Strange DOD250 behaving, pin 6 voltage decrease

[arma61]

Hi m8s

so I've got a problem with a DOD250. It takes about 10 secs to "start working"! I'm at work at the moment so I cannot
post complete voltage readings, though I've noted, when I power the crkt, that pin 6 of LM741 starts at V+ voltage (8.92v) and I get
no sound, then slowly decrease to 1/2 V+ (4.47v) and I get the normal sound and I can keep using it as long as I have
the crkt powered. If I turn off power then it acts the same, 10 secs nothing, and then normal behaving!.
It's a standard DOD250 crkt with the exception of the cap at the gain pot (a C500k) that is an electro cap
of 1uf with "-" toward ground ( the 2 pot's lugs tied together). Tried 3 IC with the same result.

Any idea about ? it sounds great as it should... just this strange behaving!

Thanks 4 help.
Ciao

[Pyr0]

Sounds like a capacitor problem. Does altering the gain control change the speed for the voltage to stabilize ? If so it might be that 1uF elec cap you have there. The usual cap in that place is only 0.047uF, I'd try something like a 0.1uF in it's place.
It might also be worth checking the 2 other electrolytic caps in the power section (100uF and 10uF), the 10uF provides Vb - is that always stable or does it ramp up/down as well ?

[samhay]

Does this happen everytime you bypass the effect or just on power up? There are some big caps in the power filtering section and these will take time to charge up in the latter instance.

[arma61]

Hi, thx for reply

only had time tonight to check it..and Alan you've got the point, capacitor problem! in this particular case is the capacitors drawers on my desk, the one with 1u is just one down the one with 47u!! so I picked up, from the 1u drawer a 47u.. (damn breadboard.. must pay more attention when re-stowing the parts in their drawer  ) and I didn't realize it until today when I pull up the cap (it's laid on the board not standing) and red it's value!! my bad, I should have checked the value of that one not just "ok, it the same of the other 3 boards I've made....."!! Usually my 47u caps are all very small and fat.. not tall and thin like this one!!

It works great now!!

Thanks for help spotting the problem... I will spend next weekend to make order in my components drawers.. promise!! 

Ciao