| Solosound |
I have been trying to repair this amplifier since 3 months.
It has been a headache!!
All the internal parts apear be fine.
The problem is:
It ignites of intermittent way.
turn´s on 15 seconds and turn´s of 5 seconds, turn´s on 15 seconds and turn´s of 5 seconds, etc.
Please help me before I take and...:smash:
This is the pic:
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| Perry Babin |
During the time that it's on, does it produce clean audio in both channels?
Is there excessive DC offset on either channel?
Does either channel have any oscillation on the output?
Does the cycle of on/off change when you change the position of any of the switches/potentiometers? |
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| Solosound |
| quote: | Originally posted by Perry Babin
During the time that it's on, does it produce clean audio in both channels?
Is there excessive DC offset on either channel?
Does either channel have any oscillation on the output?
Does the cycle of on/off change when you change the position of any of the switches/potentiometers? |
The amp produce clean audio in two channels and bridget, before shot down.
whitout signal:
without remote, the amp present 0.62 v DC in the outputs.
Whith remote, 0.006 V DC in the otputs
No changes, when I move switches and potentiometers. |
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| Solosound |
I found other measurements rare in the power source:
They are without remote, only positive and negative applied |
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| Perry Babin |
Without remote, those voltages are normal. If you apply remote, the voltage on pin 1 of the FETs will go to ~3-5v. The voltage on the rectifiers will probably go to approximately ±35v.
How many amps of current does the amplifier draw at idle (remote voltage applied, no audio).
Does it shut down with no speakers connected?
Are any of the indicators LEDs lighting except for the power LED?
Does the power LED go off when the amp shuts down?
What are you using to power the amp? |
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| Solosound |
| quote: | Originally posted by Perry Babin
Without remote, those voltages are normal. If you apply remote, the voltage on pin 1 of the FETs will go to ~3-5v. The voltage on the rectifiers will probably go to approximately ±35v.
How many amps of current does the amplifier draw at idle (remote voltage applied, no audio).
Does it shut down with no speakers connected?
Are any of the indicators LEDs lighting except for the power LED?
Does the power LED go off when the amp shuts down?
What are you using to power the amp? |
The voltage on the diodes go 44 and -44 !!!!!!
4 amp current when apply remote.
Shut down only with speaker connected and at high vol.
Only the green led is turn on, and is always present.
I’m using one 12.5 v regulated power source (ASTRON) 1 - 25 A.
Today happen something different.
[img=http://img61.imageshack.us/img61/6824/dsc00944dw4.jpg]
[img=http://img61.imageshack.us/img61/6824/dsc00944dw4.b484ea5d27.jpg]
two resistors was burn, R300 and R301
¿this gives a track to find where is the problem? |
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| Perry Babin |
The voltage on the diodes go 44 and -44 !!!!!!
**** That's good. The board says the rail voltage should be 53v but its producing rail voltage so the power supply is probably OK.
4 amp current when apply remote.
**** That seem a bit high but could be due to the bias current being set too high.
Shut down only with speaker connected and at high vol.
**** This could be due to the 25 amp Astron power supply being insufficient to power the amp at high output power. When you get the amp working again, try running one channel at a time to see if the amp shuts off. If it plays at high power with 'either' channel and only shuts down when both channels are running at high power, the amp may be working properly and is simply shutting down due to low voltage.
Today happen something different.
**** If I'm not mistaken, those are (were) 10 ohm resistors. They are used extensively to provide protection for the regulated ±15v power supply. The caps provide additional filtering near the op-amps. I don't know why they would have failed. It's not likely to be part of the original problem. Is it possible that you didn't have the preamp boards plugged in correctly to the main board? You have to be careful connecting them. You need to replace them to see if they burn again. If they do, you may have a defective op-amp in that area. |
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| Solosound |
| quote: | Originally posted by Perry Babin
The voltage on the diodes go 44 and -44 !!!!!!
**** That's good. The board says the rail voltage should be 53v but its producing rail voltage so the power supply is probably OK.
4 amp current when apply remote.
**** That seem a bit high but could be due to the bias current being set too high.
Shut down only with speaker connected and at high vol.
**** This could be due to the 25 amp Astron power supply being insufficient to power the amp at high output power. When you get the amp working again, try running one channel at a time to see if the amp shuts off. If it plays at high power with 'either' channel and only shuts down when both channels are running at high power, the amp may be working properly and is simply shutting down due to low voltage.
Today happen something different.
