KRK Rockit 8 (Gibson) Powered Speaker Cmponent ID & Troubleshooting

[ewd]

Looking for assistance for a KRK (Owned by Gibson Corp) Rockit 8 powered speaker. Trying to identify the two IC's (Amplifiers?) on the Main/Power Supply PCB, and troubleshoot the same board. Came in with the 15 pin having a hole burned through it, right through the P/N. Appears to be a TDA7293, but not sure. The 7 pin is possibly a TDA 2052, which I suspect is bad, but the markings are also nearly illegible. Reading 3.5VDC on the tweeter Positive, which is tied to the 7pin IC #1 leg. Also reading 3.5VDC on leg 6 (Inverting input?) and neg rail voltage (-22VDC) on Pin 3 (Standby?). Requested a schematic from Gibson Tech Support early last week, but no response yet. Have previously got a Rockit 10 schematic (very dissimilar design) from Gibson, but that was like pulling teeth. Must have used up my quota of schematics (one this year) from them. Any and all assistance would be greatly appreciated.
Thanks.

[Jazz P Bass]

The proof in the TDA729X is in the board layout.
The 93 & 94 are both good for 100 watts.
The TDA2050 is good for 50 watts.
(wattage depends on power supply voltage & load)
The Rockit 8 Hi Freq is a 20 watt amp & the Low Freq amp is 70 watt.

[ewd]

Thanks for the product specs. I had seen them on Gibson's website. What I need is to identify the actual IC's that are on the board so that I can replace them after I try to determine what else might be wrong with this powered speaker, particularly the 3.5VDC pin voltages and the rail voltage on the standby pin that don't appear to be correct (I think it's the standby, if it's actually a TDA 2052). Again, at this point I'm just guessing at the IC P/N's, they are either burned through or illegible. I also don't want to replace the IC's and blow out the replacements.

[Jazz P Bass]

A sevin pin TDA is most likely the 2052.
3.5Vdc on pin 3 (mute/stndby) will put the IC in Play Mode. So that is good.
It would be a big help if you posted the power supply rails.
The Main power amp IC could be a TDA 7293 or 94.
The 93 is the plain one of the two.
Again, it would help if you identified all of the pins.

[Jazz P Bass]

TDA2052 pinout

[ewd]

Thanks. I'll reply with my voltage readings on both IC locations tomorrow evening when I get back into the shop. I have them all noted, but I'm at home now. The main IC has a big hole burned through it right after the 7. All that's left of the P/N is TDA 7_____. The 7 pin P/N is just plain worn off, I can make out TDA 2xx(2?), but it is also reading 3.5 VDC on Pin 1, which is tied to the positive tweeter connection. That's why I'm pretty sure it is also bad.

[Jazz P Bass]

To me the TDA2052 is a no brainer.
It can handle a tweeter.
The TDA 729? can be determined by the board layout.
The 7294 does not use pin 5, 11 & 12.

[ewd]

Was able to find the schematics today, the IC's are supposed to be TDA2052 & TDA7294.
The voltage readings I took testerday:
TDA2052 (In Circuit)
Pin 1:+35VDC Pin 5: 0V
Pin 2:+22VDC Pin 6:+3.5VDC
Pin 3:-22VDC Pin 7: 0V
Pin 4:-22VDC

TDA7294 (Pin Locations, burnt IC removed from circuit)
Pin 7 location:+41VDC
Pin 8 location:-41VDC
Pin 9 location:-41VDC
Pin11 location:-41VDC
Pin13 location:+41VDC
Pin15 location:-41VDC
All other pin locations were either mv readings or zero (I didn't record those)

When I went to recheck the voltages today, two of the four rectifier diodes smoked before I could take any more measurements! After that, I checked the Power Supply Transformer, and got the following readings: 15.2 VAC being supplied to the set of 4 Rectifier Diodes (to supply +/-VDD to the TDA2052 and 27.4 VAC supplied to the Bridge Rectifier for the +/-VCC to the TDA7294).

[ewd]

Got new IC's on order, but have questions regarding the voltages I was seeing on the TDA2052 before my rectifier diodes smoked:
Pin 1: Output. +3.5 VDC, obviously not good-outputs directly to speaker
Pin 3: Standby/Mute. -22 VDC, not sure if this is ok.
Pin 6: Inverting input. +3.5 VDC, could this be the source of my Output pin DC Voltage via internal short in IC?
I'm making the assumption that the TDA2052 is bad, haven't noted any other circuit anomolies that could have caused both IC's to go bad (the TDA7294 had a hole burned through it -most definitely bad!), other than the rectifier diodes probably being bad before they actually smoked on me when I went to do the latest voltage checks -power transformer seems to be putting out correct voltages (results in previous post).
Any thoughts?

[Jazz P Bass]

How about posting the schematics?
If you are in doubt about the TDA2052, remove it.
If it is shorted, that would explain the rectifiers going up in smoke.

[olddawg]

I have repaired a number of these powered monitors and the most common problem I have seen is the power supply filter caps fail. They are underrated. Usually there is a double sides board involved. I have had a couple that were previously worked on and had to jumper some feed throughs, especially on the main filter cap leads. The problem comes with the caps usually buried in a large wad of silicone. If the units have been used for any time at all I would seriously consider replacing the filter caps with higher voltage rated caps if you want a truly reliable repair. There is usually room. You just leave the leads longer on the new caps.

[ewd]

TDA2052 Circuit.pdf Hope this works. Couldn't attach the pdf file for the TDA2052 circuit from the Rockit8 schematic with IE, now trying Firefox.