Marantz SR5008 Protect Mode

[mmartell]

If I restart in Diagnostic Mode the error is ThermalProtB.

If I start in Protect Bypass mode the unit runs flawless until next power up then will go back into Thermal Protect since the anomaly has not been corrected.

If I measure the Thermal Detect B line coming from the Amp it measures identical to the Thermal Detect A line (about 1v). This makes me think the problem is not in the amp but in the way the B detect is handled.

I can't tell if the cpu is looking for active low or active high to shut the unit down. I'm attaching the SM, schematics and a screenie of the pin designations of the cpu.

Any pointers definitely appreciated here.

[R_J]

Re: Marantz SR5008 Protect Mode

1 volt does seem a bit odd, most of the detection appear to be supplied by the SWM3.3V
maybe a fault on the cpu level change board, page 24 of schematic?

[mmartell]

Re: Marantz SR5008 Protect Mode

Don't think so. The output of transistor Q3615 (D.Supply pg.27) which creates SWM3.3V reads 3.3v from power on until the unit kicks off into protection.

[R_J]

Re: Marantz SR5008 Protect Mode

Have you checked the TR_THERMAL line and the RADI_THERMAL lines coming from the amp board (page 25), I would expect that they would be the same voltage, the amp board uses 5 volts for the error transistors
The TR_THERMAL line changes into THERMALDETB line. It then goes to the cpu level change board and gets convertd to 3.3 volt logic. THER_PROTB, so maybe a fault with Q3212, or the digital transistors Q3213 or Q3215.
Then it uses a resister ladder circuit to tell the cpu which error is on the THERMALB_DC_ASC line, that would explain why its around 1 volt I guess.
Looks like THER_PROTB line would drop the 3.3 volts the most so I would think the THERMALB_DC_ASC line should be close to 3.3 volts withoutany error.

[mmartell]

Re: Marantz SR5008 Protect Mode

I think I misunderstood you. Yes the fault should either be one of those two circuits on page 24 or one of the four channels monitored by the detection circuit on the Amp board, pages ten and eleven.

How to proceed knowing this ?

[mmartell]

Re: Marantz SR5008 Protect Mode

Those are the lines in no-mans land, around 1v.

[mmartell]

Re: Marantz SR5008 Protect Mode

Right so the cpu is testing the voltage on that pin to discern which fault it has. I was wondering about that...

[R_J]

Re: Marantz SR5008 Protect Mode

Have you compared the THERMALB_DC_ASO line with the THERMAL_H/P_MIC line
I would guess if the THERMALB_DC_ASO line was about 2.5 volts, the error would be DC_PROT, or 2.0 volts, error would be ASC_PROT

[mmartell]

Re: Marantz SR5008 Protect Mode

I can't measure the circuits on page 24 when powered because the flex cable from the front panel covers that. I can run a jumper giving the cpu 3.3v and see if that allows the unit to power on without error.

But how can I tell if those circuits are actually functioning properly and the problem is on the amp board ?

[mmartell]

Re: Marantz SR5008 Protect Mode

Have you compaired the THERMALB_DC_ASC line with the THERMAL_H/P_MIC line

Yes. Those lines read the same. I have the pin pulled from the connector at the moment as I was considering jumping the relevant cpu pin to 3.3v

[mmartell]

Re: Marantz SR5008 Protect Mode

There doesn't seem to be any documentation on the levels of detect but this is from the SR7008. I don't know what it's saying but maybe it's relevant to SRx008 series ?

[R_J]

Re: Marantz SR5008 Protect Mode

I would think that with out any error transistors turned on there should be 3.3 volts supplied to the cpu via the pullup R3227, the same with the THER_PROTA line, It should be 3.3v via the pullup R3251
The CPU is looking an analog input on pin 133 so its not a high or low (0 or 3.3v)

cpu pin 133 or 134: A/D converter AN0 to AN15 Input pins for the analog signals to be processed by the A/D converter

[mmartell]

Re: Marantz SR5008 Protect Mode

I would think that with out any error transistors turned on there should be 3.3 volts supplied to the cpu via the pullup R3227, the same with the THER_PROTA line, It should be 3.3v via the pullup R3251
The CPU is looking an analog input on pin 133 so its not a high or low (0 or 3.3v)

Thanks for that explanation. That makes sense.

[mmartell]

Re: Marantz SR5008 Protect Mode

...so maybe a fault with Q3212, or the digital transistors Q3213 or Q3215.

Should removing Q3215 simulate a no fault condition ?

[R_J]

Re: Marantz SR5008 Protect Mode

It should, that's if the fault was caused on the THERMALDETB line

[mmartell]

Re: Marantz SR5008 Protect Mode

That's what worries me but I'm hoping it's one of those three transistors. Will remove it and see what happens.

[mmartell]

Re: Marantz SR5008 Protect Mode

I have not yet removed this transistor because the logic doesn't seem quite right, or maybe I'm over thinking it.

This troubleshooting flowchart from the SM indicates an error condition presents with a +0.6v or -0.6v on one of the detection pins. I measure 0.7v on both thermal pins when the unit is trying to start up before it goes into protection. At that point the voltage returns to zero when the led flashes red as it says. Isn't that to be expected ? Shouldn't I see the error voltage when the unit is trying to start ?

[R_J]

Re: Marantz SR5008 Protect Mode

I never did like flow charts, especially chinglish. It seems to say if you get +- .7 volts that is good, if its 0 there is a problem. Its obvious if the amp shuts down the voltage would go to 0
What about pulling CP4001? That should eliminate any error signal coming from the amp board.

[mmartell]

Re: Marantz SR5008 Protect Mode

I read it that +/- 0.6v is amp damage (DETECTION circuits detecting something) and 0v means the PROTECTION circuits or cpu itself have a problem.

Either way I cannot find a CP4001 so I'm not sure which connector they're referencing. I think it's just a means to let the unit power up without shutting down to check what faults were registered.

Question: Should the amp error detection circuits work unplugged from the rest of the circuit (the protection circuits) ? If that's the case and the amp is NOT the problem unplugging connector C404 should allow the unit to boot up fully but it still goes into protection.

[mmartell]

Re: Marantz SR5008 Protect Mode

By the way I measured 0.3v at R3227 (leads directly to cpu pin THERMALB_DC_ASO) during boot before protect kicks in.