This 1959 Kay Tube Guitar Amp Design Is SHOCKING!

This is the famous Kay 703-C Tube Guitar Amp. Amp designs like this were called "Widowmaker" amps because the design of the chassis allowed AC Voltage to loop into the guitar if a capacitor shorted in the amplifier. I bought this 'Broke' online, let's see if we can get it to work.
We're trying to keep some of the vintage electronics out of the landfill. Many times when something stops working, it can be repaired if someone will simply take the time to attempt to repair it. This channel documents our amateur attemps at repairing vintage electronics we think are cool.
We don't typically restore anything, we're just trying to get them working again. We've found that most of this stuff was well built and with a little help will start doing what it was intended to do.
Radio Repair
Phonograph Repair
Clock Repair
Projector Repair

[@barackmycat9448]

I had a similar amp back in the `60`s learning to play. It had the same controls in the back. That was so cool. Thx..

[@AmateurRepairTime]

How did you live through it? I heard they're windowmakers and they'll kill you! It's amazing how they sold a million of them and everybody made it just fine, it must be a Musical Miracle!!!!!

[@goodun2974]

​@@AmateurRepairTime, Worst case scenario with a transformerless "widowmaker" amp would be playing guitar while standing on a concrete slab floor in a garage or basement. This one is somewhat less dangerous than most because it has capacitor isolation between the incoming AC and the chassis; an earlier "AC/DC" amp would probably have used the chassis as the return path for the AC supply (either neutral or hot, depending which way the power plug was oriented in the wall) and would not have had a capacitor for chassis isolation, nor would it have had a filament transformer for the preamp tube heater as this one does. Technically, this isn't even an AC/DC design because the filament transformer wouldn't work if fed with DC, only with AC. Anyway, in this case, the grounded cord accomplished nothing because the ground wire was flopping loose and not attached to the chassis. PS, good catch on adding the safety capacitor. Personally, I'd add an isolation transformer on the input AC for safety, but it's not really worth putting a lot of time, money or effort into these types of amps. They'll never grow up to be a Champ; they'll never even be a Monoprice amp! By the way, the weirdest and most dangerous AC/DC circuit design I ever saw was a massive Califone portable record player, marketed to schools, that had an entirely metal chassis, an AC/DC circuit (no power transformer) and a non-polarized AC plug. I wonder how many teachers and school kids got zapped by that thing! It actually had a solid-state (selenium diode!) voltage doubler inside of it to jack up the incoming AC to about 250 V DC, to drive a 12AX7 and an RCA blackplate 6L6 in single-ended Class A mode, through a beefy output transformer into a built-in or external speaker. The tonearm weighed at least several pounds. If you come across one of for $5 at a flea market they're worth cannibalizing for the tubes and output transformer. I found two of them at the dump for free.

[@ericturner7162]

When I do tube radio restorations, I always put the line (hot) through the switch to wherever it goes and direct connect the neutral to where it should be in the circuit. That keeps the internal circuits from having live voltage present with the power switched off. The neutral side does not normally have live voltage on it if your house is wired correctly.

[@AmateurRepairTime]

We talked about that in the part of the video you skipped

[@markjackson1444]

Also, treble is volume. Dialing in the right amount of treble will give you the desired amount of distortion. You can get it where the chords are mostly clean, but with enough overload so it makes a nice crunchy distortion. Not too much, but just right.

[@douro20]

Those blue Ajax capacitors are film with a paper separator and rarely cause issues. I believe the white cap in there is also a film capacitor.

[@AmateurRepairTime]

I swapped that white one but even if it shorted I don’t think it would have done anything but changed tone

[@anthill7663]

sounds good

[@myradiovideos]

This should be a fun video to watch! Don't forget the Dim-Bulb unit, not the Variac/Amp Meter... 🙂 Robert, San Diego

[@AmateurRepairTime]

I’m not going to use a dim bulb unit

[@myradiovideos]

Ok I can’t wait to see the “R” rated parts this video! Called let their be Smoke!! 😂

[@larryn2682]

​@@myradiovideos *there

[@myradiovideos]

