Gentlemen I need your help on this.
I have 2 indentical 230V prim 2x 9v sec 50 VA transformers. Connecting them back to back do they keep their va rating so at the end I have 230V at 217 ma ?
Should I connect 1 of the secondaries between them or both ?
For a 100 ma shunt what is the minimum current capacity that my transformer should have ?
I have 2 indentical 230V prim 2x 9v sec 50 VA transformers. Connecting them back to back do they keep their va rating so at the end I have 230V at 217 ma ?
Should I connect 1 of the secondaries between them or both ?
For a 100 ma shunt what is the minimum current capacity that my transformer should have ?
Can't comment from personal experience but have read about doing that a few times on diyaudio. What I remember was that you will not end up with the same VA-Rating but loose about 10%... (can't remember the thread...Baby Huey...RH84???). You also might wind up with less than 230V on the secondary but that is the smaller problem.
OK, then as of now you are not alone...
Something seems to be quite sensitive in the regulator. Just soldered in 22R as R1 , switched in on with my dummy load, and only have a somewhat low 4V output voltage.
First question; which component most likely died? I am still not good in identifying dead components...
PS. Err, how do I check transistors with my DMM
ashamed: 
). I am still on the lower portion of the learning curve with this...
BC560 most likely, those are creating Iref to be made Vref. The BCs are nesting between HV, some mishap can create a transient and kill. An IRFP could have died too if exposed to large Vin-Vout during that.
Can't tell more than logical scenarios because mine still works without a problem for many months now.
Ikoflexer has a fixed Zener Ref local CCSed reg, its quite different.
Checking BJTs with DMM
Can't tell more than logical scenarios because mine still works without a problem for many months now.
Ikoflexer has a fixed Zener Ref local CCSed reg, its quite different.
Checking BJTs with DMM
stixx, this is SOOOO familiar already. You have no idea how many times I've seen the low voltage
OK, this is what you can do with the DMM (in diode test mode). The parts should be out of the circuit (I know, it's a pain); perhaps you can just desolder the wires in a p-p construction. For testing a PNP, which you are most likely using, put the negative probe on the base, and the positive probe on the emitter first, collector after. B-E and B-C should show a similar value. If any of these connections beeps (or shows 0) then you got a short. My DMM shows about 720 for a BC560C. One of the B-E and B-C measurements is slightly larger.
It's a bit trickier with a mosfet, but you can do it. First of all, check all pairs D-G, D-S, G-S (in all directions) and if you got a short on one of them, RIP. To test the IRF840, with the DMM on diode mode:
1) pos probe on the S, neg probe on D; the DMM should show a number, something most likely in the 400s. Different values for different mosfets, but it should not be 0, or over 1000.
2) Charging: hold pos probe on G and neg probe on S for a few seconds. Then place pos probe on D and neg probe on S. This should show a number in the 600-900 range. Discharging: while holding the probes there, create a bridge between G and S with your finger. The number should all of a sudden change into a 1.
This is normal behaviour in a healthy mosfet. For the P-channel mosfet the procedure is the same, except you may have to change the polarity on the probes.
OK, this is what you can do with the DMM (in diode test mode). The parts should be out of the circuit (I know, it's a pain); perhaps you can just desolder the wires in a p-p construction. For testing a PNP, which you are most likely using, put the negative probe on the base, and the positive probe on the emitter first, collector after. B-E and B-C should show a similar value. If any of these connections beeps (or shows 0) then you got a short. My DMM shows about 720 for a BC560C. One of the B-E and B-C measurements is slightly larger.
It's a bit trickier with a mosfet, but you can do it. First of all, check all pairs D-G, D-S, G-S (in all directions) and if you got a short on one of them, RIP. To test the IRF840, with the DMM on diode mode:
1) pos probe on the S, neg probe on D; the DMM should show a number, something most likely in the 400s. Different values for different mosfets, but it should not be 0, or over 1000.
2) Charging: hold pos probe on G and neg probe on S for a few seconds. Then place pos probe on D and neg probe on S. This should show a number in the 600-900 range. Discharging: while holding the probes there, create a bridge between G and S with your finger. The number should all of a sudden change into a 1.
This is normal behaviour in a healthy mosfet. For the P-channel mosfet the procedure is the same, except you may have to change the polarity on the probes.
Since I am not the only one who's experienced this, perhaps we can think of protective circuitry to add? I know yours works, but if it happened already to two other people, this may be a sign of vulnerability to certain conditions. Perhaps voltage spikes, etc. I could think of some diodes and zeners here and there added for protection?
Alrighty, music is playing again with 100mA CCS.
Don't know what happened but likely was my own fault. One more IRFP9240
on the graveyard, but no big deal in the end.
First impression: more SLAM, everything a touch warmer and very natural.
Never heard voices, piano and cymbals better over my headphones
Everythings runs a bit hotter now, but both heatsinks don't get warmer than 40°C.
Highly recommended. PUNKTUM
Don't know what happened but likely was my own fault. One more IRFP9240
on the graveyard, but no big deal in the end.
First impression: more SLAM, everything a touch warmer and very natural.
Never heard voices, piano and cymbals better over my headphones
Everythings runs a bit hotter now, but both heatsinks don't get warmer than 40°C.
Highly recommended. PUNKTUM
