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[Boiler]

 It appears that I've managed to toast the RF output on 2 of my UR74a learning remotes!

I was performing some "RF stress testing" on my CM15a interfaces.  I wanted to see how my various interfaces (3 units of different date codes and firmware revisions) responded to repeated RF macro triggers. 

Remote 1:
After ~ 2 minutes of continuous RF transmission the CM15a activity monitor stopped indicating RF reception.  Ah ha says I, I've locked up the CM15a.  However, upon checking AHP everything appeared functional.  I assumed that I have run down the batteries on remote #1.

Remote 2:
After ~ 45 seconds of continuous RF transmission Activity monitor again stopped indicating RF reception.  Again the CM15a appeared to be fully functional.

Finally realization began to set in (Homer slap - DUH)- I've verified that the RF output on both remotes is non-functional.  I've replaced batteries, reprogrammed house codes...everything appears to function properly (IR works well) but the units do not transmit RF.

I've done a little searching but haven't been able to find any schematics for the remotes.  Has anyone on the forum seen schematics on the UR74a or similar RF remotes?  I'm curious how the RF output stage is configured (and loaded).

Both of my remotes are 2001 models (date code 01J40 to be exact) so they are a little long in the tooth (like the operator).  Granted I was performing some rather extreme tests, but there appears to be a good deal of variation in the "burn out time" between my two units.  I can't help but wonder how "other" units might handle DIM commands that could require a long RF transmission time.  Has anyone else had there RF remotes die mysteriously?

Marginally wiser (and substantially poorer),
The Boler

[Brian H]

Tried the FCC Database and did find the UR73A and it has schematics. I don't know the exact FCC ID Number for yours, but it should start with a B4S [X10s prefix]
I did get my UR19As along with the CM15A data there. maybe one of the other models maybe close if the UR74A is not found. Should be as I may have missed it or didn't have the exact ID number to search for.
I had a KC674 remote from a CK11 kit fry all by itself once. I thought the batteries died in short order and replaced them. The next morning the case had MELTED where the small RF coil in the transmitter circuit fried. Seems the output transistor shorted and the fresh batteries just discharged through the coils DC resistance.
https://gullfoss2.fcc.gov/oetcf/eas/reports/GenericSearch.cfm

[Walt2]

BTW, there are at least two different designs of the UR74a.

One design has the battery door on the lower half of the back, uses 4 batteries, and uses 3 digit codes.

The other design has the batter door on the upper half of the back, uses 2 batteries, and uses 4 digit codes.

[Boiler]

Brian and Walt,
Thanks for the replies.

I checked the externals of two of my remotes (4 battery units) for FCC ID's - found nothing.  I popped one open and again found nothing.  What I did see was a gutless wonder.  The keypad and case are a major portion of the cost for this unit.  The other thing that caught my attention was the micro-controller, or rather the lack of.  I couldn't find it.  Nothing but a RF section, a transistor, some passives and a black epoxy blob (see attached photo).

I dug out my third UR74a (actually I pried it from my daughters hand) and found the FCC ID label on the back - B4SUR- 73A.  Apparently X10 was able to use the UR73a filing for the UR74a since the RF sections are the same.  While I was having fun on the FCC site (Thanks Brian) I took a look at the parts list.  The black epoxy blob is a micro-controller die mounted to a PWB daughter board - now that's a bit of a surprise.  I'd love to see what this sub-assembly looks like (how do the protect the wire bonds, make the daughter board to motherboard connections, etc).

Anyway, I digress.  I now have a schematic and will post my findings.

The Boiler

[Walt2]

How did you open up your remote?   

I tried, and could not find any obvious screws, anywhere.   

Did you just "crack" or break it open???

[Boiler]

Walt,
Unless you're having problems (or dying of curiosity) I wouldn't open the remote.  My first unit came open easily.  The top fit rather loose and I was able to spring it open with my hands.  The cover has slots (or pockets) and the back has tabs (see pictures).

My second unit was a tight fit.  I used a 1 1/2 inch putty knife against the parting line and managed to get it apart.  However, in doing so I broke two slots (on the top).  I imagine you could build a clamp to compress both sides of the unit at the parting line (you are actually compressing the face of the unit to release the tabs). 

After opening my first unit, I noticed a lot of crap (dust etc.) by the RF daughter board.  I blew this out and to my amazement the remote began transmitting RF (RF short?? - seems a bit far fetched).

Unfortunately the same cannot be said about my second unit. No dust collection and "no worky".  I can operate the unit with the top cover off (the keypad has nice little tabs to align it to the main board.  Unfortunately, at the moment I need the back cover to hold the batteries and this prevents me from getting to the RF section.  One of these day's I'll find my little battery holder (forgot to check the kids room - he probably used it for a school project) and I'll start troubleshooting.

[Brian H]

Glad it helped. I have seen Motion Sensors using a different FCC number. Than the model I have bought.
The RF section is fairly simple. One transistor and a few parts. The IC just give the RF section an Enable and the IR circuit also keys the RF.
My UR19A has the SAME IC in; it just different number of total buttons. The 4 cell one may have more RF power as they seem to be on the full 6 Volts though the Emitter resistor is also larger. To not overpower the IC; the 6 volt one has some diodes as drops between the supply and the IC.

