Repair Log Seiko TV Watch Receiver TR02-01

Seiko T001

When I first purchased my Seiko TV watch a few years ago, I was able to set up a local TV broadcast and watch video on the watch.  This week I pulled it out to test out a new RF modulator and couldn't get a picture no matter what I tried. It would barely even show static.

If you're not familiar, the watch comes in two parts - a receiver box, and the watch itself.  The receiver box is basically a compact radio that also happens to tune in TV broadcasts and output video to the watch screen.  Given it's age I was not surprised when I opened up the receiver box to find pretty much every single electrolytic capacitor had leaked.  The fluid from a failed electrolytic capacitor is corrosive and if left unaddressed it can eat away the copper traces on a PCB.  Unfortunately this process had begun by the time I got the board out. 

Disassembly:

This was a very elegantly engineered device. There are almost no space tolerances at all which means that it's not very simple to take apart. Thankfully there aren't any screws hidden underneath stickers or anything like that.

1. Start by removing the battery cover and setting it aside

2. Next remove the two short black screws shown from the bottom of the receiver.

3. Push down on the front metal face plate to disengage the tabs. 

4. Remove the metal faceplate and set it aside.

5. Remove the short black screw from the bottom of the curved edge cap.

6. Remove another short black screw from the back of the curved edge cap.

7. Loosen the curved edge cap by gently twisting clockwise until the locking tabs disengage. If it doesn't move right away, just wiggle it. Do not attempt to remove the cap completely yet, just loosen it.

8. With the curved edge cap loosened, remove the two short steel screws from front of the top edge cap.

9. Remove the two short black screws from the back of the top edge cap.

10. Remove the top edge cap by pulling straight up.

11. Now gently pull the curved edge cap outward. Only pull as far as you need to in order to access the ribbon connector.  You do not want to straighten or otherwise stress the ribbon more than absolutely necessary.

12. Using your thumb and forefinger grip the ribbon connector.

13. Disengage the ribbon connector by pulling straight out from the connector.  Be as gentle as you can.

14. Remove the six remaining steel screws.  Three are medium length, three are long length note which screw goes where.  In the image below the screw heads point to the hole where they belong in case you need a reminder.

15. You can now remove the back half of the plastic case and set it aside.

16. Using the flat of a small screwdriver or other tool, press the end of the metal pin holding the tuner dial in place toward the outside of the case.  This will make it easier to pull the pin out in the next step.

17. Pull the tuner dial pin all the way out and set it aside.

18. Set the switches on the left edge of the case to their upmost position

19. Gently separate the front half of the case from the PCBs by pulling it away. With the switches in the upper position, it should just slide out.

20. Remove outer tuner dial by lifting outward.

21. Remove the inner tuner dial by lifting outward.

22. De-solder the black wire from the top part of the rear PCB.  Be sure to take note of the soldering points.  Also take this opportunity to remove the old Kapton tape.  

23. De-solder the points circled in red in the picture below.  The image below shows those points already de-soldered. They're connected to ribbon connectors that bridge the two PCBs. Do not use high heat or hold heat to these points for long or you will risk damaging the ribbons. 

This is the unit mostly disassembled.

Capacitor Removal:

There are two PCBs inside the receiver, and both use plated through-holes.  Under the best of circumstances, plated through-holes are difficult to work with, but when they've been partially corroded by leaked capacitor fluid there're even more fiddly.  Solder can't adhere to the oxidized and corroded surface of the metal.  When de-soldering, whether you're using a vacuum device or a de-soldering wick, you rely somewhat on capillary action to keep the solder stuck to itself long enough to draw it out. The bits of solder which were exposed to the electrolytic fluid don't melt into the other solder as easily so the components tend to stick in place.  Just be patient and keep adding and removing solder until the little buggers let go.  Do not use force because the acid in the electrolyte may have weakened the adhesive that holds the copper layer to the PCB and you could damage traces by pushing or pulling.

The PCBs in this receiver do not have a silkscreen, so there are no labels telling you the polarity or position of the capacitors on the PCB itself. This means it's vitally important to take pictures, make notes and double check everything.  I sketched a couple of drawings to keep keep track.  Since there are no capacitor designations, I just made some up to make it easier. 

Rough sketch of "PCB A" showing capacitor locations, polarity and designations I just made up.

Rough sketch of the "Main" PCB showing capacitor locations, polarity and designations I made up because there's no silkscreen. Note "C9" is actually mounted at a 45-degree angle, but the cathode is still on the left.

The capacitors I've labeled C4, C5 and C6 are underneath the bracket that holds the tuning screw.  The tuning screw drives a plastic gear which drives both the red bar that indicates what channel/frequency you're tuning to and the potentiometer that operates the tuner. If the screw is separated from the gear and the gear gets moved, the channel/frequency bar will no longer match what the tuner is actually doing. I decided not to completely remove the bracket to avoid getting these out of alignment, but as a precaution, I moved the dial so the red bar was all the way to the right, and then marked the gear teeth on the potentiometer.  I took a photo to remind me of the position.

To get at those three capacitors, I did have to desolder the left side of the bracket and pry it up out of the way slightly so the capacitors had clearance once desoldered.

Cleanup and Trace "Repair"

This is perhaps the first time I have ever opened a device and found that every single one of the electrolytic capacitors had failed and discharged electrolytic fluid.  It was not pretty.

The leaky electrolytic fluid had both formed a brown crust in places and had started corroding exposed copper into fuzzy/dusty green rust.  The brown crust is fairly easy to remove with a cotton swab and 91% IPA, but the green rust is a little trickier. 

