Determining the "Rail Cap Failure"

[juanbanzai]

Hi all.

I've posted a few other threads on the forum and I don't want to hijack my own threads to branch off to a different topic when new issues pop up with me trying to get my d8b and HDR working.

The d8b I have was going to be tossed in the dumpster simply for it being "obsolete." I never let any piece of gear get tossed without first seeing if I can repurpose it for my home studio. Long story short, last week, I powered on the d8b and it started showing the signs of the rail cap failure; loud thumping coming from the speakers, several VU meters jumping up and down, some of the pots flashing, and a loud rhythmic click coming from one of the fader boards as one or two faders were trying to reset themselves.

I powered the board down and walked away for an hour or two before I tried powering it up again. I heard a "click" and the d8b booted with no issues at all. I usually leave the board on 24/7 and for the past week it seemed to be working just fine. Last night, I was listening to some audio files and the d8b suddenly started going nuts again. Same symptoms as before but now it seemed like more than one fader was moving ever so slightly... making the rhythmic clicking even louder. Powered down and walked away. At this point, "time is money" so I was going to do what my station wanted to do; toss the d8b and not waste another minute on it. Besides that, intermittent problems are a PITA to troubleshoot and repair.

For kicks, I tried powering the unit up this morning, and lo and behold, it booted just fine. I'm almost disappointed. So am I looking at an intermittent rail cap failure, or a ribbon cable issue with one of the fader boards? Based on what's been happening, should I go ahead and replace the rail caps on the brain board? I have all the equipment necessary to work with SMDs, and I have restored numerous jukeboxes, radios, and stereo equipment. I'm just not convinced that it's worth it.

Maybe someone who's had this problem before can give me a better idea of what I'm up against and possibly talk me into it.

Thanks.

Aaron

[doktor1360]

Hi all.

I've posted a few other threads on the forum and I don't want to hijack my own threads to branch off to a different topic when new issues pop up with me trying to get my d8b and HDR working.

The d8b I have was going to be tossed in the dumpster simply for it being "obsolete." I never let any piece of gear get tossed without first seeing if I can repurpose it for my home studio. Long story short, last week, I powered on the d8b and it started showing the signs of the rail cap failure; loud thumping coming from the speakers, several VU meters jumping up and down, some of the pots flashing, and a loud rhythmic click coming from one of the fader boards as one or two faders were trying to reset themselves.

I powered the board down and walked away for an hour or two before I tried powering it up again. I heard a "click" and the d8b booted with no issues at all. I usually leave the board on 24/7 and for the past week it seemed to be working just fine. Last night, I was listening to some audio files and the d8b suddenly started going nuts again. Same symptoms as before but now it seemed like more than one fader was moving ever so slightly... making the rhythmic clicking even louder. Powered down and walked away. At this point, "time is money" so I was going to do what my station wanted to do; toss the d8b and not waste another minute on it. Besides that, intermittent problems are a PITA to troubleshoot and repair.

For kicks, I tried powering the unit up this morning, and lo and behold, it booted just fine. I'm almost disappointed. So am I looking at an intermittent rail cap failure, or a ribbon cable issue with one of the fader boards? Based on what's been happening, should I go ahead and replace the rail caps on the brain board? I have all the equipment necessary to work with SMDs, and I have restored numerous jukeboxes, radios, and stereo equipment. I'm just not convinced that it's worth it.

Maybe someone who's had this problem before can give me a better idea of what I'm up against and possibly talk me into it.

Thanks.

Aaron

See my response to your post in the HDR Forum...

[captainamerica]

I understand the headaches of debugging a problem but make sure you also review https://www.sonido-7.com/d8b/index.html first before tossing out your d8b.
Many of us on this site have experienced similar problems, only to realize it was just loose and or corrupted cables.

[captainamerica]

I understand the headaches of debugging a problem but make sure you also review https://www.sonido-7.com/d8b/index.html first before tossing out your d8b.
Many of us on this site have experienced similar problems, only to realize it was just loose and or corrupted cables.

