Sigma 22+Dynalo reversed polarity accident.

RudeWolf · 21st July 2012, 11:17 AM

Today I finished my first big DIY project- Dynalo powered by a Sigma 22. While hastily troubleshooting a minor problem I accidentally wired the amp in reverse polarity. It didn't stay on for a long time (<6s) but still- it won't work and voltages for most points are all over the place.

Can someone please tell me what parts I should be expecting to replace? Both PCB's look intact and none of the electrolytic caps even went warm.

RudeWolf · 21st July 2012, 04:40 PM

So, it seems that current sources and the input stage have survived (phew!), however the whole output stage is toast.

gmphadte · 23rd July 2012, 05:58 AM

Even if any transistors have survived, it is better u change all of them as u have wrongly biased.

Gajanan Phadte

RudeWolf · 23rd July 2012, 12:06 PM

Today I'll swap out all of the output BJT's and see what happens. According to my measurements probably some of them have even survived but I'm too lazy to check which ones.

21st July 2012, 11:17 AM	#1
RudeWolf diyAudio Member Join Date: Feb 2012	Sigma 22+Dynalo reversed polarity accident. Today I finished my first big DIY project- Dynalo powered by a Sigma 22. While hastily troubleshooting a minor problem I accidentally wired the amp in reverse polarity. It didn't stay on for a long time (<6s) but still- it won't work and voltages for most points are all over the place. Can someone please tell me what parts I should be expecting to replace? Both PCB's look intact and none of the electrolytic caps even went warm.

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21st July 2012, 04:40 PM	#2
RudeWolf diyAudio Member Join Date: Feb 2012	So, it seems that current sources and the input stage have survived (phew!), however the whole output stage is toast.

23rd July 2012, 05:58 AM	#3
gmphadte diyAudio Member Join Date: Jul 2003 Location: Dona paula, Goa	Even if any transistors have survived, it is better u change all of them as u have wrongly biased. Gajanan Phadte

23rd July 2012, 12:06 PM	#4
RudeWolf diyAudio Member Join Date: Feb 2012	Today I'll swap out all of the output BJT's and see what happens. According to my measurements probably some of them have even survived but I'm too lazy to check which ones.