Boss TR-2 rate LED mod
filed in Modifications on Mar.22, 2009
One of the latest pedals to join my pedal board is a Boss TR-2. This tremolo is a classic effect and is probably on many pedal boards around the world. There are two revisions of TR-2, the first one suffers from a volume loss when the effect is on, the second does not. If you intend on buying this effect new you should get the second revision and be all right – should you consider the volume loss an issue; be careful if you get one of these pedals second hand otherwise.
I ordered Monte Allums’s TR-2 Plus Mod Kit the shortly after receiving the TR-2, not because I wasn’t satisfied with the way the TR-2 sounded, but more for the sake of modding it – thing I am addicted to. I made all the mods in the kit appart from extra the volume potentiometer because I didn’t really want a volume control on the effect (and also because the TR-2 I have doesn’t suffer form the volume-loss problem).
Having moded the TR-2 I found quite frustrating that Boss didn’t add a small LED on the pedal in order to visually indicate at what speed the tremolo effect is set.
I found a good schematic of the TR-2 circuit on schematicheaven.com. With the schematic on screen and the pedal opened and then started experimenting with a spare LED and a two pieces of wire around the IC3B op-amp.
I found that the LED works best when grounded on one end [UPDATE: Don't ground the LED straigh away, always have a resitor in series with the LED!] and connected to the jumper J3 (see last picture). This way the rate LED is always on (even the effect is not engaged) and only the rate and wave controls have an influence on the LED blinking. I prefer this behaviour (the depth control has to impact on the LED) since the utility of the LED is to visually indicate the RATE of the effect, even with a the depth control set to a very subtle level.
Surprisingly, I couldn’t find any indications of how to do that LED mod online so, hopefully, I hope it helps!
 |
 |
 |
 |
 |
June 16th, 2009 on 0:21
Hey man…gave your tr-2 mod a try and it works but it makes
the other led flash as well in sequence and it affects the wave knob
and the depth knob it in a weird way. Any thoughts? Thanks.
June 16th, 2009 on 0:25
Hi Sean,
I think I know why you’ve got the 1st LED flashing. And it’s partly my fault: I forgot to say in my post that the LED isn’t connected on it’s own:
LEDs are never connected on their own to a circuit: it’s always +V < --> LED and resistor in series < --> ground.
The reason for this is when you apply voltage to an LED it shorts the +V to the ground if you don’t have a resistor in series with the LED.
I’ve hidden the resistor into heat-shrink and I forgot about it! I’m sorry but I won’t be able to tell you what resistor value you should use as it’s all inaccessible under the heat-shrink so you’ll have to experiment.
Please let me know what value you used (it should be something in region of a few kilo Ohms)
.
Hope this helps,
Ben
June 23rd, 2009 on 17:57
Is there a way to do this mod on version one of the tr-2? the schematic is the same but the layout and part # have changed a little. thanks
June 24th, 2009 on 10:15
Hi John,
I haven’t tried my mod on a revision 1 of the TR-2. I would say it probably would since there is a J3 jumper on the REV1 board:
– New TR-2 board.
– Old TR-2 board.
It’s probably worth giving it a go (without drilling in your pedal first!) if you’ve got a spare LED and resistor handy.
Please let me know if you are successful
August 3rd, 2009 on 0:28
Hi,
Nice post – I just opened my mate’s revision 1 TR-2 pedal up to fix it and checked the board layout. Might ask if he wants this mod adding while I’m at it
I think jumper J2 is the one you want for the LED on this board – it is connected to the output of IC3B which is the op-amp before the depth control (I assume this is what J3 is on the rev-2 board).
J3 is after the depth control pot on the revision-1 PCB.
best
Chris
August 3rd, 2009 on 8:00
Thanks for sharing the info Chris! Yes it looks like you are right about J2 on rev-1 boards…
August 3rd, 2009 on 11:13
Incidentally, it just occurred to me that if you can find a 3mm common-anode bi-colour LED, you can do this mod by replacing the “check” LED and not have to drill a hole in the metal case.
