Hollis Ultra Flanger

[craigmillard]

Hi all,

Hopefully one of you guys/gals can help me out!

I have just built the ultra flanger but am having problems with the output, it is blaty and farty sounding as if the bias is out.
I have built this to the exact hollis schematic(http://www.geofex.com/pcb_layouts/layouts/ultrafln.pdf) and etched my own board. From what i can tell all the solder joints are good and i can hear the flange effect coming through just very mildly.
This has been running off a 9v battery reading 9.1v on the DMM.

Has anyone built this or had similar probs???

i recorded some voltages off of the 2 opamps and the MN3007 to aid:-

U1:
1. 5.99
2. 6.17
3. 5.56
4. 0
5. 5.17
6. 5.77
7. 5.50
8. 8.99

U2:
1. 8.99
2. 4.10
3. 5.56
4. 0
5. 0
6. 3.20
7. 5.37
8. 5.35

U5.
1. 1.35
2. 8.12
3. 5.72
4. 0
5. 7.55
6. 4.22
7. 8.03
8. 8.68

Do you think the TR3 Addition will help my situation, seems as thou the half volt rail is slightly over by .5v?
Any help or suggestions would be greatly appreciated!!

Cheers

[oldrocker]

Mine was built on perf so I'm not sure if the pcb layout has been verified.  Since I used the geofex schem to build mine I would follow R.G.'s directions to the letter to avoid any ticking issues.  Also I would audio probe it to find where the signal loss originates.  IMHO this is a great sounding circuit with geofex mods.  If you get it working right you won't be dissappointed.

[craigmillard]

thanks for the reply oldrocker!

I have sound coming through, realised i had used a buffered 4049 instead of the unbuffered version! but now i am not recieving any flange effect and the pots seem to have little impact apart from altering the sound of the guitar a touch!?

if i turn the regen fully up i just recieve a high pitched squeel.

Any ideas of where to look would be a great help, going to try the tr3 trimmer tonight but dont think it will have a huge impact for the flange section.

I have used the yellow LED + diode options, would the zenor work better?

cheers

[cobra94]

Craig,

I'll try and help you out a bit, this flanger has been the bane of my existence but, I have it working now.  I even came up with a tick reduction scheme that I will show you later, if yours has this problem.  Before we begin and just to verify, you built the pwb on page two and you DID NOT do the mod on page three correct?  If so give these steps a try.

First, check all your component values and make sure you have the right values and polarities in place.  Second, you bias voltages look off so you need to get them right (4.9V & 3.8V),  I would add TR3 so you can dial in the 4.9V properly (don't forget to cut the traces between the pads).  Once these are correct you can look at the LFO section and see if it is working.

Oldrocker, I've followed other threads where you've chimed in and I have to agree that the PWB layout has some inherent flaws.  Would it be possible for you to show us you component placement?  I may do a perf version of this and it would help to use your placement as a reference.

Good Luck,
Peter

[lars-musik]

I don't know whether anybody still replies to new questions in ancient topics.

However, my question is closely related to this one. I am building an Ultra Flanger using Solderman's great tiny layout (here: http://www.diystompboxes.com/smfforum/index.php?topic=83321.0). This layout omits TR3 and uses fixed values like John Hollis proposed in his latest revision of the schematic. If doing this, the 4.9 bias voltage seems to be strongly correlated to the input voltage. Wouldn't it be a good idea to use a 5V voltage regulator or even a 5.1 zener? How important is the EXACT value of 4.9V? Obviously I don't want to re-set the bias if I change the battery or power supply, so the trimmer isn't exactly perfect, too. 

[ncudahy]

this post helped me figure out what was wrong with my build of this circuit. I also used the geofex pcb and had the same voltages and the same problem. i used the 2 led and diode option instead of the zener. this resulted in an incorrect bias of about 7.6 v into u5.now i should caution that i am a relative newb, but i thinkthat maybe the fault lies in the layout! if you don`t use the zener then it seems to me that you need to take the voltage after it has dropped through the leds.

i disconnected R17 and led1 at the junction shown on the schematic and connected them with alligator clip jumpers on the top side of the board. then i used another jumper to connect the junction of  led2 and d3 to pin2 of u5. hey it worked!

now if i can only get my time machine working i can go back to 2009 and help out.

PS if anyone more knowledgeable than me reads i hope they will add to the discussion!

[duck_arse]

ahhh, ncuday, what colour leds did you use? I'm guessing from the 3V8 that RG was using 2 RED leds and a 1n914/1N4148. ordinary red leds have a forward voltage of about 1V6, and the 1N914 about 0V6. green, orange, yellow are all higher, to varying degrees. blue leds can have a FV of 3V.

[ncudahy]

haha! ok well THIS post helped me get it working then  upon further reflection i now see how the whole diode voltage dropping thing works and that the layout was correct. for the record i was using green leds but that turned out to NOT be the problem. after i removed them and replaced them with red leds i measured their forward voltage as 1.7v. I finally found an almost imperceptibly small break in the trace leading from the 1N914 to ground. after a little kludging it is now flanging away.

Hey thanks for your response to my post! It really did help me work out the problem and learn a thing or two in the process!