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 Forum index » DIY Hardware and Software » The layout factory
TR-808 Snare Stripboard
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lysergist



Joined: Jan 14, 2016
Posts: 36
Location: France
Audio files: 2

PostPosted: Sun Mar 05, 2017 3:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you LektroiD for the updated components, i did the modifications. I have also added the Snappy Decay mod : C51(C6 in the stripboard version) (0,47µf) changed to 2,2µf, in parallel a 250k (B) Potentiometer with a 22k Resistor in series

Here is how it sounds, short decays and long ones :


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theauton



Joined: Feb 12, 2018
Posts: 1
Location: UK

PostPosted: Mon Feb 12, 2018 5:05 am    Post subject: Snare noise Reply with quote  Mark this post and the followings unread

I've just finished building the 808 snare to complement the other fantastic Eric Archer kick and hats modules.
The snare works ok initially and triggers fine but for some reason after a few minutes powered up it starts triggering randomly and soon descends into a constant random chaos of noise.
Anyone got any clues as to why this might be happening?
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artilect99



Joined: Oct 01, 2018
Posts: 49
Location: USA

PostPosted: Mon May 27, 2019 6:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

I recently built one, and I get nothing from the output. If I listen directly to the pin 1 of the left TL072, I can hear the tone sound for that side. If I listen to the output on the other side (pin 7) of the same TL072, it's locked into a high-pitched whine. Nothing seems to get to the output jack though.

Anyone have any ideas what might be causing something like that?
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elmegil



Joined: Mar 20, 2012
Posts: 2177
Location: Chicago
Audio files: 16

PostPosted: Mon May 27, 2019 7:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Neither one should be making any sound until you hit it with a trigger + accent.
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artilect99



Joined: Oct 01, 2018
Posts: 49
Location: USA

PostPosted: Tue May 28, 2019 11:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I have accent tied to +12v as I did when testing the 808BD. IC1A makes a tone when I give it a trigger, but IC1B is just a constant whine from power up, around 10kHz I would say. I briefly interrupts when I give it a trigger. This oscillation bleeds into the output of IC1A as well. This monitoring the output pins directly, it seems nothing is making it to the output jack.
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elmegil



Joined: Mar 20, 2012
Posts: 2177
Location: Chicago
Audio files: 16

PostPosted: Tue May 28, 2019 11:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Do you have white noise over at IC2B?

I'm suspicious of your op amps, particularly if you're not getting sound either.

After that, I'd double check all the connections and be sure there aren't any shorts.
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artilect99



Joined: Oct 01, 2018
Posts: 49
Location: USA

PostPosted: Tue May 28, 2019 12:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

Reflowing everything around the op-amp solved the oscillation, and now with a trigger I'm getting drum tones off of IC1A and IC1B, two different pitches as expected, and white noise on IC2b, but still nothing is getting to the output. The component sounds are all there on the output pins of the op-amps themsevles but it's all getting lost on its way to the output jack somewhere.
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artilect99



Joined: Oct 01, 2018
Posts: 49
Location: USA

PostPosted: Tue May 28, 2019 12:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well I got it working, but I'm not sure exactly what I did. I previously had the level pot replaced by a jumper, as I did with the 808BD, because I mix on a board externally. Replacing the jumper with a 50k pot seems to have solved it, but I can't say why exactly. Shouldn't a jumper there be equivalent to a pot at 0 resistance, i.e. max volume? Or no, because it's in the feedback loop of the op-amp. So then would a 100K give more volume? (I was out of 100k).
Last edited by artilect99 on Tue May 28, 2019 2:22 pm; edited 1 time in total
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elmegil



Joined: Mar 20, 2012
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Location: Chicago
Audio files: 16

PostPosted: Tue May 28, 2019 12:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

The level pot is in the feedback loop of the output op amp.

A 0 there brings you to 0 gain, or no output.


Errrr Except that there's a 470K there as well. I have no idea then. Very Happy
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artilect99



Joined: Oct 01, 2018
Posts: 49
Location: USA

PostPosted: Tue May 28, 2019 12:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I just hadn't looked at the schematic and was stupidly assuming it would work the same as it did on the BD, as I had used a jumper there to remove the level pot.

So would a 100K pot yield more gain than a 50k in this instance? I think I'll try just replacing it with a 100k resistor since I don't need the pot.

Appreciate the help elmegil.

