CurtPalme.com Home Theater Forum

[Nashou66]

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Well at the end of this month all the pics of my work will be gone. Apples Gallery is ending and now I need to host the pics somewhere else. I wanted to some how use my own Computer as a web host for the pics but not sure how to do it. I have the latest mac mini server which has 2 HD's so I planed to use one for that exclusively. But for the next few months bare with me . I will hopefully get everything worked out and have links to the pics.


Athanasios

[Bodi79]

@Athanasios

How much space do you need, cause i can set you up with space on one of my domains.

Cheers
Ronald

[Nashou66]

[draganm]

[draganm]

so finally got around to doing / testing the larger heatsink on the HMD for those cases where the horizontal deflection starts to Oscillate. I wanted to see how much of an improvement there was i temp. reduction. I never did figure out what went wrong with my Cree FET modified HDM or why it failed during testing, but this was something I always intended to do since this issue popped up on AVS for Ralpharch. Since then it has been posted by at least 3 or 4 other people.
http://www.avsforum.com/t/1266475/marquee-with-intermittent-horizontal-scan-problem

It always seems to crop up in situations where 2 or more of the following situations exist

1) ceiling mounted configuration
2) high scan rates
3) picture set to "short retrace".
4) warm ambient temps (summer-time viewing)

What I did, and what i'm pretty sure VDC did as well, was to modify the focus amp sink and swap it over to the HDM. One of the 5 small fins needed to be milled off to clear some board top components. However the increase in overall surface area is significant and more importantly, the new fins are directly in the air-flow of the belly fan ( like they are on the FCM). I also applied new insulating tape since the tape needs to actually make a 90 degree turn at the top and go horizontally over the perpendicular fin for 3 or 4mm. This is because the tall FET's on the HDM actually touch the top of the factory heatsink and the FCM sink didn't have the tape extend as far.

I used Silicone coated KApton tape with a dielectric rupture strength of 7000 volts+ Dielectric Silicone paste as an added thermal conductor and electrical insulator. Here are the before /after temp's in different room conditions 64Khz horizontal sweep.

1) original 07P HDM factory heat-sink
start (ambient) 79F / Finish 148F = + 69 degree's

2) with new larger heat-sink
test 1
ambient 86F / Finish 134F = + 48 degrees
test 2
ambient 79 / finish 126 = + 47 degree's

So according to my calc's the new heatsink is shedding heat faster and reaching a steady state temp. that is 32% cooler than the original Electrohome factory version. the only issue I see with this modification is
a) you need a milling machine to modify the FCM sink
and
b) you need a bad FCM or maybe an old m8000 FCM donor board ot cannibalize the heat sink from. I'm sure the correct extrusion could be sourced as "new" but there would be a minimum order. Probably a 10 foot section is what most places want to sell + oversize shipping rates. however if your seeing this issue you have an option now

[macgyver655]

I'm curious. Are you measuring the temp of the heat sink itself or the components attached to it?

[draganm]

The FET's are covered by steel spring clips which keep them securely pressed against the AL sink

[Phoenixed]

Still playing with my hdms?

[draganm]

[macgyver655]

So probing the heat sink is telling you the transistors are running cooler?

[dvh99]

nahhh, the cree fets are ok, still no problem after 100+ hrs.
it`s the new heatsink that cools better but still my heatsink stays cool to the touch at 1080p 60hz.

[draganm]

Dennis the Cree FET's are really cool, brand new technology. I just didn't have any luck with them.
This is just another option, a cheaper and simpler one, which is probably why VDC did it to any HDM you can buy new today. Here's a pic of an older and newer (current) HDM posted by HKsteve.

[danielparker]

[dvh99]

still with that heatsink it doesn`t run nearly as cool as with 2 cree fets, with the fets the heatsink gets luke warm at 1080p.
with this heatsink it still gets too hot to the touch at high scanrates and certainly in the summer.

[draganm]

[dvh99]

i suspect there is no voltage at the gate to begin with.

i have no idea what could have caused this.

you should get around 20v at the gate if i`m not mistaking.

[draganm]

[macgyver655]

Probing these components hot is never a good idea. You are better off soldering small wires to the legs and attach the ends to a piece of cardboard and measure with your DMM there.

Of course to check the 2 mosfet it would be easier to just remove them and test out of circuit with your DMM.

[dvh99]

just finished my 2nd cree fet mod on a friends hdm (older style heatsink) and no problems at all.

again i used the uc3709n as mosfet drivers and did the job in just over 2 hrs.

[dvh99]

ok, the hdm mod is not completed yet, at least not to full satisfaction.
after the mod on my own and my friends hdm the left part of the screen (till almost halfway) is darker then the right part.

i have no idea what causes this but it looks like the left part is slewed slower then the right part thus being darker (if that makes any sense)

here is a pic, notice that the darker part covers the entire left square so to say of the picture so the black line that indicates the dark to light transition goes to the top.



any suggestions are welcome.