Vibracaster - or "How to turn your Valvecaster into a Tremolo"

[frequencycentral]

my 0.47uF capacitors are polarised tantalum bead capacitors. have i made a bad?

Yeah, they should be non-polarised caps, I don't think it would work with polarised caps:

.....I also have a question: usually transistor phase shift oscillators have three capacitors performing the phase shift - can they be polarised capacitors or should they be non-polarised?

If you can guarantee that at no time is the cap reverse biased by even a fraction of a volt, they can be polarized. Otherwise, use NP or film.

[solderman]

my 0.47uF capacitors are polarised tantalum bead capacitors. have i made a bad?

Hi
No. I don't think so Most caps are exchangeable as long as you keep in the correct volt range and orient them correct if there polarised. Check http://www.diystompboxes.com/wiki/index.php?title=DIY_FAQ#CAPACITORS and let + facing the trannies and - to the left in the chem.

//Solderman

[biggy boy]

Yes !!!  I got my add on board oscillating an LED This is Ricks layout that I'm talking about.
I made another board and mounted sockets for the transistors and some of the resistors.
This allowed me to be able to temporally hook up an LED  between the collector of Q2 and V+ 12 volts and make it flash.
With the first board I made, I did not test it with an LED, just my meter which did show the base of Q2 fluctuating.
Now for the next test is to hook it up to my existing ValveCaster and see if I can get it to work.

Thanks Rick and Solderman for your help

[TotemTek]

good going biggy boy! 

thanks for your replies guys, now i'll stop bugging you and go debug my pedal.

[frequencycentral]

Yes !!!  I got my add on board oscillating an LED

Thank @#$% for that! 

[biggy boy]

Yes !!!  I got my add on board oscillating an LED

Thank @#$% for that! 

LOL
Actually when things don't go well, I don't get totally put off.
I look at it this way. If I make someone Else's project and it works the first time, I'm not really learning how the circuit works.
When a circuit is problematic (because of Me)  I spend more time working with it and tinkering with it, I learn more of how the circuit works.
It's all part of the learning curve for me.

Thanks for the encouragement Totemtec
Good luck with the debugging!!

OH one more question!
Is there enough adjustment in the depth pot to stop the effect. You know so that if I turn the pot all the way it won't effect the sound no tremolo
I ask this, because I'm not putting it into a stomp box it's going into a preamp rack with my Valvecaster or will I have to add a kill switch in the preamp cabinet to eliminate the effect?

Glen

[frequencycentral]

Is there enough adjustment in the depth pot to stop the effect. You know so that if I turn the pot all the way it won't effect the sound no tremolo
I ask this, because I'm not putting it into a stomp box it's going into a preamp rack with my Valvecaster or will I have to add a kill switch in the preamp cabinet to eliminate the effect?

Yup, with the depth pot fully counterclockwise, you'll get no trem, the cathode will be grounded as in the second stage of a stock Valvecaster.

[TotemTek]

here are some voltages -

Q1
E:0
B:11.51
C:11.55

Q2
E:0
B:11.56
C:12.08

i'm not sure if those voltages are right... i've checked over the circuit several times, i've wired it all up very nicely, it all looks correct. getting absoloutely no signal when pedal turned on. think i'll swap out 0.47uF caps for NP ones

[frequencycentral]

here are some voltages -

Q1
E:0
B:11.51
C:11.55

Q2
E:0
B:11.56
C:12.08

i'm not sure if those voltages are right... i've checked over the circuit several times, i've wired it all up very nicely, it all looks correct. getting absoloutely no signal when pedal turned on. think i'll swap out 0.47uF caps for NP ones

Sorry you're having trouble getting it going, Here's some info that should help your debug from page 6 of this thread:

OK. Pretty hard to get voltages from an oscillating oscillator!

This first set were taken with the PSO oscillating, but with the depth control removed. I still have the original PSO in a little corner of my breadboard right now. The blank values are because they are changing as the PSO oscillates.

Q1

E: 0.032
B:
C:

Q2

E:
B:
C:11.92


This second set of voltages were taken with the depth pot removed and the speed pot removed to stop the oscillating. Probably more meaningful.

Q1

E: 0.032
B: 0.657
C: 5.54

Q2

E: 4.96
B: 5.53
C: 11.92

I hope this helps. I suggest you remove the speed and depth pots and check the voltages against mine, just work with the PSO part of the circuit, thats where your problem is.

You can get a visual check on oscillation by inserting a red LED between Q2's collector and +ve. It will flash a little weakly though. You should remove it before you complete your build, as it will cause ticking otherwise.

[biggy boy]

I've done the next stage of testing.
I have left the LED in the circuit to make sure the add on oscillator keeps oscillating when hooked to pin 8 of the second stage of the tube (valve).
So with the add on board hooked up to pin 8 the board keeps oscillating LED keep flashing, but there is no effect.
The amp has the same sound with and with out the oscillating circuit connected.
Turning the depth pot does not cause the effect to work just makes the volume change slightly at the two extreams of the pot it is the loudest if the pot is set anywere else the volume is reduce slightly. I also tested it with the LED removed and the collector reconected to the circuit directly.