[KDR]

Thanks Boiler for the pics and info on opening up one of these. Wanted to clean up the inside of mine (sticky key) and now I won't need the hammer and safety glasses. (yet)

One of these day's I'll find my little battery holder (forgot to check the kids room - he probably used it for a school project) and I'll start troubleshooting.

You may want to see if maybe he took the RF daughter board as well. Maybe he is inventing his own line of X10 RF units. (be sure to let us know when they become available.  )

^{----------------KDR}

[Walt2]

Walt,
Unless you're having problems (or dying of curiosity) I wouldn't open the remote. 

My original, old, one has a couple of buttons that stopped working (like "Power"), unless you press them really hard and in just the right way.   I thought of opening it up, and giving the contacts a good cleaning to see if that helps.  I am not worried about really breaking it, since it isn't usable in its current state.

In the mean time, I bought new ones. That is when I discovered the running design changes (4 down to 2 batteries, 3 up to 4 digit codes, etc).

[dave w]

  I'd love to see what this sub-assembly looks like (how do the protect the wire bonds, make the daughter board to motherboard connections, etc).

The Boiler

Boiler -

Are you certain there is a daughter board under the blob? I have seen " cost reduced" designs, gluing the die directly to the PCB,  wire bonding to the motherboard pads, and "blobbing" with epoxy. If it does have a daughter board perhaps it is using the old "C5"  BGA technology which ends up being thin enough that it can still be "blobbed" but usally gets a ceramic cap instead.

[Brian H]

I believe the black blob is the Remotes IC. The RF daughter card looks like it is the one sticking up from near the IR LED. Shown in the inside.back.jpg photo.

[Boiler]

Are you certain there is a daughter board under the blob? I have seen " cost reduced" designs, gluing the die directly to the PCB,  wire bonding to the motherboard pads, and "blobbing" with epoxy. If it does have a daughter board perhaps it is using the old "C5"  BGA technology which ends up being thin enough that it can still be "blobbed" but usally gets a ceramic cap instead.

Dave,
No I'm not sure - the FCC parts list showed the micro-controller die as being part of a daughter board assembly.  I can't see anything components on the board that looks like it could be the micro-controller, so I'm assuming it's under the epoxy.  As you stated, this could be a cost reduced design that doesn't use the daughter board (hadn't thought of that).  I just cringe a bit when I think of epoxy (it is hard epoxy - not compliant) directly on a die and wire bond connections.  I'm used to dealing with military temp ranges and polyimide or ceramic PWB's.  As a result, I have the mind set that "thermal stresses would rip this thing apart".  Obviously my
mind set doesn't apply here.  It's always interesting to see how the commercial world packages things.

Brian,
You're correct - the RF daughter board is at the front near the IR emitter.  It consists of 5 components:

• 1 Load coil
• 1 Antenna Loop
• 1 Transistor
• 1 resistor
• 1 diode

My daughter board has 4 jumpers connecting to the mother board (schematic only shows three connections).  The fourth jumper appears to have been added for mechanical stability of the daughter board (another no-no according to my anal aerospace design background).
 
On the unit that I managed to get working, all I did (that I know of) was blow the dust off the antenna loop.  I can't quite convince myself that this was the problem.

[dave w]

Dave,
I just cringe a bit when I think of epoxy (it is hard epoxy - not compliant) directly on a die and wire bond connections.  I'm used to dealing with military temp ranges and polyimide or ceramic PWB's.  As a result, I have the mind set that "thermal stresses would rip this thing apart".
  
On the unit that I managed to get working, all I did (that I know of) was blow the dust off the antenna loop.  I can't quite convince myself that this was the problem.

Yup, I agree. Any critical electronics expected to survive wide thermal swings needs some type of thermal expansion buffer (aka chip carriers) between the silicon slab and a poly, glass, mylar, or even ceramic PCB.  But X10 company designs products to sell in high volumes at low price and I am sure the TV remote control is expected to operate in a relatively stable environment. Hence blobbing the chip directly. My experience has been; this technique is only used on the cheapest consumer "throw-a-way" electronics.

Regarding your "blowing the dust off the antenna" - did you try hitting that baby with a hot iron?

[Boiler]

Regarding your "blowing the dust off the antenna" - did you try hitting that baby with a hot iron?

No, but that's a good idea.  Actually I re-assembled the unit and was so astounded that it worked that I sat it aside and started dis-assembling the second unit.  I think my daughter has since grabbed it for the A/V system.  Unfortunately she only uses the IR functions so I won't be able to figure out if it's fixed or intermittent.

Time to strike another deal with a child (I always seem to come out on the short end of these).

[waterstom]

All - I have a program for the Palm OS that I could send anyone who wants it, it's freeware.  You can test IR devices with it.  Run it and you then point the suspect device at your Palm's IR rcvr and you see a graphical indicator, and signal strength (and maybe one other thing, it's not with me right now, I can't remember)

It's quite handy to troubleshoot whether a remote is bad, low batteries, or just a single button is going bad on an otherwise ok remote.

message me and I can email it to you beginning late tonight or tomorrow if anyone wants it.  Tiny file, won't screw up your email.

HTH
Tom