Floti
Well-known member
Hi! I did some changes to the master module in my Toft ATB and by reassembling it I connected it the wrong way. In the master module there is a connector for the optional meterbridge, but there is also a ribbon cable inside that fits that same connector and is actually intented to provide power to the optional digital card. I connected the wrong one (stupid me!) and made a short that led to my PSU fuses blowing. After fixing it the master module is fine and sounds great but there is a constant loud 100 hz hum. So I checked my PSU and the negative rail is stop on, but the positive rail is giving me 29V instead of 17. I have no schematics and forgot to take some pictures, but you guys are really smart and can probably help anyway! The PSU has one secondary per rail that goes to a chasis mount bridge rectifier followed by two tip141 voltage regulators (also per rail). After that there´s a trimpot in both rails. I checked for visibly blown capacitors or burnt components but didn´t see any. Swapped the secondaries to see if the problem was in the transformer and the negative rail was still spot on, so I guess the transformer is fine. Checked for continuity between the capacitors legs to see if there was a short somewhere but there wasn´t. Tried to change the output voltage with the trimpot with no success. Also realized there is one large IC per rail. I thought that had something to do with the LEDs in the frontpanel, but actually I have no clue. So, until now my suspects are the TIP141s, the trimpot, mabe the IC and the caps, even if they look fine. Yesterday I had no time to keep checking and playing around, but I´d like to fix this today after work. Do you guys think know where the problem might be? Have you had something similar??
Btw, the master module sounded really good and I wanted to ask if maybe the higher voltage is the reason why. Is there a way I could hot rod the PSU to work at for example +-18V? Would that be dangerous somehow?
Thanks in advance!
Btw, the master module sounded really good and I wanted to ask if maybe the higher voltage is the reason why. Is there a way I could hot rod the PSU to work at for example +-18V? Would that be dangerous somehow?
Thanks in advance!