Forum Vibe Debugging

Forum dedicated to helping people debug and troubleshoot non-functional pedals or builds. Please use an clear and informative title, indicating circuit and basic problem. Don't forget to mark the issue as fixed if this is the case.
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nikiluciano
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Post by nikiluciano »

hello guys , i have a problem with the kit forum vibe ver.5 rev 1a ,purchased on musikding ....
in the description said that he needed to 18v dc to work ,
but building it I saw that it has a power supply section with bridge rectifier 18v ac
... should I use then ? or otherwise 18v dc ?

http://www.musikding.de/Forum-Vibe-Vintage-kit

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idy
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Post by idy »

That is a little confusing. The V5 pcb, according to the forum-vibe site, is different from previous in that it copies the vintage power supply. This is not included in the documents/schematics although the BOM includes the rectifier.

Yes, rectifier= must use AC in.

The site also says you can still wire it up to use the " MOD style VReg power supply" but I don't see instructions. Typically this kind of set up delivers seperate V to the audio and LFO sections.

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benny van de locht
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Post by benny van de locht »

Idy,

I discovered the exact same problem as nickyluciano... also from Musikding.de

Do you mean we should ignore the whole power supply, or just leave the bridge rectifier out?
Regarding the bridge rectifier I would think it alone couldn,t cause any problems if fitted correctly...

I'm searching for errors in my circuit though...

Greetings, Benny

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Post by mictester »

nikiluciano wrote:hello guys , i have a problem with the kit forum vibe ver.5 rev 1a ,purchased on musikding ....
in the description said that he needed to 18v dc to work ,
but building it I saw that it has a power supply section with bridge rectifier 18v ac
... should I use then ? or otherwise 18v dc ?
http://www.musikding.de/Forum-Vibe-Vintage-kit
It wont matter! If you connect 18V AC to the input, you'll get just over 24V DC on the PCB when it has been rectified and smoothed. If you fed 24VDC to the same place, you'd get the same result (though the bridge rectifier will allow the DC input to be connected either way 'round.

If the circuit does actually need 18V, rather than 24V (as I recall, 18V was correct), if you're going to use an AC input, you'll need a transformer with a 13.6V secondary to give 18V DC on the board.
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benny van de locht
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Post by benny van de locht »

mictester,

thanks a lot for your reply, can this confirm my assumption it still has a role for evenig out an inconsistent (cheap?) wall wart supply power delivery?

Greetings, Benny.

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Post by mictester »

Not really - the big electrolytic capacitors will help get rid of supply ripple. If you want about 18V on the supply rail, either connect 13.5V AC or 18V DC to those terminals. Either will work.
"Why is it humming?" "Because it doesn't know the words!"

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yhtilhP
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Post by yhtilhP »

Hi All,

I just completed a Forum Vibe vintage using the Classis Amplification v5 board. I put it in a wah enclosure (yes it was tight :D ) and have the pedal working. I stepped up 9vDC using a Madbean road rage doubler with a LT1054 and am getting 18V at the board. My 9v supply is 600mA - plenty.

My the bulb is pretty dim with the trimmer max'd and as a consequence the throb is not as pronounced as other vibes I've used.

Then I noticed what I think is a discrepancy regarding R48 and R49, the bulb bias R's, in the populated layout which I used to as the primary reference for the build. Here: http://www.classicamplification.net/fv/ ... t2n_02.htm

Unpopulated layout here: http://www.classicamplification.net/fv/ ... t2n_03.htm.

Parts list here: http://www.classicamplification.net/fv/ ... int_05.htm

The parts list shows R48 being 100k and R49 being 48k - as per the schematic. However the layouts contradict this ie: thay are showing R48 as 47k and R49 as 100k.

So I need to know if the populated layout or the unpopulated layout is correct?

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Post by toneman »

hi,
from the pdf schematic here:
https://www.freestompboxes.org/viewtopic ... 28&t=12886

sounds like u do not have enough "bulb drive".

R47 says: 100-150 OHMS!

