A TiVo HD that I have previously repaired (power supply) a few years ago has now quit working, but all power supply voltages are good. It does not boot and it has the dreaded blinking green LED problem. Internet reports indicate that this problem can be fixed with, of all things, a hair dryer heading up all of the memory chips. I actually used a heat gun on the chips, and that caused it to reboot again on the bench, which led me to believe I had fixed it. But after a period of time and re-installation, the blinking green light came back with no boot.

So I theorized that I got it hot enough to cause the memory chip broken connection (somewhere that I have not seen) to temporarily mend, but that the further cooling of the chip caused it to fail again. So I decided to get an SMD hot air rework station to reheat the chips to hopefully get a better solder reflow. I also ordered liquid flux and solder paste just in case.

Since I have no experience with SMD hot air rework, I am wondering if I should just use hot (hotter) air on the memory chips to effect a better reflow, or if I should consider using either the liquid flux or the solder past in the last resort. I also have solder wick at hand if I need to use it.

Does anyone have any guidance on how I should start my repair with the the rework station when it arrives?

It's a pretty simple rework station costing about $80. It's a Super Deal (Zeny rebranded) 853D rework station.

 

Just to set expectations: although being a widespread belief, the re-working of existing devices is rarely a long term solution, unless you are very lucky and a BGA ball gets re-connected or some dust/moist gets burned/evaporated. Otherwise, you will be thermally stressing the device packaging and only momentarily reconnecting its internal wiring - this is particularly critical for FCBGA packaging (flip-chip).

 

Just to set expectations: although being a widespread belief, the re-working of existing devices is rarely a long term solution, unless you are very lucky and a BGA ball gets re-connected or some dust/moist gets burned/evaporated. Otherwise, you will be thermally stressing the device packaging and only momentarily reconnecting its internal wiring - this is particularly critical for FCBGA packaging (flip-chip).

The memory chips do not have BGA connections. They are SMD packages with no connections under the chip. I would never consider doing a repair on BGA chips, or chips which have connections on the underside of them. These connections are all visible (not considering any connection internal to the chip which might be broken).

 

Does anyone have any guidance on how I should start my repair with the the rework station when it arrives?

It's a pretty simple rework station costing about $80. It's a Super Deal (Zeny rebranded) 853D rework station.

Find some old boards to practice on so you can make mistakes on those instead of something you care about.

Get some paste flux, like Amtech NC-559-V2-TF or equivalent.

It will be a little messy, but it technically doesn't have to be all removed so a reasonable cleaning will be enough.

Practice first. Practice. Also, practice.

 

The memory chips do not have BGA connections. They are SMD packages with no connections under the chip. I would never consider doing a repair on BGA chips, or chips which have connections on the underside of them. These connections are all visible (not considering any connection internal to the chip which might be broken).

Ah, thanks for the clarification. That certainly changes things and you are on the right path. @Yaakov 's tips are very useful.

 

Ah, thanks for the clarification. That certainly changes things asnd you are on the right path. @Yaakov 's tips are very useful.

Thanks for the update. I got the rework station, and I fitted the air gun with the smallest of the nozzles. The temperature of the station was defaulted to 300 C, I read somewhere that lead free solder, which is probably what's on the motherboard melts at about 220 C, so I set the initial try to 250 C and started warming the chips. There are four memory chips on the motherboard of the TiVo.

I didn't see much happening -- I thought I might see solder melting to re-flow (and maybe it did) but it didn't notice it. So I set the temp up to the default of 300 C and just kept blasting all of 8 sides of the four memory chips.

Initial tests: It boots like it should. I'm giving it an overnight cool down, and will test it in the morning.

When I was doing this, I realized just what a novice I am at it. I had aluminum foil close by if I saw any tendency that nearby components were coming un-soldered but no such thing occurred. The memory pins look just a bit more shiny after the heat treatment, but I cannot say that I saw liquid solder re flowing. Maybe the solder melt is all in my mind. If it fails after a cool down, I'm going to try a little liquid flux. If that fails, I may actually try a little solder paste. Face it, if I can't fix it it is trash, but it's a TiVo unit with a lifetime service, hence the work to fix it because it is still valuable compared to what you can buy today.

