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Yep, New Old Amp Day for me.

Acquired this old rocker over the weekend from another forum member:



It's a Marshall JMP 50. Some Googling of the serial number puts it as a 1969/1970 model.

Definitely far from perfect, but that's what intrigued me about it. It's been recovered at some point in its life - BADLY. There is some evidence of some work being done on the insides, the extent of which I am not 100% sure. Some of the pots are scratchy etc. But besides that, it's in working condition and it sounds AWESOME and to me, worth giving some TLC and trying to get it back as close to original specs, aesthetically and electronically as possible/practical.

The head has already been affectionately christened "Bad Boy Boogie", or TripleB for short. ?

He came with another old friend:



I bet this cab has a story to tell. It's been through the wars. Once again, it's also been recovered badly at some point, and needs a whole lot of work. It's slightly wider than my new 1960A cabinet, you can make out routed piping channels under the tolex/vinyl/whatever its covered in on the top. The grill cloth seems to have been painted black, and if you open the cab you can make out from the edges that the grill cloth used to be an off-white/creamy sort of colour. Not sure if it is original, but the cloth also seems to have a strange sort of weave pattern to it.

Here she is with the back open:



All 4 speakers are Celestion Greenbacks. The bottom right speaker has lost its green magnet cover thingy at some point. 3 of the 4 speakers have the following model number and date code on them:
Model T1281
Date Code 04FA


Google tells me these are Celestion G12H speakers, and they date back to 4 June 1968.

The bottom left speaker is different. It's a G12M according to the T1221 model code, and the BN6 code dates it to 6 Feb 1980.


When I plugged in a speaker cable to the cab and measured it's impedance, I got a figure of 3.9ohm. That would suggest that all 4 speakers are 16ohm, and all wired in parallel, rather than the 2xseries and the 2 series sets in parallel as my 1960a cab is wired.

Would there be any problem wiring the old cab in the same way to make it a 16ohm cabinet?

Busy preparing an extensive grocery list of items that marks the start of a long term project to restore both the amp and cabinet to their former glory.






    '69/'70 JMP will be point to point wiring, pilot light was replaced too. Nice score 8)
      Some more pics:





      3 different preamp tubes:




        The guts:

        I'm guessing those yellow square thingys on the circuit board are new, as well as a couple of those newer looking caps "


        The scratchy Presence pot ? :


        The scratchy Vol II pot:


        The stiff Mid pot (on the right):


        The input jacks (Not sure what's going on here, there seems to have been some extra wiring added):
          Speaker outputs (Is that white square resistor supposed to be there?):


          Voltage selector seems to have been bypassed at some point:


          Switches and indicator light:



          Nick, you reckon the indicator light has been replaced? It looks old. I was browsing around the net over the weekend and I did come across pics of another similarly aged JMP50 that had the same indicator light, although most of the ones I've come across have that square red one. I've also only come across a couple of pics of JMP's with these black plastic toggle switches. Most of the ones I've seen have the metal ones.
            shaunf wrote: Speaker outputs (Is that white square resistor supposed to be there?):


            Voltage selector seems to have been bypassed at some point:


            Switches and indicator light:



            Nick, you reckon the indicator light has been replaced? It looks old. I was browsing around the net over the weekend and I did come across pics of another similarly aged JMP50 that had the same indicator light, although most of the ones I've come across have that square red one. I've also only come across a couple of pics of JMP's with these black plastic toggle switches. Most of the ones I've seen have the metal ones.
            Voltage selector on mine was bypassed to the correct voltage too. Apparently those selector pins fall out due to heavy vibration, on the voltage selector its not to bad as the amp will switch off, not sure what will happen on the ohmage selector. I need one of those selector pins.. hard to find ☹ Same tubes as mine came with too.

            There was a debate on some forum I read as my '69 plexi had a similair light and I was told its a replacement. As for the switches, apparently black is correct but as they were plastic they break and they are then swopped out for the metal ones.
              What value is the resistor? ? Never seen that!
                MikeM wrote: What value is the resistor? ? Never seen that!
                The one on the speaker output? No idea, will have to check when I get home.
                  I really don't know what it could be for. And it looks like it's only a 10watter too... Jeee
                    It's official - there are now too many people in Durban with cool gear. I think a GFSA Durban clan meet is in order!
                      shaunf wrote:
                      MikeM wrote: What value is the resistor? ? Never seen that!
                      The one on the speaker output? No idea, will have to check when I get home.


                      Mine doesnt have it on the speaker jacks..
                        Looks like your input jacks were replaced with Stereo instead of mono.