**** If I'm not mistaken, those are (were) 10 ohm resistors. They are used extensively to provide protection for the regulated ±15v power supply. The caps provide additional filtering near the op-amps. I don't know why they would have failed. It's not likely to be part of the original problem. Is it possible that you didn't have the preamp boards plugged in correctly to the main board? You have to be careful connecting them. You need to replace them to see if they burn again. If they do, you may have a defective op-amp in that area. |
The power supply is rigt for run the amp.
They shut down when is current only 6 A.
I change the resistors and the power suply is fine, + - 53V.
The voltage in the traks marked + /- 15 are +/ - 17V.
I have scope, if you see some more. |
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| Perry Babin |
Does the amp shut down if you run one channel at a time? There may be a problem with only one channel so this is something you need to check.
Did the resistors burn again after you replaced them?
±17 is OK. |
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| Solosound |
| quote: | Originally posted by Perry Babin
Does the amp shut down if you run one channel at a time? There may be a problem with only one channel so this is something you need to check.
Did the resistors burn again after you replaced them?
±17 is OK. |
Now the amp shut down whit out speakers, or signal.
The resistors are fine after change; I find one broken cap too. I need to change. (I will change the two). |
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| Solosound |
Just for be sure...
Some one has the right values for Q510 and Q500?
Thanks |
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| Perry Babin |
I don't have information for the 300/2 but in the 300/4, Q500 is one of the power supply FETs. The power supply FETs in most of this series of amps is an IRFZ44.
In the 300/4 Q510 is an IRFZ34. If your amp uses the 3843B to drive Q510, it's likely an IRFZ34. An IRFZ44 would also work in that location.
If you have a scope, monitor the voltage on pin 20 of the audio driver board (looking at component side of driver board, it's the last pin on the right). If it's not very near 0v on one channel or you see a short pulse on one channel, you need to determine why it's going high. |
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| Solosound |
| quote: | Originally posted by Perry Babin
I don't have information for the 300/2 but in the 300/4, Q500 is one of the power supply FETs. The power supply FETs in most of this series of amps is an IRFZ44.
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On this amp, all the power supply fets are FQP65N06, too Q510 are FQP65N06.
Always in all slash I have see the IRFZ44, this is the reason for my question.
300/2 PCB 100009
REV 1 9/22/00 |
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| Solosound |
After few days, I will follow:
The intermittent shut down is finish. They shut down only if the volume is high.
The amp works, clean audio, but the current is 4.5 Amp.
The pin 20 it’s OK. Thanks Perry
R513 and Q510 are very hot (I quit for measure, and they are ok.) |
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| Perry Babin |
Did you try adjusting the bias to reduce the current draw?
How is R513 being used?
There are probably several 4.7 ohm resistors near the filter capacitors for the small yellow transformer. Are any of them getting hot? |
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| Solosound |
the 4 resistors (4R7) are good and none hot when working.
R513 is 33 ohm, and it´s fine too. |
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| Perry Babin |
Is the diode in parallel with the 33 ohm resistor OK? You'll have to pull one end to check it.
Does the yellow transformer look like it's overheated (windings showing through the yellow tape)?
Do the waveforms look similar to these?
http://www.bcae1.com/temp/jl500slas...transformer.swf |
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| Solosound |
The diode in parallel it’s fine. Another near diodes is fine too.
The transformer not show visible overheat
When disconnect remote, The amp still turn on 5 seconds more.
In the same order:
Scope is setting to 5us, 5V.
Pin1
Pin2
Pin3
Pin4
Pin5
Pin6
Pin7
Pin8
Pin9
Pin10
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| Perry Babin |
Is the vertical amplifier set to 5v/div for all waveforms?
If the vertical amplifier setting for pins 1 and 10 is the same, it appears that the transformer may be defective. Pin 10 should have DC (approximately the same as the B+ input). |
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| Solosound |
After few months, I can bought one working condition yellow transformer.
Now the amp never shout down, but is current 4 Amp!!!!
Q510 is too hot, its a FQP65N6.
¿Any idea? |
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| Perry Babin |
I don't have a 300/2 here but the 500/1 I have here has a very similar circuit and the FET (IRFZ44) runs cool. Measure the voltage across the 33 ohm resistor near the transformer. This amp has 3v DC across the 33 ohm resistor. Yours should have something similar. If it's significantly more, there may be a problem.
If you have a scope, measure the peak voltage of the gate drive signal on Q510. If I'm not mistaken, your amp uses the 3843 driver IC. If so, you should see a drive signal of ~10v peak.
The 4 amps of current draw could be from the biasing of the audio amplifiers. Before you try adjusting them, measure the DC voltage across the test points. Be careful not to allow the probes to contact the busbars. |
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