VOX tonebender mkIII

[birt]

i've got this huge pedal from a friend who wants me to repair it.
i really couldn't just do this without showing of this great thing for you guys!

http://images5.fotopic.net/?iid=yceely&outx=600&noresize=1&nostamp=1
inside: http://sic.fotopic.net/p15788665.html

What is the right schematic for this thing? i can only find an mkII


the guy also wants to know the value of this thing, any ideas?
will the value go down if i install a led? and change to a 3pdt switch?

[petemoore]

17  R's
 2 Diodes
 2 ? Transistors...
 I don't remember having seen a schematic by that name with those parts...interesting !

[phillip]

Check out the schematic of the Jumbo ToneBender...

http://www.diystompboxes.com/pedals/Jumbo.jpg

I believe that there was also an earlier version of the Vox ToneBender MKIII that shared the same circuit as the Colorsound 3-Knob ToneBender.  But the one in your pictures looks like a Jumbo ToneBender circuit.

Phillip

[petemoore]

That's Very Pi like [BMP]

[phillip]

That's Very Pi like [BMP]

It sure is...or is the Big Muff Pi very Jumbo ToneBender like...

Phillip

[birt]

it has 3 transistors labeled: ZTX 383C

all pots are 100K

a stamp inside says: 29JUL1978

[RCZ53]

Will the value go down if you install an Led ?
If you drill a hole in the case it will diminish the value. If you change the stomp switch, you can save the old one for eventual resale and then it can always be changed back. That is a fairly rare pedal from what I understand. I would be reluctant to drill the case for that reason.

[phillip]

it has 3 transistors labeled: ZTX 383C

all pots are 100K

a stamp inside says: 29JUL1978

Yep, sounds like a Jumbo ToneBender circuit.  Apparently, according to the Sola Sound schematic, Issue 1 of the Jumbo was 4-12-73 (I think...it's a little hard to read) and Issue 2 was 9-4-80.  So if it was made in July of 1978, then it's most likely a Jumbo.  

Phillip

[george]

will the value go down if i install a led?

as RC753 says, it sure will.  Besides, surely you don't need a status LED to tell whether THIS thing is on or off?:twisted:

If I was you, I'd
- fix it
- clone it using the schematic (any old BJT trannies should work fine eg 2N3904, 2N5088, BC549 etc)
- sell it if the clone sounded the same
- put a status LED and 3PDT in the clone
- build another 5 pedals with the profit
DIY's da BOMB!!!!

[ISC]

I agree with Phillip, I own a Vox Tone Bender MkIII that I bought 69/70
It is the  same cct as the three nob Tone Bender with 3 germanium
transistors, the inside of yours looks different to mine, my components are under the board where the pots go through the case.
Phillip's 3 nob schematic matches mine and THANK you Phillip for that note about "the 220k resistor not nomally fitted" on the schematic.
I could never use this pedal live it had no guts, when I saw your note and removed the resistor I now own a vintage monster that I would not sell.

[birt]

will the value go down if i install a led?

as RC753 says, it sure will.  Besides, surely you don't need a status LED to tell whether THIS thing is on or off?:twisted:

If I was you, I'd
- fix it
- clone it using the schematic (any old BJT trannies should work fine eg 2N3904, 2N5088, BC549 etc)
- sell it if the clone sounded the same
- put a status LED and 3PDT in the clone
- build another 5 pedals with the profit
DIY's da BOMB!!!!

so it uses silicon trannies?
i'm gonna check if it matches the solasound schem and see if i can get some sound from it.
i will inform the owner that it's quite rare and drilling holes in it would be a little dumb.

[col]

The Jumbo Tonebender had 3 BC184C trannies in it and the board was used in a number of other pedals such as the B+M Fuzz Unit. I built a clone of one and you do not need an LED indicator to tell when it's on, even in a live situation! I think it sounds better than both the Si tonebender and the Ge version I built.

Col

[analogguru]

BC 184 C:
Si-NPN  30V/200mA/300mW  ÃŸ: 450 - 900/2mA  F: <4dB  ft: 150 MHz (280 MHz)

ZTX 383 C:
Si-NPN  30V/200mA/350mW  ÃŸ: 450 - 900/2mA  F: <6dB  ft: >150 Mhz





BC 109 C:
Si-NPN  20V/200mA/300mW  ÃŸ: 450 - 900/2mA  F: <4dB  ft: >150 MHz

BC 149 C:
Si-NPN  20V/200mA/250mW  ÃŸ: 450 - 900/2mA  F: <4dB  ft: >150 MHz

BC 169 C:
Si-NPN  20V/200mA/300mW  ÃŸ: 450 - 900/2mA  F: <4dB  ft: >150 MHz

BC 239 C:
Si-NPN  20V/200mA/300mW  ÃŸ: 450 - 900/2mA  F: <4dB  ft: >150 MHz

BC 413 C:
Si-NPN  30V/100mA/300mW  ÃŸ: 450 - 900/2mA  F: <3dB  ft: 250 MHz

BC 414 C:
Si-NPN  45V/100mA/300mW  ÃŸ: 450 - 900/2mA  F: <3dB  ft: 250 MHz

BC 549 C:
Si-NPN  30V/200mA/500mW  ÃŸ: 450 - 900/2mA  F: <4dB  ft: 300 MHz

BC 550 C:
Si-NPN  45V/200mA/500mW  ÃŸ: 450 - 900/2mA  F: <3dB  ft: 300 MHz



analogguru


Edit:

additional info:

on 26.Juli.1978 were used BC 184 C

on 19.Mai.1973 were used BC 349 B

BC 349 B:
Si-NPN  20V/100mA/350mW  ÃŸ: 200 - 450/2mA  F:.....   ft: >125 MHz

[col]

Cool. I have used BC184C, BC109C and BC549C to try in different pedals. Although I have chosen similar hfe out of each they do sound different with some being more bassy/less hissy than others. I don't know why this should be the case.

[EdJ]

It looks the same as the inside of my jumbo tonebender.
In the tonebender the transistors are 184`s
Ed

[birt]

i traced it and made a schem. it's very similar to the jumbo nut has some other values.
i'll upload it when i have the time.


it works now btw and it sounds great.