I have checked the PCB for a couple of times and couldnt find any short circuits as well as wrong polar. But I still got blown up for these resistors (R2, R3). Dont know what to do next !!!
Do I have to isolate the transistors from the heat sink? The heat sink is very small and do not connect to anything else.
Do I have to isolate the transistors from the heat sink? The heat sink is very small and do not connect to anything else.
hello,
BOZ should work with any TO-220 NPN transistor like BD243 (in my case). TIP41 have same pinout as TIP29, so go with it.
If your heatsinks are not touching other parts on the board (or the chassis), you don't need any isolation between heatsink and transistor case. Just don't forget adding some silicon grease
Try disconnecting R2/R3 and measuring voltages around Q1. You would expect something like 85VDC across C1, 60VDC on Q1 emitter.
If these voltages are OK, something in preamp is drawing more power than supply can provide.
As previously said, try powering up one channel at a time and see what happens.
BOZ should work with any TO-220 NPN transistor like BD243 (in my case). TIP41 have same pinout as TIP29, so go with it.
If your heatsinks are not touching other parts on the board (or the chassis), you don't need any isolation between heatsink and transistor case. Just don't forget adding some silicon grease
Try disconnecting R2/R3 and measuring voltages around Q1. You would expect something like 85VDC across C1, 60VDC on Q1 emitter.
If these voltages are OK, something in preamp is drawing more power than supply can provide.
As previously said, try powering up one channel at a time and see what happens.
After removing the resistors, I got voltage at C1 is around 80V, emitter of Q1 is around 60V, BUT, after about 10mins, the C2 is exploded. Definitely there is some shorting somewhere.
So I decided to redo it from begining which I will test as I go, and very careful about the short circuit. :-(
@Dzoli: Did you get the same problem as mine before you change to 22K?
So I decided to redo it from begining which I will test as I go, and very careful about the short circuit. :-(
@Dzoli: Did you get the same problem as mine before you change to 22K?
Hmm, electrolytic caps explode if they build excessive inner pressure. This may indicate reversed polarity on C2, faulty C2 or so...
I would replace C2 with new one, 100uF/100V.
After that, check voltages as previously mentioned. When you're sure about the supply, solder back R2/R3 and check. You might expect voltages similar to this
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