TGP V - stuck in mem test

I've come across a Theater Grand Processor V that seems to be sick. When I power it up (using the actual power switch on the back), it sits there for several seconds and then displays "MEM TEST" in the display. I've let it sit for a couple hours in this mode, and it never comes out. Front panel buttons have no effect. I tried to reset it, but cannot since none of the buttons have any effect.

Is this think now a parts source or is there something I can do to bring it back to life?

Thanks

jjptkd can probably contact Bill & see if he has any insight.

Jesse?

Just spoke with Bill, he says its the DSP chip and he can fix it. It requires new parts so its not something that can be "reset." He should be closing on his new house some time this week and he said the very first thing he's going to do when he gets the keys is setup is bench.

Another thing, that model may still be under factory warranty, 5 years from date of manufacture. The first 4 digits in the serial number is the date. If you don't have the receipt then its 4 years and 6 months.

Thanks for the clues. Unfortunately, the serial number is missing..... Label has been peeled away. Perhaps there is a dark history here?

In any case, suggesting the DSP board is consistent with its behavior just prior to it going into mem test. For several days before the mem test problem, it wouldn't produce any outputs unless it was in the "direct" mode.

I opened it up and started checking around. There are no less than 11 voltage regulator devices scattered around - all but one on the main board. There is silk screening on the board indicating the output voltage. I checked each one to see what the actual voltage was and all but one lined up with the silk screen value. The one that was off is on a board that looks like the DSP board. It hangs off the main board near the front panel. It has a big chip in the middle labeled DTS, hence my assumption that it is the DSP board. The voltage regulator output is silk screened at 1.8v. I measure 3.0v. Seems like a problem. The regulator is an LM317T. I would just replace it, but it seems unlikely that it would fail and output a voltage 1.2v high. So I'm thinking something else must be wrong.

If Bill could provide some more clues, I would be most grateful.

Sure would be good if Sunfire would let loose of a service manual.

Just took a closer look and the board is labeled "Theater Grand IV DSP Processor". Yep, this is definately a TGP V.

Anybody got an extra DSP Board laying around?

Just took a closer look and the board is labeled "Theater Grand IV DSP Processor". Yep, this is definately a TGP V.

Anybody got an extra DSP Board laying around?

I'm confused; it says "Theater Grand IV" but you state it's definitely a TG V??

Yup. Photo posted on the other site. Would post here but I'm a little unfamiliar and in the process of cooking dinner. Some nice Half Moon Bay King Salmon....

In any case. Got some new developments. I removed the board and blew it out with compressed air. I put it back and tried to repeat my measurements. Before blowing it out, the unit drew about 43 watts (plugged into my Killowatt). After the blow out it was drawing in excess of 60 watts - roughly 65. One of the regulators on the main board was heating up badly. It's mouned on a heat sink and it was "burn your finger" hot. I shut things down immediately. I then removed the DSP board and powered back up. Power consumtion was at about 37 watts. Put it back and power went up to the mid 60's again.



Seems that I need to carefully inspect the DSP board. That will have to wait since I need to get on with life right now, but I will report back in a few days.

Jesse?

A little late it seems, but yeah, logic chip. No idea if you can get a new one.

Jesse?

A little late it seems, but yeah, logic chip. No idea if you can get a new one.

Actually, jjptkd is Jesse, also~

Ok, I was kinda wondering why you were asking me.....LOL

Got back to diagnosing the TGP V last night. No break thrus, but there is a little new information.

Symptoms are now stable. When I plug the DSP board into the mother board, power consumption spikes up to 67 watts and U57 on the mother board quickly gets REAL hot. U57 is an LM317T regulator mounted on a heat sink. Silk screened voltages indicate that it provides 3.3v. Chasing connections with my meter shows that its 3.3v go to the DSP board connector on pins 24 and 25. Unplug the DSP board and power drops to 37 watts and U57 remains at a stable temp.

With the DSP board unplugged, voltages on U57 are 2/3.3/11.4 on pins 1,2 and 3. With the DSP board plugged in they are .5/.87/10. There is a regulator on the DSP board - U2. Its voltages are .5/1.8/10. It too is an LM317T. I looked up the data sheet on the DSP processor and it uses both 3.3 and 1.8v power connections. With the DSP board removed, I measured resistance between pins 25 and 1 on the connector. I believe these two pins to be +3.3v and ground. Resistance is .5 ohms.

My conclusions so far:
- U57 on the mother board provides +3.3v to the DSP board via the connector on pins 25 and 1.
- U2 on the DSP board provides +1.8v to the DSP processor (and maybe the memory).
- Something is shorting the 3.3 power on the DSP board.

What have I done so far?
- Blew the DSP board out multiple times. No changes.
- Took the board into work and handed it to the QA guys. They went after it with their microscopes and couldn't find anything.
- There are six electrolytic caps on the DSP board. I took them all off and I still get .5 ohms on the 3.3v power (pins 25 and 1). All the other components on the DSP board are surface mount.

Open Questions:
- What is shorting the 3.3v power on the DSP board?
- Why the earlier measurements where I got 3v from regulator U2 on the DSP board and power consumption of about 43 watts?

I'm still hoping that its something stupid - some debris in the wrong place or something. My fear is that a device on the DSP board has failed in a mode where it's shorting the 3.3v power.

I'm pretty much stumped at this point. Any suggestions short of turning the TGP V into a planter would be welcome.

Bill should be back in business again some time next month, he has everything "Sunfire" from Carver's old shop including new OEM parts.