Beginners Guide - Installing a Grounded Power Cord in Vintage Amps

In this video I show you how I install a 3 prong power cord in a vintage amp (in this case a 1966 Fender Pro Reverb, but the method applies to most other vintage amps with a 2 prong power cord).
Have any critiques or suggestions? Drop them in the comments below, open forum :)
Products used:
Auto Range Multimeter: www.circuitspecialists.com/pr...
Multimeter probes: www.amazon.com/dp/B0895GQ4YG?...
Snuffer Stick: www.tedweber.com/amptechtools...
Soldering Iron: www.circuitspecialists.com/pr...
Kester Solder: www.amazon.com/gp/product/B00...
Solder Sucker: www.amazon.com/gp/product/B0B...
Uncle Doug Current Limiter Video: • Build Your Own Current...
Timestamps:
0:00 Test subject
0:20 Steps to make amp safe
2:04 Discharge caps safely
2:47 Standby Switch ON/OFF
3:57 Hand in pocket trick
4:53 Inspecting 2 prong
5:37 Soldering time!
6:40 Strain Relief removal
7:49 New 3 prong
9:20 Wire placement
10:27 REMOVE FUSE
10:40 Soldering time!
11:35 Neutral wiring
13:10 Fuse / Hot wiring
17:06 BIG soldering iron
18:54 Cleaning chassis
20:40 Scoring chassis for solder
22:54 Soldering to chassis
26:00 Continuity test
27:21 Closeup overview
28:38 Checking our work
30:48 Outro
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[@YeatzeeGuitar]

Made the video I wish someone else had made when I was starting out 🙂 Let me know what you think, and if you do anything differently let's hear it!

[@Justin-lx5cz]

From someone who is starting out, this is perfect. Thank you!!

[@YeatzeeGuitar]

@@Justin-lx5cz exactly who I made it for! 🙏

[@hkguitar1984]

I'm sure your video will indeed assist others. I had to do the same for a 1947 Magnatone/MEC Troubadour M-192. Great video and great job, thank you for posting.

[@YeatzeeGuitar]

@@chickenlickin3820 sure, if you happen to find the right hour long video where he does that and scrub to the right part. The goal was to make something easy to find for someone searching how to do this specific thing.

[@YeatzeeGuitar]

@@chickenlickin3820 and, if I remember correctly he does it differently. He does not run the hot to the fuse per code, he runs it to the switch directly.

[@ItsRaymar]

this is probably the best video i've seen on this. the way you talk through what youre doing is super clear and easy to follow. Showing everything from start to finish in 30 mins without the content feeling too long and or boring, is great. good job!

[@YeatzeeGuitar]

Much appreciated!

[@JeremiahL]

I agree. It's easy to stay engaged. I fall a sleep on some of these dudes. Not going to name anyone, but some of them almost have the voice of a midnight shift radio DJ (quiet storm ASMR voice).... Also, zero hubris on this channel... When some guy you've never heard of spends 15min of a 30min show degrading a amp from a company that you have heard of... Some of it is warranted, and some of it is reductionist silliness... Thanks for the useful and helpful content.

[@Guitar5986]

Great video! This should help a lot of people. Another nice thing to do when adding a 3 prong cord is to make use of the switch as a NFB on off ala Uncle Doug. It works extremely well in blackface Fenders.

[@maskman1980]

Thanks very much for taking the time to make and share the video!

[@bohemiangroove9751]

Thank you for taking the time and effort to do this! It gives me confidence in installing a 3 prong IEC socket in an old projector amp.

[@YeatzeeGuitar]

Good luck!

[@galenslattery7561]

Here for the algorithm support 👍 awesome video dude. Just wired up an old vox pathfinder thanks to ya!

[@YeatzeeGuitar]

🙌🙌🙌

[@chrisfit]

Commenting for the algorithm! Thanks for the great video! It worked perfectly after following your instructions. Cheers

[@YeatzeeGuitar]

Hahaha thanks! Glad it was helpful 🙏

[@rjaquin31]

This channel is excellent!!!

[@Goomer]

Very clear, still a bit chicken to do it to my Old Princeton.

[@PsionicAudio]

Good job man!

[@YeatzeeGuitar]

Thanks Lyle!

[@Kilgore40]

That was fantastic. Thanks very much. I'm curious about why you didn't just remove the wires from the ground switch.

[@YeatzeeGuitar]

Mainly just to keep original wires with the amp should they ever be needed in the future.

[@ewetoobie]

at the end you show the final result, and you have not connected the outlet so the fuse concern is gone, and you also isolated the death cap, which is a great idea. I also like how you made a long loop on the ground and soldered it to the chassis, best practice for sure and to modern code.

[@scrivenervl]

Is it not to code to fasten the green ground wire to one of the transformer mounts with a locking nut? Wouldn't that be a stronger chassis ground than the green ground soldered to the chassis, which is subject to vibrations from the speakers and thus might come loose, especially if the soldering technique was sub-par? The "Recycled Sound" guy seems to think that's how Fender does it at the factory. Is he misinformed? Thanks in advance for your reply.

