Marshall 1960 stereo jack ohm problems?

  • Thread starter Thread starter GJgo
  • Start date Start date
GJgo

GJgo

Well-known member
So I just bought a well loved 1960B cab at GC for $299. :D The speakers & the wood are good, but the Tolex is tore up. No big deal.

Before I plugged it in I ohmed out the jacks to make sure it wasn't rewired, and because I've read the stereo switching jack is weak. I think there may be a problem- here's what I found. I'm not afraid to re-wire, just wanted to see where I stand first since this is my first one of these. The stock wiring is super small gauge anyway.

Mono:
The 4 ohm jack reads 8 ohms.
The 16 ohm jack sometimes read 16 ohms, other times it was some screwy numbers, and now it's open (no reading).

Stereo:
Both jacks read 8 ohms.

I was going to go ahead & run the stereo 8 ohm leads to the two 4 ohm jacks on my Boogie, but I'm thinking I should stay away from running the mono jacks till I get this sorted out. Any ideas WTF? Should I not plug in at all yet?
 
It's probably something crossed or shorted on the circuit board. I used to always hardwire the 1960 cabs to just one jack. If I used stereo I just use two cabs. Def sort it before risking your head.
 
could be that or your meter? can you test your guitar pickup and see if your reading is wacky there too// might be battery?
 
Could be battery, I'll grab another one, but the reads other than the 16 ohm jack have been consistent.

My guitars are all active so should be low impedance, first one I tested read open though.
 
Ok I fixed it, and I learned some shit. The battery was fine.

I hear a lot of negative talk about the 1960 stereo PCB, but breaking it down the board actually pretty robust. Certainly beefier than the small gauge wire they run to the speakers. The switch is pretty beefy as well, packed with dielectric grease.

The inconsistency problem was that there were a bunch of bad solder joints on the PCB- this I can definitely see being a weak spot in this design, considering all the hell they endure in a 4x12. I re-fluxed them all & added solder for more robust joints. That problem is solved. I also hit the contacts at the jacks & in the switch with Deoxit.

The other problem was in me not realizing when you stab a jack it changes the circuit.

In mono mode:
- If you're in the 16 ohm jack only, it's 16 ohms. If you jack into the other jack, even with an open cable, the circuit goes open.
- If you're in the 4 ohm jack only, it's 4 ohms. If you jack into the other jack, even with an open cable, the circuit goes to 8 ohms.
..............- This would make me very curious if this is a safe way to run the cab with a single 8 ohm load, and which speakers it runs.

In Stereo mode:
- If you're in either jack, or both jacks, doesn't matter it's always 8 ohms each.
 
good deal.. glad you got it sorted out. I have one cab with the stereo backplate, a 1960bv from 1998 and no problems at all.
 
You won't be able to run all 4 speakers and have it be 8 ohms.

From your description it sounds like the speakers are wired in parallel pairs, and each pair of 16 ohm speakers is 8 ohms. When in stereo, that's what you get. 4 ohm Mono is the two pairs in parallel. 16 ohm Mono the pairs are in series.

And note that the 16 ohm Mono wiring in those cabs is parallel-series which sounds different than series-parallel.
 
SpiderWars":2pfu3i8r said:
You won't be able to run all 4 speakers and have it be 8 ohms.

From your description it sounds like the speakers are wired in parallel pairs, and each pair of 16 ohm speakers is 8 ohms. When in stereo, that's what you get. 4 ohm Mono is the two pairs in parallel. 16 ohm Mono the pairs are in series.

And note that the 16 ohm Mono wiring in those cabs is parallel-series which sounds different than series-parallel.
Click to expand...


:yes: I actually prefer the modern wiring scheme of the marshalls
 
swd4by16sp16.jpg



Id re-wire that cab to series parallel @ 16 ohms with a single jack and be done with it.

Discard the board.
 
I just finished running it through a few heads, sounds good in most but not all. I prefer the sound of stereo running to the pair of 4 ohm outs vs. running mono to the 16 ohm out in all that I tried. IMO sounds more open that way. (It has G12T-75s in it)
 
lespaul6":10t3eg9x said:
SpiderWars":10t3eg9x said:
You won't be able to run all 4 speakers and have it be 8 ohms.

