Pairing the speakers with the amp. 1950s tube Jukebox amp

The stock speaker is 15" Perm. Magnet; Coil: 16 Ohm.
So, 2 8 ohm speakers in series would be 3-5 no jumper.
And one 8 ohm speaker 4-6 jumper 2-3.
And one 16 ohm would be 3-5 no jumper.
And this is exactly what DEWDUDE said yesterday.
Thank you Dewdude.
I really need to clean these terminals and the volume pot and hook up the Swamp Thang...
 
Last edited:
You guys are great!
I got good power and volume from the amp now with one 12" 8 ohm speaker set up terminals 4-6 jumper 2-3.

This was the encouragement I need to take the steps of recapping and buying some better tubes.

I made a short victory video on my cell phone. If you want to mock I am the fist to admit I suck big time when I record myself.

http://youtu.be/Gjkto4fnt6s
 
Last edited:
You're welcome.

The thing about jukebox amps is they are done differently than your typical hi-fi setup. Output transformers are either extra heavy duty, or contain a maze of secondaries. They're designed to be driving multiple speakers in odd configurations. That's why you see hookups for 500ohm (or whatever) speakers/CV. I learned to work on tube amps working on jukebox amps. I dislike my job, but learning to work on tubes was the one reason I stayed. Where else are you going to get OTJ training on tubes anymore? The AMI C amp is one I've worked on a few times. I think I could recap an amp in my sleep now.

My last rebuild of one was over a year ago, and I actually wrote about it.

http://www.audiokarma.org/forums/showthread.php?t=426039

Glad you didn't get hung up on terminal 4 being ground and nothing hooked up to it, just the way they designed it.

Throw some new caps in there, check your resistors; you'll be ready for years of service. On the subject of stressing the amps, that's silly. Jukebox amps are actually very conservative in how they run the tubes, its commercial equipment designed for high reliability with minimal service. I have, in 10 years, and dozens of amps; only encountered one blown OPT. Pretty good reliability in my book

AMI also had some of the best sounding amps. I was also wrong in my previous post about the RIAA stage, ceramic carts never needed it...displacement rather than velocity.

Too many amps, not enough memory.

Sent from my T-Mobile myTouch Q using Tapatalk 2
 
Yes I have to check that out! Thank you DEWDUDE!
Also, I have to take this free online course that MIT is offering. It is intro to electronics and circuits. It obviously won't give me any hands on experience, but I couldn't hoit.
I just read about it in some money magazine. The course is closed, but I can still read and listen to the lectures. Too bad I missed it live. That would be tre cool..
 
junktube said:
Yes I have to check that out! Thank you DEWDUDE!
Also, I have to take this free online course that MIT is offering. It is intro to electronics and circuits. It obviously won't give me any hands on experience, but I couldn't hoit.
I just read about it in some money magazine. The course is closed, but I can still read and listen to the lectures. Too bad I missed it live. That would be tre cool..
Click to expand...

Any modern course isn't going to help you with tubes, some stuff...yes. Maybe if you know what a capictator is, and how i t works, you'd understand what role they play in a tube amp...but something involving tubes...you're gonna have to learn youself.

I took a basic electronics course in high school..and later at community college. Didn't help me much for my line of work. The stuff I work on is so...different....but like I said...free training on tubes was great! The ironic part, just two days ago I rebuilt a Rock-Ola tube amp. Like I said, I could do these things in my sleep. :)

Sent from my T-Mobile myTouch Q using Tapatalk 2
 
+1 on Dewdude's advice. Just take pictures and keep us posted when you start the recap. We'll keep an eye on you.
 
I'm getting a strong hum now that I have EVERYTHING hooked up.
There is a grounding plate on the top of the chasis. Is this meant to get grounded to the house(center screw on a grounded outlet)?
I'm asking because I don't want to blow this up. I guess the emphasis here would be that the outlet is properly grounded.
 
I don't think running a ground from the amp to earth ground is such a hot idea. If you have a DMM, put it in AC between the earth ground and chassis, if there's no voltage then you can safely ground them and remove the hum.

You may need a ground loop isolator.....or if you're running a power strip, remove its grounding pin to remove earth ground.

Sent from my T-Mobile myTouch Q using Tapatalk 2
 
OK. Will do that. I have an automotive Multimeter with AC. I really need to get a electronics one.
My ipod is hooked up to a tuner that is plugged into the same outlet.
When I put the ipod on the chasis the hum stops..LOL.
Could this be a case of reverse polarity? I did replace the cord with a heavy duty cord I pulled off a newer vacuum cleaner. I'm pretty sure I ran the black wire to the on/off switch.

Victorian glass sells a recap kit for the AMI-DD with a schematic telling me what goes where for $75.
Frankly, even if it is twice what I'd pay for the parts individually I don't mind since it's done and it comes with a diagram.
Does it really matter if I get the cool red caps?
 
Last edited:
Let me see if I've got a schematic somewhere.

Don't ground the chassis or anything. Let me find a schematic first. If you start grounding things, problems will arise.

Chassis ground on that amp is transformer center tap.

Sent from my T-Mobile myTouch Q using Tapatalk 2
 
Ok...I have a few spare minutes.

Don't run any grounds. The center tap is chassis, and that's NOT ground. You run the risk of damaging your stuff if you do this.

I don't have a schematic right now, but that cap kit is a good idea if you don't mind paying the extra premium.

You *need* to recap that thing before trying to fix any other problems. I know I said those things were tough, but a bad cap or bad biasing resistor *will* take out a transformer.

So, get it recapped; then let's see what problems you have.

Sent from my T-Mobile myTouch Q using Tapatalk 2
 
You must log in or register to reply here.
Back
Top Bottom