sonolink

Help with Menatone Red Snapper please
« on: January 10, 2021, 07:47:32 PM »
A friend asked me to see if I could fix his Menatone Red Snapper accidentally connected to a 12v PSU. I've been trying to find a schem for this babe but there seems to be plenty of different versions.
This one has a marking on it that says "c.2013. Red Collar Revival" and somewhere else handwritten "mk3".
Also it kinda smells of burnt metal...

Any ideas, suggestions?
Thanks for your time and help

« Last Edit: January 10, 2021, 09:45:29 PM by sonolink »
Why sleep when you can mix?
M.P.Stavrou


radardoug

Re: Hekp with Menatone Red Snapper please
« Reply #1 on: January 10, 2021, 09:20:02 PM »
Are you techncal? Do you have tools? Some simple probing with a multimeter is your friend. Get the opamp pinouts and see if they have appropriate voltages.

scott2000

Re: Hekp with Menatone Red Snapper please
« Reply #2 on: January 10, 2021, 09:41:46 PM »
What's up with that one diode? Looks a bit janky...

sonolink

Re: Hekp with Menatone Red Snapper please
« Reply #3 on: January 10, 2021, 09:43:38 PM »
Thanks for your reply :)
I think I have found a dead protection diode but being without a schem is kinda daunting. I'm going to replace the zener (it reads same voltage on both directions) and see what happens

Cheers
Sono
Why sleep when you can mix?
M.P.Stavrou

sonolink

Re: Hekp with Menatone Red Snapper please
« Reply #4 on: January 10, 2021, 09:45:07 PM »
What's up with that one diode? Looks a bit janky...

Which one Scott? I'm after the one top left for now ;)
Why sleep when you can mix?
M.P.Stavrou

scott2000

Re: Hekp with Menatone Red Snapper please
« Reply #5 on: January 10, 2021, 09:50:31 PM »
Which one Scott? I'm after the one top left for now ;)

Just thought one next to the 4558 looked weird. May be pic...

radardoug

Re: Help with Menatone Red Snapper please
« Reply #6 on: January 10, 2021, 11:32:17 PM »
Pedals often have a reverse diode across the power input to catch wrong power supplies. Your meter is your friend. Use the continuity buzzer to work out where the diode connects. Normally its not a zener, just a power diode.

abbey road d enfer

Re: Help with Menatone Red Snapper please
« Reply #7 on: January 11, 2021, 06:36:46 AM »
A friend asked me to see if I could fix his Menatone Red Snapper accidentally connected to a 12v PSU.
Connecting a 9V pedal to a 12V supply of correct polarity should not result in damage. I think this particular 12V supply was also of the wrong polarity. The protection diode is very likely to be shot.
Try removing it and check if it works on battery.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with Menatone Red Snapper please
« Reply #8 on: January 11, 2021, 07:02:57 AM »
Normally its not a zener, just a power diode.
I initially thought it would be a Zener because of its orange color and appearance:


After reading you post I found a schem online and the protection diode they use to clone this pedal is a 4001. But on the other hand I got in touch with Menatone today, asking them voltage and power rating for the protection diode and they answered very kindly and quick that it should be a 12v/1 watt zener diode...
Mmmm...

I think this particular 12V supply was also of the wrong polarity. The protection diode is very likely to be shot.
I suspect you're right, Abbey. I couldn't get hold of my friend to ask him about the PSU he used by mistake but since the pedal is center negative I bet he used a 12v center positive PSU.
Without removing it from the board, my multimeter reads the same voltage across it in both directions, so most probably the diode is shot. I will try what you sugest this afternoon and report back.

If it's the protection diode, I guess I can replace it with a 1N4001, right? Or should I use a 12v/1W zener, as Menatone recommended?

Thanks to all for your help :)
Cheers
Sono
Why sleep when you can mix?
M.P.Stavrou

JohnRoberts

Re: Help with Menatone Red Snapper please
« Reply #9 on: January 11, 2021, 11:01:11 AM »
First check that the old one is bad... diodes typically fail as a short circuit (after silicon melts from overheating).

