neutron building problem

[psst]

Hi to all.
I finished my neutron PCB, I put all the components, but when trying it, it happened that when gain pot was too high, I heard like a distorsion (no filter effect), and if put lower, no distorsion and no effect either.
I doubled check everything, even I built another PCB and put new components, but same happened. I double check everything again.
For the moment, I didn't put the optional one-batt-only part of the circuit, but did it with two batts. I checked all the voltages were correct.
I put a trim pot for the "Rx" resistor, is it tricky to get the "sound"? Or should I get normal behaviour although better or worse when adjusting the trimpot?

I don't know what to do. Any hints from people that did this before. Did this happend to someone too? I built some stompboxes before, but I feel frustrated with this...   :cry:

By the way, I did the optical part with the two H11F3 option.
Thanks a lot.

[rx5]

try substituting Rx with a 100K pot..... that what i did with my mutron...
hope this helps

[Bill Bergman]

psst,
I've built 2 and the gain on both if turned up to high it blows off the scales. Not sure why. I tried the H11F1* optos first and didn't like the results. I got much better results from 2 VTL5C3's or 1 Hamamatsu P873-13 from Small Bear,

[drew]

The first thing I thought when I saw this thread was, "Just use one up quark and two down quarks!"

[psst]

Thank you for your answers. I'll try with the VTL5C3's. In the meantime, I'll try with the 100k pot like rx5 said...
I'll tell you about it when I try it.  :wink:
BTW, to all you guys that built the neutron, all of you had that behaviour with the gain crancked like Bill and me?

[rx5]

first of all, there are no errors on th mutron diagram.... you will surely have problems on tyhe opto-electronic part... I used CLOSELY matched generic LDRs...not made by the same company though...just measured both thier resistance in Light and in Dark.... thats why I said closely matched for they matched in resistances..... and used WHITE "backlight" bulb from cellphones.... and sealed those three parts in a light sealed "AM RF COIL METAL SHIELD"..... seal used was black epoxy.... U could even try RED "high brightness" type LED for starters.........  important part is you have a 100K pot as the Rx........ trust me.... amd also the 1M pot input gain..... or else youl OVERDRIVE the filters...

[PB Wilson]

I'll be building a Neutron very soon and inquired about RX before I ordered the parts. The advice I got was to hook up a 5K or 10K pot in its place, adjust it to find the correct range, measure the resistance and substitute a similar value resistor. Sounds easy enough to me.

[psst]

Bill, which "Rx" value you had to use with the VTL5C3's?

[Bill Bergman]

I used a 5k trim pot

[rx5]

psst,

hello, hows ur neutron coming?? is it working now??

[psst]

It's on the way, rx5.
Today I ordered some VTL5C3, cause I just can't make the thing work with the H11F3. So I'll tell you all when I receive it.
Anyway, one of these days I will try a REAL Mu-Tron, and the owner already told me about that behaviour I told you before with the gain pot. It seems to be "normal", the Mutron is like that.

[AlexK]

psst,  I had the same problem with mine.  I actually think the wiring diagram in the Mutron document is wrong.  I reversed the wiring on both the gain and resonance pots from what the document says and it works fine for me (besides the power supply leaking into the signal).

For the gain pot I used a reverse log 1M pot and when I turned it completely counter clockwise it was extremely loud and when I turned it down a little, there was no effect.  Switching it, it rotated the correct way, and the gain was more gradual.  Of course, I might have done something entirely different and wrong from the schematic  :wink:

-Alex

[rx5]

btw, try using a bipolar powersupply..... maybe it would solve the problem.... im using bipoplat supply cause I cant seem to find 7660...