ATSC Converter Boxes (Non-HD, Non-Recording)

RE: Access 1030d ventillation modification.



Ok, Saturday morning, back in the workshop in Kingston, here are the modifications made to the enclosure of the HD1030 to increase ventillation.

TOP:
Unit disassembled, big hole cut out of the center of the top plastic enclosure. Metal screen installed inside with four tiny #4 x 1/4" machine screws that I had spare from other project. Taking great care that I choose the position of the screws so that when assembled they do not extend down and touch any components on the circuit board.

The metal screen is salvaged from a used car air filter. Those car air filter screens are handy for many things. They don't seem to rust, so I think they may be made of stainless steel. I've used other ones as a grill over the dryer outlet outside - to keep leaves and little animals out - good if SS - they don't rust with the hot moist wet air from the dryer. Same idea for some furnace outlets - maybe.

SIDES:
The little ventilllation slits on the sides of the unit seemed too small to me to work very well, so I very carefully drilled *MOST OF* those out to around 3/32", and added a series of more holes near the front w/the same pattern. Notice the first four columns of holes near the front - those I added. Some of the side slits were NOT* drilled out because they intruded into a square plastic support inside the sides. Choose carefully which ones to drill or *NOT* Drill.

Of course, the circuit board has been removed for this procedure. Pretty simple to take out. Undo the two nuts on the coax F-connectors at back. Make sure the one screw near the back connection area is removed. One plastic clip inside to spring with a little flat screwdriver, and the circuit board lifts up an slides forward and out. Simple.

BOTTOM:
Can't see this from this picture, but I have added two rows of holes on the bottom of the enclosure, same size as the other holes on the bottom, near the front of the unit. Extended the pattern forward two rows. They are larger than the side holes - for sure.

Why did I do this? There was space, and I noticed that all the other holes in the bottom are under the circuit board and do not allow direct airflow into the area above the circuit board - where the hot component with the heatsink is.

The silver sticker on the bottom, in that area, was carefully peeled off beforehand and put on again on the top after with some clear packing tape.

RESULTS:
All reassembled, hooked up to a real antenna outside on the tower, powered up and tested. Rescanned, Works great, runs alot cooler, mostly because the heat from that heatsink can now go straight out the open screen I added. Also because air can flow in alot better from the sides and bottom now that I've opened it up a lot better.

I think the enclosure on this unit is too closed up. Needed to be opened up a fair bit more. It was holding the heat inside, probably affecting all the other components over time.

Simpler Modification ?
A much simpler modification, probably very effective as well, is just to carefully open up a hole on top as I did, and secure a screen from the outside with some glue or very small and very short screws. No need to disassemble the unit at all. Just cut or melt melt the plastic around those top holes very carefully and pop out the piece. Glue the screen and/or screw it in carefully - fit in in where the circular indentation is in the top. If drilling do so very carefully.

That one modification alone, cutting the hole in the top, allows the heat from that heatsink straight out the top much better. The plastic on top of that aluminum heatsink also acts like a sort of insulator, keeping the heat in the enclosure, rather than straight out the top. The metal screen instead is more open and does itself conduct heat right through it and straight out.


Unit runs alot cooler now.

I noticed that this unit does give a pretty nice SD - standard definition picture from a High Def sub channel - 16-3 WPBS-HD here.


As mentioned earlier:

Sound is still a little low, from the Composite outs Y R W - but ok.

Sound from RF out is a little noisy / white noise.

So with this unit, better to plan to use the Composite outs / not the RF out.

All in all, for the thirty bucks ( $30 + tax ) that I paid, Special Deal, on sale at Factory Direct store, seems like an ok deal.

But I think this unit needs a MOD to help with cooling.

Don't think it really needs a FAN now. Not sure. Will continue to test over time.

Same as ROGER1818 mentioned - it's is a very economical unit for the second TV in the other room.

I found the look ahead EPG menu, by doing the right arrow. It shows one program at a time on the screen. Seems to go ahead the full distance - like my other convertors - but just one program at a time on the screen.

Equipment Leakage Current

Loogeuil:

The voltage that you measured between the threaded antenna connector and ground is caused by leakage current. All AC connected equipment, even when operating normally, has some leakage current. A 2-wire polarized plug power cord does not ground the equipment, it only ensures that the neutral of the equipment is connected to the neutral of the power system and the hot wire is connected to the switch. You need a 3-wire power cord to ground the equipment.

I have made many tests of equipment leakage current using my Simpson 229 Leakage Current Tester. I bought it because I had three close calls with electrical shock and I thought the expense of the tester was well worth it.



