997.2 PCM Audio stopped
06-14-2020, 12:24 PM
#61
RL Community Team
Rennlist Member
Rennlist Member
Thanks Larry & Bruce. I was going to open it back up today to get the specs off the parts to order them. This is right up my alley as I have access to everything to rework such a simple board. Since these are dumb components I don’t have to worry about any programmable chips. I love doing this kind of stuff as I do it each day at work and I love my job. More to come.
Due to my car being sidelined from wheel damage and blow out, I have not tried out my new thermal paste mod...... I will wait for you to lead the pack on the soldering job and find out if that paste had any affect.
Peace
Bruce in Philly
06-14-2020, 01:18 PM
#62
Three Wheelin'
I am going to open it back up today and get all the SMT (surface mount technology) and through hole dimensions so I can do one big digikey order. This will be fun. In a warped engineering way.
I will not replace everything at once as I want to figure out which parts failed so it will help someone else down the line.
I will not replace everything at once as I want to figure out which parts failed so it will help someone else down the line.
06-14-2020, 02:36 PM
#63
Rennlist Member
Okay here is another datapoint. 3 hour trip to Dallas in 94 degree heat. Radio was fine until I turned the car off to gas up. Turned it back on and no highs. I checked and the fan that I know works was not spinning. It has been about an hour with the radio on but volume low. Still didn’t kick back on. I am going to shut the radio off for awhile and see if it comes back on after awhile. Amp didn’t feel warmer than normal.
Update: After about 15 minutes with the radio off, blank screen. I turned it back on and all is fine now.
Update: After about 15 minutes with the radio off, blank screen. I turned it back on and all is fine now.
06-14-2020, 04:08 PM
#64
Racer
If the fan wasn't spinning, do you know if the PCM told the amp to switch on? There is usually a remote power on signal connected to the source. Main power is generally connected to continuous power through a fuse and the amp is powered on via separate switched 12v signal. This could still be the PCM.
When I traced this all out, the Bose amp has continuous power. There is no "remote turn on" wire. The command to power on comes only from the optical cable. You can prove this out with a MOST converter (audio to optical). Just use an optical jumper straight to the amp and as soon as the optical thing comes to life, the amp turns on.
The subwoofer audio is filtered from the optical digital audio by the DSP and microprocessor built into the amp. The amp sends the analog signal and the subwoofer turn-on signal all from the DSP section of the Bose amp. If you get subwoofer audio, then you know the PCM head is telling the amp to turn on, and the DSP in the Bose is happily producing digital audio because it has turned on the Subwoofer and is now sending it the subwoofer audio in analog form, through the same D-A converters that send signal to the amplifiers in the amp chassis. The amp's brain in other words, thinks everything is working.
So - the troubleshooting theory would say, "what's the common thing between all 10 speaker amp channels?" Well, that's easy. The DC-DC booster in the amp that powers the 5 Class-D amp chips. (each has two channels).
A very common failure point in things of this age are the electrolytic capacitors.
It's a good guess anyway.
06-14-2020, 04:43 PM
#65
Three Wheelin'
If the fan wasn't spinning, do you know if the PCM told the amp to switch on? There is usually a remote power on signal connected to the source. Main power is generally connected to continuous power through a fuse and the amp is powered on via separate switched 12v signal. This could still be the PCM.
Update: I pulled the amp out of the car yesterday and took a bunch of pictures of the components and lots of physical measurements so I will make a list of exact parts I will systematically replace. This will be fun. No sarcasm there. It will be.
I probably will start a new thread so this issue can be found a little easier.
Last edited by doclouie; 06-15-2020 at 10:23 AM.
06-18-2020, 09:07 PM
#66
RL Community Team
Rennlist Member
Rennlist Member
Update: I took a bunch of trips.... 50 mnts out and back.... turnpike... higher speeds. Cranking a bunch of Jethro Tull classics remastered in 5.1.... fabulous Steven Wilson remixes.....
No cutouts. None. Ran hard, listened loudly... stopped for gas... turned right back on. Wow.
No, we can't conclude anything yet... but I have not had a cutout since I took larrysb's suggestion and added some thermal paste on the backs of the amp chips.
Stay tuned....
Peace
Bruce in Philly
No cutouts. None. Ran hard, listened loudly... stopped for gas... turned right back on. Wow.
No, we can't conclude anything yet... but I have not had a cutout since I took larrysb's suggestion and added some thermal paste on the backs of the amp chips.
Stay tuned....
Peace
Bruce in Philly
06-18-2020, 09:42 PM
#67
Sorry Bruce ... Android app mixes up posts between people, repeats posts, and drops posts. I'm assuming you put thermal paste on some of the components. I'm not getting this from my phone. Pics and details?
06-18-2020, 10:03 PM
#68
Three Wheelin'
The new capacitors are coming on Saturday. I may run into work and solder them on the board. Glad you haven't had any issues Bruce. Mine cut out after the paste, but I am down in Texas and we are in the 100's now.
06-18-2020, 10:12 PM
#69
RL Community Team
Rennlist Member
Rennlist Member
Wayne, yes, see earlier posts... I didn't post pics, others did of the same thing where the paste goes etc.... All I did was pull the unit, check the fan - it works with a 9V battery - and added the paste to the other side of the chips. That was it. Seems to be working... but I have declared success many times before only to be fooled.
doclouie....... I can't wait... keep going!
Peace
Bruce in Philly
doclouie....... I can't wait... keep going!
Peace
Bruce in Philly
06-18-2020, 10:27 PM
#70
RL Community Team
Rennlist Member
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Bruce,
That's potentially great news for a lot of PCM owners if this is the common failure cause and correction.
That's potentially great news for a lot of PCM owners if this is the common failure cause and correction.
06-18-2020, 10:31 PM
#71
Three Wheelin'
Wayne, yes, see earlier posts... I didn't post pics, others did of the same thing where the paste goes etc.... All I did was pull the unit, check the fan - it works with a 9V battery - and added the paste to the other side of the chips. That was it. Seems to be working... but I have declared success many times before only to be fooled.
doclouie....... I can't wait... keep going!
Peace
Bruce in Philly
doclouie....... I can't wait... keep going!
Peace
Bruce in Philly
06-18-2020, 10:32 PM
#72
RL Community Team
Rennlist Member
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Woa now..... I've declared success before I even left the bar with her many times only to end up with beer in my face. Happened..... happened over and over.....
Besides, if it did work, it was doclouie who figured it out.
Peace
Bruce in Philly
Last edited by Bruce In Philly; 06-18-2020 at 11:19 PM.
06-19-2020, 12:54 AM
#73
Sorry if I missed it if already posted on this thread, but my complete PCM Unit was replaced by the dealer last March and just today all the touch screen features do not work..essentially all buttons function (volume, display shows up, manual radio search) just no touch screen. Just wanted to share and put this issue out there as an FYI.
06-19-2020, 09:57 PM
#74
Three Wheelin'
Parts came in early. Going to install them tonight.
06-19-2020, 11:58 PM
#75
Racer