MASF Possessed glitch - volume drop

[wax+wire]

Hey.
So there is talk in other threads about the MASF Possessed pedal partially breaking and the volume suddenly dropping when engaged. Well that happened to mine

I popped it open and noticed there were 3 ICs - a the SPIN FV-1, a RAM chip and a Quad OPAMP (4558DD). One side of the opamp seems to be boosting the dry signal, and one side the processed/wet signal. The strength of the wet signal is controlled by the "Sight" pot still.

I hoped it might have been a fried opamp, but I dont think so. It gets power correctly (7~ V) and seems to be amplifying the signals

The "hearing" pot, which is the "volume" knob, while it still works, is a little strange. The centre/wiper pin is ground. That doesn't seem like how I would normally wire a volume pot. I cant trace what is meant to be going on as the board is so tightly packed, but it made me wonder if there is a blown transistor or something.

Anyone ever fixed theirs?

Ta

[backwardsvoyager]

How old is the pedal? I was under the impression this was fixed with a board revision back in like 2014 or something.

The one I had was gooped all over the place and I could barely see half the components, let alone try to repair it. I'm not aware of anyone here having been able to fix it, or even reach the builder for support. Best of luck, though.

[tremolo3]

There is a myth that only true Possessed can perform Seppuku.

[wax+wire]

Not sure the age. I picked it up second hand, and that'd be a few years ago. Actually, it came with the box which I may still have.

The goop came off fairly easily. Getting the board out will be a bit more tricky, as their may be goop on the underside hold the PCB to the pots, or maybe the PCB is being secured by the LED legs.

My best guess is that it is the transistors. I've fixed a few casio keyboards in my time by swapping out dead transistors. so that may be the process I go about. There isn't many transistors and they look like they are all through-hole

[whoismarykelly]

Id check the joints between the board and the switch and the switch itself. Could be a small resistance to ground somewhere that is cutting signal.

[wax+wire]

FIXED:

there is a MOSFET transistor, BS170 that the signal passes through at the end of the chain. it is the final gain stage. It is just next to the switch and LED. that is the transistor that was blown (nothing visible). It is a fairly easy fix if you have done some soldering. not a surface mount device, but the holes the transistors go into seem a bit smaller, or at least the soldering pads are, so desoldering and resoldering the replacement transistor is a little tricky, but not too hard.

[wax+wire]

Also, while I was on there it became clear it wouldn't be too hard to had an expression port. Taste Touch and Smell are all CV inputs into the SPIN FV-1. those are 0-3.3v.

there wouldn't be enough space for 3 x 6.5mm sockets. An option would be maybe 3x 3.5mm, or 1x6.5mm and a selector switch.

I've recently bought some TAPLFO chips for another project, but it makes me think how cool it'd be to have Taste Touch and Smell on an LFO!

[MechaGodzilla]

hell yeah, i like the way you think

[Possessed]

Hi all,

I have a Possessed with that problem too, but replacing the BS170 mentioned above fixed nothing. Does anyone have any further suggestions on what to test?

Thanks for this thread, it's about time I bring this crazy pedal to life...

[gila_crisis]

Few month ago I got a new Raptio, and at some point it started to randomly have volume-drops. I've found out there was a capacitor with a cold solder joint (when moving/touching the component the sound was going and coming). So I re-soldered the part to the pcb and problem solved!

You can also build such a audio-probe, and follow the sound in the circuit to see where the problem is:
https://www.coda-effects.com/2015/07/tr ... uitar.html