#MUSICMASTER BASS AMP MOD#
#MUSICMASTER BASS AMP PLUS#

The return from the vol pot to V1b grid should probably be a shielded wire, since it spans the chassis. All of this need to go past under the tone pot, so it's gotta come out. I'm going to put a new tab on the left so I can mount all the mains, then run the hot/neutral as a twisted pair up to the combo vol-switch. I am going to re-route the PT secondaries tucked up against the front of the chassis and twist the PT center tap with them as far as possible. so that ground needs to be on the other side of the 33K resistor. it's where the artificial center tap connects to the voltage divider for heater elevation. It's the one to the left of the B+1 filter cap in the pic above. In this case, for space purpose I need to use the tab, and it must be isolated from ground.

I'd appreciate someone chiming in to confirm I've got the V-reference correct.Īlso, I have it wired with an artificial center tap and elevated heater reference voltage. This is what I have right now with tubes in. whether they should be pin to ground, or pin to pin in some cases. I'm just not sure if I am measuring correctly.

Chopped stick-ed around a little bit - no obvious loose connections, no smoke or pops. Still fair amount of 120 cycle hum, but not as bad as before rebuild. I finished soldering and installed the power cord this morning. I’d appreciate a go-over of the schematic and layout to make sure I haven’t missed anything corrections and suggestions always welcome. I am waiting for a few more components to come in from AES, so it’ll be a week before I can start putting things back into the chassis. FWIW, I’m using 22 AWG topcoat wire from AES.

If noise is still a problem, I’ll have to get some shielded wire. Regarding the signal wire run from the volume pot back to V1B, I am going to run it under the eyelet backer board – of which I am going to cover the underside with copper tape and mount it with metal washer standoffs, so the shielding is grounded to the chassis. Also, one of the original 7-pin wafer sockets was replaced with a ceramic socket – ugly … I have found wafer sockets on eBay, but the mounting hole centers are way off. I’ve not found a replacement that is dimensionally suitable … excepting there are Richey GOLDS at that might work they’re expensive to risk them not fitting, and the being vertical mounts, the all the connections are on the same end. The original amp had a 20uf-20uf firecracker-type combo cap for B+1&2 filtering. I am not happy with where the fuse holder was installed, so I may mount a block fuse holder where the power cord comes in.

#MUSICMASTER BASS AMP PLUS#

Splitting pre-amp section and power amp section groundingĪttached is the layout and schematic, plus a pic of the eyelet board with pre-install components soldered on schematic of original amp included, too. Adding artificial center tap and heater elevationĨ. Increasing first filter cap from 20mf to 30mfħ. Changing tone control to bass frequency weighted tone tilt stack ala Blencoweĥ. Reducing noise and making it useable as a bass practice amp are the top priorities. The amp came with a replacement speaker and had some updates already done to it, including drilling the chassis to add a fuse holder – so I am not worried about keeping it stock with original components.

#MUSICMASTER BASS AMP MOD#

I have a 1973 Fender Musicmaster Bass amp that was very noisy – I’ve taken it on as a rebuild and mod platform, with some add-ons that are getting some talk on this forum.

Musicmaster bass amp