Roboto Volume Drop/Muffled

[mikeperez83]

After waiting months for my HT8950 to come in from Banzai in Berlin, all I had left to do was attach it to the PCB. I've checked all my connections, LED, bypass, all that stuff works great. When the effect is engaged, there isn't much definition to the sound, almost like if someone had a magic tone knob and put it in the negatives. The effect does cycle through the 4 modes, but there isn't much to write home about as it sounds so dull and muted, the volume overall drops as well when the effect is engaged. Volume all the way up and the internal trim

 

[p_wats]

My Roboto is almost TOO loud. Maybe start by double checking all resistor values? Is it possible the 330r has been mistaken for 330k, for instance?

 

[mikeperez83]

My Roboto is almost TOO loud. Maybe start by double checking all resistor values? Is it possible the 330r has been mistaken for 330k, for instance?

Checked it out, I’m also getting good signal into the 072, but a mess coming out, going to check voltages, but I may just have a busted op amp.

 

[p_wats]

It's possible---looks like you didn't socket the ICs, so that may be a pain to get out cleanly, but it can be done! Use flux on each joint and it should help get the solder flowing to remove.

 

[mikeperez83]

Yea, just might be a cold solder somewhere, going to have to reflux and reflow, hopefully that’s all it is.

 

[mikeperez83]

reflowed a few things and getting good input and output via the first side of the op amp, traced signal and found that once my signal gets spit out from R5 (43k) the signal is barely recognizable, just a fizzle basically of the original signal, the output of the ht8950 then just sounds like little sizzled farts.
replaced R5 with the same result, signal is fine up until that point, not sure what else to do, voltages look good as well, the signal going in from R4 into the HT8950 sounds fine though. Please any help or leads would be appreciated.

 

[p_wats]

Have you tested for continuity to ensure components are connecting as they are supposed to? I've had issues before where, for whatever reason, the right connection wasn't being made between components and it resulted in low volume or weird noise, etc.

Follow along with the schematic and test for continuity, while also confirming component values and that may reveal something.

 

[mikeperez83]

Have you tested for continuity to ensure components are connecting as they are supposed to? I've had issues before where, for whatever reason, the right connection wasn't being made between components and it resulted in low volume or weird noise, etc.

Follow along with the schematic and test for continuity, while also confirming component values and that may reveal something.

I’ve done all of that, the signal going into the 43k at R5 sounds fine, what’s coming out sounds awful and low. Pulled that resistor, cleaned the contacts and put a new one in. I desoldered the op amp and the 8950, fluxed and resoldered in case of cold joints. I’m pulling my hair.

 

[p_wats]

How are your voltages for the HT8950? Do they match the datasheet? https://www.sparkfun.com/datasheets/Components/General/8950v110.pdf

 

[mikeperez83]

audio input volts don't seem to match up, although, I'm not very good at this, here are my voltage readings per pin with signal going through it.
1- 0 18- 3.07
2- 3.08. 17- """"
3- 0 16- """"
4- 0 15- """" (15-18 are all the same)
5- 1 14- 1.18
6- 1.25ish. 13- 1.32
7- 3.3 12- 1.07
8- .15 11- 3.3
9- 3.27 10- 1.18

judging from this I should be looking at the R4 1K5 resistor as a possible culprit, as pins 5 and 6 I'm assuming should be closer to 3v? I'm a newb to this kinda thing. thanks for the help so far p_wats.

edit: swapped the 1K5, checked the signal, same, jumped from the other side of R5 to its Pin on the 8950, to check output, still garbage. could my 8950 just be trashed? was in transit for a while (2 months) , or is the board being funky?

 

[p_wats]

EDIT: sorry, I had a hard time reading the way your message was formatted---doesn't seem like there is anything wrong there (the first few pins will change depending on the mode switch).

I built a Roboto a while back (older board that doesn't use a rotary switch) and here are my voltages:

HT8950 (voltages measured with mode switch in the arp position)

1. 3.27v
2. 3.27v
3. 3.27v
4. 0
5. 1.2v
6. 1.2v
7. 3.27
8. 0.4v (this one seems to move a bit but isn't connected anyway)
9. 3.18v
10. 1.2v
11. 3.27v
12. 1.2v
13. 1.2v
14. 1.2v
15. 3.25v
16. 3.25v
17. 3.25v
18. 3.25v

TL072

1. 3.27v
2. 3.27v
3. 3.27v
4. 0
5. 3.27v
6. 3.27v
7. 3.27v
8. 9v

 

[p_wats]

edit: swapped the 1K5, checked the signal, same, jumped from the other side of R5 to its Pin on the 8950, to check output, still garbage. could my 8950 just be trashed? was in transit for a while (2 months) , or is the board being funky?

If you've measured continuity between all components as per the schematic then I can't see anything being wrong with the board.

Did you get any extra HT8950 chips?

 

[mikeperez83]

thanks! yeah, the form we formatted my post and smooshed it. so again, the signal drop/loss is occurring where R4 and R5 link up, but the drop is only occurring at Pin 5 coming from R5, the signal from the op amp is good all the way to this point...ghost in the machine.

 

[mikeperez83]

If you've measured continuity between all components as per the schematic then I can't see anything being wrong with the board.

Did you get any extra HT8950 chips?

I did not get any extra chips as they're hard to find and this is a one off for a friend, but again I'm stressing the signal drop on R5 before it gets to Pin 5 on the 8950. the effects do work, the sound is just super low and muffled.

 

[p_wats]

Aside from confirming continuity, component values and voltages I'm not sure what else to look for, unfortunately (I'm far from an expert though, so maybe someone else will chime in).

I do recall having an issue with one of my Roboto builds way back and it turned out there wasn't continuity between two components on the board where there should have been (may have damaged a trace troubleshooting), but if you've confirmed continuity is good on your board then that wouldn't it.

 

[mikeperez83]

Aside from confirming continuity, component values and voltages I'm not sure what else to look for, unfortunately (I'm far from an expert though, so maybe someone else will chime in).

I do recall having an issue with one of my Roboto builds way back and it turned out there wasn't continuity between two components on the board where there should have been (may have damaged a trace troubleshooting), but if you've confirmed continuity is good on your board then that wouldn't it.

I really do appreciate all of your help. It’s either a grounding issue on the board itself (a trace going to ground that shouldn’t be) which I ne’er stand happens, or it’s the chip, (which IS doing its job. Prior I ordered 2 of the B3k boards, one came out flawless, and one has a ground loop I can’t seem to get rid of. I’d like to see what an admin has to say about what else to look at here.

 

[p_wats]

If it makes you feel any better, I've got an older Arachnid FV-1 board that has a whine I can't get rid off even after checking everything a million times.

I guess you could always meticulously check continuity to ground for all components, to ensure nothing is grounding that shouldn't be.

Worst case, I think I have an extra HT8950 I could mail you, if need be (but I can't guarantee it's a good one, as I never had to use it).

 

[mikeperez83]

If it makes you feel any better, I've got an older Arachnid FV-1 board that has a whine I can't get rid off even after checking everything a million times.

I guess you could always meticulously check continuity to ground for all components, to ensure nothing is grounding that shouldn't be.

Worst case, I think I have an extra HT8950 I could mail you, if need be (but I can't guarantee it's a good one, as I never had to use it).

Hey man, that would be amazing. DM me with pricing and such and maybe we can figure something out. Another question I didn’t ask myself, does the 8950 amplify the signal it receives at all?