These was placed like this over D304 silkscreened on circuit board. Not soldered together overheating for 20 years and corroded through. Amplifier is simaudio moon i5. Can’t find schematic online.
They seem to be resistors but I can’t find values according to color strips.
They seem to be resistors but I can’t find values according to color strips.
Did you contact the manufacturer? I believe they are in Quebec, Canada. Some manufacturers are helpful.
Simaudio Ltd.
1345 Newton Rd.
Boucherville, Quebec, J4B 5H2
CANADA
T. 450 449-2212
Simaudio Ltd.
1345 Newton Rd.
Boucherville, Quebec, J4B 5H2
CANADA
T. 450 449-2212
Does the amp work, in other words are resistors actually 'ok'?
Those are metal oxide resistors and suited for high temperature use but colours can fade and change/discolour with heat.
They look as if they might feed a regulator??? U403.
What is U403?
Have you measured the combined value of the resistors? You will need to scrape them to get a reading.
Those are metal oxide resistors and suited for high temperature use but colours can fade and change/discolour with heat.
They look as if they might feed a regulator??? U403.
What is U403?
Have you measured the combined value of the resistors? You will need to scrape them to get a reading.
One measured 412 another 440 ohm. But color stripes make no sense unless carbon film resistors drifted out of specs.
Amp currently doesn’t work. Resistors fell off. One measured 412 another 440 ohm. Colors surely faded and make no sense. It looks like they feed a regulator Indeed.
The diode may be a reverse polarity diode across the regulator for protection.
Then the parallel resistors could be an attempt to shunt some current around the regulator to reduce its power dissipation.
So the circuit might still work without the resistors, but the regulator could get too hot. Check its operation.
Then the parallel resistors could be an attempt to shunt some current around the regulator to reduce its power dissipation.
So the circuit might still work without the resistors, but the regulator could get too hot. Check its operation.
I would begin by refitting them and looking at the voltage going into the resistors and the voltage applied to the regulator. What is the regulator type number?
It is possible there is a regulator fault or a short on its output that is burning those up. The values actually sound reasonable for a series feed resistor to a low current regulator supply so I suspect they may actually be 'ok' and that some fault is frying them. Voltage checks with them in place will help faultfinding.
Metal oxide resistors are super rugged but do discolour and they also can change value a bit under overload and even go low in value. You have to begin somewhere though. Identify the reg and look at voltages in the faulty state, even if the resistors are burning.
I was able to solder ends and measure two resistors in parallel. 213 ohm. Regulator should be ok as amplifier was working prior to these fell off.
You need to check it all and make sure. They should not run hot enough to burn the board (and themselves) in the way they have done.
You have to do measurements to make sense of it all. We still don't know what the regulator or its output voltage is. You have to look at that.
With the resistors fitted and the amp working you need to measure these things:
1/ The voltage on the input side of the resistor.
2/ The voltage on the output side of the resistor that feeds the reg.
3/ The voltage coming out of the reg.
4/ What the device number of the reg is.
5/ Is the reg running very hot?
You also need to change that electrolytic cap that looks frazzled next to the resistor.
You have to do measurements to make sense of it all. We still don't know what the regulator or its output voltage is. You have to look at that.
With the resistors fitted and the amp working you need to measure these things:
1/ The voltage on the input side of the resistor.
2/ The voltage on the output side of the resistor that feeds the reg.
3/ The voltage coming out of the reg.
4/ What the device number of the reg is.
5/ Is the reg running very hot?
You also need to change that electrolytic cap that looks frazzled next to the resistor.
+1. There's also what looks like heat discoloration over on the left where those 2 diodes are, by the red wire. That doesn't look right to me.
jeff
