Use the 10 Amp plug on your multimeter and see how much current your circuit is really drawing right at the first cap.
You seem to have some voltage drop between where you measured the transformer voltage and your measurement across the ac side of the rectifier bridge.
remove everything after C2.
test with a resistor load.
measure the primary and secondary AC voltages with and without load.
the secondary AC voltage should not drop more than 5-10% under full rated load.
many years ago I had a voltage loss under load problem that turned out to be a bad fuse holder. One side of the fuse holder would get so hot you couldnt touch it.
Another time it was the wiring to the wall outlet. Wires were all burnt inside the wall. Mind you it was a 220 volt 50AMP service. The equipment would power up fine but if you ran it the extra current draw would cause all types of crashes.
test with a resistor load.
measure the primary and secondary AC voltages with and without load.
the secondary AC voltage should not drop more than 5-10% under full rated load.
many years ago I had a voltage loss under load problem that turned out to be a bad fuse holder. One side of the fuse holder would get so hot you couldnt touch it.
Another time it was the wiring to the wall outlet. Wires were all burnt inside the wall. Mind you it was a 220 volt 50AMP service. The equipment would power up fine but if you ran it the extra current draw would cause all types of crashes.
Post 34 records little drop in transformer op when load applied - 0.3V
There's voltage drop between the transformer and bridge rectifier.
After C2 there's 0.5 A flowing.
Yes.
Also measure the AC voltage on both sides of your transformer. Perhaps the input voltage to the transformer is dropping (???) as mentioned above with the fuse contact problem.
I suggest you measure voltage between the transformer secondary and the respective ac connections to the bridge. Should be close to zero on each leg.
Previously they measured differently (both under load) but there's nothing in the circuit to explain this volt drop.
Previously they measured differently (both under load) but there's nothing in the circuit to explain this volt drop.
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It seems odd that the measured dc output is lower at the bridge than the ac input voltage to it which does tend to point to C2 not charging correctly as suggested.
Referring to post 46, use a resistor that will draw 4-5amps from the transformer. Put the resistor across the 9 volt secondaries, then after the bridge.
The reg board needs its own voltage for compliance. If it doesn't have that you won't be able to adjust it.
I figure we can go back and forth suggesting this that and the other and still not find it so this is just from my experience and hoping it might be helpful.
Checking the circuit Work in a linear sequence from one part to the next, don't take pot shots at different parts unless you have a good reason to suspect a certain part, it doesn't save you time. If you're an impatient temperament like me, it can seem like a waste of time but in the long run it's best to be linear, working along in one direction either from the output and subtract parts or from the input and add.
You can speed the process up by dividing in halves. Eg. roughly half the physical length is the board, and it's an easy place to break the circuit, so pull the board and put a load resistor across the output of the raw dc supply. If it sags there you know the trouble is in the supply. If not , you know it's the board. If its the dc supply then work back along its length toward the rectifier (or from the rectifier forward if it suits). You'll find it!
If it's the board, it will be more difficult without a schematic. You can go through it with a magnifier looking for shorts (a tiny bridge of solder between transistor pins etc. ) but if nothing visible then best to contact Rod again.
It often happens that there is more than one single problem, so if you end up fixing the supply and then discover it still doesn't work when you reconnect the board , don't let it bother you. Just trouble-shoot the board.
My 2¢. Hope it helps
I will go back to the very basic to measure one secondary at a time under load.
In other words, strip the whole circuit down to a power resistors across one secondary.
A couple observations,
Try to load one secondary with a 10R 20W resistor (it will be very hot) and measure the VAC across it. 10R should load a little lesser than 1A to the secondary. If the VAC looks reasonable, add another 10R in parallel and measure again.
If the measurement drops too much, then it is the regulation of the transformer under full load. You just need a bigger and better transformer.
If the measurement looks good, add the bridge (no cap input yet). Put the load on the DC side and measure again.
The whole idea is to take measurement after each increment circuit change to see where the symptom starts.
Hope this will help.
In other words, strip the whole circuit down to a power resistors across one secondary.
A couple observations,
if the circuit works, it draws close to 2.75A DC with a 4.7R load. 13VDC * 2.75A = 36W, your 10W load resistor is way way too small!! You need a much bigger one.
3A / 2 secondaries implies 1.5A. This is equivalent a full load on the AC side.
Try to load one secondary with a 10R 20W resistor (it will be very hot) and measure the VAC across it. 10R should load a little lesser than 1A to the secondary. If the VAC looks reasonable, add another 10R in parallel and measure again.
If the measurement drops too much, then it is the regulation of the transformer under full load. You just need a bigger and better transformer.
If the measurement looks good, add the bridge (no cap input yet). Put the load on the DC side and measure again.
The whole idea is to take measurement after each increment circuit change to see where the symptom starts.
Hope this will help.
On both secondaries:
With 8ohm 50W= 8,10V AC RMS
With an additional 8ohm 50W (4 ohm)= 5,70V AC RMS
With 8ohm 50W= 8,10V AC RMS
With an additional 8ohm 50W (4 ohm)= 5,70V AC RMS
From Post 39:
Voltage drop across 0.22 ohm resistors:
R2 (Positive Rail)= 121mV DC
R3 (Negative Rail)= -118mV DC
0.121Volts/0.22 Ohms = 0.55 Amps
Your circuit is only drawing 0.55 amps ?? Is your bridge wired correctly?
Voltage drop across 0.22 ohm resistors:
R2 (Positive Rail)= 121mV DC
R3 (Negative Rail)= -118mV DC
0.121Volts/0.22 Ohms = 0.55 Amps
Your circuit is only drawing 0.55 amps ?? Is your bridge wired correctly?
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