When I was calibrating the signal strength scale of an Apex DT502 to send to a friend, I had many pieces of equipment connected to AC:
2 Apex DT502s
2 Audiovox PLV16081 8" TVs used as monitors for the CECBs
1 Sony KDL22L5000 TV
1 CM 7777 preamp power supply
1 AC adapter for Sadelco signal level meter
1 AC adapter for RS preamp

During the tests I noticed a problem that I have seen before but couldn't track down until recently. When I touched a ground and the case of the equipment I felt a mild shock. My Fluke 25 DMM gave a reading of 58VAC. I hooked up my Simpson 229 Leakage Current Tester and found that the voltage reading was 40 volts and the leakage current was about 200 microamps; not enough to be dangerous but enough to give a tingle. (The difference in the voltage readings is because the input impedance of the two meters is not the same.) The reading of about 200 microamperes that you see in the above photo is the actual leakage current that I felt when I was shocked. It was not strong enough to be lethal, but it certainly got my attention. GFCIs are designed to trip at 5 mA, which is 25x as strong.

I then started unpluging each piece of equipment and noticed that the leakage current went down each time. The boxes have 2-wire cords so I grounded the coax shields at the splitter and the leakage current went to zero. With so many pieces of equipment connected to AC the normal equipment leakage currents were additive.

Most of the pieces of equipment use switchmode power supplies, which have more normal leakage current than the transformer power supplies for the signal level meter and RS preamp.

Even a good quality energized 3-wire extension cord will have some normal leakage current from the hot conductor to the ground and neutral conductors without any equipment being connected to it.

Since I was able to feel a leakage current of about 200 microamperes, my threshold of perception is considerably less than the mean value of 1.067 mA measured by Charles F. Dalziel as described in the 229 manual.

http://www.simpsonelectric.com/uploads/File/229-2_manual.pdf
http://www.mdsr.ecri.org/summary/detail.aspx?doc_id=8285

Since your pieces of equipment most likely have switchmode power supplies and they are interconnected through the shields of the cables between them, I suggest that the shields be connected to a ground. This demontrates the advisability of using a grounding block on the antenna downlead.

If you are able to borrow an appliance leakage current tester to see if your equipment is faulty, that would be ideal. It is also possible to assemble an inexpensive leakage current test circuit.
http://repairfaq.ece.drexel.edu/sam/safety.htm#saftes

When setting up your equipment, turn all pieces off and remove their power plugs (or the power strip plug). Connect the cables between them, plug them into AC, and then turn them on.

For maximum safety:

1. Have an electrician install a properly wired 3-wire outlet for your equipment so that the equipment that has 3-wire plugs is grounded.
2. Test all pieces of equipment to be certain that the leakage current of each piece is below 500 microamperes (0.5 mA).
3. Interconnect the pieces of equipment as required.
4. Plug the 3-wire and polarized 2-wire plugs into the outlet strip.
5. Turn the power strip and then the equipment on.

There is another step that really needs to be done between no. 3 and no. 4, which is to ground the pieces of equipment that have 2-wire polarized plugs. This is the "dirty-little-secret" that is not often mentioned, but is important because the normal within-limit leakage current of equipment that has 2-wire polarized plugs is additive when connected together. Even though my Sony Bravia is in a plastic case and has leakage current within safe limits, there exists the potential for leakage from the antenna coax shield to ground.

I did my test setup in the kitchen and had two grounds available to drain the total equipment leakage current of about 200 microamperes: the grounding pin of the 3-wire outlet and a copper cold water pipe (same ground as for electrical panel). Either one reduced the total leakage current to zero.

Details of the tests are in the attachment PDF.

Rabbit,

I then tend to assume that the 2 "faulty" boxes are ok.
Even if the shields of all the coax cables connected together are grounded to the tower's copper ground rod, i will definitely connect the in-house three way splitter to the nearby copper pipe, that way i will connect the tower
ground to the one of the house which they aren't at the moment, that way i'll make shure there's no possible electric differences between them.
I have no piece of equipment with 3 wire cord but i can replace the 2 wire cords with 3 wire ones at least on the Zenith box and the HD TV and also run a third wire from the Zinwell box's coax. connector along the cord to the ground of the outlet.

By the way could you just tell me a tip or two on how to insert a picture from my HDD on a Reply on DigitalHome forum? I went on the FAQs and found the infos about it but the correlation between the tutorial and the reply page
doesn't seems to be correct, i've worked on it for quite a while with no succes.

Thanks you so much, i really appreciate your support.

Loogeuil:

I agree with JamesK, don't change the power cords, just make sure that the coax is grounded to drain any leakage current.

I then tend to assume that the 2 "faulty" boxes are ok.

Click to expand...

