Author Topic: Univox Fazer woes  (Read 3068 times)

disorder

Univox Fazer woes
« on: August 12, 2017, 04:51:20 PM »
This Univox Micro Fazer does not faze!! I get a slightly quieter bypass signal with no phasing when effect is engaged.

http://schems.com/bmampscom/effects_misc/Univox_MicroFazer.gif

I audio probed down the line of the opamps and I get an awesome phasing sound at the output of all the opamps except the last one OP5 in the schematic. Could someone tell me what DC voltage I should expect at this output? The rest of the opamp outputs have ~4.5VDC on pins 1 and 7 except for that last one it only has about 2VDC.... strange?

disorder

Re: Univox Fazer woes
« Reply #1 on: August 12, 2017, 05:41:20 PM »
Call me crazy but I made a video. It looks like the last phaser stage is clipping off the bottom half of the signal. In my mind if it doesn't have 4.5V bias and only has 2V there then this might occur? 






GibsonGM

Re: Univox Fazer woes
« Reply #2 on: August 12, 2017, 06:42:59 PM »
Yeah, you could try some more tracing, see what's up with the power/bias to that opamp...any DC after the output cap?  If that was bad, could drain bias voltage, maybe...
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Kipper4

Re: Univox Fazer woes
« Reply #3 on: August 12, 2017, 06:44:15 PM »
I can't find any data for your D1.

However I can't see anything that should stop the voltages of the inputs of the last op amps being any different voltage wise to the others..


Anything funky going on with Q4?

I guess you have the biasing in the parish if your getting phasing on the output of the other op amps.

Hmmm
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disorder

Re: Univox Fazer woes
« Reply #4 on: August 12, 2017, 08:44:34 PM »
I can't find any data for your D1.
Anything funky going on with Q4?

D1 seems to be a 4.5V zener, and it's definitely zenering here as expected.

I just removed R18 (the 1k that connects the 4.5V supply line to that last output stage) and now I have some phasing but its still really subtle. Removing R18 brought the DC voltage of stage OP5 (pin1) to about 3VDC. So still not at the same voltage as the other stages or as the inputs to OP5 (pins 2 and 3). Hmmmmm....still hammering away. I've already swapped the "suspect" opamp with one that's outputting good phasing sound and it didn't change anything...
« Last Edit: August 13, 2017, 01:58:17 PM by disorder »

disorder

Re: Univox Fazer woes
« Reply #5 on: August 15, 2017, 08:22:15 PM »
Hello diystompboxes. I am still here. Still introducing my head to the wall. I have since done the following to try and debug...

1 - I have disconnected the LFO from the JFETs by removing C8 from the circuit board, now I can debug clean audio only. The last opamp stage still has no signal on it's output even when dealing with regular unphased audio.

2 - At slower LFO speeds the "4.5V rail" sort of fluctuates between 4.195 - 4.188V when I measure with my DMM. This is still with the LFO disconnected from the JFET gates. This could be relevant to my problem or not, but it was noted. I am using a 9V bench top supply that measures a stable 9.01V with my DMM.

3 - DC values for the opamp stages are as follows:



duck_arse

Re: Univox Fazer woes
« Reply #6 on: August 16, 2017, 11:08:11 AM »
is this on BB or circuit board? can we see pics of your build? those voltage measures are all over the place. what is your voltage at R23//D1?
Last Edit: Soon at 09:27:12 by someone sensible

disorder

Re: Univox Fazer woes
« Reply #7 on: September 08, 2017, 04:36:16 PM »
Just wanted  to put closure to this issue. Cap C1 was quite leaky, it was an old ceramic type. Replacing got this circuit back to sounding and measuring just expected.