TS9 Debugging

kev93_10 · October 21, 2008, 12:24:49 PM

Hi,
I've been building pedals for a wee while now so I have an above average level of knowledge, but this one has me stumped!

I have a TS9 that I modded to 808 specs. I then applied a Monte Allums kit. It worked for a bit, and now it doesn't! Symptoms are no sound when either bypassed or activated. Also, the LED does not work in either state.

I've taken it back to original specs as part of a logical fault finding exercise of undoing everything I'd done, and no success.

I've also been through the fault finding guide that accompanied the schematics.

The power supply voltage is correct and is giving 9V & 4.5V where it should, so the board is getting power. The obvious fault is with the effect on, I only get ~5V at the analog switch/driver.

Can anyone help me in finding out what's up with this thing? Anything obvious to check?

The pedal is the most expensive paper weight I've ever boght.

Thanks in advance

slacker · October 21, 2008, 01:50:38 PM

I could be the bypass switching that's gone wrong. What are the voltages on the transistors in the switching circuit and do they change when you press the stomp?

If you want to check if any of the circuit is working which will also help pinpoint if it's a switching problem make an audio probe and connect it to the wiper of the volume pot. If the circuit is working you should get sound there even if the switching is damaged.

kev93_10 · October 21, 2008, 03:07:45 PM

Thanks for the reply.

Will give the measurements when the footballs finished!

K

kev93_10 · October 21, 2008, 03:57:05 PM

Q102, 104 & 105 show voltages around 0.2 whether switch is on or off.

Q106 shows 5V.

Thoughts?

K

MikeH · October 21, 2008, 05:48:05 PM

Audio probe!

Zben3129 · October 21, 2008, 08:56:54 PM

The fact that it just randomly went from working to not working in bypass or effect, with no either, makes me think switch. Put one end of the DMM on the tip of your guitar cable on the input (or just tip of input jack) and the other lead on the output. Measure the resistance. It should be less than 200 ohms or completely open. My hunch is that you will find that it is completely open. Next, hit the switch. If it also gives you an open reading, then your problem is not on the board, but rather a dead switch or loose wire.

Zach

slacker · October 22, 2008, 03:23:18 PM

I don't think it will be the switch, if that failed the pedal would most likely just be stuck in bypassed, worth checking it anyway.
Assuming it is a switching problem then then to get no sound both outputs of the transistor flipflop would need to be a low voltage. This would turn the LED off and kill the bypassed and effected signal.

Quote from: kev93_10 on October 21, 2008, 03:57:05 PM
Q102, 104 & 105 show voltages around 0.2 whether switch is on or off.

Q106 shows 5V.

Sorry I don't know what the numbers relate to, mine is an old one and the components aren't labelled. There should be 3 transistors that control the switching on mine they're near the middle of the board and are close together.
You can probably identify them because the emitter leads of all 3 are connected, they're the 3 at the bottom of this schematic. Once you've found them find the one that connects to the LED and ignore it for now, the other 2 are the switch.
You should get about 0.6 volts on the emitters then one of them should have about 0.3 volts on the base and 5 volts on the collector, the other should have about 1.5 volts on the base and about 0.6 volts on the collector. On mine the collectors are the middle leg. When you press the switch the voltages on the base and collectors should flip over.

If yours doesn't do this then something's gone wrong with the switching circuit so that's where to start looking for shorts, damaged traces or whatever.

Zben3129 · October 22, 2008, 03:48:18 PM

Quote from: slacker on October 22, 2008, 03:23:18 PM
I don't think it will be the switch, if that failed the pedal would most likely just be stuck in bypassed, worth checking it anyway.
Assuming it is a switching problem then then to get no sound both outputs of the transistor flipflop would need to be a low voltage. This would turn the LED off and kill the bypassed and effected signal.

DOH!

I was thinking it was a DIY pedal that he added TS9 mods to, which would have a 3PDT, but I forgot the stock has the electronic switching

So if you have a stock (manufactured) pedal than Ian is right it is probably not the switch.

Zach

kev93_10 · October 22, 2008, 04:01:26 PM

I checked the resistance between the tips and it was infinite resistance? No signal was getting through.

K

MikeH · October 23, 2008, 12:07:32 PM

Fashion yourself an audio probe and go from input to out and you'll find where your signal is terminating.

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TS9 Debugging