[@chicolorenger1998]

Hi...good instruction. I just noticed this watching a 2nd time.and I just noticed the death cap, maybe adding it in removal...thank you Mr Yeatzee Guitar. Chico Lorenger Detroit,Mi

[@YeatzeeGuitar]

Thanks Chico! The death cap is completely out of circuit and doing nothing with the way it's wired here. There's no real reason to remove it physically when it's disconnected imo 🙂

[@tripletreyy1962]

Hi! I have inherited a 1964 Fender Bassman amp from my great grandfather. As you could imagine, I would like to swap the 2 prong power cable to a 3 prong. I have zero experience with electrical work, so I am planning on getting it taken in to be worked on. Would you be able to set a price range for this repair so that I don’t get ripped off? Other than that, it was great to see the inner workings of these amazing amps!

[@YeatzeeGuitar]

Very cool! You'll want the caps replaced, and the amp to get a full run-through before really playing it if it's just been sitting for a while. Basically nobody will just do a 3 prong swap, it's typically part of a full service package. I'd expect somewhere in the $150-300 range depending on what's needed and where you live.

[@OliverEvergreen]

could you tell me please, should I left zero/plus/minus switch as it is? this kind of switches are common for old peavey amps. I was thinking about simply wiring the third cord to a chassis and leaving everything as it is without removing a fuse etc, will it work?

[@YeatzeeGuitar]

I'm sorry I'm not familiar with that switch

[@marcoslnobrega]

Left the death cap on? Sorry if I missed the part where you talked about that

[@YeatzeeGuitar]

Yes, left in place but nothing is connected to it. The death cap is connected to the ground switch, which is completely bypassed. This way the original cap and all of the original wires stay with the amp, but are not being used.

[@scrivenervl]

How about installing a properly grounded female IEC connector in place of the auxiliary power socket, thus eliminating the hard-wired power cord install as well as the possibility that a connected power cord could be accidentally yanked out? Wouldn't that be a neater way to go? Thanks in advance for your reply.

[@YeatzeeGuitar]

I prefer to not butcher a clean original vintage chassis.

[@JeremiahL]

Great tip on removing the fuse before soldering. I probably would have learned that lesson the hard way. Is there a reason you route the hot wire to the fuse first, then carry the hot to the switch. I cant remember where, but I heard a recommendation somewhere to wire the hot directly to the switch first, then the fuse so that if someone leaves the amp plugged up and changes the fuse they won't get shocked if the power switch is off. No criticism from me on the way you are doing it in this video, but Im about to do the power chord swap on my amp, and I wanted some guidence if there is a reason to do it one way over the other. Thanks again, awesome videos as usual!

[@YeatzeeGuitar]

Yeah there are a couple people that say to do it that way, and a lot of people that say to do it this way. This way is to modern safety code, but you can get a shock trying to change the fuse with the amp still plugged in as the detractors say. I'd get yelled at endlessly if I did it any other way on video, but both ways are going to be fine in most circumstances imo.

[@JeremiahL]

@@YeatzeeGuitar thanks for the reply. Ill take that into account.

[@scrivenervl]

@@YeatzeeGuitar But how can your prescribed treatment of the fuse wiring conform to modern safety code if changing the fuse with the amp off but plugged in can give the user a shock? Could you please revisit this issue? Is there a wiring method that protects both the user and the gear? Thank you in advance.

[@YeatzeeGuitar]

There's nothing to revist, that's modern safety code which yes as you say does open you up to a shock potentially if you remove the fuse while the amp is on. I don't like that either, but it is to code. Strong proponents of both sides.@@scrivenervl

[@scrivenervl]

@@YeatzeeGuitar Thanks for the reply.

[@dobroplayer7]

Can i ask if there is an advantage to the chassis ground you did vs drilling a hole and and bolt it?

[@YeatzeeGuitar]

Yes, a bolt can loosen over time with vibration. Seen it many times, if you watch the recent super reverb series I did that amp had a totally loose ground connection.

[@dobroplayer7]

@@YeatzeeGuitar thank you. I'm working on a '67 ampeg tube Gemini 12 and was wondering. The chassis has the rubber " bushings" mount.. so it floats and I'm sure vibrates a lot!

[@mat.b.]

quick question, maybe i missed it in the video, but outside of the new ground, why is neutral wired differently than stock?

[@YeatzeeGuitar]

Neutral stock is wired to the courtesy outlet, and then the ground switch. We're bypassing the ground switch because it's not relevant with a 3 prong cable, and we're bypassing the courtesy outlet because I don't personally see much value in maintaining it since nothing I'd want to run off of the amp is 2 prong. You can easily keep it if you'd like, check out my latest video from today about a '68 Princeton where I keep it in circuit.

[@mat.b.]

@@YeatzeeGuitar thanks will do

[@theburkesmith3154]

Where did you get the three prong cord?