From your description it sounds like the speakers are wired in parallel pairs, and each pair of 16 ohm speakers is 8 ohms. When in stereo, that's what you get. 4 ohm Mono is the two pairs in parallel. 16 ohm Mono the pairs are in series.

And note that the 16 ohm Mono wiring in those cabs is parallel-series which sounds different than series-parallel.
Click to expand...


:yes: I actually prefer the modern wiring scheme of the marshalls
Click to expand...
Ha, I was careful not to say which sounds better. :thumbsup: TBH, I might like one or the other depending on day of the week. I usually wire it like the diagram Chester just posted but I don't run both pairs of wires to the jack. I connect one pair at the speaker ends. Saves quite a bit of wire.
 
-first thing I do on a MARSHALL cab is rip out that tone sucking, transformer killing piece of shit PCB & SWITCHING assembly!!!!!

-put 2 good input jacks, both wired at 8 ohms, POOF!!!! BETTER TONE FOR CHEAP $$$$, very flexible, add a quality MMF Y CABLE IF YOU wanna run more cabs,

-DONE-
 
Alright fair enough. I ordered a straight jack plate, I'm going to hard re-wire for dual stereo & up the wire gauge because I can. Thanks for the advice. :)
 
sg guy":2939nvtu said:
-first thing I do on a MARSHALL cab is rip out that tone sucking, transformer killing piece of shit PCB & SWITCHING assembly!!!!!

-put 2 good input jacks, both wired at 8 ohms, POOF!!!! BETTER TONE FOR CHEAP $$$$, very flexible, add a quality MMF Y CABLE IF YOU wanna run more cabs,

-DONE-
Click to expand...

Yeah, if you don't replace it as outlined that PCB shit will break again regardless and it'll happen at the worst possible time, like at a show after sound check... The 1960 cabs def need that pulled. I also like replacing the handles as well, nothing is worse than carrying a cab up the stairs and the plastic handle busting and the cab falls directly on your foot/knee/face
 
Inearthed":3g9ry8q7 said:
sg guy":3g9ry8q7 said:
-first thing I do on a MARSHALL cab is rip out that tone sucking, transformer killing piece of shit PCB & SWITCHING assembly!!!!!

-put 2 good input jacks, both wired at 8 ohms, POOF!!!! BETTER TONE FOR CHEAP $$$$, very flexible, add a quality MMF Y CABLE IF YOU wanna run more cabs,

-DONE-
Click to expand...

Yeah, if you don't replace it as outlined that PCB shit will break again regardless and it'll happen at the worst possible time, like at a show after sound check... The 1960 cabs def need that pulled. I also like replacing the handles as well, nothing is worse than carrying a cab up the stairs and the plastic handle busting and the cab falls directly on your foot/knee/face
Click to expand...
IIRC, Scumback has a good deal on metal handles.
 
Rewire with jacks, PCB are asking for issues and you tube heads are at risk.

YMMV on tone, they all sound different.
 
Yeah. the first thing i do on Marshall cabs is trash that circuit and rewire in mono.
 
I ended up wiring that cab in 8 ohm stereo with some 12 ga wire I had around & 60/40 solder, and it sounds great. (All my amps can run this config) Side note I have one of those butane powered soldering irons, that thing is the best iron I've ever had. IMO way better penetration than an electric iron. Thanks to all. :)

Then, the other day I found another one in rough shape but for a price too good to pass up. It's wiring was re-done with junk wire & the solder joints were cold so I'm going to re-do it. I'm debating if I should do the same setup, or do this in 16 ohm mono. (Although the speakers ohm out at 13.5-14 ohms...) My Tremoverb & JP2C could run this, but not the Mark III w/o a mismatch. If however I did 4 ohm mono, all my heads could run it.

I know it probably doesn't matter but it's giving me something to think about while it snows today. Thoughts on the tonal differences?
 
Those jacks on the stock Marshall Cabs always caused me problems. As others have mentioned, I always pulled them out and re-wired them.
 
You must log in or register to reply here.
Back
Top