The entire Guitar Community is a very interesting group of amplifier users... When I was at a local swap meet about 15 years ago, I saw a person unloading a Fender 1950's Fender Twin Amp Tweed Guitar Amplifier. I was aware of exactly what he not only had, but how much these can sell for on eBay.. So I walked fast up to his car and asked the magic question, DOES IT WORK?? He said he had no idea. He mentioned that one of the tubes were missing, and was sure that you can NO LONGER get tubes, way to old.. Naturally none of this mattered to me, but then I asked him how much he was Asking for this Broken unit?? Well he said, would $50.00 be to much??? I said that seems fair, gave him 2 $20.00 and a $10.00! I grabbed the unit and walked away with a BIG SMILE on my face.... After some minor restoration it went up on eBay for sale... Only took about 24 hours for it to be grabbed up... I wont embarrass myself on what I sold it for, but used the money to purchase a almost complete and new Ham Radio Station... 🙂 I do not play guitar, but are glad others believe so strongly in that TUBE SOUND produced by Fender... Glad you got it working, and no smoke was a good thing! 🙂 Robert San Diego

[@AmateurRepairTime]

I have a similar story :) I used to go to the flea market every weekend, about 2004 or so I had someone bring me a little guitar amp up there and sell it to me, I think it was $30 or something. It looked old and I figured out it was a tube era amp. At the time I played a little guitar but I didn't know much about amps or anything, they just brought it to me because they knew I played guitar. It might have been $50 but there's no way it was more than that. So I'm looking at it, and it looks like some old amps by Fender I saw online, but there was no logo on it. Eventually I figured out the first year of this certain amp, they didn't have the famous Fender logo on the grill, so it was very desirable. I did like you, put it on ebay but I put it up as an auction, it sold for something like $1200 or so, the guy that bought it was kind of a jerk in the conversations we had but I shipped it off to him and he paid for it of course. It didn't work and the guy really really didn't want me to plug it in as you can imagine :) I haven't seen anything similar to that since then though, lol. I just found the old pictures on my computer, it's a Princeton AA764, before it had the Fender badge. Looks like they're going for a small fortune on ebay now :) Oh well I made my money :)

[@myradiovideos]

@@AmateurRepairTime After Covid and retirement, now 76, I no longer go to the swap meets, but still have over 50 electronic items that need to be checked out , repaired and sold on eBay.. Before Covid it was closer to 300. The $$$ keep my ham radio hobby stocked with the newest and greatest, and yes expensive ham radio gear... I am also an armature astronomer, but the rain and cold keeps me inside these days, but spring is on its way.. My son Chris has been a full time swap meet person for the last 30 years. That is how he makes a living, he has something close to 10,000 feedbacks, all at 100%, I HAVE 3,934 FEEDBACK ALL AT 100%.. I use to sell 12-15 items a month, even when I was working, but now maybe 2-3 items.. After all I am retired, LOL...

[@douro20]

There is a tube called the 50C6 which has tremendously high mutual conductance and could produce 20W in class A operation with just 150V on the plate. This performance comes with the cost of very high filament current, though, as the tube has to run very hot to reach its high Gm value.

[@AmateurRepairTime]

Thank you

[@craigbrown7929]

That tube maxes out at only 6 watts. Also the heater current is only 150 milliamps, the voltage however is 50. This tube was designed to be used in radios with series string heaters with other 150 mA tubes across a 120volt ac line.

[@vhm14u2c]

Surprising has a ‘underwiter laboratories’ tag on a widowmaker. Just found this channel, Ron. Was already subbed on the Joes classic vid channel.

[@AmateurRepairTime]

Thanks for watching!

[@MrJDNJ]

I know it's fun to fix up the $25 guitars, but it sounds like you're ready to buy a nice sounding telecaster that would inspire you to practice more.

[@markjackson1444]

I think I know why Keef loved this amp. From the moment you turned this on I could tell the warm, fat sound was obvious. This quality sound only comes from tubes. …A great little amp, Ronnie. Just put some reverb with it and this will sound sweet. The chorus pedal will also sound the best it can with a tube amp like this. Great video.

[@zaptainkuboom5520]

I had an amp back in the 70s and if you touched anything that was grounded while holding the guitar it would eat you up. I threw my guitar across the room a couple of times ⚡🎸⚡

[@AmateurRepairTime]

Probably had a similar design!

