I completed two identical builds using the Marshall JTM45 1986 circuit design. This is the same as the regular JTM451987 except #1 the V1 A/B has a shared cathode cap and resistor like the original Bassman and #2 the coupling caps between the inverter and the power stage are .022uf instead of .1uf and #3 input 2 has a 500pf cap. These builds use NOS Classic Tone Transformers, OT is a bassman 2/4/8ohm, the PT is a Marshall 100, Hammond choke, Nichicon power caps, Tungsol AX7s, orange drop coupling caps in one and vishay in the other, one has tunsol EL34, the other is mullard EL34. I am amazed how low the noise floor is on these amps. I believe the grounding scheme was the key. I recommend that you do not wire the volume pots to the PCB ground plane. And make sure there is only one jumper or wire from the pre-amp ground plane to the common ground. Please note my Classic Tone PT requires a full wave bridge rectifier. See the earlier post I made pointing out the correct eyelet for the full wave. Also note the PT has a 50V winding for the grid bias. I used it and changed R29 to 33k to get my grid bias to range -20 to -45V. Both amps are biased to 18W per tube a litter under -30V on the grids. Blue Box Vishay Orange Drops

Train Express 6V6 completed. This build uses Vishay coupling caps, Nichicon power caps, Hamond 372DX PT, Hamond 1760H OT, DIY drilling on a blank JTM chassis. I have the tubes biased for 8.5 Watts. One change on the AAE layout is grid bias uses 50V tab, so R30/R31/P1 changed to 39k/30k/10k. I am still waiting for the second coupling cap on V2 (C5 2200pf), but fired up an playing anyway. Grounding is good and there is no hum. However as I turn it up I am getting a sound like the shower is on - basically white noise and static. No noise with the volume all the way down, so either in V1 A/B or the tone stack. It occurs with or without the input connected. I have checked the pots, by replacing the volume and disconnecting the tone stack ground. I am suspicious of the unused V2B, should I ground the cathode or remove the heater on 5? One other weird thing is when I change my volume on the guitar it is supper scrachy, and changing pickups makes a loud pop. This happened for two different guitars on this amp, and both guitars are fine through other amps. Any idea what this would be? Train Express Completed adsf

Does anyone have a layout for full wave rectifier on the British Board? I am using a Classic Tone 40-18053 which I thought was 350V CT, per the specification sheet. It is actually 180/180, giving me a meager 260V DC on the B+. I see the British board has eyelets on both sides of D1/D2 so seems easy enough to run the AC 180/180 for full wave rectification. I am not seeing any layouts available for the full wave, but it does appear that someone inadvertently wired it that way in the past. Maybe these layouts were removed? I believe I should ground the + end of D1/D2 and put the AC on the - end of D1/D2 Are there cap changes for the full wave rec? Should I use two 100uf caps in series instead of one 50uf, and connect the CT between them? Or leave the CT disconnected? (see spec sheet) Is the full wave intended to use diodes at D5/D6 in addition to D1-4? Why are D5/D6 on the board?

Just finished 50 watt Dumbel102. It is fully functional after resolving some issues which I will list below This is built in a Bassman chassis, which you can get on eBay standard drilled for 75 USD. I drilled additional holes for presence, standby and power in front. On top I enlarged one ax7 tube hole for the XLR, put the power jack in the unused power tube hole, and in the back drilled for the PAB and OD switches. It worked out pretty well. Then slapped on the worlds worst paint job. Issues with this build were #1 B+ power caps, problem: 22uf caps wired in wrong hole, solution: found right hole. Identified before first powerup. #2 FET input not working, solution: wired tip to FET and ring shunt to regular input. This is different from layout/schematic diagrams. #3 OD and PAB switches not working, problem: ordered 24v relays, solution: 12v relays. My bad. #4 OD not working, problem used 10k pot instead of 100k pot on v2 grid #5 OD low volume, ground issue with shield wire on Drive Pot Mostly my mistakes, except #2. Hope this helps others. One innovation I had on this build was to wire it so I could open the PCB to access the bottom even after doing the Pots and tubes. I used almost 50ft of wire, but it was worth it. It is still pretty quite at low volume and gets noisier when it is cranked. Order on front panel is Input, FET, Rock/Jazz, Master, Drive, Ratio, Volume, Bright, Deep, Treble, Mid, Bass, Presence, Standby, Power, Pilot. Back is fuse, input A/B, bias, output impedance (2,4,8 ohm), send/receive, OD, PAB. Transformers are NOS Classic Tone Twin for power, Bassman for output (50watt), Hammond choke and 6v power (relays). Tubes are Tung Sol 6L6GC and mesa 12ax7. Sounds pretty sweet. So may options for tone.

Just completed a SLO 50 watt build. Process was great with the PCB, layout, schematic and parts list. Wow. This build is in a 100w chassis, but a 50 watt build. I wired it for 2x 6L6 and 2x EL34 with a grounding switch to turn off the set that is not used. I still have to figure out how to switch the grid bias but that shouldn't be two hard. It was a 2 week process of building and another week of trouble shooting, with some minor glitches. Today it is fully functional! Just need to bias it. My original problem was a miswiring of the footswitch jack. While trouble shooting I hooked up the relay power to the heaters but forgot to switch it back after I fixed the jack. I proceeded to ground the CT of the heaters and completely fried the Bridge Rectifier for the relays. Two days later all fixed and using dedicated winding for the relays. The second issue was a non-working clean channel. Relays were good as the amp worked fine on the return input and switching channels. After going through S1/S2, V1A and C18 I found that I found that there was no connection from C18 to R21/R18. Maybe that was damaged by the Rectifier issue (it was briefly working before the Rectifier catastrophe). Not sure if I am missing something else, I did not install the C13/R50 mod. Anyway direct connection from C18 to R21 fixed it up. Cheers, Will