 

When I was doing this, I realized just what a novice I am at it. I had aluminum foil close by if I saw any tendency that nearby components were coming un-soldered but no such thing occurred. The memory pins look just a bit more shiny after the heat treatment, but I cannot say that I saw liquid solder re flowing. Maybe the solder melt is all in my mind. If it fails after a cool down, I'm going to try a little liquid flux. If that fails, I may actually try a little solder paste. Face it, if I can't fix it it is trash, but it's a TiVo unit with a lifetime service, hence the work to fix it because it is still valuable compared to what you can buy today.

For me it became hard to see with a naked eye the solder melting when using my hot air - just like you, I was never sure but in the end I got a stereo microscope and this surely helps.

If you end up using the liquid flux, just be sure to have also isopropyl alcohol as a cleaner, since the flux will be blown everywhere on the board.

Good luck!

 

For me it became hard to see with a naked eye the solder melting when using my hot air - just like you, I was never sure but in the end I got a stereo microscope and this surely helps.

If you end up using the liquid flux, just be sure to have also isopropyl alcohol as a cleaner, since the flux will be blown everywhere on the board.

Good luck!

Well, so far, the repair has held. So I will only do the liquid flux if the problem re-occurs. I'm hoping it holds for a few years.

I saw on You Tube a guy who makes his own flux by dissolving rosin 90% isopropyl alcohol. I bought some Keester liquid flux, but my grandson plays violin. One of the violins I bought him came with light colored bow rosin, but the violin teacher said to get darker (better) rosin for the bow. The guy I saw make his own liquid rosin on You Tube said that the lighter rosin is better for electronics. So I might grab the cake of old unused light rosin from my grandson/s violin case and play with making my own liquid rosin. I don't have to do much hot air work right now, but I have some old boards I could use to practice with.

 

Well, so far, the repair has held. So I will only do the liquid flux if the problem re-occurs. I'm hoping it holds for a few years.

I saw on You Tube a guy who makes his own flux by dissolving rosin 90% isopropyl alcohol. I bought some Keester liquid flux, but my grandson plays violin. One of the violins I bought him came with light colored bow rosin, but the violin teacher said to get darker (better) rosin for the bow. The guy I saw make his own liquid rosin on You Tube said that the lighter rosin is better for electronics. So I might grab the cake of old unused light rosin from my grandson/s violin case and play with making my own liquid rosin. I don't have to do much hot air work right now, but I have some old boards I could use to practice with.

If it is the video I am thinking of, I suggest you ignore it. While he seems ot have a reasonable success with his homemade flux, there is no reason to ignore the ready availability of high quality, highly engineered, modern, no clean flux. Kester no clean flux is far ahead of the rosin flux for modern work on dense boards. The cleaning is less critical and even unnecessary, and it’s been specifically formulated for the application.

Think of it this way, you might watch a guy bowl consistent 200 games without using the finger holes, but if he says, “and so that’s why you should also not use the finger holes”, you are safe to ignore him even while you admire his skill.

 

If it is the video I am thinking of, I suggest you ignore it. While he seems ot have a reasonable success with his homemade flux, there is no reason to ignore the ready availability of high quality, highly engineered, modern, no clean flux. Kester no clean flux is far ahead of the rosin flux for modern work on dense boards. The cleaning is less critical and even unnecessary, and it’s been specifically formulated for the application.

Think of it this way, you might watch a guy bowl consistent 200 games without using the finger holes, but if he says, “and so that’s why you should also not use the finger holes”, you are safe to ignore him even while you admire his skill.

Well said! I probably have more Kester liquid flux than I'll ever use. I put both the solder paste and the flux in the refrigerator to prolong their lives.