Pioneer VSX-D908S micro processor question.

This Pioneer VSX-D908S analog/digital receiver will not pass any audio as long as the dsp board is plugged into the unit.

First I'll explain what works with this set. With the dsp board removed, all analog input functions work as long as you select the direct mode. The direct mode bypasses the digital board completely. For example, if you've selected CD direct (analog) for the source, there is an electronic mode switch, located on the main control board, which selects between dsp, direct, or 5.1. This switch will select the direct mode correctly and pass the audio signal. What doesn't work is if you plug in the dsp board, the audio does not pass through the same analog/digital mode selector on the main control board even in direct (analog) mode. The dsp board is quite complex but there is a uP there that communicates with the control board's uP. Now here's where I have, hopefully, an easy question. Two of the pins on the uP of the dsp board are labeled Xin and Xout and they have no signal. On the uP of the control board, there is good signal at the uP on the Xin and Xout terminals. Can I generalize that any uP that has two terminals labeled Xin and Xout should have a continuous running clock signal on these two terminals? Also, would the uP itself be the most likely failure to cause this symptom? By the way, I spent a fair amount of time removing all the boards and soldering numerous bad connections.

Thanks for your reply.

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David Farber
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David Farber
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Something on the DSP board is locking up the I2C data bus lines. Pretty common problem during storm season on similar Pioneer models a several years ago. Had my own DSP ic fail in this way. $35 flat pack ic fixed it.

David

David Farber wrote:

Reply to
dkuhajda

Xin and Xout are usually the terminals that connect the internal clock generator to the external clock crystal, and you would normally expect to see a continuous clock signal on at least one of them, but note that you need to be using a x10 ( low capacitance ) probe on your scope to have any hope of seeing a signal ( mostly ). On some clock generators, notably one that runs a DSP chip in a Sony HC system, as soon as you come near the xtal with even a low capacitance probe, the oscillator stops, never to restart until you depower then repower to produce a reset to the DSP chip, so the upshot of all this is that your DSP oscillator may possibly be running, and nothing to do with the fault, and stops when you try to scope it. A better indication may be if there is any activity on any of the other pins. However this also does not give any certain proof of clock activity, as you may be seeing shared-bus activity, originating elsewhere.

You may yet have xtal trouble though, particularly if it is a surface mount genuine crystal, rather than a ceramic resonator, which tend to be more robust and reliable. I have had a number of these xtals fail in a variety of products. Sometimes, they are just reluctant to start up, and just removing the xtal, and soldering it back in the other way about, is enough to get them going. If the problem genuinely is clock related, then it is far more likely to be the xtal, than the chip. If it has been subject to storm activity though, then the chip becomes more likely, as suggested by the other poster.

Arfa

Reply to
Arfa Daily

That's about as an encouraging a response as I could have hoped for. I'll order the uP and expect a full recovery.

Regards.

-- David Farber David Farber's Service Center L.A., CA

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Reply to
David Farber

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I do use a x10 low capacity probe. I have tried to touch up the soldering around the xtal (it's a ceramic resonator type if I'm not mistaken) but it made no difference. I'm going to try the uP replacement and I'll report back, successful or not.

Thanks for your reply.

-- David Farber David Farber's Service Center L.A., CA

Reply to
David Farber

I think I remember these units, it's not the micro or DSP, it's the EEPROM. IC9374 I believe. Pain in the butt to solder in, very fine lead spacing even for a SMD. There was a problem with that unit, the EEPROM types were changed, I can't remember if they went from FLASH to MASK type or the other way around, but changing it usually fixed the problem. In some lucky cases you could just resolder IC9374. If you get the newer type EEPROM there are 2 jumpers (Zero ohm surface mt resistors) that have to be moved for the new type to work, unless this unit has been repaired before.

Hope this helps.

Jammy

Reply to
ampdoc

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Hi Jammy,

I was tipped off to the resoldering fix to the EEPROM on a previous repair of a Pioneer receiver and that's why that was the first thing I attempted. So the question remains that if the EEPROM is defective, would that disable the clock to the uP? Now I'm wondering about David Kuhajda's reply saying he replaced his DSP IC whether he was talking about the uP or the EEPROM.

Thanks for your reply.

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David Farber
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David Farber

I believe you are thinking of the VSX-24, 26, 27 etc models. Different model entirely.

Mark Z.

Reply to
Mark D. Zacharias

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Hi Mark,

The VSX-D908S *does* have that IC9374 EEPROM with the fine lead spacing. Unless you meant that the VSX-D908S didn't have a common failure of the EEPROM whereas the VSX-24, 26, and 27 did. My question remains whether this could be causing the uP to have problems.

Thanks for your reply.

--
David Farber
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David Farber

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I telephoned Pioneer tech assistance for their suggestion. I was told that

95% of the time replacing IC9374 will correct the problem. I replaced it and it didn't fix the problem. So then I replaced the uP and that did fix it. As usual, David Kuhajda was right on target with his advice.
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David Farber
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David Farber

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