A 12V zener across a +9V rail will look like high impedance, a 12V zener with -9V across it will look like a normal diode (sometimes two diode drops) and start conduction to clamp the reverse voltage.

For simple reverse polarity protection a typical rectifier diode will generally work. If the manufacturer calls for a zener, why argue with them?

JR
It's nice to be nice....


sonolink

Re: Help with Menatone Red Snapper please
« Reply #10 on: January 12, 2021, 10:47:55 AM »
If the manufacturer calls for a zener, why argue with them?

Not arguing with them :)
Just eager to understand why the designer used a 1N4742 for circuit protection and why the guys cloning the pedal use a 1N4001. I would guess the second is because 4001s are very common.

A 12V zener across a +9V rail will look like high impedance, a 12V zener with -9V across it will look like a normal diode (sometimes two diode drops) and start conduction to clamp the reverse voltage.
"Look like"? Excuse my language barrier but could you (or someone) rephrase that please? I'm not sure I understand everything you are saying :)

Cheers
Sono

Why sleep when you can mix?
M.P.Stavrou

abbey road d enfer

Re: Help with Menatone Red Snapper please
« Reply #11 on: January 13, 2021, 05:45:40 AM »
Not arguing with them :)
Just eager to understand why the designer used a 1N4742 for circuit protection and why the guys cloning the pedal use a 1N4001. I would guess the second is because 4001s are very common.
"Look like"? Excuse my language barrier but could you (or someone) rephrase that please? I'm not sure I understand everything you are saying :)

Cheers
Sono
A zener, connected in the reverse direction, does not conduct until the voltage exceeds the zener voltage. Below the zener voltage it appears like it was not there.
Even if the 12V supply was of the correct polarity, power supplies often deliver more than nominal. Poorly regulated PSU's often deliver 10-20% more voltage than nominal. that could be enough to shoot the zener.
Using a zener to protect has two purposes: protecting against reverse voltage, because then it's in teh forward conduction mode, protecting againg overvoltage of correct polarity, and it has the advantage over a standard diode in series that it does not introcuce voltage drop (about 0.7V). The main disadvantage is that when it goes into protection ii is often shot (melt). This does not happen with a standard diode in series.
As you see, there are pros and cons to each method.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


sonolink

Re: Help with Menatone Red Snapper please
« Reply #13 on: January 13, 2021, 09:51:18 AM »
As you see, there are pros and cons to each method.
Zeners are very interesting indeed. Thanks for the explanation ;)
I wish one day I can buy you enough beers to retribute all the knowledge you have given to me here :)

Seems like it is an OD1 clone
Thanks a lot for those links Peter!
I believe it's more like a T.Screamer on steroids with better controls (kinda like a King Of Tone 8) )

I've been fighting with my CNC this past weekend and with the snow these days but I'll try all your suggestions this week and report back.
Thanks again to all for your help.
Cheers
Sono
Why sleep when you can mix?
M.P.Stavrou

midwayfair

Re: Help with Menatone Red Snapper please
« Reply #14 on: January 13, 2021, 09:56:23 PM »
There's a lot of chasing ghosts in this thread but a few good suggestions.

Dirk's schematic is clearly wrong for this pedal: The photograph of the inside of the pedal for repair has a 1044 charge pump. There should be a 12V Zener diode in this version because the maximum voltage for the chip is 12V. However, if your friend really did plug in a 12V supply, the charge pump would survive and they would just get 24V instead of 18V distributed throughout the circuit, which is unlikely to blow up any parts.

Many guitar pedals now use a 1N4001 or similar in series with the voltage supply to protect against reverse polarity. The old technique of strapping the 1N4001 across the power pins is from the days when the only thing it would blow up was a battery, not a wall wart, and people didn't want to lose the precious 0.6V of battery power by connecting it in series. Almost all guitar pedals that use a charge pump use a Zener for overvoltage protection, in part because it's what everyone else does, in part because it's cheap and it works just enough, and in part because ... well, honestly I'm not totally sure everyone even knows that voltage regulators exist ...

