hello,
i have an old 80s guitar pedal, vestafire dsx distortion. no schematic and cluttered board. it is broken, there was a replacement alternative transistor in place. the pcb shows how to fit it, the transistor is fitted back to front. spoke to the person who i bought it from, he did the work on it. said that it worked for a few minutes and then died. i put a 9v battery on the pedal, tested the voltage and the battery was at 4.5v because the circuit was draining it fast. i tested the fitted transistor which showed collector 2.9v, base showed battery voltage and emitter a little less than battery voltage. i measured a few other spots around the circuit which showed 0.7 volts and a few chips which showed 2.9v approx. my main question is, is the transistor the cause of it? i am not sure why the transistor was put in the other way round? i thought maybe it had something to do with plug polarity, 9v adaptors having centre pin negative usually, was this altered for cnetre pin positive? i dont know much about the polarity bit.
any help would be great
thanks
stay safe
simon

 

You need to post some good pictures, of both sides of the board. That is a good place to start.

 

If you like soldering and have an iron and the time, I'd recommend some maintenance, and touch up EVERY solder joint, and get rid of the oxide layers, that are bound to be there. People change the oil in a car, but it takes passion to want your electronics to work happily. I'm trying to fix my computer speaker amplifier. Having nice equipment sure helps !!

Can you measure the current of the whole thing ? Just to see if it really is draining the battery too fast ?

A typical EBC or CBE transistor can have the base-emitter junction fried pretty easy, if wired backwards

 

Can you measure the current of the whole thing ? Just to see if it really is draining the battery too fast ?

A typical EBC or CBE transistor can have the base-emitter junction fried pretty easy, if wired backwards

hello darthvolta,
how could i do that with this circuit? i wouldnt really know where to start other than to plug in one side of the battery and put a current meter between the other side of the battery and the battery clip?
also, does the description of the voltage on the transistor indicate a fried transistor?
thanks

 

You gave us your voltage measurements for the transistor but you didn't mention what the measurement reference was. If I assume that the negative meter lead was on the battery negative, then it would appear that it may be a PNP transistor. Can you read the part number on the transistor? Then we will know what it is, which lead is what and whether it is in the wrong way round?
Regards,
Keith

 

the transistor is a bc182c, i removed and tested it, it seems to be working ok. the voltage on the transistor seems to have changed since i put it back. before it seemed to be showing the battery voltage which was around 3 volts.
i managed to get the board apart a bit more, there are two boards connected by plug and socket. so i removed the smaller board and the voltage drain seemed to slow down. any ideas on what i could do to get a better picture of what is happening?
thanks

EDIT: i removed the replaced capacitor by the 9v socket adaptor. now the battery is not draining. red light comes on without any sound at all except a single capacitor discharge. you know the basic laser sound from a simple discharging capacitor circuit. it makes that noise once, lasts about a second or so and then nothing. red probe on ground, black probe on negative battery +7v the battery is around 7v from discharge

 

hello,
i have an old 80s guitar pedal, vestafire dsx distortion. no schematic and cluttered board. it is broken, there was a replacement alternative transistor in place. the pcb shows how to fit it, the transistor is fitted back to front.

It is probably in the right way round. See the attached clipping from the datasheet. The leads are in the reverse order to most modern transistors:

 

the transistor is a bc182c, i removed and tested it, it seems to be working ok. the voltage on the transistor seems to have changed since i put it back. before it seemed to be showing the battery voltage which was around 3 volts.
i managed to get the board apart a bit more, there are two boards connected by plug and socket. so i removed the smaller board and the voltage drain seemed to slow down. any ideas on what i could do to get a better picture of pedal what is happening?
thanks
EDIT: i removed the replaced capacitor by the 9v socket adaptor. now the battery is not draining. red light comes on without any sound at all except a single capacitor discharge. you know the basic laser sound from a simple discharging capacitor circuit. it makes that noise once, lasts about a second or so and then nothing. red probe on ground, black probe on negative battery +7v the battery is around 7v from discharge

Ho did it end?