Max Landegren from Billion Dollar Babies came by with his other JCM800 and wanted me to rebuild the distortion channel in it. I’ve modded his other JCM800 before and he asked me to make this amp more suited for soloing with a fatter sound with more compression and gain.
Stock JCM800 2205, not my favorite Marshall but soon it will be sounding like I want it to do.
I made this small turret board for the distortion channel.
The new turret board for the distortion channel is in place and some changes are made to the power amp and power supply.
The faceplate in the upper right corner that makes all the difference 🙂
Here’s Max trying out the amp for the first time after the modification:
As I always do with these major PA rebuilds, I clean them completely from the old parts:
Clean it from the old dirt:
Point to point boards:
Wiring around the power tube sockets:
Cables for the boards:
And components for the boards:
And get the boards into the amp and try to remember where all cables where supposed to go:
And here we have the finished result:
It’s a three channel amp with a tube buffered effects loop, dual switchable master volumes and a solo boost.
Control for each channel: gain, volume, treble, middle, bass. Channel two and three also has a tightness control. Channel two has a three way mid boost switch (low mid/normal/high mid) and channel three has a switchable solo boost that gives a push in the low end, a push in the mids at 600hz and flat out the highs.
Controls for the power amp: Dual master volumes, presence, punch and a three way range switch for the punch.
Here’s a clip of the amp:
Bonus clip of channel 2 and 3 before the amp was finished:
I’ve built a new preamp section for this amp. There are some changes to the power amp and power supply section as well.
It was modded with a MarkIIIb mod by Tommy Folkesson before but there isn’t anything left of that mod now.
Unfortunately all pics from this project were lost in a computer crash so this video is all I’ve got left.
I did a mod to this Sovtek MIG-50, changed the preamp circuit and made some minor changes to the power amp and the power supply.
Now it has a gain control and a master volume as well that works for both inputs. Input I: three gain stages. Input II: two gain stages.
Time for another Selmer PA 100! This amp was as most old British PA’s from the 60s and 70s an all tube amp with excellent transformers. Therefor they are a great platform for guitar projects and a bonus is that there’s room for a lot of controls on the big front panels. It has now become a two channel guitar amp with dual footswitchable master volumes and a tube buffered effects loop.
Here it is in original shape:
Taking out the old point to point board to make room for new ones.
These amps are more than often filled with 40 year old dust and dirt.
So I prefer to clean them before working in them 🙂
New turret boards made for this amp:
And here they are populated with components and cables:
Installing the boards inside the amp:
And here’s the finished result:
It’s now a totally rebuilt amp with a new preamp, new power amp and new power supply section. It has two independent channels with gain, tightness, bass, middle, treble and volume. The mastersection has presence, punch and two switchable master volumes as well as a tube buffered loop.
My latest project is this Sound City PA 120R which had a solid state preamp and a tube power amp section. It was a good platform with it’s big transfromers and room for a lot of controls and functions on the big front panel. It has now become a four channel amp, all tube of course with a footswitchable gain boost (extra tube stage) for each channel and dual footswitchable master volumes. So it has eight footswitchable sounds which can all get a volume boost for solos. Other features are tube buffered effects loop and bias potentiometers and test point jacks for each of the six EL34’s on the back panel.
Here it is in original shape:
Here you can see the guts of the amp before I did my work in it:
I took out all parts except for the good old transformers and the tube sockets + impedance and voltage switches:
Making turret boards:
All cables attached to the turret boards:
Turret boards populated with components which makes it a totally different amp:
Preparing the amp to receive the turret boards:
And attaching all the cables where they are supose to be:
And here we have the finished result:Controls for each of the four channels: gain, three way mid boost switch, bass, middle, treble and volume + a footswitchable gain boost.
Controls for the power amp: dual footswitchable master volumes, presence and punch both with a three way range switch to match the amp to different cabinets.
Turret boards filled with NOS Mustard Capacitors and Iskra resistors along with some new components.
Installing the new circuits in the amp.
Here’s the finished result:
It has two channels with gain, volume, treble, middle, bass and a three way gain structure switch. Channel 2 also has a tightness control and a growl control. The controls for the power amp is master volume, presence, punch and deep.
My latest project is this Selmer PA 100! It will be a three channel amp with a footswitchable gain boost that kicks in an extra gain stage on each channel. It will have a tube buffered loop and a lot of voicing options and as always it will be built point to point using NOS mustard caps and Iskra resistors 🙂
Giving a new finish to the front panel. Cleaning it from the old board and make room for new ones.
Renovating the old switches.
New turret boards are done.
Installing new potentiometers and switches.
The boards are ready to be installed!Just need to remember where all the houndred cables are suposed to go 🙂
Here is the finished result:
Here are some clips:
First test of the amp using my Hagström Swede.
Showing some metal sounds. Guitar straight into the amp, nothing in the loop.
Overall demo of the amp using my Greco EGF-1000. I’m running a TC G-major 2 in the loop for some delays. The cab is a Malmberg 4×12 with Celestion Greenbacks
I’ve installed a tube buffered loop and modified this Marshall JCM 800 1959. It’s a smaller mod since the main PCB is still there and the power amp is almost untouched, but the change in tone, gain, dynamic response and feeling is huge!
Before mod. You can see that someone has installed a master volume, and it has been modded with an extra preamp tube at some point before but is restored to stock.
After mod. Effects loop installed and the preamp is changed pretty much along with some minor changes in the power amp and the power supply. I’m using shielded cable for the signal to avoid hiss and noise.
I’m playing a Greco EGF 1000 with Seymour duncan JB + 59 straight into the amp and running a G major II in the loop for some delays. The cab is a Malmberg 4×12 with old Celestion Greenbacks.