Separate names with a comma.
Discussion in 'Amp Tech Center' started by Phrygian77, Nov 7, 2017.
Parts to built the ultimate light bulb limiter...
I like it.
I'm waiting to see the result! I'm surprised you could shoehorn an ammeter in there also!
(Mine is the minimalist design).
Could you please provide a parts list?
Is this a build thread? I like toys...
Well, I should have done my homework better. The big rocker switch is about 2 inches deep with the 1/4" blade terminals. The box is 2" in height inside, so I'm going to have to mount the switch on the side. That obviously wasn't the plan. Also, cutting the hole for the volt/ammeter, I gouged the box with the Dremel.
Hey, if it doesn't have a little "character", folks would think we paid somebody else to do it!
If you don't use an incandescent lamp, would that make it a solid-state limiter (wink,wink)?
I know, I know...it's all about the positive temperature coefficient of the tungsten filament.
It's ugly, but it works perfectly...
Very cool and nicely done. I like the character scar.
Sweet! Would be cool to incorporate a switchable bucking transformer in there as well.
this thing is a test instrument when trying out a new build/repair, or when troubleshooting an amp that is blowing fuses. You can't really play the amp with this thing in line - it will sound all wrong. And you can't even take voltage readings inside the amp because they, too, will be all wrong.
It is a device that will show you very quickly when something is wrong, and with proper use, can help you to localize the problem. It should be taken out of the circuit as soon as possible, lest you forget that it is in place and start taking incorrect voltage measurements and trying to 'fix' problems that don't exist. I know, because I have done it more than once.
Knowing the AC voltage might be useful, a little bit. Knowing the current is not really necessary. Can anyone tell me what the current should be for their Fender amp when it is operating correctly? When the light bulb shines brightly, something is wrong. When the lamp is dim, things are OK. It isn't really useful or helpful to have the meters.
But they do LOOK cool, and I will probably put some on next time I build a light-bulb limiter!
I've used all my psychic powers, but I can't come up with a bill of materials and a schematic. Could you please provide these?
Depending on how this thing is wired and or switched, I bet Phrygian can tell us.
I know its a tool that has valuable however limited use. But its cool as ever
This is exactly why you shouldn't Dremel and drive, or drink and Dremel. I don't advise trying either. Although, a drink or two can certainly help with soldering, like any old school marksman or surgeon might tell you ... wink wink.
I didn't really want to post pics of the exterior, but it does what it's supposed to so well, I thought, "why not."
The ammeter is a nice useful feature. There's not a lot of resolution though, and it seems to round up 100mA, but it works.
I wired the limiter with an on-off-on switch. It's a big DPDT rocker, but I only used one pole. One side puts the hot lead in series with the bulb, and the other is full on. The big rocker is nice because you can quickly and easy flip the positions.
I'll put the parts list up tomorrow, and draw up a layout/schematic. Most of it came from Mouser except the the volt/ammeter, which I got from amazon.
The Princeton Reverb I just built is pulling .4-.5A at 124VAC, or around 60 watts. That's idling with 422 on the plates and 22.5mA on the cathodes. That should be about right because of the inefficiency of a tube amp.
can you read the ammeter with the limiter out of circuit? I wonder what happens when you really crank the amp..
Yes, because the hot lead from the IEC inlet runs through the current transformer. The voltmeter is also wired to the inlet.
My guess is, at full output, it'll draw 800-900mA. I can tell you when I do my output power test.
My BF Bassman build puts out 45 watts clean. I had inadvertently put a 1 amp slow blow fuse in it instead of a 2 amp. It blew the fuse when I dimed it at the end of a 3 hour practice. So, it was obviously drawing well over 120 watts. Again, it just shows you how inefficient a tube amp is.
what is the 'current transformer'? Is that part of the ammeter?