4x12 wiring help please!!

riffpowers

I need to rewire my 4x12 and change the horrible marshall mono/stereo socket.

The cab has 4 g1265's, and I think they're 15 ohm, woudl I go parallel-series wiring for  these??

The horrible PCB has broken on the switchable jack, so what I was wanting to do was bin the PCB and switch but keep the socket.
But, as the jacks are covered, I don't know which is the sleeve or the tip, does anyone know??

https://www.tubesandmore.com/sites/default/files/uc_products/s-h800_0_0.png

Winny_Pooh

Do you have a multimeter? 

riffpowers

Winny_Pooh said:

Do you have a multimeter? 

sadly not.

ecc83

If a standard metal plate will fit I have one I can jiffy over to you if you send me an address. Get some new jacks from Maplin.

Four 15 Ohm 12s will likely sound different when wired all in parallel compared to  series/pllel and 15 Ohms.  I think generally 15 is the preferred Z? Certainly makes most efficient use of the OP transformer.

Dave.

ecc83

Ooo! DO get a multimeter. About 8 quid for a Halfords cheapy. A score for rather better at Maplin.

Dave.

ICBM

Keep the plate but remove the PCB and the jacks. Replace the jacks with two of these

http://www.ebay.co.uk/itm/CLIFF-ELECTRONIC-COMPONENTS-S2SNS-SOCKET-1-4-JACK-UNSWITCHED-2POLE-/171118832795?hash=item27d77a2c9b:g:~t4AAOxyoVZTIj~8

hardwired in parallel (so you can daisy-chain the cab, or as a spare), with the speakers wired for 15 (16) ohms in parallel-series - two series pairs in parallel - which is the classic Marshall arrangement.

ie

Jack tip to speaker A and B +
Speaker A - to speaker C +
Speaker B - to speaker D +
Jack sleeve to speaker C and D -

The tip connection is the one furthest from the panel.

Also either peel off the sticker in the plate recess or ink over where it says 4 ohms, so no-one accidentally connects the wrong amp impedance to it...

riffpowers

ICBM said:

Keep the plate but remove the PCB and the jacks. Replace the jacks with two of these

http://www.ebay.co.uk/itm/CLIFF-ELECTRONIC-COMPONENTS-S2SNS-SOCKET-1-4-JACK-UNSWITCHED-2POLE-/171118832795?hash=item27d77a2c9b:g:~t4AAOxyoVZTIj~8

hardwired in parallel (so you can daisy-chain the cab, or as a spare), with the speakers wired for 15 (16) ohms in parallel-series - two series pairs in parallel - which is the classic Marshall arrangement.

ie

Jack tip to speaker A and B +
Speaker A - to speaker C +
Speaker B - to speaker D +
Jack sleeve to speaker C and D -

The tip connection is the one furthest from the panel.

Also either peel off the sticker in the plate recess or ink over where it says 4 ohms, so no-one accidentally connects the wrong amp impedance to it...

Thanks for the info. I've just ordered those jacks.

riffpowers

ecc83 said:

If a standard metal plate will fit I have one I can jiffy over to you if you send me an address. Get some new jacks from Maplin.

Four 15 Ohm 12s will likely sound different when wired all in parallel compared to  series/pllel and 15 Ohms.  I think generally 15 is the preferred Z? Certainly makes most efficient use of the OP transformer.

Dave.

THanks a lot!!
 I'll drop you a PM.

ICBM

I forgot to say - with these jacks you can solder the wires (I always do), but if you prefer and you make sure the push connectors are really tight (squeeze them gently with pliers before you push them on - but be careful not to squash them flat) you should be able to use the existing wiring. They aren't a perfect fit but if they're tight to begin with, they won't come off. There are enough push terminals on each speaker to connect everything up correctly even with two jacks.

Dave will be astonished at this post I know , but it does work and it's still better than that awful scheme with the switching jacks!

riffpowers

ICBM said:

I forgot to say - with these jacks you can solder the wires (I always do), but if you prefer and you make sure the push connectors are really tight (squeeze them gently with pliers before you push them on - but be careful not to squash them flat) you should be able to use the existing wiring. They aren't a perfect fit but if they're tight to begin with, they won't come off. There are enough push terminals on each speaker to connect everything up correctly even with two jacks.

Dave will be astonished at this post I know , but it does work and it's still better than that awful scheme with the switching jacks!

Anything is better than those awful pcb jacks !

ICBM

riffpowers said:

Anything is better than those awful pcb jacks !

Yes. It's a really, really stupid idea that has been responsible for a lot of blown amp transformers. It's almost guaranteed that with a bit of time and the cable getting tugged, the jack contacts will get strained and fail, even if the PCB pin joints don't crack. When you're using it in 16-ohm mode, a failure at *any* of these points - which are then all in series - will leave the amp with no load.

I wouldn't be at all surprised if the relatively high failure rate of modern Marshall OTs is more down to this than the quality of the transformers. (Or the equal stupidity of using a switching jack in the DSL/TSL amps as well, at 4 or 8 ohms.)

ecc83

Dave will be astonished at this post I know , but it does work and it's still better than that awful scheme with the switching jacks!

Yes, well, a bit! I never had the problem you see. Of course, Blackstar cabs have only been around 10yrs tops but I don't recall ever having a problem with jacks or the connectors.

I do in fact have one of the 4/16 R/ stereo PCBs in front of me. I don't know the Marshall unit but this does not use the same jacks. On this PCB they are 'vertical ' and the board and print is very heavy duty, 1.2mm board and double sided, printed thru' holes.

The PCB is not secured to the plate except by the two jack and so any force applied will cause the board to move as whole and not transfer 'wiggle' to the joints. Won't help with the jack switches of course but at least they are not open to the air as are those above.

As I say, never had a problem except of course where GROSS force was applied. Artist 'loaner' freebies got a very hard life! Note too, all B's jacks are PCB mounted except the Artisans.

Dave.

ICBM

ecc83 said:

I do in fact have one of the 4/16 R/ stereo PCBs in front of me. I don't know the Marshall unit but this does not use the same jacks. On this PCB they are 'vertical ' and the board and print is very heavy duty, 1.2mm board and double sided, printed thru' holes.

Better, but still not ideal if they use the jack switches.

ecc83 said:

The PCB is not secured to the plate except by the two jack and so any force applied will cause the board to move as whole and not transfer 'wiggle' to the joints. Won't help with the jack switches of course but at least they are not open to the air as are those above.

As I say, never had a problem except of course where GROSS force was applied.

You mean the gross force applied when someone forgets to unplug the head from the cab before walking away with it?



Musicians can break *anything*, remember!

If you're going to have the 4/16-ohm option (which I agree can occasionally be useful) the right way to do it is with a separate heavy-duty DPDT.