MKII pedals, germanium and outdoor weather...

[Orpheus]

Hi, all.  I played an outdoor show last night and it was right around 50 degrees at showtime.  I have an MKII tone-bender type pedal with the standard three germanium transitors.   Well the pedal started fading and then it would not work at all during the show.  I know germanium is temp sensitive, but is that normal for an MKII to just stop working at 50 degrees?  There is a bias control inside too - would adjustment have helped (didn't have time to open it up and adjust during the show of course)?  It works fine now at normal room temp...

Thanks much,

-Mike

[R.G.]

I don't know that this was the entire problem with your pedal. It seems odd for it to completely quit. Usually I would expect the sound/tone to drift away from how it sounds at room temperature. But it's not unknown for germanium to drift a LOT, so it's possible that it was all temperature drift. Has it drifted back to working now that it's warmed up?

There's no way to say whether or not it's normal for a MKII or any other Ge pedal to stop working at 50 degrees. It depends too much on the particular devices inside.

[Orpheus]

I don't know that this was the entire problem with your pedal. It seems odd for it to completely quit. Usually I would expect the sound/tone to drift away from how it sounds at room temperature. But it's not unknown for germanium to drift a LOT, so it's possible that it was all temperature drift. Has it drifted back to working now that it's warmed up?

There's no way to say whether or not it's normal for a MKII or any other Ge pedal to stop working at 50 degrees. It depends too much on the particular devices inside.

Thank you, R.G..  It works fine again now at room temp.  I will also specify that I had it adjusted at midpoint on the internal bias pot - right in the middle, so bias was lower than average to start too. 

[Timebutt]

I can confirm the Mk II is very sensitive to temperature changes: when I was working on my circuit the other day all of a sudden I noticed the sustain and tone were not right: notes were fading out in a very odd way. When I measured the voltage on Q3 I got something way off -4,5V as I had biased it: apparently just because the circuit was lying in pretty intense direct sunlight the biasing changed. The same happened when breathing on the transistors: weird things with sustain etc.
Incredible pedal nonetheless

[petemoore]

  Yes, GE's can drift alot...
  I had a 'theremin' going in an octave pedal, the pitch controlled by the heat of the GE as influenced by touching it with just the thumb on it's top !
  TBMkII, was unusably biased in the hot sun, also when it came in from freezing, those same TB's sounds fine if not too hot, not too cool.
  But I think they were probably biased near an 'edge', and a bias tweek in some cases can allow much wider temperature functioning...ie keeping the bias 'centered' means it takes more drift to push it past a 'parameter' which causes misbias.

[Orpheus]

I can confirm the Mk II is very sensitive to temperature changes: when I was working on my circuit the other day all of a sudden I noticed the sustain and tone were not right: notes were fading out in a very odd way. When I measured the voltage on Q3 I got something way off -4,5V as I had biased it: apparently just because the circuit was lying in pretty intense direct sunlight the biasing changed. The same happened when breathing on the transistors: weird things with sustain etc.
Incredible pedal nonetheless

Thanks for sharing, Timebutt.  That is exactly what I noticed - notes fading in an odd way at first, but then after it got colder it completely went silent...

[Orpheus]

  Yes, GE's can drift alot...
  I had a 'theremin' going in an octave pedal, the pitch controlled by the heat of the GE as influenced by touching it with just the thumb on it's top !
  TBMkII, was unusably biased in the hot sun, also when it came in from freezing, those same TB's sounds fine if not too hot, not too cool.
  But I think they were probably biased near an 'edge', and a bias tweek in some cases can allow much wider temperature functioning...ie keeping the bias 'centered' means it takes more drift to push it past a 'parameter' which causes misbias.

Interesting!  Well I decided to put the bias back near max on the trim pot.  It sounds a lot stronger there anyway, and in retrospect I don't know how I managed to think the pedal was sounding good with the bias I had it adjusted at earlier.  Thanks!

[zombiwoof]

A good reason to put the bias control on the outside of the pedal, as many have concluded.

Al