Ampeg VT40 (top mount) ext. speaker problems

methodofcontrol · 06-14-2009, 04:35 AM

hey guys, i just dusted off my old VT40. it sounds fantastic, but it has a few issues that i can't figure out. i'm hoping you guys can tell me where to start.

so here's the first problem i'd like to iron out. when you plug something into the extension speaker jack, the whole amp mutes.
the combo 4x10's AND the extension speaker are supposed to project sound, but instead there's nothing from either. i check out the jack itself, and it is wired correctly. the 8 ohm tap is wired through the jack as though it were a switch, and the amp works fine without anything plugged in.

i do NOT have a scope at my disposal. otherwise, i am prepared to tackle this thing. any advice?

rf7 · 06-19-2009, 10:18 AM

The extension speaker jack should switch the OT output from the 8 ohm tap to the 4 ohm tap, when a jack is plugged in. Is the 4 ohm tap wired to the jack correctly?

What is the impedance of your extension speaker? It should be 8 ohms for this application.

methodofcontrol · 06-19-2009, 02:08 PM

got it all figured out. thanks for the reply, though. turned out the jack was corroded and a little out of shape.
i ran some sandpaper between the contacts and re-tensioned the tip connector and now it works like a charm!
i just assumed the problem was going to be more involved, so i posted prematurely. sorry about that. thanks again!

Dave Curtis, dB AudioTech · 06-23-2009, 02:55 PM

Quote:

Originally Posted by methodofcontrol

got it all figured out. thanks for the reply, though. turned out the jack was corroded and a little out of shape.
i ran some sandpaper between the contacts and re-tensioned the tip connector and now it works like a charm!
i just assumed the problem was going to be more involved, so i posted prematurely. sorry about that. thanks again!

Replace the jack. It will fail again, sooner than later. Sandpaper takes off whatever plating was left, exposing the base metal. Next time you need to clean contacts, use a fresh dollar bill. You want to burnish/polish rather than scrape or sand. A shot of Deoxit goes a long way, too.

methodofcontrol · 06-24-2009, 03:33 AM

thanks for the tip!
i looked for a replacement, but i couldn't find the right jack.
so i figure i'll just have to tough it out for the time being.

Dave Curtis, dB AudioTech · 06-25-2009, 01:10 AM

I think you're looking for the 13A:

http://www.switchcraft.com/products/..._schematic.pdf

Unless it just has one contact (like on my '70s VT22), then you want the 12A.

methodofcontrol · 06-25-2009, 02:54 AM

thanks dave! i looked everywhere for that. i'll order one of those soon. you're correct, 13a is the model in question.

06-14-2009, 04:35 AM	#1
methodofcontrol Senior Member Join Date: Aug 2006 Posts: 158	Ampeg VT40 (top mount) ext. speaker problems hey guys, i just dusted off my old VT40. it sounds fantastic, but it has a few issues that i can't figure out. i'm hoping you guys can tell me where to start. so here's the first problem i'd like to iron out. when you plug something into the extension speaker jack, the whole amp mutes. the combo 4x10's AND the extension speaker are supposed to project sound, but instead there's nothing from either. i check out the jack itself, and it is wired correctly. the 8 ohm tap is wired through the jack as though it were a switch, and the amp works fine without anything plugged in. i do NOT have a scope at my disposal. otherwise, i am prepared to tackle this thing. any advice?

06-25-2009, 01:10 AM	#6
Dave Curtis, dB AudioTech Senior Member Join Date: Jun 2007 Location: USA Posts: 274 Member's Picture Albums	I think you're looking for the 13A: http://www.switchcraft.com/products/..._schematic.pdf Unless it just has one contact (like on my '70s VT22), then you want the 12A. Last edited by Dave Curtis, dB AudioTech; 06-25-2009 at 01:25 AM.

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06-19-2009, 10:18 AM	#2
rf7 Supporting Member Join Date: Sep 2007 Posts: 203	The extension speaker jack should switch the OT output from the 8 ohm tap to the 4 ohm tap, when a jack is plugged in. Is the 4 ohm tap wired to the jack correctly? What is the impedance of your extension speaker? It should be 8 ohms for this application.

06-19-2009, 02:08 PM	#3
methodofcontrol Senior Member Join Date: Aug 2006 Posts: 158	got it all figured out. thanks for the reply, though. turned out the jack was corroded and a little out of shape. i ran some sandpaper between the contacts and re-tensioned the tip connector and now it works like a charm! i just assumed the problem was going to be more involved, so i posted prematurely. sorry about that. thanks again!

06-24-2009, 03:33 AM	#5
methodofcontrol Senior Member Join Date: Aug 2006 Posts: 158	thanks for the tip! i looked for a replacement, but i couldn't find the right jack. so i figure i'll just have to tough it out for the time being.

06-25-2009, 02:54 AM	#7
methodofcontrol Senior Member Join Date: Aug 2006 Posts: 158	thanks dave! i looked everywhere for that. i'll order one of those soon. you're correct, 13a is the model in question.

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