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Cluster inverter reverse engineering project
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<blockquote data-quote="mwolson" data-source="post: 16813086" data-attributes="member: 16006"><p>Thanks to Cobra_Clark98 (from a different forum), who sent me his 2002 Lightning cluster with a definitely blown inverter, I have learned that the similar vintage Lightnings use the same inverter to drive their EL panels. He also shared some Lightning forum posts that showed me that what I had thought was a choke filter inductor is actually a soldered in 1/4A fuse.</p><p></p><p>The fuse is a Littelfuse R251.250 available at electronics distributors such as Digikey. This is what it looks like:</p><p></p><p></p><p><img src="https://www.corral.net/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.corral.net/attachments/1661611224374-jpeg.1089940/" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p></p><p>According to the Lightning forum posts, many inverter failures are due to this fuse blowing. That can be easily fixed by simply replacing that fuse. The fuse is the first thing you should check if you suspect a blown inverter. You can do this check with an ohmmeter across the two leads. You should read very close to 0 ohms across the two leads. To make the test easy, I have annotated a photo of the bottom of the PCB:</p><p></p><p><img src="https://www.corral.net/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.corral.net/attachments/1661611465156-jpeg.1089941/" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p></p><p>On the Lightning forum, someone suggested that the 1/4A fuse be replaced with a 1/3A fuse. I think this is a bad idea. The fuse is designed to protect the components on the PCB. The fuse is easy to source, but the other components on the PCB are not, so if they burn out instead of the fuse, then your inverter may not be repairable. I recommend that you stick with the 1/4A fuse.</p><p></p><p>This led me to compare the good inverter with the blown inverter. I was able to figure out which transformer pins were connected via windings and what the in-circuit resistances should be. The second test you can do is to check the resistances between the 3 pin pairs to see if the transformer is blown. Between Pins 2 and 3, you should see about 140 Ohms. Between Pins 1 and 4, you should see about 7 ohms. Between Pins 5 and 6, you should see about 12 ohms. Here is an annotated photo of the bottom of the PCB showing the pins you should test:</p><p></p><p><img src="https://www.corral.net/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.corral.net/attachments/1661612151042-jpeg.1089942/" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p></p><p>With the blown Lightning inverter, the resistance across pins 1 and 4 was in the 10s of K Ohms, which means that the primary winding of the transformer was blown out. Interestingly, the fuse is still intact, which doesn't make sense to me. The 120 ohm current limiting resistor should have limited the current through that winding to about 100mA. And the fuse should have limited the current through that winding to 250mA, so I can't understand why it blew out.</p><p></p><p>Unfortunately, I have not been able to find a source for a replacement transformer. It is possible that Ford had a custom transformer made for these clusters. At this point I have no way of repairing this Lightning inverter unless I can find an off-the-shelf transformer.</p><p></p><p>The next question is, what are the other common failure mechanisms and how frequently do they occur? In order to answer that question, we will have to look at more failed inverters. So I am still on the hunt for failed inverters to analyze and possibly repair.</p></blockquote><p></p>
[QUOTE="mwolson, post: 16813086, member: 16006"] Thanks to Cobra_Clark98 (from a different forum), who sent me his 2002 Lightning cluster with a definitely blown inverter, I have learned that the similar vintage Lightnings use the same inverter to drive their EL panels. He also shared some Lightning forum posts that showed me that what I had thought was a choke filter inductor is actually a soldered in 1/4A fuse. The fuse is a Littelfuse R251.250 available at electronics distributors such as Digikey. This is what it looks like: [IMG]https://www.corral.net/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.corral.net/attachments/1661611224374-jpeg.1089940/[/IMG] According to the Lightning forum posts, many inverter failures are due to this fuse blowing. That can be easily fixed by simply replacing that fuse. The fuse is the first thing you should check if you suspect a blown inverter. You can do this check with an ohmmeter across the two leads. You should read very close to 0 ohms across the two leads. To make the test easy, I have annotated a photo of the bottom of the PCB: [IMG]https://www.corral.net/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.corral.net/attachments/1661611465156-jpeg.1089941/[/IMG] On the Lightning forum, someone suggested that the 1/4A fuse be replaced with a 1/3A fuse. I think this is a bad idea. The fuse is designed to protect the components on the PCB. The fuse is easy to source, but the other components on the PCB are not, so if they burn out instead of the fuse, then your inverter may not be repairable. I recommend that you stick with the 1/4A fuse. This led me to compare the good inverter with the blown inverter. I was able to figure out which transformer pins were connected via windings and what the in-circuit resistances should be. The second test you can do is to check the resistances between the 3 pin pairs to see if the transformer is blown. Between Pins 2 and 3, you should see about 140 Ohms. Between Pins 1 and 4, you should see about 7 ohms. Between Pins 5 and 6, you should see about 12 ohms. Here is an annotated photo of the bottom of the PCB showing the pins you should test: [IMG]https://www.corral.net/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.corral.net/attachments/1661612151042-jpeg.1089942/[/IMG] With the blown Lightning inverter, the resistance across pins 1 and 4 was in the 10s of K Ohms, which means that the primary winding of the transformer was blown out. Interestingly, the fuse is still intact, which doesn't make sense to me. The 120 ohm current limiting resistor should have limited the current through that winding to about 100mA. And the fuse should have limited the current through that winding to 250mA, so I can't understand why it blew out. Unfortunately, I have not been able to find a source for a replacement transformer. It is possible that Ford had a custom transformer made for these clusters. At this point I have no way of repairing this Lightning inverter unless I can find an off-the-shelf transformer. The next question is, what are the other common failure mechanisms and how frequently do they occur? In order to answer that question, we will have to look at more failed inverters. So I am still on the hunt for failed inverters to analyze and possibly repair. [/QUOTE]
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