Just fixed my Ibanez TS-808 pedal.

[DrNomis_44]

Hi Everyone,

I couldn't think which forum section would be most appropriate place for me to start this thread, but the amplifiers section seemed the most appropriate cause we guitarists tend to use pedals with our amps anyway, I just had a bit of a win with regards to fixing my Ibanez TS-808 Tube Screamer pedal.

So what was wrong with it?, basically, it wasn't foot-switching reliably, sometimes it was a bit intermittent, other times it would simply refuse to foot-switch at all, sometimes it would stay bypassed, or un-bypassed, I decided to open it up and have a good look around on both sides of the circuit board using a magnifying glass to see if I could spot anything that might be causing the foot-switching to malfunction, this is a classic example of where you need to have a clear head while doing any troubleshooting, at the time I was doing the troubleshooting, I was feeling a bit tired so my mind wasn't as sharp as it could have been.

While looking at all the components on top of the circuit board with my magnifying glass, I noticed some whitish-looking substance underneath a small ceramic capacitor, one terminal of the capacitor was connected to a resistor that connected to one of the contacts of the foot-switch, the other terminal of the foot-switch was connected to circuit-ground, on a hunch I grabbed my digital multimeter, set it to the 20M resistance range, and measured the resistance of the capacitor, which should have measured close to infinity, it actually measured about 7.5 kilo ohms, that looked very suspicious to me, so I tried de-soldering the capacitor and then scraping away the whitish substance with a Stanley-knife blade, then I soldered the cap back into it's place on the circuit-board, result....that fixed the foot-switching malfunction completely and now the foot-switching reliably functioned as it was supposed to.

I'm going to take my Ibanez TS-808 pedal into uni tomorrow to give it a good test out with my Marshall amp along with my Boss BD-2 Blues Driver pedal (it had been playing-up too, but I believe I have also fixed it as well), will let you know how it goes.

[stan]

good work Doc, nice when it's easier than expected

[Andy40]

Nice work Doc. I still have all my pedals to fix.

[DrNomis_44]

Update:

I just tried the TS-808 pedal out a few minutes ago, and it is playing up again, so I'm going to take it back home and have another look at it, it doesn't seem to be foot-switching properly, so maybe there's a faulty component somewhere.

[DrNomis_44]

Update:

Apologies if this sounds a bit technical.

As far as I can determine, the circuitry on the TS-808's PCB that's responsible for turning on/off the two Fets (Field Effect Transistor) that do the footswitching, appears to be working okay, I verified this by using my signal-generator set to put out a square-wave at about 10Hz, when I applied the signal to one side of the two terminals of the mechanical footswitch, the indicator led blinked on and off, so, my conclusion is that either the mechanical footswitch has dirty intermittent contacts, or, something related to it is causing the pedal to footswitch intermittently.

Here's a schematic for the TS-808 that I found on the internet:




In the schematic there are two resistors (a 62k and a 22k) connected in series going from V+ to circuit-ground, there's also another resistor (a 1M) connected to the junction between the 62k resistor and the 22k resistor, the 1M resistor is connected via a 22 Ohm resistor to one of the contacts on the mechanical footswitch, I think the cause of the intermittent footswitching has to be somewhere around this part of the circuitry.


Note: The two Fets in the schematic are the components marked 2SK30A.


The two 2SK30A Fets are being used as electronically controlled switches, and these route the input signal either straight-through to the output, or through the two Op-Amps (the two triangular shapes), when the mechanical footswitch is stomped-on, one of the 2SK30A Fets turns on and the other turns off.

[DrNomis_44]

Update:

I was just doing some more work on my Ibanez TS808 pedal and I think I have finally cracked it this time round, in the schematic I posted, there is a small value capacitor (1000pf) going from one end of a 22 Ohm resistor to circuit ground, in my pedal it is a 10,000pF (10nF) ceramic capacitor, which appears to be the cause of the footswitching issue I've been experiencing, what I believe is going on with the capacitor is that it has gone leaky, but to detect it I had to set my digital multimeter to it's highest resistance range, I compared it with another known good 10nF cap (a yellow polypropylene type) and got very different results, so I tried using the yellow 10nF cap as a replacement, and now the pedal seems to reliably footswitching again like it's supposed to, I'll give it some soak-testing for some time just to be sure that I have finally fixed it for good now.

[Simon Barden]

Is yours an original model or a re-issue? I've had mine since I bought it in 1980 and it's still working fine, though the pots are a bit scratchy and needs fairly regular doses of cleaner.

[DrNomis_44]

Is yours an original model or a re-issue? I've had mine since I bought it in 1980 and it's still working fine, though the pots are a bit scratchy and needs fairly regular doses of cleaner.

Mine's actually a later re-issue, probably circa 2015 or so, I bought it last year from the Top End Sounds pro music shop, I have another pedal that needs some servicing work done on it to get it working again, it's my Boss Compressor/Sustainer, for some reason it doesn't seem to work at all, I'll need to find a schematic diagram for it and then do some tests on it.

Now that I think I've finally got my TS-808 working properly, I'm going to do one mod to it, which is to swap out the stock red indicator led for a blue one, the red one is a bit too dim for my tastes, should be a fairly straightforward mod to do.


Here's a pic of my TS-808 pedal:




I've tried it out a few times after working on it and it definitely does seem to be working a lot better than before....touchwood.


I'm going to wait till tomorrow morning and give it another test out, if it is still footswitching reliably when I test it out, then I'll know that it is well and truly fixed for sure, I want to make sure because I'm not entirely 100% convinced that it is fixed though, last time I thought I had fixed it, it proved me wrong, and the last thing I want is for it to go bad again right in the middle of a gig, or jam session.

I'm pretty keen on using it as a booster pedal with my Marshall amp, because of it's midrangey tone, apparently these TS series pedals tend to shine best when used as a booster pedal to kick an amp that's just breaking up into overdrive, this involves setting the Drive control to a low setting and then turning up the level/volume control.

I'm guessing that it would work pretty well with my Fender Super Twin amp, and my Gold Strat.

[stan]

Nice detective work Doc, hopefully it all stays put now

[Simon Barden]

The super twin at least has a gain + master volume control. If not, you'd be up around 200W before any amp drive was apparent, and the volume boost from a tube screamer would be truly frightening.

The tube screamers are supposed to work best with Fender style amps, which generally have a dip in the mids as their standard sound. Boosting with a mid-rich pedal is suppose to fill that gap and make a Fender sound a lot more meaty (especially with single coils). Marshals are a lot more mid-heavy in character to start with, so a TS makes the sound even more so, which doesn't always work so well (though if you've cut most of the mids on the EQ for a scooped sound, then it will fill those back in).