I have an elderly DM800 Clone with revision J motherboard and tuner. It has always had an overheating problem, which I've overcome by standing the box on its end (tuner at the top) and it has run fine for years like that. On occasions it had the "tuner fail" problem which eventually happened everytime. It's a strange one because I've tried that particular tuner in a genuine box (J M/B) and a clone (L M/B) and it works fine! I tried the L tuner in this box which worked, so decided to get a new M tuner which did indeed solve the glitching and tuner failed problem. It did not however solve the overheating problem and I would get the green screen of death after 30 minutes or so with the box in its normal position - again it was fine standing on it's end - probably due to convection cooling. I decided to install a permanent cooling solution and used the following threads as an inspiration, thanks to all the posters involved.
With the box in normal running conditions, measurements showed the tuner getting above 40 Degrees C and the heatsink on the CPU above 70. Trials with a 5v 30mm X 30mm X 5mm fan both external and internal to the box did not provide sufficient cooling. After further testing I settled on a 12v 60mm X 60mm X 10mm fan powered from the TV USB port, which obviously powers down when the TV is off. The fan runs well at 5v, is quiet and easily provides enough cooling. My DM800's are running Open Pli 2.1 and pin 8 always seems to measure approximately 6 volts when the box is on and 0 volts at standby, I have found nowhere to influence this behaviour in the software but it is consistent so I decided to live with it. This voltage was not high enough to pull in a 12 volt relay so I went with a 6 volt version.
My motherboard does not have a power connector for the fan but I did find what appeared to be a USB 5v power supply from two pins next to the USB connector near the card reader. I've used these pins for the fan power supply and soldered a couple of wires to them and then run these to the veroboard mounted relay. As I'm using this part of the box to mount the hard drive, I've insulated both these and other exposed pins on the motherboard with insulation tape. Power to the relay coil has been taken by soldering a couple wires to the back of the SCART connector (Pin 8 = 6v Pin 21 = GND). As both the relay and the fan are inductive loads I've fitted on the veroboard a couple of general purpose protection diodes (IN4006) in parallel with both power supplies to protect any CMOS circuitry.
Within the box I've removed the SATA extension lead/connector, the modem and the hard drive cradle. I've mounted the relay above the external USB ports near the gap vacated by the SATA connector and attached it to the rear of the case using a double sided sticky pad. The hard drive now sits on top of the card reader and in turn the fan sits loose on top of the drive. The fan has been cable tied to the internal SATA cable to stop it sliding out of position as you fit the case. It's all a bit of a tight fit and personally I see no need for additional fixings to either the fan or the drive as it all seems pretty secure once you've refitted the case. The one thing that you must ensure is that the fan is sitting flat and is not snagging anything. So far this modification has worked flawlessly for a few weeks now, the only minor issue I have is that the fan does not switch on for standby recording but I'm not sure whether overheating is a problem in this mode.
I hope some of you find this post useful.
Regards
Smith.
DM800Cooling (1).jpg
DM800Cooling (2).jpg
With the box in normal running conditions, measurements showed the tuner getting above 40 Degrees C and the heatsink on the CPU above 70. Trials with a 5v 30mm X 30mm X 5mm fan both external and internal to the box did not provide sufficient cooling. After further testing I settled on a 12v 60mm X 60mm X 10mm fan powered from the TV USB port, which obviously powers down when the TV is off. The fan runs well at 5v, is quiet and easily provides enough cooling. My DM800's are running Open Pli 2.1 and pin 8 always seems to measure approximately 6 volts when the box is on and 0 volts at standby, I have found nowhere to influence this behaviour in the software but it is consistent so I decided to live with it. This voltage was not high enough to pull in a 12 volt relay so I went with a 6 volt version.
My motherboard does not have a power connector for the fan but I did find what appeared to be a USB 5v power supply from two pins next to the USB connector near the card reader. I've used these pins for the fan power supply and soldered a couple of wires to them and then run these to the veroboard mounted relay. As I'm using this part of the box to mount the hard drive, I've insulated both these and other exposed pins on the motherboard with insulation tape. Power to the relay coil has been taken by soldering a couple wires to the back of the SCART connector (Pin 8 = 6v Pin 21 = GND). As both the relay and the fan are inductive loads I've fitted on the veroboard a couple of general purpose protection diodes (IN4006) in parallel with both power supplies to protect any CMOS circuitry.
Within the box I've removed the SATA extension lead/connector, the modem and the hard drive cradle. I've mounted the relay above the external USB ports near the gap vacated by the SATA connector and attached it to the rear of the case using a double sided sticky pad. The hard drive now sits on top of the card reader and in turn the fan sits loose on top of the drive. The fan has been cable tied to the internal SATA cable to stop it sliding out of position as you fit the case. It's all a bit of a tight fit and personally I see no need for additional fixings to either the fan or the drive as it all seems pretty secure once you've refitted the case. The one thing that you must ensure is that the fan is sitting flat and is not snagging anything. So far this modification has worked flawlessly for a few weeks now, the only minor issue I have is that the fan does not switch on for standby recording but I'm not sure whether overheating is a problem in this mode.
I hope some of you find this post useful.
Regards
Smith.
DM800Cooling (1).jpg
DM800Cooling (2).jpg
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