Anyone got schematics for this amp?
All the schematics I have, have the 3525 power supply chip.
It’s a bit hard tracing with the silk screen and then the bus bars over the smd components.
I got 8.92vdc occasionally on pin 16, sending the amp into protect and I’m trying to trace through the circuit.
All the schematics I have, have the 3525 power supply chip.
It’s a bit hard tracing with the silk screen and then the bus bars over the smd components.
I got 8.92vdc occasionally on pin 16, sending the amp into protect and I’m trying to trace through the circuit.
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Soundstream is hit and miss on it but they have supplied diagrams for some amplifiers. If you explain that there are no service centers where you are and it's impractical to ship the amp for service, that may help.
Arite,
No luck with soundstream. I ended up replacing the tl494 as I didn’t have the 5v ref and sawtooth.
Resistors around pin 16 on the 494 tested ok.
Amp goes into protect, output transistors tested ok without shorts, I dont have any DC at the outputs, I forced it on by shorting pins 15 and 16. Amp powered up and remains on, passes clean audio.
However when I power down and up again it goes into protect.
I found two suspected transistors and replaced them with to92 replacements until I get smd in, however amp still has 8.92v on pin 16.
I’m somewhat leaning towards the opto circuit but these I never know to be intermittent.
No luck with soundstream. I ended up replacing the tl494 as I didn’t have the 5v ref and sawtooth.
Resistors around pin 16 on the 494 tested ok.
Amp goes into protect, output transistors tested ok without shorts, I dont have any DC at the outputs, I forced it on by shorting pins 15 and 16. Amp powered up and remains on, passes clean audio.
However when I power down and up again it goes into protect.
I found two suspected transistors and replaced them with to92 replacements until I get smd in, however amp still has 8.92v on pin 16.
I’m somewhat leaning towards the opto circuit but these I never know to be intermittent.
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QA40 may be for over-current protection. Check it and the other transistors in the corresponding locations in the other channels.
If you remove them to check them, see if the amp will power up with it out of the circuit (pin 16, unshorted).
If you remove them to check them, see if the amp will power up with it out of the circuit (pin 16, unshorted).
I checked the q40** transistors, all check ok.
I powered up the amp removing one at a time and the amp came up in protect with 8v on pin 16 each time.
Funny thing about this amp, it came in with this momentary in and out of protection.
Whilst probing around the regulators the amp came out of protect.
I noticed one cap and regulator was a bit warm to touch, I replaced both caps (one each per regulator) and the amp powered up fine.
Switched it on multiple times and it came on ok.
I left it without power for the entire day today and tried powering again this afternoon, amp goes into protect again with 8v on pin 16.
I powered up the amp removing one at a time and the amp came up in protect with 8v on pin 16 each time.
Funny thing about this amp, it came in with this momentary in and out of protection.
Whilst probing around the regulators the amp came out of protect.
I noticed one cap and regulator was a bit warm to touch, I replaced both caps (one each per regulator) and the amp powered up fine.
Switched it on multiple times and it came on ok.
I left it without power for the entire day today and tried powering again this afternoon, amp goes into protect again with 8v on pin 16.
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Out of protect I have +/-15 off the opamps and on the regulators, +/-32v across the output transistors.
When the amp goes into protect, if you have a speaker on each channel, does any channel cause the speaker to pop?
I connected a speaker to channel 4 first and powered up, amp went into protect, no pop or other sound.
I repeated with channel 3, powered up, amp went into protect, no pop or other sound.
I switched to channel 2 when powered up, amp came on without protect.
Repeated with channel 1, amp powered up without protect, no pop or other sounds.
I repeated with channel 3, powered up, amp went into protect, no pop or other sound.
I switched to channel 2 when powered up, amp came on without protect.
Repeated with channel 1, amp powered up without protect, no pop or other sounds.
So, are you saying that when you have a speaker connected to channel 1 or 2, the amp works perfectly?
No,
The amp randomly goes into protect (less often) I’ved noticed it goes into protect after I leave it totally disconnected overnight. After a couple power ups in and out of protect it starts to power up normally and wouldn’t return to the protect mode unless I leave it disconnected for a lengthy period of time.
The amp randomly goes into protect (less often) I’ved noticed it goes into protect after I leave it totally disconnected overnight. After a couple power ups in and out of protect it starts to power up normally and wouldn’t return to the protect mode unless I leave it disconnected for a lengthy period of time.
Try discharging each individual cap after the amp is coming on normally to see if you can find one cap, when discharged, that makes the amp go into protect.
I checked all four caps in the OC circuitry (ca26....and its equivalents) discharging one at a time whilst powered on (out of protect). None of the four sent the amp into protect.
I pulled each capacitor and checked, only one was out of tolerance (it read 2uf, should be closer to 10uf)
I replaced all four with new.
I moved across to where the OC circuit runs into the 494 circuit, there was one cap cp17, if discharge it did nothing, amp remained powered, but if removed amp went into protect, this cap tested ok out of circuit but I replaced with new.
I pulled each capacitor and checked, only one was out of tolerance (it read 2uf, should be closer to 10uf)
I replaced all four with new.
I moved across to where the OC circuit runs into the 494 circuit, there was one cap cp17, if discharge it did nothing, amp remained powered, but if removed amp went into protect, this cap tested ok out of circuit but I replaced with new.
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You may have to do this (discharging) with every capacitor in the amp. You don't have to remove every one. Just short across it's terminals (confirm that it's at 0v) with the amp powered down, then power on.