Last edited by artilect99 on Tue May 28, 2019 12:57 pm; edited 1 time in total
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elmegil



Joined: Mar 20, 2012
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Audio files: 16

PostPosted: Tue May 28, 2019 12:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Except of course 0 in parallel with 470K or anything else for that matter is still 0. So yeah, the logic I described is right. I'm just having a bad brain day. Very Happy
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elmegil



Joined: Mar 20, 2012
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PostPosted: Tue May 28, 2019 12:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

The level pot in the bass drum is a voltage divider. If you jumper pin 1 to pin 2, that's the same as having the pot all the way up.

Since the snare does level differently by adjusting gain instead of being a voltage divider, that's why it's different.

The equivalent circuit would be to use a 50K or 47K resistor in place of the pot.
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artilect99



Joined: Oct 01, 2018
Posts: 49
Location: USA

PostPosted: Tue May 28, 2019 1:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yup I get it. It calls for a 100k pot for level, and I only had a 50k pot on hand, is why I was asking about 50k versus 100k.
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Harry Manback



Joined: Mar 15, 2022
Posts: 2
Location: USA

PostPosted: Tue Mar 15, 2022 10:43 am    Post subject: 808 Snare Help Reply with quote  Mark this post and the followings unread

Hello all. This is my first time posting here but i am a long time viewer of this forum. I am also an electronics noobie with probably a super noob question but here it goes:

I have spent MANY hours on this layout trying to get it to work. I have done all of the troubleshooting i know how to do. I have checked for shorts, checked for appropriate components, swapped out op amps, i have re-flowed everything, i have checked for continuity, i have double checked all of the track cuts and the continuity of those as well to make sure i didn't miss anything. I also tried the diode, resistor, cap trigger network. I get white noise from the output of TL072(B) (using a 2n3904) but i get nothing out of the main output. I am also not getting any discernible output signal from the TL072 (A). I have traced my trigger signal to T2 where it seems to end. I can detect the trigger signal on R3, R4, and the middle leg of T2. Outside of that, its silence.

I've spent a BUNCH of time with the schematic as well as the really awesome diagrams created by Minus and I've got a couple questions. This may be super obvious but i am wondering about the accent piece. I keep seeing people say "tie accent to +12V". That seems simple enough but in looking at the diagram, the accent input appears to be on a track that is also connected to -12V (Row 13) which also appears to be supplying the TL072 with -12V on pin 4. I'm not sure if i am supposed to connect accent right to +12v and remove it from the -12V track? It seems rather counter intuitive to "tie" this to +12V while its also on the -12V track so i must be misunderstanding. I also don't really see this sequence represented in the schematic as far as I can tell. This is most likely me just misinterpreting because I am a newbie but I was wondering if anyone could shed some light on this. I REALLY want an 808 snare. Thanks so much!
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elmegil



Joined: Mar 20, 2012
Posts: 2177
Location: Chicago
Audio files: 16

PostPosted: Tue Mar 15, 2022 12:37 pm    Post subject: Re: 808 Snare Help Reply with quote  Mark this post and the followings unread

Harry Manback wrote:
I keep seeing people say "tie accent to +12V". That seems simple enough but in looking at the diagram, the accent input appears to be on a track that is also connected to -12V (Row 13) which also appears to be supplying the TL072 with -12V on pin 4. I'm not sure if i am supposed to connect accent right to +12v and remove it from the -12V track?


Yes, definitely.

Quote:

It seems rather counter intuitive to "tie" this to +12V while its also on the -12V track so i must be misunderstanding. I also don't really see this sequence represented in the schematic as far as I can tell. This is most likely me just misinterpreting because I am a newbie but I was wondering if anyone could shed some light on this. I REALLY want an 808 snare. Thanks so much!


I will go look at the original layout, but if it does in fact tie this to -12V then that is a mistake.
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elmegil



Joined: Mar 20, 2012
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Location: Chicago
Audio files: 16

PostPosted: Tue Mar 15, 2022 12:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

If you look at the "back side" view, accent is on row 13, and there is a "cut" in the 8th column. This cut is directly underneath R5, and therefore not visible in the "front side" view. This cut is immediately before the wire bringing the -12V down to the op amp.

I would recommend comparing the rest of your cuts to the backside view of the layout an ensure they're all where they ought to be. Smile

I hope this helps.
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Harry Manback



Joined: Mar 15, 2022
Posts: 2
Location: USA

PostPosted: Wed Mar 16, 2022 4:08 am    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
If you look at the "back side" view, accent is on row 13, and there is a "cut" in the 8th column. This cut is directly underneath R5, and therefore not visible in the "front side" view. This cut is immediately before the wire bringing the -12V down to the op amp.


