problem with marantz sr6300 digital settings

[victa1]

I am having trouble with my Marantz sr6300, when connected to a dvd player (Marantz dvd 4300) using the coax or optical cable it works fine for about 10mins when it gets hot usually one of the surround speakers pops then ommits a high pitched scream, which works its way to all of the speakers. It can be instantly stopped by switching the control knob to any other setting but the noise returns in several minutes. I took the unit back to the retailer who exchanged it and said there were issues with some of the units starting with the serial number 237, which mine had. He swapped it for another unit also with serial number 237 and it continues to have the same problems. The unit appears to get extremely hot, I have had other brands in the past that got warm but not as hot as this particular unit. It is only 4 days old. It also has a problem that it drops the audio signal from the HD dgtech set top box. Has anyone got any suggestions as to how to determine that this is a fault with the amp?
Im thinking of returning the unit for a exchange to a Yamaha rxv 740, does anybody think this unit is in the same league as the Marantz or any suggestions on a more suitable unit? Please remember I live in Australia and not all models are available here. That is why the sr6300 is still the current model in Australia.
The unit works perfectly when using analogue cables from the dvd player
It works fine on the cd player, tv box when it ommits audio, and the receiver (all analogue)
The problem seems to be the digital connections

[markw]

Since you say they have replaced your originally defective unit with another defective unit, I'd say it's a problem with the receiver itself. After having gone through two units, both being losers, I'd say it's time to move on to another manufacturer, or at least another model from Marantz. Were these purchased NIB or as refurbs?

Not being from Oz, I don't know what's available there but I'm sure there are other alternatives that fall withhin your price/feature range. There's a lot of competiton nowadays. Denon and Yamaha come to mind immediately.