they deal with this.

Disclaimer: this is not the complete assembly. The one I tested was fully populated.
 
Last edited:
Sort by date Sort by votes
Everything looks okay component and orientation-wise for the electrolytics, but I didn't check resistor values--except I can't see the 5817 stripe on either shot--could that be it?

If not, I'd doublecheck that the Traco module is a correctly compatible one. Maybe check for continuity between points of the circuit and/or jumper 9v in front of the 5817.

Are you measuring the output for 15V+/VA+ and 15V-/VA- from the daughterboard outs?

Waiiiittt a minute... Your daughterboard is wired upside-down, so are the wires still going to the right place on the main board? I would think not. Maybe that's not the issue, but I'm sure it could contribute to non-functionality.
 
Upvote 0 Downvote
comradehoser said:
Everything looks okay component and orientation-wise for the electrolytics, but I didn't check resistor values--except I can't see the 5817 stripe on either shot--could that be it?

If not, I'd doublecheck that the Traco module is a correctly compatible one. Maybe check for continuity between points of the circuit and/or jumper 9v in front of the 5817.

Are you measuring the output for 15V+/VA+ and 15V-/VA- from the daughterboard outs?

Waiiiittt a minute... Your daughterboard is wired upside-down, so are the wires still going to the right place on the main board? I would think not. Maybe that's not the issue, but I'm sure it could contribute to non-functionality.
Click to expand...
I think those are ok, the board is just out and flipped.
 
Upvote 0 Downvote
Nic said:
I think those are ok, the board is just out and flipped.
Click to expand...
Right, but then the daughterboard wires are referencing the wrong/opposite connections on the main board. Like -15 is going into +15. No? I mean, my spatial reasoning can't be that off, right?

I'm specifically looking at the pic in post 16 showing the full assembly and daughterboard connected upside down.

[edit: ah, I think I get it.]
 
Last edited:
Upvote 0 Downvote
comradehoser said:
Well if you can see it on the 5817 (bottom pic) alright, I still can't. [edit: not bottom pic, that's the 4742; the 5817 is to the left of the rightmost switch. I don't see a stripe at all]

IC 4 is upside down?
Click to expand...

Apple-polly-woggies!

Talk about epic fails... me trying to help. I know what a 1N5817 looks like yet I still got muddled with the (Zener?) pink outlines, yer talkin' bout the bit in green.

L4 FOOT-SW DAUGHTERBOARD.png

My L4 build-doc's representation of the footswitch daughterboard is bare minimum, and the only thing on the build-doc board diagram that says "D1" is actually labelled "RPD1" which is a pulldown resistor between IC4 and IC1.


Anyway, trying to help but I'm just gettin' in the way...

[cat, bowing profusely, backs away]
 
Upvote 0 Downvote
Feral Feline said:
Apple-polly-woggies!
Click to expand...

My fair Canadian brother,

It's totally all good. Sorry for being unclear, I don't know how to do the drawing on pictures thing.

I don't think I'm helping much either, but I am all in for helping my bud figure this out, and since I can't really speak to complex circuit analysis and diagnostic (Chuck D Bones I ain't) I tend to focus on the dumb stuff that I can understand first or have effed up personally.

Have done backwards 5817 and have done reversed ICs (it's why I use sockets now). Pretty sure I also did the wrong traco module at least once.

Go Oilers!
 
Upvote 0 Downvote
As per your updated photo... the IC below Vol 2 is upside down, and R14 is unpopulated. There is also a missing resistor just to the left of the upside down IC

edit.. also a missing component just below Volume 1

These big builds are an exercise in stamina
 
Last edited:
  • Like
Reactions: Nic
Upvote 0 Downvote
falco_femoralis said:
As per your updated photo... the IC below Vol 2 is upside down, and R14 is unpopulated. There is also a missing resistor just to the left of the upside down IC

edit.. also a missing component just below Volume 1

These big builds are an exercise in stamina
Click to expand...
Yes, you're quite right: not my finest hour, it seems. The missing resistors are 'correct' because I used A2k pots instead of Kevin's more complicated arrangement of different values with taper adjustments, as per the build doc.

