put in a new rectifier and capacitor today, i've been running the amp for a little over an hour now and all is good
upon touching the diode now I noticed that it is really hot, but not uncomfortably hot.
i'm wondering if the heat being dissipated from the heatsink of the 5v regulator (U123) located right by the rectifier together with the heat from the power supply transformer also nearby is causing the rectifier to heat up too much?
the data sheet say the rectifier is good from -55 to 125 degrees celcius
upon touching the diode now I noticed that it is really hot, but not uncomfortably hot.
i'm wondering if the heat being dissipated from the heatsink of the 5v regulator (U123) located right by the rectifier together with the heat from the power supply transformer also nearby is causing the rectifier to heat up too much?
the data sheet say the rectifier is good from -55 to 125 degrees celcius
maybe its a good idea to get a bridge with a slightly higher ampere rateing....forget about the full operating temperature range... because for most components output is only 100% in a small band...
If you can hold your finger on it for any length of time it is probably doing fine... a very crude, but useful, rule of thumb. It does not apply to evrything though. Caps should never be "hot". Resistors can be hotter than hell.
🙂
🙂
But in time will burn the circuit board. 😱 😉
Hot components should be spaced off the board for improved cooling unless the board is designed as a heatsink with extra copper. Larger heatsinks on the regulators may help a lot, also a higher rated rectifier as Nordic mentioned. Sit the new one higher off the board if you can safely.
-Chris
So I replaced the bride rectifier and cap on August 27th with similar spec parts (low esr cap, 105 degree cap). All was well all this time and just today while watching family guy that all too familiar distortion resurfaces.
Soulds like a continous series of clicks, pops and crackles.
So I'm guessing the problem must be starting elsewhere around the circuit board as it has cooked the cap and rectifier for a second time.
Anybody have any ideas or insights about where to start looking?
Soulds like a continous series of clicks, pops and crackles.
So I'm guessing the problem must be starting elsewhere around the circuit board as it has cooked the cap and rectifier for a second time.
Anybody have any ideas or insights about where to start looking?
Hi Dis, ....sorry to hear about the failure. The load that the rectifier and cap are feeding might be bad. ...but the regulator is hanging in there, eh?
With the power off, perform a resistance check across that Hi-temp filter. Not so much to measure the cap, but in order to measure the load that the cap "see's". You should just see the cap charging up. This will look on the meter as if the resistance is climbing. If the resistnace stay's at something low like 10 ohms, look for a small poly cap paralleled with the big filter. It is possible that a low resistance load might be causing excessive ripple, perhaps causing too much heating in the cap. ...It's a reach. Another place to check for a low resistance load is after the regulator. If it's a positive regulator (sounds like +5V) in a TO-220 package, measure pin 3 to ground. You should see a charge up to a high resistance there too.
With the power off, perform a resistance check across that Hi-temp filter. Not so much to measure the cap, but in order to measure the load that the cap "see's". You should just see the cap charging up. This will look on the meter as if the resistance is climbing. If the resistnace stay's at something low like 10 ohms, look for a small poly cap paralleled with the big filter. It is possible that a low resistance load might be causing excessive ripple, perhaps causing too much heating in the cap. ...It's a reach. Another place to check for a low resistance load is after the regulator. If it's a positive regulator (sounds like +5V) in a TO-220 package, measure pin 3 to ground. You should see a charge up to a high resistance there too.
Hi dis,
There must be something going on in the amplifier stages. Check the bias currents. All that current has to be going somewhere.
-Chris
There must be something going on in the amplifier stages. Check the bias currents. All that current has to be going somewhere.
-Chris
Hi mrshow4u,
That may be so, I didn't re read the entire thread. Thanks.
I would be looking for something that draws excessive current. Possibly a defective decoupling cap (I've seen ceramics shorting). A properly designed supply should not be running that hot. It sounds like the cap may be dying from excessive ripple current.
-Chris
That may be so, I didn't re read the entire thread. Thanks.
I would be looking for something that draws excessive current. Possibly a defective decoupling cap (I've seen ceramics shorting). A properly designed supply should not be running that hot. It sounds like the cap may be dying from excessive ripple current.
-Chris
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