[@brianclark2370]

One day you will be a rock star😅😅😅

[@AmateurRepairTime]

I’m already a rock star!

[@hestheMaster]

The covering is called Tolex. Would love to see you tackle something like putting a new covering on it one day Ronnie.

[@OhRonaldo]

Oh come ON Ron! That voltage on ground is there to give just a little tingle of creativity! Without it how would we have had Buddy Holly's Peggy Sue? 🤣 Run that chassis to ground and measure the input amperage! (Would it trip a GFCI? I betchya)

[@jimp.7286]

Keith Relf of the yardbirds died from an improperly grounded guitar but it wouldn't have been an amp like this. I have an amp made this way. The output is a 50c5 from the famous 5 tube 40's table radios. I think the amp pumps out 2 watts. I plugged it in once but found out the output tube was bad and then got news how I needed an isolation trans so I wouldn't die. Never got around to it. It's somewhere in storage where it can't hurt anyone. The reason amp makers used them was left over stock was pennies on the dollar in the 50's/60's as the world moved towards transistors. And amp makers back then could be super cheapskates. Kid got fried playing his silver tone? Sorry bout that.

[@goodun2974]

To the best of my knowledge, British electrical codes never allowed AC/DC, transformerless "widowmaker" type amp circuits, so it would have been pretty unlikely for one of these to make its way over to England considering the high cost of customs duties and requiring a step-down transformer to use it at 220 to 240 VAC.

[@IAmSurfer]

I picked up this exact amp and have been looking for a guide on this. Could you share a link to the mod schematic you’re referencing layer in the video?

[@Jason-lx3zu]

Someone's been practicing their Beatles tunes, I heard two of them

[@wackyworldofwindios3476]

Howdy Ron

[@AmateurRepairTime]

Howdy Dano!

[@zx8401ztv]

No mains transformer to isolate the mains, what a pile of Poo lol. I'm a lover of a real earth a rod hammered into the damp soil. A good earth helps radios 😀

[@craigbrown7929]

This whole amp screams “bad idea” from the original design to the “repairs”. If this was brought to me for repair/restoration I would redesign it to use a proper power transformer. The way the filter caps were installed and that fuse is the absolute worst way of doing a restoration.

[@AmateurRepairTime]

Oh you'll be alright Craig, luckily you're smarter than me and would do it different. You're also smarter than the original designers, and the guy who put the caps in this one beforehand, and all the other people who owned it, and you're also smarter than Keith Richards. You're a really smart guy, thanks for letting us know.

[@larryn2682]

​@AmateurRepairTime you are a smart ass.

[@timbober1]

It’s an electric guitar come on. I read Keith’s book, didn’t write about the Kay amp, but said he recorded the opening of “street fighting man” on a Panasonic battery cassette recorder with built in microphone, no one could figure out how to recreate the sound.

[@AmateurRepairTime]

It ain’t rocket science !

[@larryn2682]

*Phillips cassette player.

[@cliff_hewitt]

Not quite getting the "microfarad" song. Care to explain?

[@naytch2003]

You must be new here..he says Micro farad to take the piss outta people who mispronounce it or insist on saying UF 😁

[@Jason-lx3zu]

Other way around, people were getting on him for saying UF so he says microfarad in a sissy voice as an FU to them

[@naytch2003]

@@Jason-lx3zu Haha

[@cliff_hewitt]

@@naytch2003Yeah, close enough to new, I suppose. Alright, as long as I have a reference for a joke, I'm good, thanks!

[@cliff_hewitt]

@@Jason-lx3zuYes, nice to know the joke is all. I'm thinking this is a question people are going to ask quite a lot if the channel grows.

[@rjcc7989]

Gut it and build a 5e1.

[@hiredgun7186]

Hot chasis units were always a pain in the ass, they often came with non polarized plugs and it was a crap shoot when you plugged them in , I used them back in the day , they were cheap and plentiful in the 80's and I couldnt afford a more modern tube amp

[@goodun2974]

The cheaper Silvertone ( Danelectro) amp-in-case model that had just one pickup on the guitar used a similar AC/DC widowmaker amp circuit; the amp in case that came with the 2 pickup Silvertone guitar was more like a Fender Champ and included a power transformer.

[@zx8401ztv]

Ha ha Micro farad, yep :-D