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Any DIY pedal builders on TB? Strut your stuff!
- Thread starter SubHuman
- Start date
Alright, so I've spent quite a bit of time poring over this Pumpernickel with the multimeter. I've been looking at both the THAT datasheet and the schematic above.
Everything on my THAT matches the expected connections on the datasheet and the schematic except pin 10.
If I'm reading the datasheet right, 10 should be VEE (in this case, -9V) and the easiest "touch" is the -9V for the LED bar.
If someone would confirm that their THAT Pin 10 and -9V are continuous on their pumpernickel, I would be forever in your debt.
Everything on my THAT matches the expected connections on the datasheet and the schematic except pin 10.
If I'm reading the datasheet right, 10 should be VEE (in this case, -9V) and the easiest "touch" is the -9V for the LED bar.
If someone would confirm that their THAT Pin 10 and -9V are continuous on their pumpernickel, I would be forever in your debt.
Thank you! I can't wait to put a jumper wire on it this evening. I suspect I may have partially lifted the pad but can't see it, explaining the short.
Could that be why it's heating up so bad?
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Well I got THAT Vee tied into -9V, but it seems I also have a short between -9V and GND somewhere 
Guess I'll keep poking around!
Guess I'll keep poking around!
Forgot to add that at least my THAT isn't overheating anymore. Took a feel of both the charge pump and the op-amp though and sure enough the charge pump is heating up - hence the other short I found.
No overheating on any of the ICs anymore, but decidedly no sound out of the pedal, and the LED doesn't come on.
Found the short between -9V and GND ON the THAT retrofit module (I checked it before and so this is new). No other shorts between any other rails.
Would this be expected if the module was fried? I wouldn't know how to tell if there was a "fuse" that maybe shorts to ground or something. I fluxed + cleaned up pins 9 and 10 on it to be sure but I'm getting a beep all the same. Seems hard to believe that there could be a bridge on the header side of the chip, which is why I'm wondering if it's just blown.
Thanks again for all your help. I would not have known for sure to hook up Pin 10 and -9V without it.
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My first real journey into ALL smd. Its a 2 band MusicMan Pre. I did manage to find the LM4250 ICs. Sounds pretty good. Found the project on GitHub , credit for schematic and pcb go to Russell McClellan. I used his open source files and had pcbs made. It it tiny. This thing had my eyes buggin. Bass pick next to it for reference.
Matt
Matt
daft question ... 2 band musicman preamp on through hole uses one 8 pin IC - you've got three going on here - how come?
Passinwind
I know nothing.
- Dec 3, 2003
- 23,079
- 46,041
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
This week on the test bench:
Variable HPF in 1590A enclosure. Soon to be open source for DIYers, maybe more easily done in 1590B format though.
And then this will be V3 of the long running Bass/Mids/Resonant LPF pedal project:
I also whipped up a new two band version, just Bass/LPF. It gives a very different vibe, I like it a lot so far.
Variable HPF in 1590A enclosure. Soon to be open source for DIYers, maybe more easily done in 1590B format though.
And then this will be V3 of the long running Bass/Mids/Resonant LPF pedal project:
I also whipped up a new two band version, just Bass/LPF. It gives a very different vibe, I like it a lot so far.
I'm still new to building myself SO I will do my best to explain the way I THINK the designer created the circuit and why he used 3 ICs. Ther is a lot of information on his GitHub. GitHub - russellmcc/basspre-mm2: MusicMan-inspired 2 band bass pre-amp
I think his intentions were to use a LM4250 for each band, 1 for treb , 1 for Bass. Also 2 LM4250 equate to one 8 pin IC .
The 3rd IC is a TLE2426 used for a split rail power supply (not sure why this is needed).
Again, it is Based on the MusicMan Pre. I take no credit for the creation or design. I'm not an electrical engineer just a guy that loves sniffing solder.
Its questions like these that help me grow my knowledge and get better so Thank you for asking. I have said why I think he did what he did, and I will post the schematic and maybe those with more knowledge can weigh in and we can all learn more together.
thanks
Matt
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Upon further research I have found the reason for the Rail Splitter. This is from the creators page.
The pre-amp has a buffered input to maintain very low thermal noise, it uses a rail-splitter IC instead of a resistor divider to ensure clean tone with very low power, and the voicing is modified to be less treble-heavy to ensure low EM interference.
Baja's trace of Leo's preamp (with modifications from that guy who used to be on here lots, and then wasn't) for comparison
Passinwind
I know nothing.
- Dec 3, 2003
- 23,079
- 46,041
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
what I like about the MM preamp is the way it was designed with this (for the time) crazy bass pickup, fed straight into the preamp, and the volume at the output stage of the preamp...
If you feed different pickup combinations into, say with series, single coil, parallel on dual MM style pickups, and then a 5 position switch for pickup blend you can have the original MM setup and then different options.
In reality I built that and it wasn't that fun as the input impedance changes lots the sound jumped all over the place and I would have been better off with a single pickup bass like the ray was originally designed.
If you feed different pickup combinations into, say with series, single coil, parallel on dual MM style pickups, and then a 5 position switch for pickup blend you can have the original MM setup and then different options.
In reality I built that and it wasn't that fun as the input impedance changes lots the sound jumped all over the place and I would have been better off with a single pickup bass like the ray was originally designed.
First builds of 2023.
FLOCK - a harmonizing fuzz (PedalPCB).
Love the sounds you can get out of this, it's PLL allright, but "a bit tamed" - or less annoying - than other PLL things. Then again, I love PLL things, even the annoying sounds.
ENGORGED GHERKIN is what the lads from Fuzzdog call their take of the Swollen Pickle.
A totally tricked out, massive Muff, that brings all the bass you want and then some. The Clip knob, blending between diodes, is very cool.
I used 4x 2N3904.
FLOCK - a harmonizing fuzz (PedalPCB).
Love the sounds you can get out of this, it's PLL allright, but "a bit tamed" - or less annoying - than other PLL things. Then again, I love PLL things, even the annoying sounds.
ENGORGED GHERKIN is what the lads from Fuzzdog call their take of the Swollen Pickle.
A totally tricked out, massive Muff, that brings all the bass you want and then some. The Clip knob, blending between diodes, is very cool.
I used 4x 2N3904.
Love it, Engorged Gherkin, lol great name. Good lookin builds .
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