Need another set of eyes for my turkeyday project.

[Mustachio]

Hey guys , I really didn't want to ask for help but I'm hitting a wall here.

I've been trying to redraw and update the Mutron Micro V, I used schematics and layouts from pisotones and the effects database. But I replaced the ca3080 with an lm13700. and left off the millennium bypass from the pisotones layout .

Schems and layouts I used as reference.

http://files.effectsdatabase.com/docs/schematics/musitronics_mu-tronmicrov.jpg

http://www.pisotones.com/MuTron_Micro-V/Mutron-Micro-V.htm

As far as I can tell q1 and q2 are npn and q3 is pnp . I didn't have the transistors on hand suggested in the pisotones. But I did have some 2n5089's the original called for. For the pnp I tried a few different ones like 3906's


Here's what I drew up Hoping I made a simple mistake some one else can spot.



In case the pcb layout is to hard to see I cropped a larger one Photobucket seems to like to compress things a bit.



Ive been doing some volt tests from the points on the original schem it has points for 9 and 4.5v to test and I am not getting the right voltage yet.

Also I left J1 J2 on the board there but I included a trace so a jumper wouldn't be needed there. So at the moment I have no signal ( if i run an overdrive in front and crank it I get a weak small signal through) I have this wired up direct at the moment. Gonna take an audio probe to it later tonight but I have a feeling somethings wrong right at the front of the circuit (q1 area). I just cant put my finger on it yet.

Hoping a fresh set of eyes and a smarter brain can help me out here! thanks for lookn' fellas!

[Ronan]

BC547 and 2N5089 have reversed pinout, is that the problem perhaps?

[Jdansti]

Sorry I can't advise on transistor selection, but I've got one of the original Micro V's.  I can get some voltages for you in a day or two if that would help. I can also give you photos of both sides of the board.

[Mustachio]

Thanks guys. I checked the pin outs on the transistors looks like i got em right. I even rotated them around just to check and tested about 15 different transistors so far. I checked and had a bad connection at Q1 and now I'm getting voltage all in the spots I thought I should. getting near 9v on pin 8 of the 4558. I wasnt getting voltage there before because of the bad connection it shared with Q1.

So now I get signal through it. Its clean signal quieter then unity by a good amount and the pot and switch have no effect on the signal. Now I'm wondering if it is around the lm13700. So I get signal just no WHOMP filter sweep.

Voltages would be awesome jan! If anyone spots something in my layout from the schems that I missed let me know please and thanks !

Ill post my voltages here in a bit gotta write em down. Was trying to go over the original schem and test the points that say their suposed to read 4.5 and I'm not getting that. gotta figure out which ones.

Jim

[Mustachio]

Here's the voltages I just got.

jrc4558

1-9.02
2-1.31
3-8.96
4-0
5-8.96
6-1.30
7-8.95
8-9.63


q1

c-9.63
b-2.00
e-1.49

q2

c-0
b-0
e-4.03

q3

c-0
b-6.93
e-4.03

LM13700

1-0
2-1.87
3-8.96
4-8.96
5-1.26
6-0
7-0
8-0
9-0
10-0
11-9.24
12-0
13-0
14-0
15-0
16-0

Some looks right but some I don't know.

[Ronan]

See TP1 near Q2, on the musitronics schematic, the voltage there should be around 5V, and obviously its not, otherwise there would be around 5V at the LM1458 pins 3 and 5. Check your R12 and R13, maybe R12 is 2K2 instead of 22K on your pcb. Or just measure the voltage on your pcb at the junction of R12 and R13, it should be around 5.6V.

Also R10 and R8 on your layout need to swap positions, R10 is common to the 2 emitters, R8 is common to the 2 collectors. You can check for mistakes like that by printing out the layout, and printing out the schematic, grab a highlighter pen and highlight each and every connection on the schematic compared to the layout, that way, everything gets double checked. I check all my layouts like that, because its often quicker than troubleshooting.

[Mustachio]

checked the resistors in that spot r12 and 13 are correct. looking at the musitronics shem looks like tp1 is more off one side of R1 for my layout (r18 musitronic schem) and there I get 4.38v ,on the IC pins 3 and 5 I get  8.96. Looking at my layout Im not sure how the base of Q2 or the junction would get 4.5v between r12 and 13 hmm Gonna have to stare at this some more.

Thanks for the help , am I just not understanding why there would be the voltage there or should it be tested at the upper side of R1 100K resistor from my layout ?

[Mustachio]

Oh yeah Also I'm using 2n5089 for Q1 and Q2 and a 2n3906 for Q3

[Mustachio]

I think I spotted it top side of r12 should connect to v+ but I didn't put a trace there.  On mobile now will test it soon. Thanks for that area to look at ronan!  I knew I was missing something!  Lets hope that's the only problem. Thanks again !

[Ronan]

Missed your post, but...

Looking at the layout to see what pin 5 of the 1458 connects to, it connects to 1458 pin 3, C2, R15, LM13700 pin 4, C10, C9, and R14. But according to the schematic, it should also connect to R1, C7, Q2 emitter, R10, R9, C6, and R3. That is a minor problem that will stop the circuit from working too.

Don't forget R8 and R10 look funny too.

[Mustachio]

Good eye ! thanks a ton you really helped me out here! I jumpered the one spot you mentioned earlier and got correct voltage. Now I need to jumper 2 more spots haha and get this working then I think Im gonna redraw it all again once I know it works right. Taken a break now ill jumper those spots later.

Thanks again !

[Mustachio]

Got it working! will post a revision in a little bit! tested a ton of transistors and found a few good combinations , will post the models and hfe's I found best with the new revision in a lil while.

Its sounding really good almost rivaling my Mutron III maybe even beating it in some aspects! Now to see what I can do with the left overs on the LM13700!

Thanks again Ronan you helped a ton here!

[Ronan]

Just glad to hear you got it working, that's the main objective!

[Jdansti]

Looking forward to hearing your results to see if its an improvement on my old Micro V. If so I might have to build one.

[Mustachio]

Ronan helped me out a lot with understanding this circuit a lot more, And I have it running with both halfs of the LM13700 and it definatly has more voice to the filtered sound! Will be posting it in the turkey comp here in the next few days! Have some ideas for this after the comp gonna try adding another 1 or 2 lm13700's and see how far we can push this circuit! I think your gonna like it !