Thank you so much for taking the time to respond. I wasn’t sure if this topic was abandoned or not. I went back and double checked and I did in fact have that track cut.



elmegil wrote:
I would recommend comparing the rest of your cuts to the backside view of the layout an ensure they're all where they ought to be. Smile


Everything looks ok from that side. I did check this previously and went back and rechecked last night.

Again, I really appreciate your help. I think I am going to step away from this for a bit and come back with some fresh eyes in a little while.

elmegil wrote:
I hope this helps.


Again, thanks so much for taking the time to help
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elmegil



Joined: Mar 20, 2012
Posts: 2177
Location: Chicago
Audio files: 16

PostPosted: Wed Mar 16, 2022 6:12 am    Post subject: Reply with quote  Mark this post and the followings unread

So you do need to have a positive voltage on the accent in when you send a trigger. And as you see it's not tied to that -12V rail. When you're ready to come back to it, I would start at the trigger and accent circuitry and make sure the pulse is making it through the initial pair of transistors. Hoping you have an oscilloscope.....
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fou-rieux



Joined: Oct 13, 2022
Posts: 2
Location: Germany

PostPosted: Thu Oct 13, 2022 8:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey guys. First of all thank you for all the knowledge here. Almost every post/topic helped me Very Happy
I started building this 808 snare 10 months ago and i still had some issues. The Snare noise came out late. While checking my stripboard and connecting it again, unfortunately I connected the Power reverse so the -12 went to +12 in the stripboard layout and the +12 connected to -12.
Something was smelling, burning etc pp...
However now its not working. I exchanged the ICs for two new one but still nothing. I can't see any damaged parts.
How would you start to search the burnt parts?
What could be the parts that could be damaged directly?

Thanks and greetings,
fou-rieux

ps: one good result anyhow: while trying to find the bad parts i found out i had R9 missing. That could be the error that I was searching for before Smile
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elmegil



Joined: Mar 20, 2012
Posts: 2177
Location: Chicago
Audio files: 16

PostPosted: Thu Oct 13, 2022 5:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

If it's neither of the chips, then the next most likely candidates are the transistors. T3, T4, or T5 in particular because they're basically tied right to the rails.

Also be aware that sometimes the pinouts even for standard things like the BC546's aren't always correct. Not a bad idea to get a cheap component tester off ebay or from alibaba to verify such things.

Since you say you've read all the threads, I will assume you aren't having any issue because of the whole accent/trigger thing. Smile

After that, it's down to sending in your trigger and observing what happens. There are two primary signal paths through the voice -- the "drum" generators and the "snare" generators. The white noise is basically going through a rough VCA whose amplitude varies with the "snappy" pot.

Hopefully you have a scope of some sort, otherwise it will be pretty difficult....
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fou-rieux



Joined: Oct 13, 2022
Posts: 2
Location: Germany

PostPosted: Fri Oct 14, 2022 4:44 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey,
I checked the Transistors based on this how to: https://www.pcbway.com/blog/Engineering_Technical/How_to_Find_Faulty_Components_on_PCB.html
they all seem to be fine...

I also checked all the resistors with the multimeter and couldnt find any damaged resistors.

The electrolytic caps all rise in their resistance value so i guess they are ok to. Just with the ceramic capacitors i don't know.... the value of some of them rises and then stops. If I inverse the polarity of the multimeter the value goes down and some dont show anything. Could that be the problem? I'm too much of a noob to get that right Very Happy
Unfortunatly I don't have a scope :/

If the transistors have different pinouts, I guess it would not have been worked in the first place before my disaster. First of all i want to get back to that state...

I guess I will try by headphones and do some random connections to see where is which sound... O.o

Thanks for you quick reply!

Greets,
fou-rieux
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elmegil



Joined: Mar 20, 2012
Posts: 2177
Location: Chicago
Audio files: 16

PostPosted: Fri Oct 14, 2022 5:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Ceramic caps are highly unlikely to be damaged by reverse voltage.

That is correct about the transistors.... mostly. Sometimes BJTs will work "backwards", just not as efficiently. That said, it shouldn't destroy them either.

Be careful with your hearing using head phones, but I do agree without a scope, you might be able to make something of it with an audio probe.
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