Search found 329 matches

by mauman
21 Feb 2024, 18:45
Forum: Boutique Stompboxes dissected...
Topic: Amptweaker - BigRock/TightMetal Pro [traced]
Replies: 63
Views: 35556

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: 364

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: 646

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: 23
Views: 8863

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: 6334

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: 71497

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: 3912

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: 707

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: 707

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: 5124

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: 3349

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: 505

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: 258

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: 18248

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
by mauman
27 Jan 2024, 17:41
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Ibanez - Overdrive II OD-855
Replies: 12
Views: 1464

Re: Ibanez - Overdrive II OD-855

I see they use the M1458. I also tried it and it has a different output stage than opamps 741 and 4558. I tested it once and it distorted differently (than the 4558 in the same situation) , but I didn't test it further. The Motorola 1458 was also the op amp used in the Maestro PS-1/A/B phaser, alth...
by mauman
24 Jan 2024, 02:46
Forum: Pedal Debugging & Troubleshooting Support
Topic: Unvibe build noise
Replies: 5
Views: 446

Re: Unvibe build noise

+1 to blackboarcult's suggestion, let's see it!

And welcome to the forum.
by mauman
22 Jan 2024, 13:44
Forum: Pedal Debugging & Troubleshooting Support
Topic: charge pump voltage divider issues?
Replies: 5
Views: 586

Re: charge pump voltage divider issues?

Welcome karsten_h! Are you saying that you measure 9.69V at the output of your divider when it's not loaded, but when you connect it to the Road Rage input, the divider's output drops from 9.69V to 2.7V? If so, it sounds like your 12V supply can't generate enough current for both your divider and th...
by mauman
19 Jan 2024, 21:46
Forum: Pedal Debugging & Troubleshooting Support
Topic: Green Russian Big Muff Build Issues!
Replies: 3
Views: 463

Re: Green Russian Big Muff Build Issues!

Welcome benhaynie, and congrats on making your first post!

I think the point Rocket Roll is making is that the pinout of your 2N5089 transistors (E-B-C) is opposite that of the vero layout, which was designed for BC549 (C-B-E.) Try rotating all of your transistors 180 degrees.
by mauman
18 Jan 2024, 22:22
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: EHX - Echoflanger [schematic]
Replies: 197
Views: 141511

Re: EH Echoflanger [schematic]

I have two questions regarding this schematic. This really relates to the original schematic but Paul's re-draw here is much easier to follow so we'll go with that. 1. Are C6 (50uF) and C7 (50uF) redundant parts? This looks to me like they could be replaced with a 25uF bipolar cap, but there may be...