Peavey Triflex II assistance needed

[Michael27]

Good day

I have a Peavey Triflex II. Complaint is that the amplifier powers on with the power-peak LED illuminated red. It suppose to switch to Green to indicate everything is okay. When a XLR signal is applied I am getting audio from the satellite speakers and bass bin. The Power-peak Led then illuminates Green. BUT, the bass Cutts off while the satellite speakers still plays.

Tda8954th has been replaced on both channels. Kind of sus.

Has anyone experienced this type of issue?

Thanks in advance.

[The Dude]

Schematic?

[Michael27]

None sadly !

[Enzo]

Have we experienced an amp failing to drive a speaker? Yes, thousands of times. Your woofer amp is not driving the woofer, but the high freq amp is driving the highs.

So maybe the woofer amp has failed, maybe the crossover is not feeding signal to that amp.

[Michael27]

Yes, but the woofer cutting out sounds like a DC offset from the amplifier. When volume is lowered there's no cutting out.

[Enzo]

Maybe, but all manner of things can cause a loss of signal.

[J M Fahey]

Just thinking aloud:
* as suggested above, check for DC at output.

* also find power amp input , scope it to see whether any signal reaches it or not.

* kludge an audio cable, one end matching board Audio in, the other an RCA or miniplug and feed audio straight to power amp, what happens?

* write Peavey, in general (at least inside USA) they positively answer schematic requests, include serial number just in case.
That said, "maybe" local ZA Peavey distributor has some "exclusive rights agreement" so as to *force* you to go trough them, it has happened other times.

* probably you already did that, in general with Class D being a new and complex technology, most manufacturers tend to follow the datasheet application, so use it to troubleshoot/test/check "as if" it were a generic Tda8954 circuit.
Check proper supply voltages reach it, DC at speaker out pins, that Audio reaches it.

* there are 2 "diagnostic pins" , not sure what should be read there or what they connect to, but maybe you find another amp using Tda8954 and compare it to what you have. ANY amp: PA/DJ/Subwoofer/Bass Guitar/you-name-it

* in a way, this is an "easy" amp to repair , practically no external components used, just a few compensation/bypass capacitors and 2 resistors for Mute and Standby, so "replacing the chip should solve the problem", period.

Of course, as long as chip receives proper supply, signal, load is not shorted, etc. , all "external" problems you should check.

Check all this and report.

]PS: where did you buy the replacements? Hope not in EBay,Alibaba, etc. but a serious supplier.
Also check they were properly seated, soldered, attached to heatsink, etc.

For reference on dubious suppliers:
https://community.nxp.com/t5/NFC/TDA...em/td-p/858083

I have a problem with the TDA8954TH amplifier, after connecting the power supply, I burn the R2 resistor and DC appears on both outputs.

I tested on 7 IC, pcb checked several times for assembly errors.

Power supply +/- 40V

Integrated circuits ordered on ebay from china in August 2017. I suspect TDA8954 fakes. This offer is no longer available on eBay, but the title was:

10PCS TDA8954TH Encapsulation: HSOP24,2X150W class-D power amplifier # Q1186 ZX

[Michael27]

Just thinking aloud:
* as suggested above, check for DC at output.

* also find power amp input , scope it to see whether any signal reaches it or not.

* kludge an audio cable, one end matching board Audio in, the other an RCA or miniplug and feed audio straight to power amp, what happens?

* write Peavey, in general (at least inside USA) they positively answer schematic requests, include serial number just in case.
That said, "maybe" local ZA Peavey distributor has some "exclusive rights agreement" so as to *force* you to go trough them, it has happened other times.

* probably you already did that, in general with Class D being a new and complex technology, most manufacturers tend to follow the datasheet application, so use it to troubleshoot/test/check "as if" it were a generic Tda8954 circuit.
Check proper supply voltages reach it, DC at speaker out pins, that Audio reaches it.

* there are 2 "diagnostic pins" , not sure what should be read there or what they connect to, but maybe you find another amp using Tda8954 and compare it to what you have. ANY amp: PA/DJ/Subwoofer/Bass Guitar/you-name-it

* in a way, this is an "easy" amp to repair , practically no external components used, just a few compensation/bypass capacitors and 2 resistors for Mute and Standby, so "replacing the chip should solve the problem", period.

Of course, as long as chip receives proper supply, signal, load is not shorted, etc. , all "external" problems you should check.

Check all this and report.

]PS: where did you buy the replacements? Hope not in EBay,Alibaba, etc. but a serious supplier.
Also check they were properly seated, soldered, attached to heatsink, etc.

For reference on dubious suppliers:
https://community.nxp.com/t5/NFC/TDA...em/td-p/858083

Hi thank you for your reply. I've purchased the chip from Rs components. I've tried 4 with no luck. The speaker plays fine on a low volume once I pick up over 12 o'clock volume control starts making a cutting of sound as if DC is passing.

[dmeek]

It could be a problem with the speaker itself. Try the woofer with a different amp. More than once I have seen speakers cut out at high volume because of an intermittent connection at the coil.

[Michael27]

It could be a problem with the speaker itself. Try the woofer with a different amp. More than once I have seen speakers cut out at high volume because of an intermittent connection at the coil.

I've tried the amplifier on a different speaker already.