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FDP Forum / Amp Mods, Repairs, and Projects / 5e3 kit standby switch

darrengoleafs
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WNY

I played Black Sabbath at 78 speed
Apr 15th, 2019 07:16 AM   Edit   Profile  

Let me see if I got this right.
The mojotone 5e3 deluxe kit has a standby switch in the schematic that is not fully functional but is there if you would like to make it functional...but you really dont need it?

Leftee
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VA

Knuckleheading
Apr 15th, 2019 07:30 AM   Edit   Profile  

You really don’t need it. If it were there, I’d wire it up. I prefer to have one.

darrengoleafs
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WNY

I played Black Sabbath at 78 speed
Apr 15th, 2019 07:41 AM   Edit   Profile  

Leftee take a look at the wiring diagram on the mojotone site (I cant link it here at work).
It is partially wired and non functional. I want to hook it up, just got sidetracked during the build.

(This message was last edited by darrengoleafs at 09:48 AM, Apr 15th, 2019)

Leftee
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Knuckleheading
Apr 15th, 2019 07:45 AM   Edit   Profile  

It’s a bit hard for me to look, now. I’m on my iPhone.

Peegoo
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Just beyond Mars

there's a world of fools
Apr 15th, 2019 07:57 AM   Edit   Profile  

In a diode-rectified amp like an older Marshall or blackface Twin Reverb, a standby switch helps extend the life of the tubes; you turn the amp on with the power switch, and then a minute later you turn on the standby switch. In a tube-rectified amp, a standby switch really isn't necessary.

But like Leftee says, if the parts are there and the hole is punched for the switch, I'd wire it up.

An option, however, is to forget the standby switch idea and use it as a switch to enable/disable a NFB loop. Switching it in cleans up the amp; switching it off gives you a more 'raw' sound.

I added an NFB switch to my Vibro Champ and it is a useful feature.

Look here, first mod at the top of the list.

Leftee
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VA

Knuckleheading
Apr 15th, 2019 08:25 AM   Edit   Profile  

^ I would suspect that’s why Mojotone left it unwired.^
To do something groovy with it.

Sometimes with a tube-rectified amp with no standby switch you'll get some crackles and pops during warmup. It ain’t no thing.

ECS-3
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USA / Virginia

Apr 15th, 2019 08:26 AM   Edit   Profile  

I always found standby switches useful to quiet the amp during breaks and making/breaking connections.

Having the amp in standby also let's it cool down a bit.

darrengoleafs
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WNY

I played Black Sabbath at 78 speed
Apr 15th, 2019 08:37 AM   Edit   Profile  

I will do that NFB mod. It makes sense why monotone left it there. Thanks gents!

Peegoo, is it ok to run a wire from the switch at the top of the chassis(standby switch) down to the bottom jack lug and the 56 k resistor?
I would be running the other leads as well so maybe I answer myself. He shows the NFB switch on the chassis underside next to the speaker jacks and tube socket.

Also, it looks like he mounted a turret to the board to seperate the connections to the piggybacked 1.5k and 22uF...? Can I just connect to the leads of each and leave them piggybacked? Thanks.

(This message was last edited by darrengoleafs at 10:38 AM, Apr 16th, 2019)

darrengoleafs
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WNY

I played Black Sabbath at 78 speed
Apr 17th, 2019 11:02 AM   Edit   Profile  

Peegoo, you are familiar with the NFB switch mod, see above please, I have a couple questions in reference to your link. Thanks.

pdf64

UK

Apr 19th, 2019 05:25 AM   Edit   Profile  

I've had a look at Mojotone's Tweed Deluxe info and can't find any reference to a standby switch, much less one that's 'partly wired' (heck, how can a standby switch be partly wired!)?
As per the 5E3, there's a 'ground switch' but it's completely out of circuit, no connection to mains, the only connection to it is the 'death cap'.
Is that actually is being referred to?
It's bad practice to use components in the mains circuit that don't have specific approval for that use, so if you wish to wire up the ground switch, the orange drop cap supplied by Mojo should not be used for that purpose.

Peegoo
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Just beyond Mars

there's a world of fools
Apr 19th, 2019 07:00 AM   Edit   Profile  

Yes, you can run a long wire to the switch with no issues.

The connections to the 1.5k resistor and 22uF cap must be separated. Look at the schematic; on the left side where the NFB switch is labeled in red, you can see the resistor and cap are separated.

darrengoleafs
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WNY

I played Black Sabbath at 78 speed
Apr 19th, 2019 07:31 AM   Edit   Profile  

Thanks Peegoo!

It looks like (in the pic below diagram) that he put a turret into the eyelet board for the resistor to connect to...? Sorry if this is common but im a newbie. And I dont read schematics as well as I should...yet.
I am however, being quite certain to drain caps!

pdf64, check the wiring diagram at the mojotone site. i wired an orange cap and a ground wire to the ground switch per the diagram......it doesnt do anything.

pdf64

UK

Apr 20th, 2019 03:03 AM   Edit   Profile  

The thread title and OP is in regard of a STANDBY switch, not a GROUND switch. They are very different things.

As your amp has a tube rectifier, and as you will hopefully be using it with properly grounded electrical installations, neither standby or ground switches would be beneficial, and both would have drawbacks.

So yes, use the switch for something else :-)

Peegoo
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Planet Peegoo

Lewd guitar player
Apr 20th, 2019 04:03 PM   Edit   Profile  

It does look like he added a turret. This is good practice where flying leads (wires running from the board to a switch, socket, etc.) are attached. you never want a ‘flying lead to depend on a component like a resistor or cap to maintain the connection to the board. The only exception to this rule is probably the shielded lead from the input to V1 with the resistor at the socket end.

darrengoleafs
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WNY

I played Black Sabbath at 78 speed
Apr 20th, 2019 06:25 PM   Edit   Profile  

I apologize. I meant ground switch from the beginning. I also learned along the way that they are different. Thanks for bearing with me.

I installed the NFB switch and it is definitely worth doing when building this kit. Its like having 2 different and very usable amps in addition to the 5e3. I am falling in love with this amp and the interaction of the 2 channels and jumping them as well. This has been a very educational project and I want to learn more. I am eyeing up the tweed vibrolux kit.

Peegoo thanks, I understand why a turret (or eyelet) is best practice here but I was unable to attach it to the board. Drilled a hole for it.
So for now there is a flying lead from the 1.5k resistor to the switch. Seems pretty sturdy.

I’m so glad I built this. It sounds phenomenal.

pdf64

UK

Apr 22nd, 2019 11:07 AM   Edit   Profile  

Yes, I thought you might have written one when you meant the other. No problem, we all get things mixed up, one way or another, now and again :-)

Peegoo
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Planet Peegoo

Rhythm & Lewd Guitarist
Apr 22nd, 2019 08:26 PM   Edit   Profile  

Cool! Glad the amp is sounding great.

On small combo amps the NFB switch is super handy when you need that vintage squawk for a harp player. Flip the NFB out and you have it.

FDP Forum / Amp Mods, Repairs, and Projects / 5e3 kit standby switch




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