Anyway, here's a simple procedure for fixing a guitar pedal you don't have the schematic for:

1. Hook up your DC meter to ground and the tip of the power jack. Plug in a normal 9V supply and check that you have 9V across the DC jack. If you don't, put your meter on continuity and start locating the parts connected to the DC jack. You want to check for the following: (a) shorted electrolytics, (b) burned out diodes (e.g. a zener that's been fried by overvoltage will have let the magic smoke out), (c) A dead charge pump chip.
2. Here's the datasheet for the charge pump: http://ww1.microchip.com/downloads/en/devicedoc/21348a.pdf. If you need to see one in use, the Madbean Road Rage is a useful enough schematic: https://www.madbeanpedals.com/projects/_folders/BreadBuddies/schematics/RoadRage2019.gif. Check the voltages on the charge pump; if it's working, the easiest thing to check is that pin 5 is -9V. Post the voltages on all the pins of the 1044.
3. There would be a pair of rectifier diodes if the charge pump were being used as a voltage doubler, and I don't see them in the picture; this leads me to believe that it's being used for a bipolar supply on the 4558. Take voltages (and post them) on the 4558. You're either going to have something like 1,2,3,5,6,7: 0V, 4: -9V and 8: +9V or something like 1,2,3,5,6,7: +9v,  4: 0V, 8: 18V. If you have voltages on the charge pump and NOT on the 4558, switch to continuity again and start backtracing. The bottom line is that it's not a very complicated circuit. The distortion is the two back-to-back diodes next to the 4559, and the resitors and capacitors there are tone shaping and gain setting. About a third of the capacitors on the board are for power filtering, and there's what looks like the parts for a simple tone control in the bottom left (for the bite control). The axial just south of the power supply is the cut cap, probably 10nF. All of those parts are going to be fine.

The worst possible thing that's happened is that the 1044 is blown and you have to replace it. It happens a lot. Notice that the road rage uses a 1054 instead --- we all switched over to those after getting tired of everyone asking why their Klone/whatever blew up. The 1054 can take 15V and survive short exposure to 18V inputs, it's just MUCH less likely to blow up if someone plugs in the wrong thing. Anyway, if you have to order a part, you might as well pay an extra dollar for the better one.
I'm Jon. Myself's music and things I make: jonpattonmusic.com. My band: www.midwayfair.org. [Disclaimer: PCBs of guitar pedals I've designed are sold by Madbean, 1776 Effects, and JMK PCBs.]

sonolink

Re: Help with Menatone Red Snapper please
« Reply #15 on: January 14, 2021, 07:12:06 AM »
Thanks a lot for your detailed input Jon :)
Do you think Dirk's schem is correct regarding the audio circuit? Just guessing here but maybe he decided to keep things simple and stick to 9v? Although that probably wouldn't keep the character of the original pedal since the dynamic range would be reduced I guess...

Cheers
Sono
Why sleep when you can mix?
M.P.Stavrou

midwayfair

Re: Help with Menatone Red Snapper please
« Reply #16 on: January 14, 2021, 10:28:20 AM »
Do you think Dirk's schem is correct regarding the audio circuit? Just guessing here but maybe he decided to keep things simple and stick to 9v? Although that probably wouldn't keep the character of the original pedal since the dynamic range would be reduced I guess...

I'm not sure, but most of the other schematics I've seen from him were accurate to the pedal guts photos. I think it's more likely that Menatone changed the pedal at some point -- they've been around for a long time now.

The 47nF for the negative feedback (bite control) is there, as is the 10nF for the cut control and a silver mica that's small enough to be the 100pF cap, so all the caps look the same. I don't see the asymmetric diode in the feedback loop (there are three in Dirk's schem but I can only see two), but maybe it's the angle.
I'm Jon. Myself's music and things I make: jonpattonmusic.com. My band: www.midwayfair.org. [Disclaimer: PCBs of guitar pedals I've designed are sold by Madbean, 1776 Effects, and JMK PCBs.]

analogguru

Re: Help with Menatone Red Snapper please
« Reply #17 on: January 14, 2021, 11:07:05 AM »
I don't see the asymmetric diode in the feedback loop (there are three in Dirk's schem but I can only see two), but maybe it's the angle.
There are three diodes, have a closer look... the left one are two


 

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