[Crash]

My trusty d8b would occasionally due the thumpy dance. It always eventually booted up fine.

[JoeJoe]

I'm also getting intermitten Thump Thump on bootup, usually letting it sit for a while (say 15 minutes) it might boot up fine again. Immediate reboot will just go thump thump. One time the thump thump of death happened in a normal listening session. It sure feels like a cap somewhere, especially since heat seems to affect it.

I never had any strange fader movement , the VU leds pulse ramdomly at the thump thump situation though.

Does my issue sound like the rail cap to you?

[captainamerica]

I have never (so far) experienced the Thump Thump issue. I've had my board since 2003 and have done regular maintenance and most of my problems have always been related to bad cables connections or boot-up sequence.
I assume you have reviewed the database link: https://www.sonido-7.com/d8b/index.html


8. The Dreaded Rail Cap Failure

This problem occurs on older d8bs and is accompanied by the following symptoms:

A loud thump from every output. Thump Thump Thump (somewhere around 80 BPM)
Lights and meters flashing on and off in double time to the thump
The lights on the pan pots twirl around
No control over the console from the GUI
GUI shows no signs of trouble
Sometimes audio will pass and sometimes not
Sometimes a restart will help but then it comes back
Eventually nothing will stop it
Note: Some d8bs will have similar symptoms if there is an interruption to clock or if an incoming clock is present when the d8b is booted up or if any digital device connected to the digital cards is on when the d8b is booted up. For instance, some boards will act up every time a MOTU 2408 is connected to the DIO8 card when booting. In these cases the thump does not always occur (though sometimes it does), and the pan pot lights don't twirl around, but there will be flashing lights and meters, and the monitor may (but not always) show "DSP Error, Last State Unknown" or similar.

If you have these symptoms and are not an expert audio maintenance technician, you need the help of an authorized Mackie Service Center.

[doktor1360]

I'm also getting intermitten Thump Thump on bootup, usually letting it sit for a while (say 15 minutes) it might boot up fine again. Immediate reboot will just go thump thump. One time the thump thump of death happened in a normal listening session. It sure feels like a cap somewhere, especially since heat seems to affect it.

I never had any strange fader movement , the VU leds pulse ramdomly at the thump thump situation though.

Does my issue sound like the rail cap to you?

Perhaps...

However, I'd try performing the following to ensure it's not what I call the "unknown & enigmatic" anomalies of this console / host combo are mitigated without much effort... disconnect the ac power (cable) from the rear of the D8B's cpu host rack case at the connector. Then simply walk away for about 5-10 minutes (grab a beverage and/or something to eat, take a short walk, etal) and when you return, plug it back up and reboot the D8B host / console. I've had this eliminate everything from the occasional "Thumpy Dance" (Thx Crash!) to the annoying (and somewhat alarming) "Broadway Lights" where the console is disabled and lit up like an x-mas tree in Macy's window during the holiday season in December...

Of course, captainamerica's reply makes a ton of sense too, good pointers to check...

I get the sense that, yes, it is capacitor related... in this case the non-volatile caps (primarily electrolytic) don't drain, and they're holding a subsequent 'charge' and affecting something that's memory-related... holding some sort of weird (or more likely corrupt) runtime values of some arcane parameter(s) used for the runtime configuration. I'm honestly speculating, but from experience until someone else suggests something other more appropriately logical and/or 'concrete' therein...

I stand corrected if any of this is erroneous, however these triage steps have and do work (on more than one instance)... I would say at the least for myself...

This much you can always expect, and of course here it is:
[Standard Mgmt Disclaimer] - "Your actual mileage may vary..."

[Phil.c]

That also makes sense as I’ve also had things put right with a BFC removal, in my case, I didn’t have to wait, just off and on.

[doktor1360]

That also makes sense as I’ve also had things put right with a BFC removal, in my case, I didn’t have to wait, just off and on.

I can second that, Phil... that's always the 'next step' for me in the triage I described above - just adding the BFC and data cable to the list...