Rick what does the last section of the circuit do in relation to the second stage Cathode? The section I have circled in the diagram, the voltage divider.
Does it create a modulation ( vary the resistace to ground from the Cathode), which would causes the gain to increase, decrease, increase, decrease........
Or does it connect, disconnect, connect, disconnect....... the Cathode to ground?

Keep in mind my ValveCaste ris using 157 volts to the anode plate so the current though the tube would probably be higher, I'm thinking I may need to ajust the resistor values in that last section to make it work.




Thanks
Glen

[frequencycentral]

Rick what does the last section of the circuit do in relation to the second stage Cathode? The section I have circled in the diagram, the voltage divider.
Does it create a modulation ( vary the resistace to ground from the Cathode), which would causes the gain to increase, decrease, increase, decrease........

With that pot full counter-clockwise the cathode is directly grounded. With the pot full clockwise the LFO modulates the cathode.

Is the PSO definately oscillating?

Maybe you should test your circuit with 12 volts at the plates, then you'll know it works. Then its a matter of tweaking it to work at higher voltage.

Rick

[biggy boy]

Rick what does the last section of the circuit do in relation to the second stage Cathode? The section I have circled in the diagram, the voltage divider.
Does it create a modulation ( vary the resistace to ground from the Cathode), which would causes the gain to increase, decrease, increase, decrease........

With that pot full counter-clockwise the cathode is directly grounded. With the pot full clockwise the LFO modulates the cathode.

Is the PSO definately oscillating?

Maybe you should test your circuit with 12 volts at the plates, then you'll know it works. Then its a matter of tweaking it to work at higher voltage.

Rick

Yes the LFO oscillates during the entire time of testing. The LED is located between the Q2 collector and v+12 volts it keeps flashing and I can adjust the rate at which it flashes with
the speed pot.

OK I'll try the 12 volts to the Valves and post back





Glen

[frequencycentral]

I sold the original, this is it's replacement.

[GeorgeM2]

HI! Im guitarmaster & beginner diyer from russia. Sorry for my english.

I like valvecasters and other lowvoltage tube stompboxes, tremolo - it s very interesting!

At first i try one transistor oscillator schematic from Solderman - i dont like it, bad regulated deep of tremolo, no very good sound. 

At second i try schematics from Frequencycentral - good old sound. Very GoOoOoOoOoD sOuNd! 
Big sanks for the idea and schematics!

I designed in DLC "add vibrato module" 7x7 holes perfboard, and full "vibracaster plate" for "GAINTA G0473" box, 119 х 93 х 33 mm. Anybody need?

[Renegadrian]

yeah, Rick circuit is so good...

[frequencycentral]

At second i try schematics from Frequencycentral - good old sound. Very GoOoOoOoOoD sOuNd!  
Big sanks for the idea and schematics!

Hehehe - so glad you like it, here's me drinking to your success:



Welcome to the forum!

I designed in DLC "add vibrato module" 7x7 holes perfboard, and full "vibracaster plate" for "GAINTA G0473" box, 119 х 93 х 33 mm. Anybody need?

Please feel free to add your layouts to this thread - will be a useful addition for some people in the future.

[GeorgeM2]

With pleasure I show

1) VibraCaster add-on oscillator module 7x7 holes. Designed by DiamondDog. Redesigned by GeorgeM2.  


2) on this base: VibraCaster 12at7 with partlist, 12volt. work. Designed by GeorgeM2. Indicator LED worked with left 3pdt i be test  in the evening, with only right 3pdt - worked correctly. Potentiometers "VOL" "TONE" & "GAIN" are shown not precisely, see photos. Tube socket mount reverce plate(!), see photos.

i try 12au7, 12at7 and 12ax7 from ElectroHarmonics and Tung-Sol - 12at7 EH i biggest like...

3) without partlist, best view wire


4) my maquette:

In a box while is not drilled hole for the indicator, I will make it in the evening. gain poti - dublied 2x100k, in parallel - no more hum.  
Boxart - decal paper + laserjet.  


big green caps - soviet type K71-17, look as from a scrap   but sound is good, blue - K71-7, yellow "C3" no electrolit(!) - it s china mft type cap.
big caps - big sound  

Best regards, George (Anatoliy Martynenko).

[edd101]

привет!

и добро пожаловать!

Эд)))

[Renegadrian]

what!?

Anatoliy, I am sure your Vibracaster will turn out GREAT!!! I like the design of the box...And yeah I love AT7 too!

[GeorgeM2]

I do it!

1) guts:


2) top view


3) The Ventures - "Vibrations" from my modded (   ) FenderBluesJunior? It s better than sex!  


Upd: green caps type K71-7B, in previous post error.

p.s. About "strange blinking LED": i have this "problem" and i think: on the maquette i use soviet type green LED "AL307", his the blinking correctly, after i use blue china LED - his blinking BLINK-blink-blink-blink-BLINK-blink-blink-blink (I don t have oscillograf   ) - 4 times on the one tact. Why?
- AL307 is the first generation LED, rough, low light, blue LED - is the modern LED - HI light, hi sensivity(?).
fin: For me it not a problem. For other - may be simply increase R14? Or use old bad LED  

p.p.s.a box no have ventilations holes - nevermind! I 'burn" 8 hours power on - air temp = 18 grad. celsius, box temp = 25 grad. celsius, power adapter temp = 45 grad. celsius.  

p.p.p.s. Once again: soung is fantastic!