Let's build an amp! Greg's journey to electrocution

[Bubba]

This has been an excellent thread to follow. What I'm most impressed with is your ethos during the build, Greg. The routing, the quality of soldering, the continuous testing and checking that everything is performing exactly to spec has left you with an amp build that is of professional quality. I suspect that somebody could throw this kit together without all your planning, meticulous testing and skill and they may even end up with it working if they're very lucky but it would not be a patch on what you've accomplished.

Very, very well done.

[JD01]

Cool. Not that id ever expect you to play SRV tunes, was just wondering what sort of thing it was. Looking forward to hearing it properly cranked.

[Greg_L]

That is impressive man. Hella impressive. I can only imagine the rewarding full fillment you must have right now man. Holy fuck.

For some reason i had it in my head it was going to be a combo amp but it's you. I should have known better. Looks awesome. purple tolex is deadly. It looks right at home with it's cousins.

Very stoked to hear what that rig can do Hombre.

Thanks man. Yeah I have no use for a combo. The plan all along was to have this built as a head to be used with my Marshall cabs. That's why I had to use a different output transformer and finagle that impedance selector switch to work. Fender stack? Sure! I can do it now.

This has been an excellent thread to follow. What I'm most impressed with is your ethos during the build, Greg. The routing, the quality of soldering, the continuous testing and checking that everything is performing exactly to spec has left you with an amp build that is of professional quality. I suspect that somebody could throw this kit together without all your planning, meticulous testing and skill and they may even end up with it working if they're very lucky but it would not be a patch on what you've accomplished.

Very, very well done.

Thank you man, I appreciate that. Since I don't/didn't really know what I was up against I have to assume that my slow and steady attention to every little detail is why I have a working amp and not a pile of parts with problems. I can honestly say that I didn't let anything slide. I'm satisfied with my work on every single wire and blob of solder. Besides my one terribly boneheaded tube socket fuckup, it's ended up pretty much perfect. I expected to be chasing down bugs for weeks. But it seems that so far I've dodged that bullet. Maybe it's beginner's luck, maybe it's my careful attention to detail, but whatever it is I'll take it.

I've read many horror stories from people building these amps and then I see their pics and I'm like, no fucking wonder. It looks like a 5 year old built it. You CANNOT just throw these things together. But if you look at the guts of an original 60s Blackface Fender, they look like total hell inside, so who knows. Lol. Whatever.

Cool. Not that id ever expect you to play SRV tunes, was just wondering what sort of thing it was. Looking forward to hearing it properly cranked.

I can try some SRV, but that would be a massive LOL.

[Greg_L]

Hold the phone, I think I found a problem.

My #2 jacks seem to be hotter than my #1 jacks on each channel. That aint right. I did something goofy with my jack hookups. Dammit.

That stupid layout diagram bit me again. The schematic and diagram are different.

[JD01]

Shit a bollock! Easy fix?

[Greg_L]

Shit a bollock! Easy fix?

Shouldn't be too bad. I know what I need to do.

[JD01]

Shit a bollock! Easy fix?

Shouldn't be too bad. I know what I need to do.

That's alright then. I was worried (fuck, I'm worried about your project) that it would be something that you'd have to hunt for!

[Greg_L]

That's alright then. I was worried (fuck, I'm worried about your project) that it would be something that you'd have to hunt for!

No no, I'm just trying to decipher if my way of wiring it still functions as it should, but with the jack's roles just being reversed.

I'm okay with 2 being the high input and 1 being low. That's fine. But I need to know that the impedances are correct.

[Greg_L]

Okay so I measured across a guitar cable plugged into each jack. My 2s are measuring at 1M and my 1s are measuring around 118k....which is about right, but they are backwards to what I thought they should be.

So my 2 is indeed the high input, and 1 is the low input. No big deal, and I understand why now. I think I'll just leave it.

[rayc]

My 1st thought on thta fault was label & leave - just leave works too. Excellent journey with no hair tearing or tears on my part.

[jonny deep]

Nice work, Greg! Look forward to hearing it.

[Greg_L]

My 1st thought on thta fault was label & leave - just leave works too. Excellent journey with no hair tearing or tears on my part.

Nice work, Greg! Look forward to hearing it.

Thanks dudes. Tones coming today!

[JD01]

Thanks dudes. Tones coming today!

Cool - I imagine its a bit early in the morning there to go cranking amps. Looking forward to it though.

[Greg_L]

Cool - I imagine its a bit early in the morning there to go cranking amps. Looking forward to it though.

It's 6 am. Lol. I could do it. I can do whatever I want. But out of respect for the rest of the family, I'll wait a little while.

[JD01]

Cool - I imagine its a bit early in the morning there to go cranking amps. Looking forward to it though.

It's 6 am. Lol. I could do it. I can do whatever I want. But out of respect for the rest of the family, I'll wait a little while.

Would make an excellent alarm clock.

[liv_rong]

Excellent work man! Can’t wait to hear it.

[Greg_L]

Sound clips in the Tone Thread!

[muttley]

Place holder.. halfway down page..

[Greg_L]

I'm just talking about undischarged caps when the power is off ..... almost by definition it can't go thru your heart because you have to short the leads of the cap with your skin ..... butthere is a full-blown OMG reaction about those caps even with power off and I say it's a way overreaction

I went back into the amp today. New power tubes, checked some things out. Still looking good. Power tubes are matched well now and perfectly in spec. I'm gonna put it on my new scope and see if I can make any sense of it.

I was thinking about this today so I checked the filter caps. The first cap still had 250 VDC in it after days of doing nothing. That's enough to give you a solid jolt. Probably not lethal. But it sure didn't discharge much from two day of sitting turned off. Creepy. All of Marshalls discharge way faster than that for some reason.

[Lt. Bob]

some designs have those caps fairly isolated so there's little leakage ...... 250 volts discharged at once'll wake you up .... no way it's lethal from those smallish caps .... there's just no way they can have enough amperage.
You have to have both and amperage is actually a bigger factor.

You can use a Van de Graf generator and pop yourself with an inch long spark of 1,000,000 volts and it will not harm ya'.

The biggest danger IMO, speaking as one who has been zapped by amp innards quite a few times is injuring your hand when you reflexively jerk it back at hyperspeed and slam it into the corner of the chassis.

IMPORTANT NOTE: I am NOT suggesting anyone shove their face on a big cap! Use some common sense to avoid pain .... especially if you're wussy about getting shocked.
I'm not but I understand some folks are really squeamish about it ... even finding the idea of touching your tongue to a 9 volt a frightening idea.
But I don't believe caps in an amp will kill you and a search found zero examples of it happening in guitar amps.

The only amplifier caused death I can find is that guy from Counting Crows I think it was and that wasn't working on an amp ...... that was on stage and I think he was using an Ampeg and if so, the same thing that happened to me happened to him only I didn't croak.
And that was a power switch had got knocked loose and put wall voltage to the ground and thus 110 volts to the strings of my bass so when I went to sing and my lips touched the mic BAM*!*@#@! ...... I was on the floor. It was like someone hit me in the face with a bat.

But getting pooped by a cap ...... I'd prefer not to and am careful to avoid it but I've been around amps and amp techs and worked on amps all my life and I personally don't buy into the fear factor.