Marshall JMP Model 1992 Super Bass Head 100w 1969

No Sales Tax For Customers Outside Of California.

I just wrapped a re-cap on this amazing 1969 Marshall Model 1992 Super Bass, While the amp came in sounding amazing, it was clear that it was time to tackle the work to set the amp for the coming decades.  Any parts I changed were retained and will be included with the amp.

The amp retains the original transformers and most internal parts.  There are no holes drilled in the chassis and no sign of previous mods.  The handle, feet, logo, tolex, and knobs are all original as well.  The original inspection tag is in place on the chassis.  The brads that held the model number tag on the back of the amp are there, but the tag is gone.  There are four small holes in the back panel.  Several internal caps were changed before I received the amp, the result of prior maintenance that was done correctly.  There are no other issues to mention.  

I updated all of the can capacitors - 6 in all.  It is a good deal of work that takes some time and requires the careful manipulation of two of the boards.  The work is necessary to continue reliable service of the amp.  Previous to the amp's arrival here, the power cable was changed out.

I was forced to change out the original impedance selector.  This is known as the weakest point in a vintage Marshall, causing countless output transformer failures over the years. 

The original part is a good concept that was poorly executed, on which the user pulls out a two-pin plug and re-insert it for the appropriate selection - 4, 8,or 16 ohms.  The selection shows through a window.  The weak point is inside the part.  The pins on the selector slide into two of four tube-socket-like sleeves, which are soldered onto leads from the output transformer.  The pins and sleeves corrode easily, which can cause intermittent connections. 

The impedance selector on this amp hadn't been used in years.  I could feel it fail when I pulled the plug to check the connections.  The sleeves inside separated from the exterior plate of the connector.  Operating the amp with the part in this state would certainly have caused an issue with the transformer.

Replacing the selector is a challenge as the only Marshall style replacement has a bigger footprint, requiring new holes in the chassis.  I dug around for alternatives and managed to fashion a secure means of mounting the most robust selector switch I could find.  I wrangled the switch so that the attached knob doesn't stick out past the profile of the cabinet, protecting it from future damage.

The amp runs very quiet and super strong.  It sounds absolutely amazing, producing the richest cleans to legendary overdrive.  

We will ship the amp in two boxes - one for the cabinet and one for the chassis.  I have devised a way to ship these amps safely.  Assembly is simple.

• Case/Cover?: No
• Color: Black
• Dimensions: W29" x H11-1/2" x D 8-1/2"
• Weight: 47 lbs
• Watts: 100 Watts
• Date: 1969
• Where is Date Noted?: Serial #, Chassis
• Power Transformer Brand/Codes: See Pics
• Choke Transformer Brand/Codes: See Pics
• Output Transformer Brand/Codes: See Pics
• Extension Speaker Out? Yes
  
• Reverb or other effects?: No
• Power Tubes: 4 x 6CA7 (EL34)
• Power Tube Brand: Phillips
• Preamp Tubes: 3 x 12AX7
• Preamp Tube Brand: ?, RCA, ?
• Filter Caps: Replaced, originals included
• Pedal: No
• Pots/Codes: Original
• Tolex/Tweed: Original
• Grille: Original
• Knobs: Original, except ohm output selector
• Handle: Original
• Power Cord: Original
• Notes: 

Shipping policy:

When you purchase this item you are hereby agreeing to this shipping policy. We remove tubes from amps that could be damaged in shipping.  We remove the chassis from some amps so that the large transformers don't damage a chassis or cabinet.  We remove heavy speakers from some amps so they don't damage baffles.  These cases result in multiple box shipments, and they require the buyer to do some assembly on delivery.  We do this because we have experienced shipping issues in the past, and this is our prevention measure.  Shipments will require signature on delivery, no exceptions.  If there is damage, the buyer must retain all packing materials intact and picture them immediately and send them to sales@maharsvintageguitars.com.  Less than 1% of our shipments are damaged in transit, and we are committed to making sure your item arrives safely, but we are taking these additional measures to make sure you are happy with your purchase.