Schematics

Here's the schematic for the guts of a TS-808 or TS-9/TS-9R (click on the image to enlarge). This circuit omits the footswitch and its circuit and it omits the Half-Supply resistor divider. The nodes marked Vhs are connected to half-supply or 4.5V here.

NOTE: The only difference in the TS-808 and TS-9 is in the output buffer circuit. These include two resistors in the output, R1 and R2 here.

MOD NOTES:

• The conversion to TS-808 involves swapping out the above resistors
• The TS-808 and original TS-9's used a JRC4885 Op-Amp - this needs to be changed out if it is not the same type to get back to TS-808/TS-9 reference
• The Distortion Mod involves switching in 3 diodes in series into one of the diode-feedback branches, resulting in asymmetric clipping and a brighter, more British sound
• The Bass Boost (aka Brown Sound) is done by modifying the 0.047uF capacitor on the inverting input which sets the low frequency rolloff of the distortion stage
• The Level Bypass shorts across the output (level) control giving a full-out setting. By using a second footswitch, this make a Solo-Boost footswitch - or allows two different output volume settings, footswitchable.

Home | Schematics | Disassembly | TS-808 | Bass Boost | Level Bypass | Distortion

Disassembly

Taking apart the TS-9 is straightforward. There are four screws on the bottom, plus 2 more inside to remove. Then, tackle the pots and jacks. For each of these pictures, you can get a super close-up, high resolution view by double-clicking on the photo.

STEP 1: Remove the Screws Remove the 4 screws on back; pull out the battery compartment top to expose 2 more hidden screws. Remove the back plate and the black plastic insulator sitting between the backplate and the circuit board. Make sure to save all the screws and especially the insulator! Once you have the insulator off, remove the single ground screw at the upper left which holds the circuit board in place.
STEP 2: Remove the Nuts Remove the 3 plastic knobs by just pulling upward. Remove the 3 nuts holding the potentiometers in place. Remove the input and output jack nuts on the sides of the unit. This will completely free the circuit board, pots and jacks. The only 2 wires left to the footswitch - you can remove these if you want (I chose not too) -- it will make it easier to work on. If you do choose to remove them, unsolder the connections and write down the colors of the wires to each terminal.
STEP 3: Remove the LED PCB Pull up on the main PCB to expose the potentiometers and LED PCB. The LED PCB is held in place by a single screw. Once you get this screw out, you can pull out the PCB and then pull apart and separate the main PCB and potentiometer wiring harness from the unit.
Here is the Main PCB and the pots and their harness. You might want to write down the colors of the wires for the harness and the potentiometer names (gain, tone, level). You will be moving the PCB board around quite a bit and it will not be uncommon for a harness wire to break on you. For this reason, it might be worth the effort to take a picture or make a schematic of the harness.

Home | Schematics | Disassembly | TS-808 | Bass Boost | Level Bypass | Distortion

TS-808 Conversion

Conversion to TS-808 requires two parts: first, make sure the Op-Amp is a JRC4558 and change it if it is not. I strongly recommend socketing the new Op-Amp so that you can easily swap it out, and because you might damage the op-amp if you try to solder it in. If you damage the socket, its just a few cents destroyed.

STEP 1: Swap the Op-Amp

Here's the back of the Main PCB with the op-amp area highlighted. You will need to use solder-wick, a solder-sucker or de-solder station to remove the excess solder. If you don't know what those terms mean, don't try these mods yourself. The PCB is crowded and it will be easy to really mess things up. td>
Here's the JRC4558 mounted in the op-amp socket. Make sure you have the orientation of the op-amp correct (pin 1 is marked with the little circle on the top). With the op-amp in a socket, you can now easily swap it out for just about any dual-op-amp with the standardized dual-op-amp pinout. Some op-amps to try are the LM833, LF353, or TL082.
STEP 2: Swap the output resistors Trace back from the white wire (for TS-9) which goes to the output jack. The output resistors R1 and R2 are located very near where the white wire connects to the harness. Click on the picture to enlarge it. Carefully de-solder the old resistors and swap out with the TS-808 values (R1 = 100 ohms, R2 = 10k). Presto-change-O, you now have a full fledged TS-808! At this point, you are done and you can re-assemble if you want to. Otherwise, read on for more mods!

Home | Schematics | Disassembly | TS-808 | Bass Boost | Level Bypass | Distortion

Bass Boost

The Bass-Boost mod might be the easiest conceptually, but requires a lot of finessing because of the sizes of the elements involved. First, make sure you have "micro" sized toggle switches for the Bass Boost and Distortion mods. Refer back to the schematic - the bass boost mod involves adding another capacitor across the 0.047uF cap in the inverting input section.

For all mods, prep the enclosure by drilling out the necessary hole. Here, I have 3 holes - two small ones for the Bass Boost and Distortion switches and a huge 3/4" hole for the heavy duty footswitch (level bypass mod).

You will need to take time and measure out the distances you need using the existing components (like the pots) to figure out how much room you have to work with. Measure twice and drill once because this is the only enclosure you get.

