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FDP Forum / Fender Amps: Vintage (before 1985) / 3-prong amp, 2-prong Fender Reverb unit


S.F. Bay Area

May 12th, 2019 03:32 PM   Edit   Profile  

Is there any safe scenario using an amp with a 3-prong cord (Blonde Tremoluxe or Tweed Twin R.I.) with a vintage 2-prong Fender Reverb Unit? Or is converting the Reverb to a 3-prong the only safe solution?

(This message was last edited by Paulsy at 05:33 PM, May 12th, 2019)

Moderator Emeritus
(with many stars)

Ja! Nein!

May 12th, 2019 03:47 PM   Edit   Profile  

The 3-prong conversion is pretty simple to do, so...



May 12th, 2019 04:01 PM   Edit   Profile  

If you're just playing it a home then reverse the plug on the reverb unit for the least amount of noise. If you're going to gig it, then have a three prong installed.

Contributing Member

Planet Peegoo

Rhythm & Lewd Guitarist
May 12th, 2019 05:35 PM   Edit   Profile  

Flipping a two-wire plug can be deadly...

If in doubt, use a meter to test for AC voltage between the chassis and ground. You may discover the metal chassis is live at mains voltage.

Best solution is to convert any two-wire equipment to grounded three wire. It's super simple; anyone that can operate a screwdriver and pliers can do it.

Here's how.

Contributing Member


May 13th, 2019 06:58 AM   Edit   Profile  

Another vote for 3-prong. If I get a 2-prong amp, it the first thing I do to it.


usa Thumb area Mi

May 13th, 2019 02:18 PM   Edit   Profile  

I have a 69 Bassmen Head w/ 3 prongs and I think a 68 solid state reverb FR100 w/2.

Just have to make sure you have the right polarity, you will hear a hum if you don't.

Contributing Member


When I get older, losing my hair...
Jun 24th, 2019 06:12 PM   Edit   Profile  

Safety first! I vote for making the upgrade to 3 prong using Peegoo's easy directions, or have someone familiar with such things do it.

PS: I have a SS FR100 with 2 and now am motivated to make the upgrade before I get zapped.

Contributing Member

Whitehorse Canada

I don't get out much
Jun 24th, 2019 10:26 PM   Edit   Profile  

Not heeding the advice mentioned above would be foolish.

Contributing Member


Jun 25th, 2019 07:26 AM   Edit   Profile  

I've been an electrician for 40 years. My business partner grabbed a fluorescent light that was mounted on wood with one hand and a steel beam with the other while standing on a ladder. The output of the ballast (high voltage) was shorted to the light fixture. He was shocked such that he couldn't let go. Luckily an employee came into the room and grabbed him from the ladder. Permanent nerve damage. Dangerous stuff. 3-prong.

(This message was last edited by stl80 at 09:30 AM, Nov 4th, 2019)



Nov 3rd, 2019 03:11 PM   Edit   Profile  

Thanx Peegoo on the easy safety fix. Chico Al Lorenger



Why do I keep fixing things that work?
Nov 3rd, 2019 05:08 PM   Edit   Profile  

Here's a scenario that I could use some clarity on, if the amp is converted to a 3 prong plug and the reverb unit is a 2 prong plug and the reverb unit is plugged into the amp via the onboard plug, would the reverb unit be grounded by the amplifiers provided AC outlet, like on an older Fender amp?
I was wondering if this is the scenario that the original poster was referring to.
Probably not, but it was a question that I thought needed exploring.
Thanks, Woody

Contributing Member


Nov 3rd, 2019 07:30 PM   Edit   Profile  

If the reverb unit has a leaky cap or short to its chassis, it’s going to find ground back through the shield of the instrument cable to the properly-grounded amp. I’d rather it find a more direct route.

Contributing Member


a tractor
Nov 3rd, 2019 08:53 PM   Edit   Profile  

Cal, you really should disable any two-hole AC outlet on any piece of equipment that's been converted to three-wire.

That "courtesy" outlet can still courteously electrocute you to a courteous death. The reason is those outlets are not polarized. Stick a plug in the wrong way and it may mean a permanent lights-out for you or someone else.

Disconnect that outlet internally by snipping the jumper wires completely out of it.

Pulse Adjust


Nov 6th, 2019 07:22 PM   Edit   Profile  


FDP Forum / Fender Amps: Vintage (before 1985) / 3-prong amp, 2-prong Fender Reverb unit

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