Search found 335 matches

by mauman
25 Mar 2024, 13:11
Forum: Printed/Published Online Designs
Topic: EarthTonesAudio: "Buster" boost/buffer
Replies: 11
Views: 3084

Re: EarthTonesAudio: "Buster" boost/buffer

You may have problems with hum if you split the output to two different amps without some sort of isolation. Here is some previous work on that topic, with possible solutions: https://www.freestompboxes.org/viewtopic.php?p=296138 Split the input rather than the output, but it reduces the buffer's in...
by mauman
23 Mar 2024, 01:14
Forum: Pedal Debugging & Troubleshooting Support
Topic: TA-100 'touchy' transistor
Replies: 2
Views: 186

Re: TA-100 'touchy' transistor

Sounds like you have a problem with your ground. Touching the case of Q2 grounds the collector thru you, when it should be grounded thru a 10k resistor already. Pin 1 of the volume pot should already be tied to ground, so grounding it directly shouldn't make any difference. Check your ground bus.
by mauman
21 Mar 2024, 13:52
Forum: Electric Guitar/Bass Wiring
Topic: Baja Active EMG Schematic [schematic]
Replies: 11
Views: 14331

Re: Baja Active EMG Schematic [schematic]

I wonder if its suitable to use a 071 or 741 instead of 4250, as its an unobtanium already.. Either one of these should work OK, just omit the programming resistor R8 and leave the op amp pin 8 floating. I just ran across another substitute for the 4250, though it's also obsolete. If you can locate...
by mauman
19 Mar 2024, 13:17
Forum: Electric Guitar/Bass Wiring
Topic: Baja Active EMG Schematic [schematic]
Replies: 11
Views: 14331

Re: Baja Active EMG Schematic [schematic]

slammer88 wrote: 19 Mar 2024, 09:12 I wonder if its suitable to use a 071 or 741 instead of 4250, as its an unobtanium already..
Either one of these should work OK, just omit the programming resistor R8 and leave the op amp pin 8 floating.
by mauman
10 Mar 2024, 02:32
Forum: Pedal Debugging & Troubleshooting Support
Topic: Oneder Red Ryder clone
Replies: 3
Views: 324

Re: Oneder Red Ryder clone

Yeah, just decrease the value of R10, that first 15k resistor after the clean buffer IC2.4, to increase the clean signal level. Or increase the value of the corresponding resistor after IC2.1 (R11) to decrease the effect level.
by mauman
22 Feb 2024, 03:36
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Digitech - PDS 8000 Echo Plus 8 [schematic]
Replies: 9
Views: 23158

Re: Digitech PDS 8000 schematic [schematic]

The resolution on the PDS-8000 schematic is poor, but this source says the PDS-2000 is similar: https://falseelectronics.blogspot.com/2 ... -8000.html

So here are both.
by mauman
21 Feb 2024, 18:45
Forum: Boutique Stompboxes dissected...
Topic: Amptweaker - BigRock/TightMetal Pro [traced]
Replies: 63
Views: 50800

Re: Amptweaker - BigRock/TightMetal Pro [traced]

Hi Aleksandar, Hi guys. I have a few questions and I need your advice. Can POT 100KC (antilog), LOW and TIGHT be replaced in the following way? Yes, those will work, and will give you approximately 100k antilog for each one. I have a little confusion about the A,B and C pot markings. Is this correct...
by mauman
15 Feb 2024, 14:43
Forum: Pedal Debugging & Troubleshooting Support
Topic: TC Electronic Sustain + EQ low volume
Replies: 2
Views: 410

Re: TC Electronic Sustain + EQ low volume

For continuity and to assist troubleshooting, here's a thread on this pedal: https://www.freestompboxes.org/viewtopic.php?t=9043 Various posts there include links to the layout, BOM, service manual and schematic. Below is Harald Sabro's redrawn schematic with his notes. I would suspect either the co...
by mauman
15 Feb 2024, 04:21
Forum: Pedal Debugging & Troubleshooting Support
Topic: Dunlop Cry baby JH-1 low headroom [SOLVED]
Replies: 8
Views: 14661

Re: Dunlop Cry baby JH-1 low headroom [SOLVED]

I don't think it should do that. If the output is clipping, I would suspect a transistor. Here's a starting point for schematics, apparently there have been several revisions of the JH-1 across time. viewtopic.php?p=267574
by mauman
14 Feb 2024, 18:31
Forum: Boutique Stompboxes dissected...
Topic: Bogner - Harlow Compressor (gut shots) [traced]
Replies: 40
Views: 53707

Re: Bogner - Harlow Compressor (gut shots) [traced]

If you have a tone generator and a scope (or true-RMS VOM) you can use a signal to do the same. Inject 60 hz at 1V on the primary, and measure the voltage on the secondaries to get your ratio.
by mauman
14 Feb 2024, 18:22
Forum: Pedal Debugging & Troubleshooting Support
Topic: True Bypass Clipping? Possible? [SOLVED]
Replies: 14
Views: 19335