The Schematic The schematic to the left show the mod. Click the picture to enlarge if you need to. The mod is to wire a cap in parallel with the 0.047uF one. The switch puts the two caps in parallel in one position. The other side of the switch is disconnected so the cap is out of the circuit and the tubescreamer is operating in factory mode again.
Step 1: Locate the 0.047uF Cap and wire across it The 0.047uF cap is located near the op-amp. It is the only 0.047uF cap close to the op-amp and may be marked 473k or the like. It is the little yellow cap here wit the two blue wired on either side of it. It is better to do this from the component side of the PCB because of the orientation of the board when it is replaced. You can use the other side, but you will need much longer wires and your harness may get more complex. Connect the 0.22uF cap to one side of the capacitor and use heat shrink tubing to insulate the leads.
STEP 2: Wire the switch in series Wire the switch in series with the other leg of the 0.22uF capacitor.
STEP 3: Mount the Switch NOTE: This should be the last step in all the mods. If you want to do other mods, stop here and finish the rest. The reason is that once you start wiring the switches in place, things will get very tight with space and you won't have room to do the other mods. If you are ready to mount the switches, this figure shows the location of the Bass Boost switch, just under the Drive control. You can just see the two blue wires which attach to the switch.
This shows the same Bass Boost switch from the other side. In this photo you can clearly see the two blue wires to the switch as well as the new 0.22uF cap (green) which is resting in place, about where it will be once the PCB is back in place. Remember to insulate the leads and take care with the installation of the switch and location of the cap once the PCB is back in place. Test it out - the bass boost is clearly audible and adds more girth to the low end of the screamer.

Home | Schematics | Disassembly | TS-808 | Bass Boost | Level Bypass | Distortion

Level Bypass

The Level Bypass mod allows you to have a second channel with a different level (output volume) setting. It works by shorting over the level control which gives the maximum volume available. Engage the footswitch, and the current level setting takes affect. By adjusting the level control, you can get two different settings, one with "boost" (the level bypassed) and the other "normal" (level not bypassed, using current level setting on knob.)

The Schematic Here is the schematic for the level bypass mod. It simply shorts across the level pot to create an "all out" volume level. Click on the picture to enlarge it.
STEP 1: Re-Wire The Level Pot The level pot is marked 100KL or 100KB. On my model, the three wires connecting it were light blue, orange and purple. The orange wire was the middle (wiper) one. Unsolder the wiper (middle) wire from the potentiometer. Replace it by a length of wire (black, here). Next, solder another wire (red, here) to the light-blue wire side so that both wires connect at the same point. This is the upper side of the potentiometer and marks the full-volume location.
STEP 2: Wire the Switch I used a DPDT switch, though you only need one side, so a SPDT would do just fine. Solder the orange wire (or whichever wire connected to the level's wiper pin) to the center pin of the switch. Then, wire the black and red wires above to either side of the switch. It doesn't matter which side because this is a push-button footswitch.
STEP 3: Mount the Switch Finally, as the last step for all the mods, mount the switch in the hole you drilled earlier. Here you can see the switch in the lower portion of the picture. That's it! To test, plug in to an amp and find the setting of the switch where the level (volume) knob has no effect - this is the max output. Then, lower the gain a bit for your "rhythm" sound. There you have it - 2 channel TubeScreamer!

Home | Schematics | Disassembly | TS-808 | Bass Boost | Level Bypass | Distortion

Distortion

The Distortion Mod might be the most complex from the standpoint of the wiring. Getting the diode wiring can be tricky. I decided to wire mine so that I could change all the diodes without having to mess with the circuit board. You might choose to do it differently after you check the schematic. This mod gives the distortion a bright, British character and sounds like a different distortion box altogether. Pair it with the Bass Boost mod and you get yet another channel sound!

The Schematic Here's the schematic for this mod. The two distortion diodes are both 1N914 variety. One diode clips the upper portion of the input signal, the other the lower portion. By replacing the other diode with 3 diodes in series, it drastically changes the threshold for clipping for one side. This creates an asymmetry in the signal that is a completely different kind of sound than the traditional Tube Screamer.
STEP 1: Remove and Re-Route the Diodes The first thing I did was remove the two 1N914 diodes which are right next to the op amp. Click on the picture to enlarge it. I wired red wires into one side and black wires to the other side right through the component holes. By doing this and relocating the diodes to be near the switch, it saves time and complexity and makes it easier to modify the mod in the future.
STEP 2: Prep the Diodes You can find 1N914 diodes easily. There is nothing inherent in the original parts that is magic, but if you really want to re-use them, feel free to do so. Here, I have prepped the 3-diodes in series, connected to a single diode. The switch will choose either the 3 in series, or the single diode and this is how the mod functions.
STEP 3: Wire the Diodes and Switch Here you can see how I have wired the DPDT switch. One side handles the negative side (3 or 1 diodes) the other handles the positive side. In this case, the positive side gets 1 diode either way so that is a bit redundant. But, if I decide to change the mod later it will be much easier now.
Now connect the switch/diode combo to the black and red wires from Step 1. The red wires go to the center poles, while the black wires connect the other ends of the diode assemblies.
STEP 4: Mount the Switch As with the other mods, make this the last step. Here you can see the distortion switch mounted just under the Drive knob. You can also see the rest of the mods in place. To test, plug and play. The distortion sound is drastically different so you will definitely be able to hear it. If not, check your wiring.

Home | Schematics | Disassembly | TS-808 | Bass Boost | Level Bypass | Distortion