Search found 389 matches

by george giblet
10 Nov 2023, 04:21
Forum: Amplifiers
Topic: Fender H.O.T. practice amp hum (50hz) noise even the guitar is un plugged.
Replies: 20
Views: 3104

Re: Fender H.O.T. practice amp hum (50hz) noise even the guitar is un plugged.

any ideas? thanks a lot If the amp circuit ground is floating from the chassis then Manfred's scheme is the best option. If the Jacks are not isolating then maybe not. If the inputs hot line are floating then it could cause noise. If all is working pin 4 or Jack J1 should short the input to ground ...
by george giblet
09 Nov 2023, 06:45
Forum: Electric Guitar/Bass Wiring
Topic: 9V Low Battery Indicator (Layout)
Replies: 15
Views: 4437

Re: 9V Low Battery Indicator (Layout)

Thanks for the info and sorry for the wrong schematics. I did not fully realize the characteristics of the Zener diode. And I found this topic addressed with a schematic here: https://www.freestompboxes.org/viewtopic.php?t=31502. The voltage reference on that circuit (ZXRE330), is designed to work ...
by george giblet
09 Nov 2023, 06:42
Forum: DIY Projects
Topic: Re-amp box transformer quest and 0 Ohm resistor
Replies: 18
Views: 702

Re: Re-amp box transformer quest and 0 Ohm resistor

Thanks George, really helpful! I measured the transformer's dimensions and the resistance between all leads, I only get values at these points here: Between leads marked in red (1 and 3 in your marked up schematic) = 836 Ohm in all switch positions. Between leads in blue (6 and 5 in your marked up ...
by george giblet
08 Nov 2023, 10:39
Forum: DIY Projects
Topic: Re-amp box transformer quest and 0 Ohm resistor
Replies: 18
Views: 702

Re: Re-amp box transformer quest and 0 Ohm resistor

There's actually a patent which became the Reamp units, Radial Engineering - Patent US6005950 1999.png The transformer in the patent has multiple taps so it's unclear exactly how it is connected up. The thing about the different reamp products s the basic idea is the same but there doesn't seem to b...
by george giblet
08 Nov 2023, 02:06
Forum: Electric Guitar/Bass Wiring
Topic: 9V Low Battery Indicator (Layout)
Replies: 15
Views: 4437

Re: 9V Low Battery Indicator (Layout)

And there is second option, which I found it. So just a basic simulation and a list of low power opamps and comparators. This scheme was also in the datasheet of one of them about the application. The threshold from simulation was set to 7.4V (the preferred value will depend on when the sound from ...
by george giblet
08 Nov 2023, 02:00
Forum: DIY Projects
Topic: Re-amp box transformer quest and 0 Ohm resistor
Replies: 18
Views: 702

Re: Re-amp box transformer quest and 0 Ohm resistor

You should measure the DC resistances of the transformer primary and secondary to help judge the transformer impedance. Measure the primary with no input connected and the switch in the -10dBV position to prevent loading. Also the transformer dimensions. I've made a few tweaks to the schematic: - tr...
by george giblet
07 Nov 2023, 22:25
Forum: DIY Projects
Topic: Diode Compressor design, and the issues with it
Replies: 2
Views: 816

Re: Diode Compressor design, and the issues with it

Try disconnecting the diode to the indicator circuit. The diode + base-emitter looks like it is hogging compression diode current. I suspect you will need to add a resistor in series with the diode on the indicator ckt to reduce loading.
(In fact the original ckt has a resistor.)
by george giblet
22 Sep 2023, 02:46
Forum: Pimp-My-Cheap-Pedal
Topic: Behringer Ultra Chorus UC200 Rehouse Issue
Replies: 6
Views: 1371

Re: Behringer Ultra Chorus UC200 Rehouse Issue

Measure the supply rail between ground the the anode of the LED. If the supply is low, like 5V, the LED won't light. Next, for both effect and bypass modes: measure the voltage between ground and the collector of T10 and the voltage across the LED. From that you should be able to workout if the LED ...
by george giblet
21 Sep 2023, 22:16
Forum: Boutique Stompboxes dissected...
Topic: JHS - Bender [traced]
Replies: 13
Views: 4069

Re: JHS - Bender [traced]

I suspect "mictester's" version should be used, since otherwise the gain pot setting slightly affects the bias. Is it correct that the switch bypasses the hot cake-style tonestack and simultaneously alters the bias point to lower the total output, compensating for the perceived boost from...
by george giblet
19 Sep 2023, 06:55
Forum: Boutique Stompboxes dissected...
Topic: JHS - Bender [traced]
Replies: 13
Views: 4069

Re: JHS - Bender [traced]

I found a few things and updated the schematic.

I didn't check the switch wiring to see if the each half of the switch selects the correct components.

