Need help guys, does anyone know this circuitry or have any info on this amp so I can replace the missing parts?
I don't have your answer, but I do have some advice.
When you find the right parts to replace the dead ones with, you really ought to have a think about what caused them to fail in the first place.
Diodes and resistors do not (generally) spontaneously combust - I am not being cheeky here...
Diodes and resistors are really very reliable parts. Resistors almost always fail open circuit (and not catch on fire). Diodes are just super reliable except where abused.
Both diodes and resistors generally fail when something else has failed and is drawing too much current. Capacitors and big semi's being common culprits. Before you swap these out, it would be instructive to get a hold of the schematic, which by the way will answer your initial question, and look around for what else might be at fault in there.
When you find the right parts to replace the dead ones with, you really ought to have a think about what caused them to fail in the first place.
Diodes and resistors do not (generally) spontaneously combust - I am not being cheeky here...
Diodes and resistors are really very reliable parts. Resistors almost always fail open circuit (and not catch on fire). Diodes are just super reliable except where abused.
Both diodes and resistors generally fail when something else has failed and is drawing too much current. Capacitors and big semi's being common culprits. Before you swap these out, it would be instructive to get a hold of the schematic, which by the way will answer your initial question, and look around for what else might be at fault in there.
The resistors are 6.8k. The diode is a 12v Zener (PTZ12B - check dimensions).
http://www.mouser.com/ds/2/348/ptz12b-220154.pdf
http://www.mouser.com/ds/2/348/ptz12b-220154.pdf
Ive replaced the parts that was missing, i didnt replaced the zener diode as it checked off good, the amp is playing but only with minimal gain, when i adjust the gain control knob it cuts off to protection and wont resume until i minimise the gain knob fully. There is nothing been overheated and no DC volts on the output. i even bypass the audio input opamp board and put audio to the input pin on the main amp board and still chips to protection only plays with limited or low attenuation. is there any possibly suspects or pin test that can used to temporary disable the protection circuit?
Post the DC voltage on all terminals of U231. Place the black probe on pin 4 when measuring the voltage.
1. 12.10
2. 0.00
3. 0.35
4. Ref
5. 6.09
6. 11.95
7. 0.07
8. 12.24
I've changed that ic before you requested the volts specs but it's the same problem I've also replaced U02 (LM339)
2. 0.00
3. 0.35
4. Ref
5. 6.09
6. 11.95
7. 0.07
8. 12.24
I've changed that ic before you requested the volts specs but it's the same problem I've also replaced U02 (LM339)
Those look OK.
Removing Q232 will defeat the over-current protection circuit. Bear in mind that if there is a legitimate over-current fault, defeating the protection circuit could cause the amp to be damaged.
Removing Q232 will defeat the over-current protection circuit. Bear in mind that if there is a legitimate over-current fault, defeating the protection circuit could cause the amp to be damaged.
With that transistor removed it’s still going in protection when by turning up the gain. Nothing is overheating. Is there any way to totally override the protection circuit?
It plays as expected when removed the Q04, Played it for minutes even without the heat sink at 50% gain adj and it seems efficient and stable.
However, what could be causing it to protect with such minute sensitivity? The collector of Q04 goes thru R09 (4.7ohms) to the DTC pin on the 494chip, if increasing the value of the resistor will that decrease the sensitivity?
However, what could be causing it to protect with such minute sensitivity? The collector of Q04 goes thru R09 (4.7ohms) to the DTC pin on the 494chip, if increasing the value of the resistor will that decrease the sensitivity?
1. 0.05
2. 0.06
3. 13.09
4. 4.97
5. 3.94
6. 7.19
7. 4.97
8. 3.64
9. 1.59
10. 0.82
11. 0.00
12. 0.00
13. 0.00
14. 0.04
I had replaced that ic from earlier post, it didn’t changed the way the amp behaves in terms of the protection sensitivity.
2. 0.06
3. 13.09
4. 4.97
5. 3.94
6. 7.19
7. 4.97
8. 3.64
9. 1.59
10. 0.82
11. 0.00
12. 0.00
13. 0.00
14. 0.04
I had replaced that ic from earlier post, it didn’t changed the way the amp behaves in terms of the protection sensitivity.
I was looking for some voltage that was well off of what it should be (could be due to an input). I don't see a problem. Reinstall Q04. One at a time, lift D15 and D16. Which of the two, when lifted, eliminates the problem?
What section of the amp I find D15 and D16? The closest I’ve seen is D13 and D14 which I think is the two coupling diodes on the gate drive circuit for the power supply mosfets. I don’t know if those that you ask is under the silicone glue which is holding the toroidal PS transformer.
Attachments
Sorry about that I was more searching for a traditional diode package instead of going thru the legends.
With D16 removed it plays as expected, with D15 removed (one at a time was carried out) it triggered protection.
With D16 removed it plays as expected, with D15 removed (one at a time was carried out) it triggered protection.
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