One half of my cab is dead

WiresDreamDisasters

Well it seems like one half of my cab is dead. The two speakers on the right are putting out practically no high-end, whereas the speakers on the left are putting out the full range. Could this be the cones? Something in the wiring of the jackplate that has gone iffy? What else??

Do I use this as an excuse to just blow a fat wad of cash on a new 4x12, or two 2x12's?

I noticed it a few weeks ago, but I didn't realise it was actually the cab at fault until today. I had been blaming my SM57!

PolarityMan

What blew it? My VH4 destroyed my little 1x12.

WiresDreamDisasters

PolarityMan said:

What blew it? My VH4 destroyed my little 1x12.

Hhmmmmmm. Could be. Could be. As you know, I also have a VH4. I honestly have no idea. All I know is, when I mic up either of the two right-hand speakers, I get what sounds like a room microphone. Not a microphone on a speaker!

Might need to buy two new speakers I guess? Or as I said... just spaff some cash.

SunDevil

Suggest some basics first - check the wiring to the speakers and ensure all of the spade connectors are attached as they should be and tight fitting and any solder joints are sound?

its unlikely to be the jack itself, as you are getting sound to some of the circuit

Egg sucking time - if you have a wiring issue in the cab, you might end up spaffing cash on a new amp instead  ..the amp might not be seeing the impedance it expects to and that could lead to some serious issues

octatonic

If it is a 4x12 then I’d bet it is a wiring issue.
It would be unlikely for two speakers to blow at the same time.

Cayn you take the back off and take some detailed photos?
Do you own a multimeter?

ecc83

If you don't own a m'meter 'king get one! Nobody that uses "electric" instruments should be without one. How to test batteries FCS?  First step is to drop out the jackplate, should be enough wire to get it out far enough to twist it about.  Then take a photo of the connections if they are 6mm spades onto a PCB, mark them with a Sharpie so you can put them back aright should you need to remove them.

If it is a dual impedance/stereo-mono cab it could have fallen foul of the problems ICBM is always telling us about, dodgy jack switches. dodgy print or a bad spade crimp.  Run the amp in at a very low level* (feed in phone or something) and have a wriggle and a pull. If you are lucky it will be print or spade and that can easily be fixed. If you have a broken jack switch replacing that is a bit more skilled.

If you need to get onto the speakers, again photograph and mark the wiring.

*At a few  milliwatts the amp will suffer no damage if the cab momemtarily goes O/C or you could drive it from a headphone output from a pod/phone.

Dave.

prowla

octatonic said:

If it is a 4x12 then I’d bet it is a wiring issue.
It would be unlikely for two speakers to blow at the same time.

Cayn you take the back off and take some detailed photos?
Do you own a multimeter?

My thoughts too - I think 4x12s tend to have two pairs of speakers wired in parallel.

ICBM

prowla said:

octatonic said:

If it is a 4x12 then I’d bet it is a wiring issue.
It would be unlikely for two speakers to blow at the same time.

My thoughts too - I think 4x12s tend to have two pairs of speakers wired in parallel.

Yes. If it’s a standard 4x12” wired parallel-series, one dead speaker or one bad wiring connection will stop both speakers on one side working.

What make of cab and speakers are they?

The low-volume dull sound is the two speakers being driven as ‘passive radiators’ by the air inside the cab by the way, not them partly working.

WiresDreamDisasters

It's my Egnater Tourmaster 4x12 cab, with Chinese V30's inside it. It has one of these socket-plates on it.



I do own a multimeter. What should I do?

octatonic

Do you know how to test for continuity in a circuit?

WiresDreamDisasters

Okay, I know what it is. When I'm plugged into the 16ohm mono jack, which is what I always tend to use, something is a bit wobbly inside the jack. If I push the cable then I get the full connection and the full sound out of all 4 speakers.

So I guess I need to replace the jack?

WiresDreamDisasters

Images show the top two jack sockets, but the bottom one is the same.

octatonic

I can't see the photos but you could try resoldering the jack, otherwise replace.

WiresDreamDisasters

Bah! Images fixed.

WiresDreamDisasters

I guess for now I can use 4ohms mono until I can replace the jack. Just gotta find the right part. Any tips on that peeps?

octatonic

Circuit board complicated things a bit.
I’ll defer to ICBM and ecc83 as I am not completely sure of the part.
I’d be making up a wiring loom though if it was my cab but appreciate you probably just want a simple like for like part swap.

WiresDreamDisasters

octatonic said:

Circuit board complicated things a bit.
I’ll defer to ICBM and ecc83 as I am not completely sure of the part.
I’d be making up a wiring loom though if it was my cab but appreciate you probably just want a simple like for like part swap.

If it's possible, yeah. But I'm not averse to changing out the whole plate for something a bit more sturdy, if that is even possible. To be fair, this is the first time I've had a problem with the cab in the five years since I bought it!

maltingsaudio

Maybe as simple as re wetting the solder joints, sounds like a dry somewhere

ICBM

It's probably the contact inside the jack, not the solder joints. (Although have a look at them anyway.) The faulty contact is actually going to be in one of the other two jacks I think, these will be opened when you put a jack in to break the series connection.

Using jack switches to reconfigure cab impedance is a recipe for this, as Dave said I would say . The switch contacts are simply not adequate or robust enough to handle the sort of currents involved, and a small amount of corrosion getting in, or the jack being strained by the cable being tugged, is enough to make a bad contact. Depending on how it's wired, if you're unlucky it can leave the cab open circuit and blow valves or the amp's transformer.

Personally, unless you really need the two different impedances or the stereo option, I would remove the whole contraption and hardwire the cab for 16 ohms to one standard Switchcraft open-frame panel jack. (Or two in parallel, which gives you a backup or a method of daisy-chaining cabs.)

WiresDreamDisasters

Right, guess I'll go find a socket then and get to work!