                        great amp, so is there gonna be an AFD 100 up for sale one of these days? ?
                          Donovan Banks wrote: Looks like your input jacks were replaced with Stereo instead of mono.

                          great amp, so is there gonna be an AFD 100 up for sale one of these days? ?
                          LOL! The AFD will be buried in the same hole as me! ?
                            Ok, here's my grocery list for the head and cab:

                            Quantity Part Number Description
                            1 S-G403 Grill Cloth - Original Marshall, Salt & Pepper, 32" Width
                            1 S-G402 Grill Cloth - Original Marshall, Large Check, 32" Width
                            6 S-G404 Tolex / Covering - Original Marshall, Black Levant, 50" Width
                            12 S-GP001 Piping - Original Marshall, Gold, Thick, Sold per foot
                            12 S-GP002 Piping - Original Marshall, Gold, Thin, Sold per foot
                            12 S-GP003 Piping - Original Marshall, White, Sold per foot
                            1 S-M600 Logo - Genuine Marshall, 6", White
                            2 S-M603 Logo - Genuine Marshall, 6", Gold
                            1 S-M604 Logo - Genuine Marshall, Gold Lettering, "100"
                            2 P-H295-GC Gold Cap, for Marshall Old Style Handles, sold individually
                            1 P-H295 Handle - Marshall, Vintage Strap, Large, Black with Gold Caps
                            2 P-H295-CMP Inner Clamp for Marshall Old Style Handle, sold individually
                            4 P-HW05 Caster and Socket - Marshall
                            1 P-SP2-106 Receptacle - Power Cord - Mates with S-W123 and S-W124
                            3 R-V38-1MA 1 Meg Log (Audio) Potentiometer
                            1 R-V38-250KL 250K Lin Potentiometer
                            1 R-V38-25KL 25K Lin Potentiometer
                            1 R-V38-5KL 5K Lin Potentiometer

                            I'm ordering enough tolex to make sure I have extra in case I bugger some up.
                            I'm ordering 2 different grill cloths because I can't make up my mind which I like better.

                            What I'm missing and don't seem to be able to find is a replacement Front Panel.
                              shaunf wrote: Ok, here's my grocery list for the head and cab:

                              Quantity Part Number Description
                              1 S-G403 Grill Cloth - Original Marshall, Salt & Pepper, 32" Width
                              1 S-G402 Grill Cloth - Original Marshall, Large Check, 32" Width
                              6 S-G404 Tolex / Covering - Original Marshall, Black Levant, 50" Width
                              12 S-GP001 Piping - Original Marshall, Gold, Thick, Sold per foot
                              12 S-GP002 Piping - Original Marshall, Gold, Thin, Sold per foot
                              12 S-GP003 Piping - Original Marshall, White, Sold per foot
                              1 S-M600 Logo - Genuine Marshall, 6", White
                              2 S-M603 Logo - Genuine Marshall, 6", Gold
                              1 S-M604 Logo - Genuine Marshall, Gold Lettering, "100"
                              2 P-H295-GC Gold Cap, for Marshall Old Style Handles, sold individually
                              1 P-H295 Handle - Marshall, Vintage Strap, Large, Black with Gold Caps
                              2 P-H295-CMP Inner Clamp for Marshall Old Style Handle, sold individually
                              4 P-HW05 Caster and Socket - Marshall
                              1 P-SP2-106 Receptacle - Power Cord - Mates with S-W123 and S-W124
                              3 R-V38-1MA 1 Meg Log (Audio) Potentiometer
                              1 R-V38-250KL 250K Lin Potentiometer
                              1 R-V38-25KL 25K Lin Potentiometer
                              1 R-V38-5KL 5K Lin Potentiometer

                              I'm ordering enough tolex to make sure I have extra in case I bugger some up.
                              I'm ordering 2 different grill cloths because I can't make up my mind which I like better.

                              What I'm missing and don't seem to be able to find is a replacement Front Panel.
                              Any way I can get in on it? I need an indicator lamp for my plexi, one or two replacement marshall vol knobs and some grille cloth to redo my 2x12.
                                When you remove the tolex, keep the old tolex as a template to cut the new tolex.

                                Congrats on the old girl! Looking forward to see it restored to former glory.

                                  Congrats Shaun....wow ! What a find ! Good luck with the restoration....and keep us posted OK ?
                                    nick wrote:
                                    Any way I can get in on it? I need an indicator lamp for my plexi, one or two replacement marshall vol knobs and some grille cloth to redo my 2x12.
                                    Hi Nick,

                                    Sorry I only saw this now. I actually by chance ended up piggybacking on someone else's order, on the condition that I sent my order through to him this afternoon, so I fear he has already placed the order. Sorry man!