Takota Echomachine (Ibanez EM5 clone) not working

[dperry]

Hi all,

Bought this PCB a few months ago and finally got around to building it and I can't get it to work. 

https://www.watersish.com/docs/TAKOTA_EchoMachinex.pdf?fbclid=IwAR1ZBO_JvTCNY4Y6VT86NT43GQknQBcIjdYn87h_Lm5p5LMYXXtNCMqGmg0

I am using TL072s, 2n3906 in the place of the SA1015 and BC549Cs in the place of the 2 x SC1815.

Its not wired into an enclosure yet, so just testing using crocodile clips and some audio running in.  I get the dry signal, and when I cut the power the signal no longer passes, so it's "working" to an extent.

I've also checked the delay chip is getting the correct voltage, which it is.

Any hints or tips would be most welcome

[ElectricDruid]

Well, the logical way to approach it would be to get an audio probe and go through from the front of the circuit seeing how far the signal gets before it disappears.

That said, you say you've got dry signal but not wet, and that's a classic symptom of "clock not working", and since this circuit has a clock circuit built with quite a few discrete parts, there's a lot that could go wrong, so I'd probably start there.

And the most obvious thing to go wrong would be transistor pinouts: do the transistors you used as replacements have the same pinout as the ones they are replacing? Otherwise, I'm sure the replacement transistors will be fine - I can't see anything that they're doing there that couldn't be done by pretty much any jellybean part.

[duck_arse]

and as Tom always says, "please", post photos of the thing you have built.

[dperry]

*EDIT* First time I built it, I had the orientation of my voltage regulator wrong, so I think i fried the delay chip, and subsequently ordered a new one, I just checked the hex inverter and it has a 6V max voltage, so that probably fried too, so I'll order a new one.

Otherwise....
I found a few dull looking joints so have fluxed them up and re-soldered.

Since I did the substitution for transistors, I have just put them based off the silkscreen but having buzzed the connection, the silkscreen was meant for ECB transistors, so I've bent the transistor legs to accommodate that - Is there a chance they could have blown from incorrect orientation?

And just one other thing - the Takota schematic says the Q3 carrier goes to pin 13 of the SN74HCU04, whereas the Aion FX Elysium schematic (same EM5 clone, different company) says it goes to pin 11 - could this be problematic?

Could you please advise me to basic clock tests and where to probe? I have a function generator, digital scope and multimeter.

[ElectricDruid]

*EDIT* First time I built it, I had the orientation of my voltage regulator wrong, so I think i fried the delay chip, and subsequently ordered a new one, I just checked the hex inverter and it has a 6V max voltage, so that probably fried too, so I'll order a new one.

In my experience, reversed voltage regulators generally don't provide *enough* voltage, and that's why nothing works, rather than too much. So you may well have got away with it. I know I have, lots of times.

Since I did the substitution for transistors, I have just put them based off the silkscreen but having buzzed the connection, the silkscreen was meant for ECB transistors, so I've bent the transistor legs to accommodate that - Is there a chance they could have blown from incorrect orientation?

Possible, but unlikely at 5V, I'd have thought. They don't like it, but they'll live.

And just one other thing - the Takota schematic says the Q3 carrier goes to pin 13 of the SN74HCU04, whereas the Aion FX Elysium schematic (same EM5 clone, different company) says it goes to pin 11 - could this be problematic?

No, they're just using different inverters in the same package. Presumably it suited their PCB layout better.

Could you please advise me to basic clock tests and where to probe? I have a function generator, digital scope and multimeter.

If you've got a scope, you're looking for a high frequency clock on pin 2 of the delay chip. The datasheet says 1-3MHz, 2MHz nominal.


PS: One other thing - the schematic in the watersish.com sheet shows the delay chip flipped left to right, so the pin numbering on the chip is completely unlike reality, which is very naughty of them.

[BJF]

Hi there,

Very cool build.

Definitely good replacement transistors while the pinning may make that confusing

2SA1015 and 2SC1815 have collector as middle leg
 whereas BC549C and 2N3906 have base as middle leg
 If those are not corectly oriented clock will not work.

Bjorn Juhl
 

[duck_arse]

as BJF says, and from my reading of the silkscreen, the emitters of those three transistors points towards that 680pF cap. so get your datasheets for the BC549 and for the 2N3906, and note well where the emitter is on each. anchor that leg on each transistor, and twist the other two leads to fit the board.

[dperry]

PS: One other thing - the schematic in the watersish.com sheet shows the delay chip flipped left to right, so the pin numbering on the chip is completely unlike reality, which is very naughty of them.


Well spotted!

So after a new hex inverter was put in, and I re-orientated the transistors it kinda works - but only really gives 1 repeat and sounds very quiet.  I will mess around with it a bit more (probably swap out transistors and reflow a bit and see where it gets me.

Thanks for all the help so far

[ElectricDruid]

"Only 1 repeat" means the feedback path isn't working properly for some reason.

"Sounds very quiet" could be a lot of things, but "dry joint" is up there, so reflowing is quite a good bet.

Good luck! Let us know how you get on.

[dperry]

Hello again

***UPDATED BELOW****
Sorry it's taken me so long to reply.  It's back on the bench now - I've double and triple checked all my joints and transistor sub orientations, but i'm still only getting 1 repeat, so I am not going to investiqate the feedback path.

Can anyone confirm the highlighted section is the correct pathway to check?

 

**UPDATE**
It works, had an issue with one of legs of the voltage regulator not being soldered down properly!

Just because I hate myself, but love repeat hold on delays - I have noticed the Inchdown Redux (DeadendFX Echomachine clone) has a repeat hold button, but the schematic is incomplete, how would I go about adding this to the circuit?

https://drive.google.com/file/d/1Y0w6E5yRH5_b5Zk2b3HlfIm2SNVJSqwe/view

And there is also this...
https://www.tinkercitymusic.com/gearheads/modalert/xacttonesolutionsechomachine

[digi2t]

I have noticed the Inchdown Redux (DeadendFX Echomachine clone) has a repeat hold button, but the schematic is incomplete, how would I go about adding this to the circuit?

https://drive.google.com/file/d/1Y0w6E5yRH5_b5Zk2b3HlfIm2SNVJSqwe/view

The DEFX Inchindown schematic is spread over the last two pages, and is complete.
Take a closer look.

[dperry]

Whoops!

I got confused by the sw1b being left at the bottom of the page unattached. 

Thanks Great pedal!