Common-anode bi-colours aren’t so easy to get hold of though – I can only find one UK supplier that carries them:
http://www.dccsupplies.com/shop/product_info.php?products_id=798
Using a red/white one, connecting the red side of the LED in the same place as the original check LED and connecting the cathode of the white to J3 (or J2 on rev 1 PCB) should give you an on/off flashing white led when the effect is off and a red/white flash when the effect is on. You also wouldn’t need a current limit resistor if you mod it like that because the anode would already be limited through the original resistor and zener for the check LED.
best
Chris
August 5th, 2009 on 3:06
Hey, great mod, been looking ages to do something like this. Has anyone figured out what value resistor to use?
Thanks
August 6th, 2009 on 1:24
Hi,
I just finished modifying my mate’s pedal with a bi-colour LED and it looks very nice
The check LED now flashes white on/off when the effect is bypassed and flashes red on/off when the effect is in.
For information, the voltage on the output of IC3B (the signal on J3 for rev2 or J2 for rev 1 boards) oscillates between 4V and 5V. That means the mod idea I suggested in my earlier post won’t work quite as I described it. It also means if you want to do the mod that Ben described in the original post then you probably want a current limit resistor in the region of 500 to 1k ohms.
If you’re interested in the bi-colour mod, these are the steps to follow:
1) De-solder the “check” LED connections P2 and P3.
2) Replace the old LED with the 3mm bi-colour but keep the old LED to hand (You can remove the old LED from the small PCB and solder two legs of the bi-colour in its place – I found I needed to file a small slot out of the plastic spacer that holds the LED off the board to fit round the third leg of the bi-colour).
3) Connect the output of IC3B (J2 or 3 depending on your board) to a 680 ohm resistor.
4) Connect the other end of the resistor to the anode of the old red LED.
5) Connect the cathode of the old LED to the anode of the bi-colour LED. Make sure that the connection of the old LED and resistor are insulated with heat shrink or electrical tape.
6) Connect the red cathode of the bi-colour to P3
7) Connect the white cathode to jumper J15 (that’s on the rev1 board – it appears to be J21 on the rev 2 board).
Explanation of the cathode connections: P3 is where the original check LED cathode was connected and goes to the collector of one of the transistors (Q5) that makes up the bistable circuit that controls the effect bypass/on switching circuit. J15 is the collector of the other transistor (Q7) in the bistable.
Why keep the old LED? I used the old red LED in my circuit (wrapped up with the 680 ohm resistor inside the pedal) to drop an extra 1.8 volts so that the LED flashed properly.
Best
Chris
August 6th, 2009 on 5:57
Hey just wondering what kind of LED to use for this… kind of a newbie to pedal modification. THANKS!
August 6th, 2009 on 22:25
Many thanks Chris for the very detailed instructions. If I get the opportunity to mod a TR-2 again I’ll definitely give it a go
!
Bryan, the LED you are after are of the 5V 3mm type. Hope this helps.
January 13th, 2010 on 16:49
hey there! ive never posted before, but saw this thread when i was looking to do an LED rate mod on my TR-2…i do pro mods on ALL brands of pedals, and had already modded this one to have better high end response and not lose ANY volume when engaged…just wanted to tell everyone: i used a 10K resistor on the LED instead of what has been said before (ie 1k, or 2.2K)…i think this makes the effect WAY more dramatic because the resistance is higher…use a 10k or possibly 15k for this…also, i think i have the rev 3, my pedal has j2 and j3 jumpered already stock…i found that hooking the LED to j2 made the effect more dramatic again and NOT go away when the depth knob is turned down…just thought id share my experience with this mod! if anyone has any questions or is curious about getting a pedal pro modded, i do everything, my company name is Carson Lane FX, and my email is madmanmike7@hotmail.com so just hit me up if you want. thanks!
February 6th, 2010 on 0:17
Hello. So I did the mod today and its sweet. Thanks for all the info guys!
I do have a question about the check led: It’s not bright and would like it to be!
Do any of you know if I can do that?
Thanks
February 8th, 2010 on 11:13
Hello Jordan,
Have you checked your battery isn’t running dry (if you use a battery to power your TR-2)?
If you want a brighter check led I’d try to either:
– Get a brighter LED (blue ones are really bright)
– Adjust R17 (if you lower it a bit, more current will flow through the ‘check’ LED and it will glow brighter).
Hope this help!
February 15th, 2010 on 8:26
Hello again.
I use a godlyke power all setup so its not the battery.
