CHASM REVERB

[Ice-9]

Great looking boards Rob, love the little heavy metal little stick spaceman.  

[J0K3RX]

A few quick questions. Sorry for my noobyness on this.

1) I have been unable to find a 22k Lin pot anywhere to use for the Decay knob. Can I just use a 25k in place of it or do you know of a place I can order one in the US?

2) I was also unable to find a LM7805 voltage regulator on Mouser, Mammoth or Small Bear Elec. To my knowledge/understanding a LM78L05ACZ would work fine correct? If so is the orientation the same as the 7805?

Thanks in advance!

1) 25k linear is fine...

2) LM7805...? You can't find at mouser?

http://www.mouser.com/Search/Refine.aspx?Keyword=LM7805&gclid=CjwKEAjw8_idBRCExfC15My3owwSJACSDX_WjKTRRzpEfGgCAD0swiNWc6w9jb_Ms6BdY2s-ZzthRxoCMBTw_wcB

or

http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/LM7805CT/?qs=sGAEpiMZZMtdAabcSkQOlwJydEoyhc9b

or

http://www.taydaelectronics.com/lm7805-l7805-7805-voltage-regulator-ic-5v-1-5a.html

or

probably a LM2940

[bluebunny]

4) I'm assuming it uses Mono/Mono jacks on the input and outputs?

5) What size enclosure is the PCB layout meant for? Assuming 125B should work fine...looks like most builds are 1590BB anyone fit it in anything smaller (excluding crazy stuff like 1590A)?

4) That would be fine, since you're unlikely to be using a battery for this build.

5) The board shows four pots in a line, plus a switch, so this isn't going to fit in a 125B.  Not unless you smash it into tiny pieces with a large hammer.      I'd go for the BB.

[0ron124]

Thanks for the replies guys!

I guess I'll just do that and go for the BB and after looking at the specs for the Belton I think that the LM78L05ACZ would work fine which is the only thing that Small Bear and Mammoth have in stock and since I usually order everything there I'll just try that out instead. If it doesn't work I'll get the LM7805 from Mouser thanks for finding it, for some reason it wasn't coming up 

As for #3, I went back and looked at the Schematic and I'm stupid...the wiring is there thanks guys!

[Jdansti]

Tayda has the LM7805 for $0.23.

http://www.taydaelectronics.com/catalogsearch/result/?q=Lm7805

[GiulioGratz]

Hi guys! I have a problem with my build: also if not engaged, the pedal make a very bad, very loud noise (perfectly tuned in A), something like self oscillation... The volume pot works fine (if i turn it down, the motorboating stops), the mix pot works fine (if the pedal is engaged and i turn up the mix pot i can hear, under the oscillation, the instrument i'm playing), the damp pot works fine (i notice a variation in tone turning it). The decay doesnt' probably works. Any idea?

[deadastronaut]

@gg... I take i it you made your own pcb?...

there is a lot of off board wiring in the diy pcb layout..

triple check it over...its easy to get distracted and put wire in the wrong place.

many others have built from the diy pcb layout with success
..ok..

[GiulioGratz]

Yeah, i made my own pcb from your layout and double, triple checked the wiring... all in the right place... What part of the circuit can be related to motorboating?

[chi_boy]

Take a really good look at your 78L05.  Check the datasheet and compare the pinout to the schematic.  Don't just look at the flat spot and assume it's all good.  Make absolutely sure the pins are oriented correctly. 

I had a very similar problem with my first reverb build and traced it to the regulator.

[GiulioGratz]

Mmmm, it shouldn't be a problem if i used a 7805 in place of the 78L05, right? Pins are oriented correctly, input, ground, output... don't know... however i'll try to re-control all the traces! Could it be a short? 

[deadastronaut]

you want 9v at the top of the reg, and 5v at the bottom...  7805/78l05 have different pin outs...

7805:

https://www.google.co.uk/search?q=7805&client=opera&hs=chY&tbm=isch&imgil=gNku2Al1T4jp_M%253A%253Bhttps%253A%252F%252Fencrypted-tbn2.gstatic.com%252Fimages%253Fq%253Dtbn%253AANd9GcTCQ8xpW5cX8T7eW5ILO0nPGOa0LfZ0AQS02OLX-pjNLF6gWngd%253B305%253B242%253B4w70rj_UNgIfdM%253Bhttps%25253A%25252F%25252Fwiki.techinc.nl%25252Findex.php%25252F78xx_power_supply&source=iu&usg=__iHAt4VAtR5sw60_jTYxNJY_NQZ0%3D&sa=X&ei=OFbaU534JtGv7AaB5oHgCA&ved=0CDEQ9QEwAg&biw=1871&bih=955#facrc=_&imgdii=_&imgrc=gNku2Al1T4jp_M%253A%3B4w70rj_UNgIfdM%3Bhttps%253A%252F%252Fwiki.techinc.nl%252Fimages%252F5%252F54%252FLm7805-pinout-diagram.gif%3Bhttps%253A%252F%252Fwiki.techinc.nl%252Findex.php%252F78xx_power_supply%3B305%3B242

78l05
https://www.google.co.uk/search?q=78l05&client=opera&hs=0Nt&source=lnms&tbm=isch&sa=X&ei=e1baU7XvH47y7Aa72oDYCQ&ved=0CAYQ_AUoAQ&biw=1871&bih=955#facrc=_&imgdii=_&imgrc=XHpOVAlDj4OV7M%253A%3BtlGHvXy-2BCUQM%3Bhttp%253A%252F%252Fwww.piclist.com%252Fimages%252Fwww%252Fhobby_elec%252Fgif%252F78l05e.gif%3Bhttp%253A%252F%252Fwww.piclist.com%252Fimages%252Fwww%252Fhobby_elec%252Fe_oscillo7.htm%3B200%3B200

[GiulioGratz]

Confirmed: pins oriented correctly; now i'm re-wiring all the offboard cables!

[chi_boy]

Might be time for some voltages, pictures, and a proper debugging thread.

[mmlee]

Just finished building mine up last night (posted in the pictures thread).  This thing is loads of fun.

I want to increase the overall level of the thing though as I'm finding I'm only using the last quarter of the 'Level' control, all dry mix means unity at around 3 o'clock, would like to get it around 12 o'clock.  Am I right in thinking altering R16 (currently 22k) should achieve this...? ... or is it R15 (15k).

Cheers,
Marcus

[samhay]

There aren't any 15k resistor in this build (this might be the problem; I'm going by this layout: https://dl.dropboxusercontent.com/u/7464107/CHASMREVERBLAYOUT.pdf).  

If you want to keep the bypassed signal at unity gain, then you need to reduce the value of the resistor connected to lug 2 of the volume pot. This will increase the maximum wet/non-bypassed signal. This is 5.6k in Rob's build and should give you a max gain of ~4 and unity roughly at noon.

[mmlee]

ha, I did mean to write 5.6k but as it was R15, I wrote 15 again....

Cheers Samhay, I'll have a look around that area.

[samhay]

If it is 5k6, try dropping it to 3k3.

[threepwood]

Hey there

Just wondering if anyone has a BOM for Rob's PCB of this circuit that they wouldn't mind sharing? I don't trust myself using the schematic!

Cheers guys!

[deadastronaut]

here ya go..

[threepwood]

Perfect! Thank you, greatly appreciated.

Will this work for the regulator? http://www.musikding.de/7805CKC_1

The geulators in all the build reports I've seen don't have the metal tab.

Thanks again Rob