Mutron Micro V (+?) build guide

[Ronan]

Here's some ideas for CV for a Micro V, just be careful not to put too much current into the control pin, 0.75mA usually gives full sweep for an LM13700 in my minimal experience. More than 1.5mA is pushing into the danger zone. For 2 input pins, as in this circuit in this thread, 2mA is a safe maximum. You can measure the current going into the control pins by measuring the voltage drop across R17 the 4k7 resistor connected to the emitter of Q3, that will get you ballpark figures.

[deadastronaut]

hi guys: hmmmm had another go on it, still no joy on the auto filter side of things....

double+triple checked connections , checked around the opamp, all looks ok....

swapped out all trannies too and swapped the 13700....hmmmm...bummer i was really looking forward to tinkering wth this..

[Ronan]

Rob, you got the two diodes the right way around?  tried a different opamp?

[garcho]

Have you tried cursing, loudly?

[LucifersTrip]

Transistors

Q1-2n5089 Hfe 104
Q2-2n5089 Hfe 106
Q3-2n5087-2N3906 Hfe 80
I used the 2n3906 in Q3 and those are the hfe my cheapo MM read out at. I did have some 5087's on hand at the end but had already found the 2n3906 to be working great so I never tried out a 5087 yet. But in the next few days Ill open it up and test out more OTA's and the 5087s

...just checkin' in on this thread for the first time and quickly skimmed it. A couple questions. I just saw people posting voltages for troubleshooting but did Jim ever post the voltages from his working one? Sorry if I missed em, but that would seem like the most important thing before starting a build.

...and how is it possible those 5087 and 5089's have such low hfe. They commonly have hfe's in the 300-500+ range.

[deadastronaut]

Rob, you got the two diodes the right way around?  tried a different opamp?

yep everything checked, opamp changed too....triple checked from in to out etc...

@garcho: yeah i tried that too.. my missus helps by saying ''well you obviously aren't doing it right are you''...she's very helpful that way..

@lucifer: hmmmm...i tried various npn's 5088/3904/2n2222's no joy.

[garcho]

@lucifer: hmmmm...i tried various npn's 5088/3904/2n2222's no joy.

The 3904/2222 shouldn't be that low either. Faulty multimeter?

[Mustachio]

Could Be faulty meter , I used a really cheap DMM to test the HFE. Its the only meter that checks transistor that I own. I have a fluke but it doesn't do hfe.

Either way I tested a bunch of transistors and swapped them in and out and the ones that tested with a lower hfe sounded better to my ear then the ones that tested with a higher hfe. Weather those readings where legit or not if anyone wants to test their transistors they have on hand to pick out ones they want to use you might find lower hfe sound better. Its not in stone on what hfe you must use just that those sounded better to me.

Q3 It calls for a 2n5087 I actually used the 2n3906. And again the hfe may not be exact since I used a cheap DMM but it was the lowest reading one I had on hand. So its basicly a suggestion to say try out the lowest gain transistors you have on hand that fit the bill.

I have been really busy lately and just haven't had the time to do anything fun with electronics. I will take more voltage readings of this today and post them later. Another person here actually did get this working on breadboard and posted his voltages too. But I really should post mine since I have the original working one on hand.

Thinking about picking up a peak atlas dca55 soon.

Rob hope you get it going. Ronan mentioned the 2 diodes coming off the opamp. I was thinking the same thing it seemed like that area at least will have something to do with the sweep. also If the OTA is miss biased you get no sweep. It will just be stuck down at the low end . And adjusting the bias manually like  you mentioned will give you sweep, which is what you explained happened to you earlier. So I think something around there is a miss. Maybe go back through and check your breadboard along with the pcb I made and see if things are connected right. Might just be one missing jumper or something.

I'll post voltages in a bit after some coffee.

[LucifersTrip]

Thinking about picking up a peak atlas dca55 soon.

You can set this up in a few minutes:
http://www.geofex.com/Article_Folders/ffselect.htm

[Mustachio]

Ah yeah I've seen it at RG's site I'll bread board it later and test the ones I have in there again against the DMM I have.

Here's some Voltage

V ref. 9.69

lm13700

1.156
0
5.229
5.229
5.232
0
0
0
0
0
9.23
5.232
5.229
5.229
0
1.156


DualOpamp

5.232
5.234
5.230
0
5.231
5.232
5.128
9.69


q1

4.527
5.060
9.69

q2

5.232
5.772
9.69

q3

5.232
5.221
1.144


hope that helps

[deadastronaut]

cheers jim, i'll give it another look over later...

[styrene]

Hi ...

I tried the layout this afternoon .. Works nice but I experience huge poping sounds when I switch HI-LO or a pedal after it.. I tried to change my caps but no change.. I hear a slight hum with the effect on...
(I have no zener, 5088 and 5457 and my 13700 is JRC)

1 hour later I edit my message ... It was my 10uf cap that I mis-oriented.... (Seen the "-" stripe in the layout where I should have seen the square meaning "positive"... )  Now I only have big pop when I switch from HI to LO setting... Maybe because it is not boxed/grounded yet..

[Perrow]

Styrene, which layout? Link?

[styrene]

The one drawn by GGBB (on page 2)

[GGBB]

The one drawn by GGBB (on page 2)

Did you ever sort this out?  If it turns out to be a layout problem, please let me know so I can fix it.  I have just modified the layout with a new PCB transfer - it's the same layout with better ground fills.  The page 2 post image has been updated.

[deadastronaut]

@gord:/ perrow is your layout verified now..

i still fancy building this..

[GGBB]

@gord:/ perrow is your layout verified now..

i still fancy building this..

I have only verified it visually against the schematic - I have not built it (yet), and have not heard from anyone that has built it other than Styrene above who had a problem with the hi/lo switch popping, but we don't know how it ended up.  So other than that I suppose we could say Styrene has verified it (note that he used different transistors and omitted the reverse polarity zener, but those aren't layout-relevant changes).  Are there any rules/guidelines around here for what makes a layout officially "verified"?

[Mustachio]

I think verified is usually if some one builds it and it works, The first one I built for the contest is verified as well

Soon I'm going to rebuild it with more mods and post all the info for it.

Its a pretty cheap build no expensive parts.

[deadastronaut]

@ronan:  or anyone, could you please re post the schemo, as ive lost it,

i found your link, but it wont let me save it....cheers!.

[nocentelli]

Can you download it from this?



... or just "printscrn" and paste it into MS Paint and save a copy.