I’m going to try the blue led first and then go to the resistor.
Thanks.
June 6th, 2010 on 21:49
Hey ! Cool stuff !
I’ve just finished performing the mod (adding a second led, wired to a resistor on one side and connected it to J2 on an older model).
It works, but the flashing is not really obvious. I’d like to exaggerate the effect. Any idea how i could do that ? What is the value of the resistor you are using ?
June 12th, 2010 on 20:50
Hey guys,
i came up with another easy mod. I wired a switch in place of R31 which controls the Rate of the LFO. This way i either have the stock value (50k) or the mod (jumper) which gives me some pretty crazy rates and FM sounds. It even self-oscillates when turned all the way up. Nice if you are looking for some special effects.
June 13th, 2010 on 14:25
Hello François,
Thanks for sharing your R31 bypass mod! I just gave it a go and was able to generate interesting weird noises!
July 1st, 2010 on 11:30
just’ve finished doing the mod. the led ain’t blinking properly. tried many resistors, not helping at all. any suggestions?
July 7th, 2010 on 13:11
me again. indeed, 15k resistor is the thing. with 10k the led blinks brighter, though you can hardly see blinking of sine wave form. with 15k the led blinks not so bright, but blinking is more obvious.
November 23rd, 2010 on 17:57
Hello again,
Haven’t seen this post in a while, but saw some questions on the rate led and thought id leave anyone who’s looking some answers on the tr-2….
Just like george said, making the value of your resistor that is connected to either J2 or J3 depending on your version of the tr-2 10K – 15K – this will make the “blinking” effect MUCH more prevelent…(ALSO – IMPORTANT NOTE – IF you put the resistor on the “wrong” side of the jumper, you WILL get a pulsing noise coming through your amp – at least if you’re using a vintage fender, thats all i have so thats all i know, but i think it will happen with any amp!!
So make sure you have it open when doing this mod and just touch it to the sides of the jumper, seeing which one does the blinking effect WITHOUT the pulsing noise coming through…
ALSO you want to make sure you hook it up to the most dramatic jumper point, which again is DIFFERENT on different versions!
Like i said, just keep it open when determining where you will hook up the resistor end of the LED and find the best place for effect, making sure you are on a spot where the blinking does NOT go away as u turn the depth knob down!
Ok, sorry to ramble, but thought that was important to you all to know the easiest way is just to have it plugged in and probe around with the resistor…doing this on your solid state practice amp would be preferable, as pops and whatnot are TERRIBLE for your TUBE amp… so having a squier amp or something like that is great for these kinds of tests while modding pedals…
In closing, make the resistor value 10K-15K depending on the brightness type on your particular LED, and make sure that the resistor side is on the positive side (longer leg) of the LED…
And one more thing you could do while you’re in there is putting in a RAD rate led, go ahead and put a tiny 10K trimpot on R9 (i believe?? – the “volume” resistor if you will) and then you can set the volume how you like it while the pedal is open, then close it up and u can always adjust the volume of the effect!!!
You could also use a REAL pot mounted to the pedal but wouldnt that be resembling a very popular “big name” mod??
The tr-2 CAN be the best trem pedal on the market with the right adjustments… I swear I’ve owned a lot of vintage fenders with “vibrato” (actually tremolo) in them, and have opted to keep my blackface bassmans instead, despite the no vibrato and no reverb. My tr-2 sounds great, really natural and almost sounds like it is in the amp if you set the volume trimpot right and my holy grail nano for reverb… heaven…
Hit me up at madmanmike7@hotmail.com if you have any more tr-2 or other mod questions… good luck!
Thanks for reading my super long post! lol
January 7th, 2011 on 3:28
Great stuff. I’m going to try these in a couple of days. A few question though:
Has anyone determined whether this Rate L.E.D. method lights up in phase with the effect?
Any volume or signal loss due to this? I’ve seen other methods for this that give the L.E.D. it’s own power-supply. – http://indyguitarist.com/forum/index.php?topic=1537.0
January 18th, 2011 on 7:28
Thanks for the link.
As far as I have noticed: my moded pedal don’t suffer from a volume loss. And yes the LED blinking is synced with the effect. We divert the LFO output voltage (that controls the VCA) to feed the LED directly.