CHASM REVERB

[Sporasankari]

Jep I make diy pcb.

[hammer8994]

howdy! the pedal was sounding awesome but now the signal when bypassed (and when on) sounds overly distorted in a nasty way. could this be one of the ICs/transistors?

[samhay]

>howdy! the pedal was sounding awesome but now the signal when bypassed (and when on) sounds overly distorted in a nasty way. could this be one of the ICs/transistors?

Yes - it's not true bypass so there are a couple of op-amps and a MOSFET in the dry signal path. Did something happen to it / change before this problem started. Is it still getting 9V?

[hammer8994]

Thanks sam! I only finished assembling it today and it dropped in and out of the distorted sound (from a normal operation) and eventually stayed distorted after a few minutes! I'll check voltages on the op amps. Is there an easy way to test the Transistors with a multimeter?

Cheers

[samhay]

Are you powering it with a battery?
If so, this won't work for very long and you need to find a power supply.
If you are running from a power supply and it died after a few minutes, check the orientation of your electrolytic capacitors and look for a broken wire or cold solder joint.

[snorkel54]

I have a volume drop when engaging the pedal    I have checked the polarity of capacitors, diodes, solder bridges etc... 
I have used TL072BCN instead of TL072P, is this causing it?

[slaveunit]

Just finished mine up this morning.  Thanks for the GREAT circuit!!  I love it.

[deadastronaut]

awesome....love the ufo design.... 8)1

[stallik]

Nice build.

[abakuzam]

i built this, awesome reverb But my 78l05 is kinda warm, should i concerned about it? Maybe i can change it to 7805? Also how much current chasm reverb uses? İ don't want to destroy my belton, its quite expensive for me, thanks

[Cozybuilder]

The Belton brick has 3 PT2399s in it. The data sheet for the PT2399 shows typical current draw of 30mA, and max of 40mA. Based on that, the brick could be expected to draw 90mA, and up to 120mA would not be out of specification. The 78L05 regulator is rated for 100mA. IMHO, it would be better to use the device with a higher current rating (the LM7805), which has a current rating of 1.5A. Many have built Belton brick based reverbs using the 78L05, perhaps the Belton brick draws significantly less current than the 3 PT2399s it is constructed of would lead you to believe, or lady luck has been smiling on them, or they haven't burned a finger on their regulator yet.

[abakuzam]

The Belton brick has 3 PT2399s in it. The data sheet for the PT2399 shows typical current draw of 30mA, and max of 40mA. Based on that, the brick could be expected to draw 90mA, and up to 120mA would not be out of specification. The 78L05 regulator is rated for 100mA. IMHO, it would be better to use the device with a higher current rating (the LM7805), which has a current rating of 1.5A. Many have built Belton brick based reverbs using the 78L05, perhaps the Belton brick draws significantly less current than the 3 PT2399s it is constructed of would lead you to believe, or lady luck has been smiling on them, or they haven't burned a finger on their regulator yet.

İ played like 1 hour today , ver slightly warm, i think my hands were too cold last night, but i should give any chance that regulator to get hot, its time to make a space for that big ass regulator, any body ekese had that kinda suspicion? Or 78l05 is just good forever? Thanks btw mate

[armdnrdy]

The data sheet for the PT2399 shows typical current draw of 30mA, and max of 40ma.

This Princeton Technologies PT2399 data sheet lists supply current as:

typ       max
15ma   30ma

http://www.princeton.com.tw/Portals/0/Product/PT2399_1.pdf


The Belton BTDR-2 & 3 data sheets list the supply current at:

typ       max
60ma   100ma

Also of note:
The BTDR-2 is comprised of 3 PT2399s, a TS321, (single op amp) and a 74HC14, (Schmitt trigger)
The last two ICs draw current in the µA.

[Cozybuilder]

It seems there is more than one data sheet for the PT2399. I took my data from the full data sheet from June 1998, the table on p.6.
http://www.diyaudiocircuits.com/wp-content/uploads/2012/09/2399.pdf

Still, from an engineering view do you want to use a regulator that has a 100mA rating to power a chip that has a 100mA spec? If cost were a consideration, the LM7805 is currently $0.23, while the 78L05 is $0.09. My pedal and peace of mind knowing that the regulator will perform on a hot day is worth spending the extra 14 cents. Size? I fit it all in a 1590A, including the LM7805. Surely it will fit in a larger enclosure.

[armdnrdy]

I wonder if the IC was redesigned for better efficiency over the span of 12 years from 1998 to 2010. 

[Cozybuilder]

I wonder if the IC was redesigned for better efficiency over the span of 12 years from 1998 to 2010. 

Probably.

Still, the Brick specs 100mA.

[armdnrdy]

Looking into this a bit further...

I took a measurement of one of my reverb builds.

The draw was 89ma! (unboxed, no LED yet)

This circuit used a BTDR-3 and was fashioned after the BYOC reverb 2. (with a tone control)

Thanks Cozy for bringing this to our attention.

All of the reverb brick projects use a 78L05. 

[samhay]

>All of the reverb brick projects use a 78L05. 
Not mine, but then I only use the TO-220 regulators these days.

But to muddy the water, I have measured current draw by BTDR-2s in the 60's mA, which is pretty safe for a 'L' model regulator. This is also the 'typical' value in this data sheet: http://www.accutronicsreverb.com/main/?skin=sub01_05_1.html
Also, your build will also have a couple of dual op-amps and associated gubbins that will be eating maybe 10 mA that isn't going through the voltage regulator, so you're not flying that close to the sun.

[deadastronaut]

my regulator 78l05 stays cool...no issue there....hmmmm...

[abakuzam]

my regulator 78l05 stays cool...no issue there....hmmmm...

Maybe my regulator is not rated 100mA, i have 7805 brand is Kia, it says it's rated 500mA, i think it should be okay, i'm using layout v1.6 btw. You sir, you are awesome, i played 5 hours of Pink Floyd with that pedal Cheers.