DM7020 Component Video Fix

[avtech]

Hi All,

Thought some of you may be interested in a mod I have come across and adapted for the DM 7020 to correct the appearance of red band and flickering in the top 1/3 of the screen running in component (YPbPr) mode.

Example



The modification requires the addition of 3 x 1uF 16v capacitors (I have used 1uF 50v available from Jaycar Cat RC5499) in parallel with caps on the board marked C3202, C3302 & C3402 (All surface mount 47 nF) as pictured below.





Final result :-



I also fitted a cooling fan (Jaycar Cat XC5054 and filter Cat YX2550)as I found the unit produces a lot of heat when a large HDD is fitted (I have a Western Digital 320Gb in mine) and used a Floppy Drive Y power cable to power it from power supply connector. The fan is a 12v job but runs quite happily (and a lot quieter) on the 5 v rail as well as fitting a 4700uF 16v electrolytic across the 12v rail to eliminate any startup voltage fluctuations caused by the HDD.

Finished product :-



Hopefully some may find this useful, and I hope it ll comes up ok, this is the first time I have tried to upload photo's to a thread.

Cheers,

avtech

[z80]

Nice work, you put the fan in a great spot.
If you ever need the LNBP21PD chip, I have a tube of them.
It is the LNB controller, symptoms, no 12 or 18v lnb voltage.

You can also fit a heatsink on the black 7812 3 terminal regulator diagonally opposite the on/off switch, next to the yellow wire coming from the psu to the HDD.
It runs quite warm and is the main culprit for thermal issues in a 7020.
So if you relocate your fan to the front of the psu you will find it more effective I think.

Hard to believe it's a panasonic supply, it's the roughest part of a 7020.

I also have a dozen of those just lying around.


Actually I think I will try relocating the 7812 with a bit of thermal paste and mount it on the rear panel as a heatsink.



.

[ol' boy]

Fantastic stuff avtech. Thank you for your post. I wonder if it can be adapted for the DM7000

[solly]

how to get color bar enigma ?

[avtech]

Hey Oceanboy,

The cap numbers and fix are exactly the same in the DM7000, only the physical location is different for the 3 caps.

See below photo



The cap values are exactly the same

Be careful when fitting these caps as they are quite small, you require a steady hand and a good soldering iron to perform mod.

z80, you make a good point about the fan location, I did consider it when installing to mount closer to the secondary side of the supply, but was a little concerned about any rfi the fan may induce so close to the supply so opted for primary side instead.

Cheers and good luck to all who try the mods

avtech

[ol' boy]

Fantastic information once again avtech!! Many Thanks for sharing this with us. And thanks for the photos too! This has been the only real problem that bugs me sometimes with the DM7xxx units. That sure is some fine soldering work.... not for the morning after
So i take it that is your unit you have done the Mod on? All works good as pictures show?

I've never seen a fix for it anywhere, and here it is in good old Oz

Do you think it would be possible to run 2 fans avtech? maybe is series on the 12V line or both in parallel on the 5V line? Just so you could cover both sides of the PSU? And as a point of interest, do you set them up to draw air out of the unit or blow air over the PSU?

Interesting you have used the Cap mod for the DM7020, i have not found a start current issue with the DM7020 as i find with the DM7000 (which has PSU on mainboard)

Thanks again for your brilliant info

[z80]

z80, you make a good point about the fan location, I did consider it when installing to mount closer to the secondary side of the supply, but was a little concerned about any rfi the fan may induce so close to the supply so opted for primary side instead.

I tried it and it seems to be okay placing it there.
I hate placing stuff around 240v areas...it hurts when you slip..

[weirdo]

I hate placing stuff around 240v areas...it hurts when you slip..

pussy
Great stuff avtech!
Oceanblob you better leave that fine soldering to the experts mate

[avtech]

I hear you z80, in my job, you get those 240v tickles just about daily.

Oceanboy, i would tend to be careful how much you load up the psu in these things, especially the clones. I have found the fan descibed blowing air on to the psu is sufficient considering I am running 3.5" HDD and not a little laptop job. The fan I have selected draws only 80mA so the supply shouldn't struggle with that load. The other thing to take into consideration is the noise generated by the fan, I originally tried a 5v fan on the 5v rail and I could hear it humming when I was in bed at the other end of my house. After trying a few different fans I concluded that for me, this was the best result. One thing that the photo's don't show is the hole i cut in the side casing the same diameter as the fan blade to allow air to flow more freely, hence the need for filter/finger protector (I have a 2 yr old daughter who loves to touch and fiddle) and I am sure she don't need that tickle!

The cap mod came on recomendation from z80, so I figured I would do it, and I like his idea of moving the reg to the back case with some heat transfer compound. As for fan placement, i guess either place will be better than no fan at all, and there are "for" and "against" for either method, I guess the choice comes down to the individual.

[z80]

One thing that the photo's don't show is the hole I cut in the side casing .

that's it then...no warranty for you

[avtech]

that's it then...no warranty for you

whats a bloke to do!!!!!!!

Amusing that soldering caps to the video matrix wasn't enough to push you over the edge though!!!!!!!!!!

[admin]

Excellent thread avtech which I am sure will be of interest to many.

[ShaK]

NP Electro caps, ceramic or polarised? If polarised, what points are +/- for each cap?

[avtech]

I used ceramic caps which are non polarised, if you follow the Jaycar part number I supplied earlier, you should have no trouble at all

Good Luck

[vk6xlr]

Hmm, interesting. My 7020's colour looks fine using component to a projector without doing this mod.
So the question, why only some 7020's need the mod?

[avtech]

Hi vk6xlr,

Its actually not really the box so much as the type of display the is driving, I found i had problems on some CRT and LCD TV's but not on Plasma's that I have access to. I run a 40" HD LCD and Panasonic HD LCD Projector at home and only had problems on the LCD Panel not the projector. I guess the simple answer is - do the mod if you see the problem.
The other thing is the units I modded are all clone types, you may have a genuine unit and not suffer the problem, I have no genuine unit to form a basis for comparison.

Cheers

[z80]

Got a genuine 7020 here Avtech, it's the same "problem".

[vk6xlr]

Hi vk6xlr,

Its actually not really the box so much as the type of display the is driving, I found i had problems on some CRT and LCD TV's but not on Plasma's that I have access to. I run a 40" HD LCD and Panasonic HD LCD Projector at home and only had problems on the LCD Panel not the projector. I guess the simple answer is - do the mod if you see the problem.
The other thing is the units I modded are all clone types, you may have a genuine unit and not suffer the problem, I have no genuine unit to form a basis for comparison.

Cheers

Thanks avtech It is a clone. I bought caps when I first read of the mod, just in case. So might as well install them coz have to open the box again, lol.

[ol' boy]

This seriously should be made a sticky. It's common to most Dreamboxes and is a wonderful fix.
Should be on hand for quick reference IMO

People can then add there results or quotes from Technicians if they don't perform the Fix themselves.

[d4g]

for the 4700uf cap where did u connect it to cant see in the pics

thax