I get the same impression. The only way to know how much leakage current is on your boxes would be to measure it. But, whatever it is, grounding the coax would take care of it. If you have a voltmeter, you also probably have an ohmmeter, so you could make the checks in the drexel link given above without too much expense. Sam Goldwasser shows how to make a simple circuit consisting of a 1.5K ohm, 10 Watt resistor in parallel with a 0.15 uF, 150 V capacitor to use with your meter to measure leakage current.

The drexel link doesn't seem to be working now, maybe this one will:
http://www.repairfaq.org/sam/safety.htm#saftes

By the way could you just tell me a tip or two on how to insert a picture from my HDD on a Reply on DigitalHome forum? I went on the FAQs and found the infos about it but the correlation between the tutorial and the reply page doesn't seems to be correct, i've worked on it for quite a while with no succes.

Click to expand...

The two threads that have helped me are:

How to create a photo album for use on the Digital Forum
http://www.digitalhome.ca/forum/showthread.php?t=92167

To show an image in your post you must put an image in your album. Then, before using the image, you must wait for the moderator to approve your image. When you then want to show the image in your post, heed the warning about using the BB Code.

An alternate way to show an image in your post would be to upload it to an image host like photobucket and then link to it in your post like I did with my image of the Simpson 229 Tester.

Post Pic or attachments
http://www.digitalhome.ca/forum/showthread.php?t=132164

This thread gives some more tips on showing your image. In particular, note post #11 by downbeat that says you must have a check by show images in your CP:
http://www.digitalhome.ca/forum/showpost.php?p=1177653&postcount=11

You are not able to post images as an attachment unless you are a DHC Supporter.

Thank you both very much. Merci beaucoup !

Click to expand...

You are welcome!

I'm glad that I was able to help. I'm also glad that you asked about it, so that I would have a chance to talk about leakage current. It exists in all AC operated equipment, but not many people are aware of it. In equipment with a 3-wire power cord the leakage current goes to ground; in equipment with a 2-wire polarized plug cord the current can go through you to ground.

In your equipment, what is important is the strength of the leakage current. Most guidelines say the leakage current must be less than 500 microamperes (uA), (0.5 mA). A measurement of the voltage is not sufficient to let you know if the amount of leakage current is safe or not.

You said that you had a Zenith box, so I made some measurements of my boxes:

All three boxes pass the test for leakage current. The voltage readings with the Fluke DMM are higher because its input impedance is higher which means that it doesn't load the circuit as much. I also tried voltage measurements with an analog VOM; the voltage readings would vary according to the range used because of the changing input impedance.

The Apex and the Zenith have built-in power supplies, but the Artec has a separate AC adapter that is a switchmode power supply 100 - 240 VAC input to 12 VDC at 0.5 A output.

Some people think that a polarized 2-wire plug will ground the equipment, giving a false sense of security. It doesn't; it only connects the neutral wire in the equipment to the neutral wire in the electrical system. You can verify this for yourself by using an ohmmeter between the antenna jack threads and the wider blade of the polarized plug. It should show an open circuit.

In spite of the fact that a polarized plug doesn't ground the equipment, it has some safety advantages. In the case of a table lamp the threaded shell of the socket is connected to the neutral (white) wire and the hot (black) wire is connected to the switch. When a bulb burns out, most people don't unlug the lamp or even turn the switch off. The polarized plug keeps the voltage off the threaded shell so that you don't get a shock if you happen to touch it when changing the bulb.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/hsehld.html

My third TV is a Samsung Series 7 (LCD) and i get no voltage at all measuring the same way.

Click to expand...

I also have a Samsung TV. It is a 19-inch set with a 3-wire power cord and there is no voltage on the antenna jack. I was surprised that it had a 3-wire cord and thought they did that because it can also be used a computer monitor.

I made some measurements of the TV with the grounding pin not connected to ground to check its leakage current as mentioned in the manual. I didn't cut the pin off but used a 2-wire to 3-wire adapter:

Fluke 25 DMM: 58.1 VAC

Simpson 229: 32 VAC
Simpson 229: 85 uA

The input impedance of the Fluke 25 DMM on the AC Volts range is 10 Meg ohms.

The input impedance of the Simpson 229 Leakage Current Tester on the AC Volts range is 500K ohms.

If I put a 500K or 510K resistor in parallel with the input of the Fluke 25, the voltage readings would probably be similar.

So you see, even equipment with a 3-wire power cord has leakage current, but it is shunted to ground.

Heyjohn,

You could get along with a 2 output splitter and an A-B switch.

___ Antenna >>> Splitter >>> Converter >>> Recorder >>> B-Input of the Switch

___ Other output of the Splitter >>> A-Input of Switch

___ Switch output >>> TV

B-position to watch the recorder on your TV

A-position to watch TV only (while the recorder does its job)
.