The first order of business was to neutralize any remaining acid, so I used a cotton swab to dab the affected areas with a 1:5 dilution of clear ammonia and distilled water.  Following that, while observing through a microscope I used a combination of dental pics and scraping tip of an X-acto blade sideways to break off the corrosion and scratch through the oxidation.  I followed that up with a fiberglass pen. A good deal of the corrosion had work its way into the vias and through-holes, so I used an extremly fine width tungsten carbide hand drill to gently scrape the corrosion away.  When you get the corroded areas back down to bare copper, you'll have a better idea of the extent of the damage and how to proceed with fixing it.  It's also a good idea to cover the bare copper with something to discourage oxidation in the future - it doesn't have to be anything fancy, clear nail polish will work fine.

In a couple of cases the traces had been almost completely eaten away, but thankfully there was enough left that I could see where things were supposed to be connected.

Using a DMM, I buzzed out all of the traces to see what was still connected and what wasn't. Unfortunately I did miss one damaged trace during this process which made me have to open everything back up after I put it all back together.  I missed it because I only tested continuity from one side of the board and the copper fill between the layers had worn away.

The circled trace connects the audio capacitor the headphone jack. The ring on the left of the circled area, while obviously damaged is still connected to the trace that leads to the right ring, however the copper pour that connects the left ring to the other side of the board is no longer connected to the ring on this side of the board.

There are a number of different ways to repair damaged traces. For simplicity sake, I decided to use 32AWG wrapping wire to reconnect the broken connections.  

Capacitor Re-installation

As I mentioned earlier, there's almost no space tolerance inside this device. The diameter, length and lead spacing are all just as important as the capacitance and voltage.  In case anyone else finds themselves in this position, I've made a chart (again, the designations "C1, C2" etc are just something I made up, but you can scroll up to the sketch to determine the locations):

Location	Designation	Capacitance	Voltage	Diameter mm	Length mm	Lead Spacing mm
Tuner board	C1	47uF	6.3	5	5.5	2
	C2	47uF	6.3	5	5.5	2
	C3	47uF	6.3	5	5.5	2
Main Board	C4	22uF	6.3	4	5.5	1.5
	C5	100uF	6.3	6.3	5.5	2.5
	C6	100uF	6.3	6.3	5.5	2.5
	C7	47uF	16	6.3	5.5	2.5
	C8	1uF	50	4	5.5	1.5
	C9	10uF	16	4	5.5	1.5
	C10	33uF	25	6.3	5.5	2.5
	C11	33uF	25	6.3	5.5	2.5
	C12	100uF	25	8.2	9.3	3.5
	C13	220uF	6.3	8.2	9.3	3.5
	C15	100uF	6.3	6.3	5.5	2.5
	C16	100uF	6.3	6.3	5.5	2.5

If you can't find exact matches for these capacitors, you can get away with higher voltage tolerances, smaller diameters and smaller lengths. The lead spacing has to be exact for everything except C1, C15 and C16.  You can sometimes get away with larger capacitance values for the power capacitors like C12 and C13, but I do not have the expertise to know when this is safe and when it's not, so stick with the values of the capacitors as you find them.

And lastly, make sure you have a good pair of flush cutters and clip the leads very short when the new capacitors are installed. Even half a millimeter too long and the case will not go back together correctly.

While you're in there...

While you have the unit open and before you start putting it back together, it wouldn't hurt to:

• Apply a drop of Deoxit to each of the four sliding switches
• Inspect the battery contacts and clean them if necessary.  If alcohol will not clear away any discoloration or corrosion, use a rotary tool and a wire wheel. If you needed to use a wire wheel to clear away corrosion, apply some Deoxit to help condition and seal the surface.
• Inspect the barrel plug socket (for the power adapter) and clean if necessary, alcohol and/or a wire wheel.  Apply some Deoxit.

(You can tell I like Deoxit, right?)

Reassembly

Reassembly is basically assembly in reverse, but there are a couple of things to be aware of. 

• When re-attaching the two PCBs it is crucially important that they be perfectly flat. The black wire that runs along the back may cause the two halves to rock and sit crooked. If you accidentally solder them in that position, you'll have to de-solder and try again - the case will not fit if the two PCBs aren't aligned perfectly. 
• When re-installing the black wire pay special attention to the position it lays in across the rear PCB - the wire has to be flat up against the PCB - if it gets routed over top of any components, the case will not close up properly.
  

• When I attempted to re-install the black wire, it was hard to keep the ground wire from getting uncomfortably close to the leg of the left audio jack, so I put a small strip of Kapton tape underneath the ground wire of the black cable to ensure that they would not touch. It's very hard to see in the image below, so I've outlined where I placed the yellow strip of tape under the black wire.
  

• I'll mention here again that you have to clip the new component leads very very short or the case will not fit together properly.  
• When installing the top "cap" piece over the tuner bar, make sure the switch covers are slid into the same position as the switches themselves.
• When re-installing the ribbon go slowly and do not use much force. 
• If any of the screws do not align properly when re-assembling, go back and check that the black wire is not sitting on top of any components, and that your component leads have been trimmed all the way down (can you tell I made these mistakes yet?).

Back in Business

With everything put back together, I fired up my RF Modulator, put in my favorite test material - The Transformers: The Movie, and switched it on.  It was a cinch to get it tuned in.  Since it was much easier to get a good picture than it ever was before, I suspect the capacitors were failing even years ago when I first bought it.  I kind of wish I had taken the time then to open it up and inspect it - might have prevented some of this damage.  But who knows?