My RAT's gone queer.

[Sea Chief]

My RAT clone isnt working properly. The bass is lacking, the pots distort and crackle a bit turning, and the distortion is thin and trebly. How queer.

Ive changed the pots but no change. So I think its a component or something. Any ideas?

Thanks S.Chief.

[Leo_Gnardo]

Thread title wins an award!

DC on pots will give you a crackle that isn't resolved by cleaning or replacing them. Likely a capacitor serving signal to the volume/tone has gone leaky. Stand by, rattologists certain to ring in with good suggestions any minute now.

[Sea Chief]

Thread title wins an award!

DC on pots will give you a crackle that isn't resolved by cleaning or replacing them. Likely a capacitor serving signal to the volume/tone has gone leaky. Stand by, rattologists certain to ring in with good suggestions any minute now.

(I was going to start by explaining how my rat had started acting effeminately, & that I was rather concerned.)

Capacitor? ah ok I was wondering about one of these.. if I could narrow the possible culprits down that would be good.

Any other RAT folks about? thx SC

[nosaj]

(I was going to start by explaining how my rat had started acting effeminately, & that I was rather concerned.)

Capacitor? ah ok I was wondering about one of these.. if I could narrow the possible culprits down that would be good.

Any other RAT folks about? thx SC

What schematic did you use to build the clone? There's not many electrolytics in a RAT.
nosaj

[Sea Chief]

What schematic did you use to build the clone? There's not many electrolytics in a RAT.
nosaj

Hi nosaj- Its the tonepad one, pg here (Click Here) tonepad -- file information

[Leo_Gnardo]

Hi nosaj- Its the tonepad one, pg here (Click Here) tonepad -- file information

nosaj is having a well deserved sleep in, or maybe enjoying a stack of pancakes by now. I'll pitch in while he's occupied.

OK, had a look, there's only a few electrolytics, true. If installed reverse-polarity, there's a DC leaker. Or overheated on being soldered-in. Meter on the pots, if you read DC that will clue you as to which cap is suspect. The "distortion" pot is floating at half the battery level relative to ground, but shouldn't have DC from one pin of the pot to the other though. If there is, one of the caps 2.2 or 4.7 uF from FB loop to ground is suspect. If the 4.7 uF at op amp's output is leaky, that would put DC both on the dist. pot and filter. If 1 uF feeding volume control leaks, ratty skritch skratch noises to be expected. Thin sound? Bad caps often measure a fraction what they should. Had a 10 uF last week, measured 0.02 uF, sure kept all but high frequencies from moving thru. You may have something similar going on. No cap meter? Just sub in a fresh part, caps-R-cheap.

That's the Sunday morning view from the exterminator's office, good luck Chief!



Next, we work on the music critic neighbor... hope he's stayed out of your hair lately.

[Sea Chief]

ok thanks leo. I think I'll sub all the 'lytics, as all check ok for polarity. nothing looks leaky & got a ton of these diddy jobs. 6 mind you/ more than I 1st thought I had in this build.

cheers SC

[Leo_Gnardo]

nothing looks leaky

DC leaky is what we're concerned about. A voltmeter clipped to pot terminals will narrow down the list of suspects; if you read DC even millivolts across pot terminals there's your clue. Not likely the 100 uF reservoir cap nor 1 uF in voltage splitter are problems. Easy enough to check that V splitter, you should see half the battery voltage across the 1 uF. No need to shotgun = replace all caps. Put on your Sherlock Holmes hat, break out the meter, follow clues to the trouble spot.

[Sea Chief]

DC leaky is what we're concerned about. A voltmeter clipped to pot terminals will narrow down the list of suspects; if you read DC even millivolts across pot terminals there's your clue. Not likely the 100 uF reservoir cap nor 1 uF in voltage splitter are problems. Easy enough to check that V splitter, you should see half the battery voltage across the 1 uF. No need to shotgun = replace all caps. Put on your Sherlock Holmes hat, break out the meter, follow clues to the trouble spot.

Ah yes not leaky caps ok.

Ive gone over all cap values & polarity, swapped in fresh 'lytics and still same. I did notice my 2N5458 3-pronged transistor's flat face was facing outwards (not inwards as in the layout).. but changing it round the RAT doesnt work. So for some reason it must be a "t'other way round 2N5458" I can't remember. Im putting it back around again now.

Ok so what do I need to plug in (jacks) to do DC leaky measurings?

[Leo_Gnardo]

Drat that rat, I'm outta simple most-likely solutions now. Calling expert rattologists now!

Search for DC on pots should be done with the unit on. By the schematic that means a plug in the input jack & battery or power supply attached. All fresh caps serving those pots, DC scratchy noises should be nonexistent. Stumped I am...

[nosaj]

Drat that rat, I'm outta simple most-likely solutions now. Calling expert rattologists now!

Search for DC on pots should be done with the unit on. By the schematic that means a plug in the input jack & battery or power supply attached. All fresh caps serving those pots, DC scratchy noises should be nonexistent. Stumped I am...

Well if no DC on the pot. Look at it like an amp and work backwards with signal injection. Start injecting at the volume pot, if it's scratchy there I'd suspect solder joints, if injection sound is ok there just keep working backwards through the signal chain until it gets scratchy.

nosaj
PS. What are you using to power the pedal ? 9v or or ac adapter?
What voltages do you measure on the IC and at the transistor?