two problems with the LoFiNator

[listenForward]

Hey friends

I finally built my LoFiNatotor from a kit,
Had some initial trouble in that I wired all the pots backwards (and trying to test it with the thing effectively turned OFF...),
but I fixed that, and now that "clockwise is up"...
I'm testing it out I find two main concerns:

• the output volume remains surprisingly quiet (even for a lo-fi pedal). Even quieter than bypass when GAIN and VOLUME are at max, and the filters are wide open.
• the HI tone control doesn't seem to do anything to make any difference at any setting. I'm pushing some pretty wide-band synth through it, and while the LO does plenty to suck out the bass, the HI doesn't do anything, even to a sawtooth

I've been inspecting the circuit, and I assume C9 and C10 are the main Caps to define the filter. However, the HI tone control is littered with resitors and VERY crowded. I even switched the (identical) IC2 and IC3 to see if one was burnt, but no change.

Any advice in how to debug or improve these problems is appreciated.
cheers,
LF.

 

[Nostradoomus]

Post some pictures! Can’t go into these things blindly.

 

[listenForward]

Roger.


As you can see, things get pretty crowded around both IC 3 (" highEQ ") and IC2 (" low EQ " ),
but IC 2works fine, wile IC2 seems does not seem to be "doing it's job"

Here are some pics of the top and bottom (trace) side.

Obviously, I should have sourced some smaller caps, and probably should have run the iron cooler, given how much the board is blushing.
(I'd appreciate any advice on what temp to run for these boards).


Top side: angled for C09



TOP side, angled for C10




Underside, angled for CENTER, side of C09


Underside, Angled from EDGE side of C10




Any of you good doctors see anything out of the ordinary ?

 

[Nostradoomus]

I think we’re going to have to leave visual inspection up to you. Print out the parts list and slowly work your way through the resistor list, check them off as you go. Also you may want to buy some clips with rubber on the ends for your helping hands, they’re absolutely slaughtering your board.

 

[Nostradoomus]

Also I run my iron at about 340 Celsius (640F)

 

[listenForward]

You're right about the clips
I actually put some rubber muzzles on the lower two clips (that usually hold the board) after I saw this scraping... I only put the board in the "sharp teeth" so I could hold it up to the light.
Guess I should put rubber on all 4 clips.

...so before I start checking all the parts (again), can I confirm that my build is indeed faulted:

• Is the output volume is supposed to be able to meet or exceed unity with Drive at minimum ? Mine barely meets equal loudness to bypass when the Gain is at max.
• For the HI Tone control, What should be the minimum corner frequency when it's at it's deepest hi-cut ?. I can't hear any top getting rolled off (testing with a pocket synth and a portable amp), which I know passes at least up to 12 kHz.

If I recall correctly, I bought the PCB separate, and made a cart for all the parts from Mouser. I didn't expect certain components to be so crowdingly large.

• Do the parts that come with this kit available form MusikDing fit all nice and snug to spec ?

It may be worth more time than money just to buy and built it again from scratch.

Thanks again for the prompt and informative responses.

cheers !

 

[Robert]

Don't reorder a kit just yet, someone else reported a similar volume issue a while back (I don't recall a problem with the High control though). Let me look over this and see if anything comes to mind.

As far as part sizes, the board was designed for 1/8W resistors and box film caps (5mm spacing).

 

[listenForward]

Ok.

I will stand by.

cheers,
P.

 

[max-xam]

Hi everybody, I have the same problem with the HI filter. When I tested just the main board it was still working.

After assembling it into the housing, it stoped working and after some analysing I had it working again, but only for a short time. There seam to be a loose connection or shortcut, but I can’t find it.
I checked the voltage on PIN 1 and 16 of IC3 and it varies from 1.21V to 1.37V. And I was wondering why R17 is damping the signal so much. But it seams to be the design of the circuit. Actually, I don’t understand the filter, so I'm having trouble finding the problem. Any suggestion for advanced debugging?

To answer the question of ListenForward. I bought my lofinator at musikding and the parts mostly fit, except of three caps. C101 does even not fit on the board. It stands above the other parts.

 

[listenForward]

Hey Max-Xam
Thanks for chiming in.
VERY interesting to see that I'm not alone.
I was wondering why and how the signal was coming out so weak.
I wonder if reducing R17 (with a smaller resistance) would boost the output up ?

cheers,
P.

 

[max-xam]

Hi listenForward,
I don't think reducing R17 would boost anything up. But reducing R36 should boost up the output level.

 

[max-xam]

Hey, I fixed the problem with the not working HI filter. After a long time of analysing and comparing the voltages on IC2 and IC3 I found, that the VREF voltage on the resistors R21 and R23 was missing. I don't have a clue how that happend but I just made a wire connection from that point to R101 and now it works.
If you want to check yours, on the PINs 4,5,13 and 14 ( the inputs of the two OTAs on the chip ) should be a d.c. voltage from round about 4.2V.