After looking at mictester's silicon bender, should the alternative pot wiring be used?
JHS Bender Schematic (paz 2023_09) GG V1.1 fixes.png
by george giblet
14 Sep 2023, 02:23
Forum: Modern Stompbox Effects (1975 - ...)
Topic: MXR - Super Badass Variac Fuzz [schematic]
Replies: 17
Views: 13293

Re: MXR - Super Badass Variac Fuzz [schematic]

The issue here is that without knowing what U3 (G115) is, it would be very hard anyway to replicate the circuit. Unless there is an alternative circuit which can still generate the same voltage swing that this pedal has. The earlier parts list had: R1154H115B Nisshinbo Micro Devices Inc https://www...
by george giblet
11 Sep 2023, 22:29
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Reagun - Overdrive [schematic]
Replies: 10
Views: 5789

Re: Reagun - Overdrive [schematic]

Good stuff Manfred, thanks. I suspect the diode+150 ohm resistor connects in series with the -ve lead of the DC in (but not the battery -ve lead). Similar to the Boss ACA power inlet, https://www.hobby-hour.com/electronics/s/boss-ce2-chorus-schematic.php FYI, I came across this version. https://reve...
by george giblet
10 Sep 2023, 04:00
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Reagun - Overdrive [schematic]
Replies: 10
Views: 5789

Re: Reagun - Overdrive [schematic]

Something caught my eye when I was looking at the schematic: there is a HPF before the clipper stage. However, the schematic shows the clean signal is post the HPF. I checked the PCB and Manfred's overlay and I'm certain the clean path should connect to the emitter of buffer transistor, before the H...
by george giblet
19 Jul 2023, 00:44
Forum: Pedal Debugging & Troubleshooting Support
Topic: Measure signal in dBm
Replies: 10
Views: 1145

Re: Measure signal in dBm

A friend who worked in the telecom industry gave me a Siemens level meter on permanent loan. That thing definitely had a dBm scale. It was great because it had quite high sensitivity and wide bandwidth. I've a got very large tube-based noise and distortion meter. Built like a tank. Analog meter. Can...
by george giblet
18 Jul 2023, 02:18
Forum: Pedal Debugging & Troubleshooting Support
Topic: Measure signal in dBm
Replies: 10
Views: 1145

Re: Measure signal in dBm

For dBm, the 600 ohm reference is an "artificial" scaling factor. The 600 ohm value is used for the reference impedance in calculations even though there's no termination or there may even be some other impedance in the actual circuit. It's kind of a weird thing to do but that's how it is...
by george giblet
17 Jul 2023, 02:28
Forum: Pedal Debugging & Troubleshooting Support
Topic: Measure signal in dBm
Replies: 10
Views: 1145

Re: Measure signal in dBm

I assume that these values in the schematic are meant independent of the 600Ohm terminating resistor and thus the reference voltage level is 1 Vrms. dBm in audio is essentially dBu (ref voltage 775mV rms) For dBm, the 600 ohm reference is an "artificial" scaling factor. The 600 ohm value ...
by george giblet
16 Jul 2023, 06:33
Forum: Pedal Debugging & Troubleshooting Support
Topic: Measure signal in dBm
Replies: 10
Views: 1145

Re: Measure signal in dBm

When I see dBm (as opposed to dBmV) I read it as dB relative to a reference *power* level of Pref = 1mW, dBm = 10*log10(P / Pref) = 10*log10(P / 1mW) For audio we actually want voltages and we can't convert voltage to mW unless we know the reference impedance. For audio the reference impedance is 60...
by george giblet
22 Jun 2023, 04:47
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Budda - Chakra Compressor [schematic]
Replies: 11
Views: 7724

Re: Budda - Chakra Compressor [schematic]

With the addition of one wire things change a lot. BuddhaComp - possible sch fix GG_2023_06_22.jpg The things hanging would be the 47k on the opamp and the precise wiring of the Attack pot. As drawn the pot isn't really attack but could be perceived as affecting the attack. It would help a lot if we...
by george giblet
21 Jun 2023, 23:57
Forum: Parts & Tools Sourcing & Trading
Topic: 2n5457 original ou fake?
Replies: 7
Views: 1683

Re: 2n5457 original ou fake?

What you really need to do is build your own tester then compare the results against the TC1. I don't have much faith in component testers for JFETs. In some cases what they report is "true" but only if you know how to interpret what the numbers mean. In many cases they don't report the ID...
by george giblet
19 Jun 2023, 08:57
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Budda - Chakra Compressor [schematic]
Replies: 11
Views: 7724

Re: Budda - Chakra Compressor [schematic]

The schematic can't work as shown. Also, if you look at the parts on the PCB they don't quite add-up with the schematic. It's too hard to fix or rebuild the schematic from the top side of the PCB. To me it looks like John Hollis's Flatline compressor except: - buffer added at input and output - atta...