Re: True Bypass Clipping? Possible? [SOLVED]

I think you'd need to bypass the pedal completely, since whatever it is, remains in the signal path during the current bypass method. It's a pretty small enclosure, and the bypass switch is mounted on the PCB so that might be tough unless you rehouse it in a larger enclosure to make room for a separ...
by mauman
13 Feb 2024, 18:36
Forum: Modern Stompbox Effects (1975 - ...)
Topic: MXR / CAE - MC401 - Boost/Line Driver [schematic]
Replies: 84
Views: 83227

Re: MXR / CAE - MC401 - Boost/Line Driver [schematic]

Hi, everyone. I would like to ask it's the correct schematic? I am confused about the voltage line (V+) connects to non-inverting input but it should be connected to pin8 accordingly to the datasheet. Welcome to the forum, Eugene! This schematic, like many, doesn't show the V+/V- connections to the...
by mauman
10 Feb 2024, 21:02
Forum: Announcements and Forum Rules
Topic: Heavy Spam Attacks - manual account activation [RESOLVED]
Replies: 4
Views: 17628

Re: Heavy Spam Attacks - manual account activation [RESOLVED]

Good job in finding and fixing this, Johan. For those who didn't see it, it was pretty bad for a day or two. Mike
by mauman
10 Feb 2024, 15:08
Forum: DIY Projects
Topic: OGBip-2 overdrive on 2n5088 bipolar transistor
Replies: 11
Views: 844

Re: OGBip-2 overdrive on 2n5088 bipolar transistor

plush wrote: 10 Feb 2024, 10:31 I'd bootstrap vt6 to increase it's input impedance.
How would you select the value for a bootstrap cap here? Is there a rule of thumb, or a formula, or is it just by ear? I've built circuits that use them, but have never added one.
by mauman
09 Feb 2024, 23:31
Forum: DIY Projects
Topic: OGBip-2 overdrive on 2n5088 bipolar transistor
Replies: 11
Views: 844

Re: OGBip-2 overdrive on 2n5088 bipolar transistor

Sounds good! Your bias plan looks interesting with the two 1N4007 diodes. So the bias voltage will be about 1.2 V?
by mauman
09 Feb 2024, 22:18
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Goodrich - Model 7A Super Sustain Match Box [schematic]
Replies: 4
Views: 14943

Re: Goodrich Model 7A Super Sustain Match Box [schematic] [schematic]

I'm repairing yet another one of these, and this one has a Motorola MC33171P op amp. It's similar to the MC34181, with slightly worse specs, but still plenty good enough for this device. This op amp has a noisy output, but both the 33171 and 34181 are obsolete in PDIP, I will probably get a used one...
by mauman
07 Feb 2024, 03:58
Forum: Boutique Stompboxes dissected...
Topic: 29 pedals - Euna [traced]
Replies: 16
Views: 14557

Re: 29 pedals - Euna [traced]

I'm curious of someone can explain to me, in as simple of terms as possible what the harmonics switch accomplishes. Thanks. If I'm reading the schematic labels right, the "harmonics" switch (labelled H+ here) puts C28 in series with C27, making an effective capacitance of 69 nF (220 nF + ...
by mauman
03 Feb 2024, 17:01
Forum: Amplifiers
Topic: Roland Jazz Chorus JC-77 Pre-amp
Replies: 3
Views: 560

Re: Roland Jazz Chorus JC-77 Pre-amp

Your breadboard schematics match the original schematic, so I think your actual breadboard wiring must be a little different than your schematic. The manual says the Distortion pot will increase output volume. Since Roland made the Distortion switch part of the pot, you can't turn up the original Di...
by mauman
01 Feb 2024, 14:22
Forum: PCB Guitar Mania - pedal builders group and debug
Topic: footswitch breakout
Replies: 2
Views: 303

Re: footswitch breakout

Welcome! And congrats on your first post, it's a good question. They hid their wiring instructions here: https://pcbguitarmania.com/wp-content/uploads/2019/03/Pedal-Wiring-Guide-1.pdf You'll need to see document section 3 (jacks) and 4 (3PDT footswitch.) And the "D1" holes in the bottom ro...
by mauman
29 Jan 2024, 18:34
Forum: Modern Stompbox Effects (1975 - ...)
Topic: DOD - FX75B Stereo Flanger [schematic]
Replies: 20
Views: 19003

Re: DOD - FX75B Stereo Flanger [schematic]

slammer88 wrote: 29 Jan 2024, 06:14 This pedal seems to suck my tone a bit too much from treble side even when bypassed. Can anyone tell me what can I do to fix that?
See viewtopic.php?t=33027