Equinox: Easy PT2399 Reverb

[alparent]

Quick question: What's the point of transistor Q1? Am I right in thinking the output from the first opamp feeds into the input of the first PT? I just don't understand Q1.

Q1 in an analog switch. When the base is pulled low the transistor switches off, and no signal is passed to the delay line. This is how bypass with tails is achieved. You could also use a FET in this position, if the base resistor is replaced with a diode, which might look more familiar to you?

OK what I'm trying to do is use a togle switch to have ether a true bypass or have a tail.
Will try to draw something up tonight at home. Shouldn't be that hard?
Any ideas?

[merlinb]

OK what I'm trying to do is use a togle switch to have ether a true bypass or have a tail.
Will try to draw something up tonight at home. Shouldn't be that hard?
Any ideas?

Obvious method:

The 3PDT footswitch (green) handles the true bypass AND also controls the tails+LED on the PCB. The DPDT toggle switch (red) simple directs the bypass signal either through the circuit or through the true bypass.

[alparent]

Your not only smart. You are also helpfull.
What a guy!
Thanks for that marlinb.  

And you even took the time to draw it!

This forum is just great!!!

[waltk]

I'm having a little trouble with my Equinox, and looking for ideas/suggestions. 

Here are some details:

Built on Merlin's PCB layout.
Not mounted in a box yet.
First built almost completely stock (subbed a 1n5817 for the 1n4001).
Checked all the obvious things - power, shorts, bridges, etc.
Jumpered the transistor.
Plugged in a fixed 15K resistor in place of the trim pot.
Replaced c26 and c28 with 47uF tantalum caps.

Here are the symptoms:
When powered up it gets straight guitar signal all the way through but no delay/reverb.
It draws ~260 ma and the voltage regulator gets warm.

I have it hooked up to an adjustable power supply, and I can make it work by turning on the power supply at low voltage, and then turning it up to 9V.
When I do this, it works fine (will all the expected delay) and only draws ~42ma.  This makes me think that the PT2399(s) are latching up on startup.  If I hadn't tried the "slow start" trick, I might still be thinking there was some other problem.

Any ideas?  I'm willing to measure things, and replace parts if necessary.

[alparent]

OK just finished this one also.

I do get reverb.

The regulator is running hot.....not to much (normal I guess?..I used a 75L05)
But the 2 PTs or also running warm (is that normal?) The one near the regulator is the hottest. Nothing that will burn my finger.....but warm?

What about that 20k trim? I've used a 25k pot to bring it off-board....but I don't notice any changes from one end to the other?

Thanks for the help.

[ORK]

OK what I'm trying to do is use a togle switch to have ether a true bypass or have a tail.
Will try to draw something up tonight at home. Shouldn't be that hard?
Any ideas?

Obvious method:

The 3PDT footswitch (green) handles the true bypass AND also controls the tails+LED on the PCB. The DPDT toggle switch (red) simple directs the bypass signal either through the circuit or through the true bypass.

Can`t see no colours there, it looks like all black and white to me. Is it the browser, the schematic draw, or my eyes?

[alparent]

You don't see the red middle box?

[merlinb]

I'm having a little trouble with my Equinox, and looking for ideas/suggestions.  

Can you double check that R26 is 4.7k and not 470R?
Also, you haven't used these PTs for any other previous projects have you? If they latch up once, they will do it again and again, even when the delay resistance is increased to a 'safe' value.

[alparent]

OK just finished this one also.

I do get reverb.

The regulator is running hot.....not to much (normal I guess?..I used a 75L05)
But the 2 PTs or also running warm (is that normal?) The one near the regulator is the hottest. Nothing that will burn my finger.....but warm?

What about that 20k trim? I've used a 25k pot to bring it off-board....but I don't notice any changes from one end to the other?

Thanks for the help.

I've also measured the output of the regulator...I get 4.8v is that good? Just asking 'cause on my Arduino projects the output is always 5v on the dot.

[merlinb]

I've also measured the output of the regulator...I get 4.8v is that good? Just asking 'cause on my Arduino projects the output is always 5v on the dot.

It shouldn't be that low normally, but it will do this when the PTs latch up and the regulator goes into shut down.

[waltk]

Can you double check that R26 is 4.7k and not 470R?
Also, you haven't used these PTs for any other previous projects have you? If they latch up once, they will do it again and again, even when the delay resistance is increased to a 'safe' value.

Thanks for the suggestion.  I'll check this when I get back home on Friday.  These were new unused PTs.  I've used other PTs from this batch in other projects and haven't had an issue before, but I've seen a lot of other posts about how touchy they are.  I guess it's my turn to have problems with them.

[LaceSensor]

Hi

Built this, I can get bypass and effected, the LED works, howevever, I only get a weak sounding delay when effected.
I have changed the PT2399's out for another pair.
The regulator is doing its job.

If you adjust the trimpot, it changes the delay time up til about half way in its travel ,then you dont seem to get any effect on the signal (sounds like bypass)
Any ideas or anyone suffered this before?

[merlinb]

Built this, I can get bypass and effected, the LED works, howevever, I only get a weak sounding delay when effected.

Best guess, an incorrect resistor value somewhere.

Photos, people!

[LaceSensor]

my gf has taken my camera on holiday.

Ill check resistor values.

thanks for the tip

[LaceSensor]

one thing I didnt have a small enough toggle, so I havent wired anything there yet. Problem?

[merlinb]

one thing I didnt have a small enough toggle, so I havent wired anything there yet. Problem?

No, it should work fine without the switch.

[alparent]

I've also measured the output of the regulator...I get 4.8v is that good? Just asking 'cause on my Arduino projects the output is always 5v on the dot.

It shouldn't be that low normally, but it will do this when the PTs latch up and the regulator goes into shut down.

I swapped for 2 other PTs but nothing changed. The PT neer the regutaltor is running hot and only 4.8v

Will have to wolk the trace tonight to find if anything is sucking power?
Any tips on where to start looking? I've also checked all caps orientation. I did use a Tant. 10uf.... and I used 1uf NP caps.

 

[merlinb]

Will have to wolk the trace tonight to find if anything is sucking power?
Any tips on where to start looking? I've also checked all caps orientation. I did use a Tant. 10uf.... and I used 1uf NP caps.

The main (only?) reason why a PT will latch up is if the delay resistor is too small- check for wrong value R25/26, and for solder bridges/shorts around the delay pins (pin 6).

Also, to anyone reading this, be aware some if you sub a different transistor you may have to check the pinout, as some BJTs have different configurations from the BC337 I used. I mention this because if you get it wrong it could cause the dry sound to work, but not the wet sound, which a couple of people have mentioned.

[alparent]

The main (only?) reason why a PT will latch up is if the delay resistor is too small.

WRONG! 

If you short pin 1 and 5 you get the same results!

That was my problem a short between pin5 and the trace of pin1.

Thanks for all the help!

One last question...I swapped the 20k trim for a 25k pot so I could play with it from the front panel.
The 10k pot is the "REVERB" what would you call the 20k pot? Stupid question I know

[merlinb]

One last question...I swapped the 20k trim for a 25k pot so I could play with it from the front panel.
The 10k pot is the "REVERB" what would you call the 20k pot? Stupid question I know

Hmm... interesting question. I guess you could call it "ROOM SIZE", or "AMBIANCE" or "LATE REFLECTIONS" or RT60" (a technical term you can google), or something like that?

The main "REVERB" control is actually a bit like controlling how many soft furnishings are in the imaginary room, which damp the echoes and cause the reverb to die away quicker, so you could have "ROOM TYPE" and "SOFT FURNISHINGS" as your controls!