Meatball Clone Stopped Working

[Radamus]

Hello,

I built a Meatball clone (http://www.pisotones.com/Meatball/psst/McMeat.pdf)  about a year ago and I've had a lot of fun with it. I ran into a problem recently where the envelope section seemed to stop working. That is, I could change the up and down switch and the LEDs would come on, and intensity would change the brightness, but my bass signal changed nothing. I opened it up and found that the v- of the 1451 was not connected. I fixed that, boxed it up again and plugged it in.

It works, but it's not what I remember at all. I have to work very hard to get the LEDs to change, and the sound is not as good as it was before. I went from no envelope to a very weak one.

I went over the entire envelope section checking resistances. They're all what they should be, except I replaced R6 with a 2.2M because I could not find 1.8. I did that when I built the pedal, and I can't imagine why it should be causing problems now. Every other resistor value is very close to what it should be, all the way from pin 2 of the 1458 to where the LEDs touch ground. My indicator LED is a purple LED, rather than green like the ones in the LED/LDR combos. I can see where this is a completely different kind of LED, but that wouldn't affect anything, would it?

I also sound probed the entire thing, and I can hear the various different filter phases (weak envelope) and I can hear the 1451 distort greatly after the 2.2M resistor, so it's getting plenty of gain. Then, the signal gets quieter and quieter all the way to the LEDs (100Ω here, 330Ω there...). The LEDs aren't turning on enough, and in the reverse setting, I can barely get the LEDs to dim. Before, it would take some slapping to get the LED to really dim, but now it's almost impossible.

I would like to try swapping out my 1458, but I don't have any more of those. Loads of 4558, if that'll do it. They're both general purpose op amps and you don't hear this part of the pedal, but you guys can tell me if I'm wrong here. I also have TL072, and maybe some others.

In short, I've never been completely thrilled with the strength of my particular envelope section, but now it's really weak, to the point of being unusable.

Voltages
1458
1: 2.00v
2: 1.86v
3: 0
4: 0
5: 1.26
6: 1.92
7: 1.92
8: 11.10

Using a 7812 12v regulator that reads around 11.8v.

Any help would be great. This board has always been very nice to me. Thank in advance.

Conrad

[MarcoMike]

i think you could try a different op amp... If I remember correctly I had a tl072 in mine for some reason... (but maybe I switched back to the 1458 because it didn't work... bah.. shitty memory...)

and check if the vactrols or LED/LDR are working... last year I had a really bad time debugging it after it stopped working (the filter was really poor and totally different). it was the lug of one LDR that was disconnected (probably it wasn't properly soldered from the beginning)

[Radamus]

I checked all of the LEDs and they all had diode drops of over 1V. I don't know if that means anything, but I think it means they're not blown. I'll try the 4558. I think the 1458 is common in envelope sections all over, but I don't know if it means anything. It's socketed, and I've got a load of 4558s, so I might as well try.

Is it possible the bias voltage is screwed? I don't know much about that.

[axg20202]

I remember having similar symptoms to you. I had been fumbling around the back of the pedal and glanced the power jack (positive shield) on one of the 1/4 sockets by accident. The fault? Blown IC. Can't remember which one but replacing it fixed it right up, so your current line of enquiry may well get you up and running again. If they are socketed as mine were then you're laughing.

[Radamus]

Well, I did some experimenting. I replaced the 1458 with a 4558. No sound at pin 1. A 741. No sound at pin 1. A tl072. No sound at pin one. I found an HA17458, which I remember coming with the group of 1458s. It works in the circuit about as well as the current 1458 does. Still very weak envelope. I was testing it with my guitar, and, while playing the guitar is enough to make the LED come on briefly, it doesn't come on for long and it's definitely not the sound I remember. The guitar seemed to be enough to make the LED blink in the up position, but not enough to turn the led off for very long, again. I played with decay, attack, and sensitivity. Sensitivity is maxed and I'm getting nothing. I used to only have it at 70-80% with good results.

I can try radio shack for another 1458 (wonder why it's so unique), but something tells me my problem may be elsewhere. Is it possible my 1458 is misbiased? Is my reference voltage wrong? I'm not used to a blown IC working at all, and two of them even. I should mention that it's possible this HA17458 was in this circuit for a while and I took it out. Don't remember. Legs were slightly bent.

Thanks for the help guys. I have a feeling this is going to wind up being something simple, I'm just looking in the wrong place.