[@YeatzeeGuitar]

They're available all over. Amazon, hardware stores, antique electronics, etc

[@theburkesmith3154]

Is there a way to make sure I don’t get one under rated for my amp? Want to make sure I don’t fry something.

[@YeatzeeGuitar]

You won't, anything that's sold today will be fine. Typically see 18 gauge as the most common

[@lunathir]

I might do this with my cheapy amp that also has a two-prong cord, though maybe I’d install an IEC jack rather than hardwire a cord into it. Unfortunately though, the entire thing is made of wood so I might have to find somewhere else to ground it.

[@YeatzeeGuitar]

Good luck!

[@ewetoobie]

you mentioned taking the output of the fuse holder (black/hot) to the AC outlet as well as to the power switch, but I would not do that. If you want to keep the outlet active, wire it directly to the incoming power cord, then from there connect the fuse, power switch, etc. Since you might only have a 1 or 2 amp fuse, if you plug in something that draws more than that you're blow your fuse needlessly. If it happens at a gig that's no bueno!! Just use an AC outlet strip for your gear that has a circuit breaker if you are worried about overloads. The fuse in the amp is not designed for that application.

[@YeatzeeGuitar]

Not sure what you're referring to, time stamp? To keep the courtesy outlet in circuit I go hot off three prong to the available end of the courtesy outlet just like what was done for the neutral here, then a wire from that same location to the fuse tip, wire from other end of fuse to switch then power transformer primary other end of the switch.

[@60retired]

You know I really don’t get why everyone makes a big deal about not using the 2 prong outlet on the back of these amps because they say they aren’t grounded. Every outlet in my house is 3 prong and the majority of everything that’s plugged in has a 2 prong cord. The only thing in the house thats 3 prong are small appliances like a dehumidifier, AC, refrigerator, space heater. Microwave. Lamps, phone chargers, wi-fi router, TV, toaster, coffee pot, clocks, Alexa, security cameras, the list goes on and on. If you were to install a 3 prong outlet on your amp and plug a 2 prong corded device into it it still isn’t grounded. Your not going to get a shock anymore than you would in your house. You have to have a 3 prong plug on the device to complete the grounded circuit. You cannot plug a 3 prong plug into a 2 prong outlet unless your an idiot and break off the ground prong or use a cheater plug which is technically suppose to be grounded by screwing the metal tab thats connected to the ground terminal on the cheater plug to the screw that holds the outlet cover plate on which is grounded. I can see definitely iInstalling a 3 prong cord in the amp and ground the chassis but why not keep the AC outlet for things like a light, wireless charger, fan, 9v power supply etc. these things are not grounded items and don’t require 3 prong. If you have something that requires a 3 prong plug use a extension cord and plug it into the wall.

[@YeatzeeGuitar]

I didn't make it a big deal did I? I do it both ways, depending on whether the customer wants it connected or not. I don't personally see a point to it with my amps, like this pro reverb, so I did not connect it. Nothing I own that I'd want to connect is 2 prong.

[@thegusk520]

There seemed to be many available grounds, why not use a simple loop connector on your ground wire and use one of them?

[@YeatzeeGuitar]

Earth connection on the power cord needs to have its own separate connection.

[@danielbarbieri8199]

Putting an on/off switch on the ground wire is a must. Sometime you got a strong buzz comming from ground. Another great improvement is to put a switch to invert main wires. This will often help with 60 cycle hum.

[@YeatzeeGuitar]

Wut? The whole point of a 3 prong is to have a constant earth connection, there is only danger if you decide to lift the ground.

[@ewetoobie]

why standby off? don't you also want to drain the caps on the other side of the switch? You said to turn standby OFF, but it looks like you actually turned it ON, which would be the correct way to do this. You can speed up the process by playing the guitar thru the amp and turn off the power with standby ON, and when you can't hear anything anymore you should have drained the caps. Always measure to be sure.

[@YeatzeeGuitar]

You're mixing up what standby on/off is on these amps. In standby the caps on the other side of the switch are isolated so if you discharge the voltage in the circuit from outside the doghouse it won't drain what's in the doghouse due to being in standby. On this amp when the switch is up it is OFF standby. It's confusing because the faceplate says standby above the switch but up is OFF standby not on. When the amp is up and able to produce sound, both switches are up.

[@ewetoobie]

@@YeatzeeGuitar ok, I see your point, but I'm not sure many folks look at it that way. There's a power switch and a standby switch, and yes both need to be UP, but most people think of up as on. My Mesa Boogie actually is labeled that way. The standby switch says ON on the panel for the up position for playing. I would be super clear about that if you make another video about any of this, both switches need to be UP to discharge all the caps.

[@YeatzeeGuitar]

@@ewetoobie Everyone I know of calls when the amp on, but not able to produce sound as "the amp is on standby". I've never heard it referred to as the opposite... doesn't really make any sense. It's "off" standby but the amp is actually not able to make noise? So standby = amp is producing output? First I've heard of that! Not surprised that's what Mesa labels it as though, seems on brand for them lol