The upside down IC is a silly mistake and clearly I seemed to have dropped the ball at the last minute. Of course I should have saved the final testing for another day but I didn't.

Pacing myself better (i.e., stamina) is a lesson learnt for future builds. Thanks for your comments.
 
Upvote 0 Downvote
mybud said:
Yes, you're quite right: not my finest hour, it seems. The missing resistors are 'correct' because I used A2k pots instead of Kevin's more complicated arrangement of different values with taper adjustments, as per the build doc.

The upside down IC is a silly mistake and clearly I seemed to have dropped the ball at the last minute. Of course I should have saved the final testing for another day but I didn't.

Pacing myself better (i.e., stamina) is a lesson learnt for future builds. Thanks for your comments.
Click to expand...
Did you get it working?
 
Upvote 0 Downvote
Erik S said:
Did you get it working?
Click to expand...
No. The voltage readings are still peculiar. I may in due course try to rebuild the offboard power supply on veroboard as a temporary solution to test the main board.

There’s a slim possibility that the voltage converter was defective because I don’t recall ever measuring the required +-15V called for. But slim I say, because it’s more likely some other stupidity on my part.
 
Upvote 0 Downvote
Feral Feline said:
Good to see progress has been made; steps taken have brought you that much closer to journey's end.

Since I can offer no practical help, I'll cheer you on.
Just a few more steps...
Click to expand...
Yes, absolutely FF. Update follows:

Kevin got back to me with the generous offer of a discount on a reorder, which is seriously cool IMO. I’m by no means a power client so I appreciate the gesture no end.

But I want to try fixing the PSU on the existing build first by building a +-15V power supply on Veroboard. My plan is to socket the Traco for reuse if necessary but build the PSU assembly small enough to fit in the case. The Traco costs nearly $18 landed here, so not cheap and, if all else fails, I can use it for a subsequent reorder if I’ve fried the main board into the bargain.

I’m hoping that the small voltages that I measured imply no harm to the main board but having the correct power at hand will confirm this or otherwise.

I feel like I’ve recovered from my earlier slough of despond and I’m itching to get this beast up and running. Thanks for all your interest and support meanwhile. I’ll keep you all posted on further developments.
 
Last edited:
Upvote 0 Downvote
I know from experience that those TRACO modules can take a fair bit of abuse and survive, so there is a good chance it is fine. I have before tested them on a breadboard just by providing voltage in the specified range to the correct pins and measuring the output pins. For me at the time I got it out of my board (not the L4, totally different circuit) by soldering a solid copper wire joined to all the pins, and then using that to heat them all up at the same time and gently pry it out. Of course if you have better tools or more skill then use them :-)
 
Upvote 0 Downvote
Thanks, @PJS. It’s quite tricky to desolder the Traco, I’ve found, but again a good pointer. I’ve ordered a replacement meanwhile and definitely intend to test it in advance for correct voltages.
 
Upvote 0 Downvote
I've found the easiest way to uninstall IC's is to yank the bulk of the solder out with good desoldering braid (I use Superwick 425-LF, tho I don't use lead free solder), from both the top and the bottom of the PCB, let it cool, then push each pin over inside its solder pad with the soldering iron, and go back and scoop up the remnant solder. Then take a small flathead screwdriver and slip the tip of it under one side of the IC while applying heat to each pin to try to lift up that side. Gradually stick more of the screwdriver under the IC while applying heat, using the screwdriver as a wedge. Go slow and watch each pin as you go. Some of them stick while others come free. Take your time and learn which pins are going to give you trouble, and spend more time with those. Stop periodically so you don't overheat the board.
 
Upvote 0 Downvote
You must log in or register to reply here.
Back
Top