[Radamus]

Can someone verify my voltages on the 1458? I'll try to pick some up later.

[ChanchoPancho]

Hi, I'm having a very similar problem. I built it in a protoboard with all the wiring to pots and switches and the 1458 section didnt wotk correctly. I could tell it was filtering because when I moved the pots the leds responded and I was able to listen to the filtered signal. However, despite of my playing the filter didn't automatically like it suppose to. Did you solve your problem? I'm using the unit with 9v not 12 like oyu but if you want I can measure the voltages in every pin of the 1458. Regards, Francisco.

[ChanchoPancho]

Problem solved. check out this thread:
http://www.diystompboxes.com/smfforum/index.php?topic=54508.0

[Radamus]

Hi, I'm having a very similar problem. I built it in a protoboard with all the wiring to pots and switches and the 1458 section didnt wotk correctly. I could tell it was filtering because when I moved the pots the leds responded and I was able to listen to the filtered signal. However, despite of my playing the filter didn't automatically like it suppose to. Did you solve your problem? I'm using the unit with 9v not 12 like oyu but if you want I can measure the voltages in every pin of the 1458. Regards, Francisco.

I'm sorry I didn't get back to you sooner. I am glad you fixed your problem. I think it is opposite of mine (which I still haven't fixed). I put in an order for 1458's today, and a couple more LDR's to test, but I'm not sure what my issue is. I started running it on 9v just to make it standard with everyone else. The 1458 distorts greatly, which I think is the point. It creates a lot of gain and turns the LED on, but it is brief and not ideal. I wind up getting a very slight sweep with sensitivity and intensity maxed (attack all the way down, decay in different places). It stays partially lit always and blinks strongly when a strike a note, but it then blinks out immediately, not matter how much I raise decay.

The pedal worked for a while, so the problem has to be in something that either fried or disconnected. I've changed out the 1458 with the two others I have (can't remember if they worked before. I swapped them out for some reason) and I tried buying an equivalent (it seems there isn't one). The other 1458's or 17458's are about the same in terms of performance. I ordered some more chips, so I should be able to put that part of the diagnosis to rest soon.

So to recap: Symptoms - little amounts of sweep, LED's are responsive, but they don't seem to get enough current or voltage to really work. The sound is really bassy (on my bass) with a hint of low pitch feed back and some distortion. In the other position, sound is bright, but the guitar signal does not turn off the LED much. I followed the entire signal path with my audio probe, and there was sound everywhere there should be, and I followed the sound in the envelope section as well, and there was always sound. The 1458's output was loud and distorted, but also somewhat gated. I don't have a good chip to replace it with.

Anybody have any thoughts?

[ChanchoPancho]

I don't think it's the chip that's causing the problem. Have you checked the pot's? I believe there's the problem. If you want I can measure pins in the 1458 to make sure yours is ok. regards, Francisco.

[charbot]

I agree, it may be a pot, possibly a short.  I had a similar problem when I installed the pedal jacks.  With out insulation, the #2 jack contacts ground on the chassis  and shorts  the decay pot resulting very short decay times....  similar to what you describe.   maybe you pot rotated in the enclosure and is in contact with something it shouldnt.

[Radamus]

I pulled the whole thing out of the enclosure, so I don't think it's any contact like that. The pedal used to work this way. I can measure the voltages on any of the pots if you guys think that would help. I don't remember if this sounds like a non existent decay time or not. That's a very plausible diagnosis, though. I suppose I could check to see if it's working. I might give that a try tomorrow.

Any suggestions on anything else to check?

Thanks.

[Radamus]

So I got my package from Thailand last night with some fresh 1458's in it. I waited until this afternoon to try them out, and I found that there was no difference. So then I tried your idea ChanchoPancho, and I examined the decay pot. Sure enough, two thin little wires were running from ground over to the signal part and once I clipped them, everything worked fine. I'm going to go put it back in the box now. I wish I had checked that earlier. This pedal didn't need to be out of commission so long.

Thanks a lot. I'm going to go plug it in now.

Conrad

[ChanchoPancho]

lol.... told you so... the same thing happened to me and I also thought "I should have done this earlier"

[seedseed]

i can't get my meatball to trigger at all if you try different LED vactorals iam using the nsl 32 and some home made jobs should you change the 100 ohm resistors feeding them to something lower to make them trigger. It doesn't matter how i do it i can't get this thing to trigger it won't light the indicator led also is 12 volts a better voltage to run these pedals on?