Hi everyone! First post here - want to start by saying thanks in advance :)
I finally finished building my Total Recall (2024 version - 18v positive ground). When I went to start testing I had a problem right away with the voltage regulator not outputting the expected 15v.
I've tried two known working power supplies (a ciocks using two 9v outs w stack cables & a supply for our projector that is 19v DC) I measured the voltage coming from the barrel of the supply as ~18v. Made sure I have the polarity oriented correctly. Tested for continuity between the first few components prior to the voltage regulator.
The regulator itself is a L7915CV (the build calls for LM7915 but I think they are the same unless I'm mistaken). One thing I noticed is it gets extremely hot, easily causing severe burns or melting things within a second of contact - I'm hoping someone can tell me if this is normal?
The other thing to note is, this regulator's legs are a little too thick to fit through the pcb holes, so I had to file them down a bit, and I messed up the first one - one of the legs ended up breaking off as I was soldering it in, so I had to remove it and empty the pcb holes using the "melt and tap" method. I since tried two other L7915CV regulators. Anything I should try with the currently installed regulator? Possible that both regulators were defective and I should just order new ones?
I've done complicated builds before like a monome norns kit, and also did kicad design and building of my own arduinoboy (midi interface for a gameboy), as well as several pedal/amp mods. That said, I've never had to test voltages, so it got me wondering am I going about probing/testing the wrong way? I had a couple sparks fly once or twice when I was testing (accidentally shorted the supply I guess) - hoping that doesn't mean I'm fried and need to start over.
Okay think that's everything relevant. Thanks anyone who can help!
Hi & Welcome,, :icon_wink:
Check regulator's output to GND resistance..
P.S. A link to particular version buld should be useful.. :icon_wink:
Check the pinout for the regulator and compare it with the other version.
I seem to remember having a similar problem when I replaced a small TO92 package regulator with a larger TO220 package one - it turned out the pinout wasn't the same. That would explain the "unusual warmth"...;)
Also check the orientation of the regulator. I have a bad habit of putting them in back-to-front. They don't work so well that way around, but they do survive the mishap!
Ahh, I have made an error on the BOM. You need a 79L15, not L7915. I really hate these regulator naming conventions and the different pinouts. Anyway, it uses a TO-92 package, not 220.
I will correct that. In the meantime, I have a few of the correct regulators on hand. PM me and I will get one in the mail to you tomorrow.
It may have come up on the mbp forum before and I forgot to upload the correction. In any case, very sorry for the dumb mistake.
(https://i.postimg.cc/mhNGywsS/Total-Recall-Power.gif) (https://postimg.cc/mhNGywsS)
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Thanks everyone for the suggestions! I definitely will note these for future troubleshooting if I encounter a similar situation. In this case it was simply just a wrong part that I had.
Thanks so much Brian for seeing this and taking the time to reply!
Sent you a message :)
I now have the pedal working, however am getting the exact same problem as described in another forum regarding the 2024 total recall.
https://forum.pedalpcb.com/threads/madbean-total-recall-2024-cant-calibrate.25396/
Essentially there is a high pitched noise present when audio probing test points 2, 3, and 4.
I'm understand that the clock comes from IC 7, so I have visually checked all the solder points on that IC socket. Are there any other suggestions? Maybe worth noting this high pitched noise goes away if the delay time is made shorter (I think bc it's shifted up into inaudible frequency range above 20khz).
Also present in the pedal's output is the exact same kind of noise present in the recordings posted in the pedalpcb link below. The noise I experience is much more prominent at higher delay settings, but I've seen numerous youtube demos of Total Recall that don't exhibit this behavior.
Overall I have the pedal dialed in (in terms of bias & impedance) sounding pretty great, the high pitched noise isn't an issue in the final output of the pedal, but the white noise that sort of "follows" the curve of the modulation is something I'd like to troubleshoot. Are there any suggestions on ways to eliminate (or minimize) it?
Thanks again for reading, and for any help
Also is there a way to edit my OP? Sorry if this is obvious but I'm just not seeing it :icon_frown:
Quote from: vires on March 19, 2025, 05:43:46 PMis there a way to edit my OP?
The EDIT function is available for only a short time (hours? a day?). If minor error, let it fly, everybody has followed-up with corrections. If a serious mix-up, look under "More..." "Report to moderator" say it is
your post, and ask for help correcting.
>
noise present when audio probingDon't do that on stage? Any high-gain audio amplifier will squeal if you have 3 feet unshielded wire to a sensitive point.
I'm specifically talking about clock noise coming from the pedal, whether this is to be expected at the test points, or if it indicates a problem that should be addressed. The documentation says to use the test points with audio probe but doesn't mention to expect clock noise.
The white noise on the output of the pedal is a bigger concern to me. It's a swish/woosh kind of noise that is more noticable with modulation on the pedal being greater than 0, as the "swish" (frequency sweep of the white noise) follows the modulation curve.
The noise is worse/better depending on the delay knob setting. At various points from 0-max, the noise disappears, and at other points it it becomes excessively loud. What's weird is it's not the typical "long delay time = noisy"... Some very noisy spots on the low end of the knob, some in the middle some towards the top. The noisy/quiet spots are pretty evenly distributed through the range of the knob.
I really appreciate any troubleshooting ideas :)