R47 and the trimmer TR3 set the idle current for Q13 and Q14 which drive the lamp.

i dont see a R48 or R49(?) different numbering(?)

see page 8 for lamp/bulb offset bias mods......

also, Q13 and Q14 are setup in "darlington" configuration.
make sure the emitters and collectors are oriented correctly.

back the the game......
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yhtilhP
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Post by yhtilhP »

thanks for the reply

that's an old schemo. THe current TR3/R47 combo is 500k/100k I think.

see here:
http://www.google.com.au/url?sa=t&rct=j ... u9BXO1TiFQ

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yhtilhP
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Post by yhtilhP »


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toneman
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Post by toneman »

thanks for the new link,
i think the top resistor for base biasing of Q13 should be 100K, the lower,47K, to gnd.
this biases the current source Q13.
with TR1 at minimum resistance, only the 150ohm is the current limiter.
check emitter and collector orientation on Q11, Q12 & Q13.
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yhtilhP
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Post by yhtilhP »

Had a play with this again last night.

Swapped the 100k/47k with no luck - LFO stopped working.
Removed the 150R limiting resistor - light became brighter. LFO still not working.
Swapped the 100k/47k back to where I had them (ie: in accordance with this: http://www.classicamplification.net/fv/ ... t2n_02.htm ) and voila, we have a working univibe :D
Still had some rotation left in the trimmer at the optimal spot. Measured my voltage at the board and I was getting 17v now so maybe I am a little low and the additional 150R was too much.
I did try the pedal at 12v(22v at the board) at is sounded relatively harsh at the revised sweet spot on the trimmer. I think the preamp is seeing too much voltage @22v.

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Haus94
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Post by Haus94 »

Hello,

i finished building my Uni Vibe Clone called "Forum Vibe FV5 REV5"

Project documentation files:


http://www.classicamplification.net/fv/ ... t2n_02.htm
http://www.classicamplification.net/fv/ ... t2n_03.htm
http://diy.musikding.de/downloads/forvibevint_en.pdf
http://diy.musikding.de/downloads/wire_04.jpg
http://basicaudio.net/univibe-ForumVibe-final.pdf

Problems:

1) There is noise. It disappears when i touch C1. How can i fix this? I can't touch it all the time obviously :icon_mrgreen:
2) When i turn down the speed, the LFO LED is contantly light up instead of just lighting up slowly matched to the set speed.
When i turn up the speed it works though, it does light up machted to the speed then.
3) The effect in slow speeds isn't really noticable. I pretty much cant hear the throb anymore in very slow speeds.

Changes i did:

1) I removed/shorted R47, the one in front of the Trimpot. I did this because the light bulb wasnt bright enough to get the throb even when i turned the trimpot all the way down.
2) I am using a 18V DC power supply, therefore i removed the bridge rectifier. (the noise isnt coming from the power supply, i tested with 2x9V batteries in series - same issue)
3) One leg of the LFO LED broke, so i changed the LED. i measured both types. Original: 1,82V C=9pF New: Uf = 1,85V C=4pF so pretty much the same.
4) C14 is supposed to be a 470pF Capacitor, in the kit i got one with roughly double of that value though.

List with Transistor values is attached
Attachments
071935c6-b5ed-4d7d-99d1-7aa6b371734a.jpg
7e45818e-4884-44aa-ab93-2f538d5b5b27.jpg

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Post by dave_b »

I'm probably not going to be of much assistance here. Just to be clear, though, when you refer to the LFO LED, are you referring to the light bulb? I built the Madbean version. It has an LED that mounts on the box to show what the light bulb is doing, but I don't see an LED on this one.
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Redhouse
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Post by Redhouse »

Did you ever solve your build problem?

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holm
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Post by holm »

Hello
I'm finishing up a Forum-vibe build, but can't find any info on 2 unlabeled pads, I've marked them on the photo. Is it for powering the LFO separately? Should I just leave them as is if I don't want to power the LFO separately?
Image
In advance thanks
Erik

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plush
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Post by plush »

holm wrote:Hello
I'm finishing up a Forum-vibe build, but can't find any info on 2 unlabeled pads, I've marked them on the photo. Is it for powering the LFO separately? Should I just leave them as is if I don't want to power the LFO separately?
[ Image ]
In advance thanks
Erik
Yes, they are present in case you want to power LFO separately from the signal part. Leave them as is.

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holm
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Post by holm »

great, thank you.

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holm
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Post by holm »

Hi all
I recently finished a Forum-vibe, and wired the speed LED as shown here: https://musikding.de/docs/web/wire_04.jpg
but without the cancel switch. Hence the speed LED is on when the vibe is bypassed, could I ground the speed LED to the 3PDT's ground in order to bypass it as well?

In advance thanks
Erik

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holm
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Post by holm »

Well it works that way!

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