Gilat AN8004 mod.

[Zapping]

After seeing your setups I already have some good ideas to protect the lnb from the rain without raising the temperature, next time I go up to the roof I already know how to solve it.

 

[Zapping]

Bad news my friends, unfortunately I think my adventure in the Ka band is over.

Today my Ka-band stopped working, I went to the roof to see what was going on but everything was ok, I removed the lnb and I noticed that even though it was well insulated there was water in the F connector socket that ended up being absorbed into lnb, I opened everything to clean it up but there was no more sign of life.

Using previous images you can see that there is an affected circuit, is there any way to recover this?

 

[s-band]

is there any way to recover this?

The area you highlight is unlikely to make much difference. Those are chokes to keep high frequencies (probably the LO or LO/2) coming out of the IF port. That shouldn't stop it working.



First, bake it for a few hours at about 80 degrees.

I've highlighted the areas that are more likely to have stopped it working. It's hard to see from the photos but there may be connections across the inter-stage coupling lines. Before you start, measure the current drawn by just the LNB and record the noise profile on Crazyscan or IQ Monitor etc. From memory, the current is normally around 120-130mA.

I would get a small, short haired, stiff brush and some IPA (Propan 2 ol). Scrub the whole board paying special attention to the corroded areas. Also clean up the soldered areas. That is best done under a stereo microscope or good magnifier. Take care not to do any more damage when scrubbing. You might need to us a needle to clear areas between tracks but make sure those areas are meant to be clear. Give it another clean after using a needle to remove anything disturbed. Make sure that the oscillator under the board looks clean. Once you've cleaned it, check again to see if there are any breaks in the thin tracks.

Re-check the current and noise profile. Has anything changed? If so, it is worth testing again on the dish.

Good luck.

 

[John]

The area you highlight is unlikely to make much difference. Those are chokes to keep high frequencies (probably the LO or LO/2) coming out of the IF port. That shouldn't stop it working.

View attachment 151427

First, bake it for a few hours at about 80 degrees.

I've highlighted the areas that are more likely to have stopped it working. It's hard to see from the photos but there may be connections across the inter-stage coupling lines. Before you start, measure the current drawn by just the LNB and record the noise profile on Crazyscan or IQ Monitor etc. From memory, the current is normally around 120-130mA.

I would get a small, short haired, stiff brush and some IPA (Propan 2 ol). Scrub the whole board paying special attention to the corroded areas. Also clean up the soldered areas. That is best done under a stereo microscope or good magnifier. Take care not to do any more damage when scrubbing. You might need to us a needle to clear areas between tracks but make sure those areas are meant to be clear. Give it another clean after using a needle to remove anything disturbed. Make sure that the oscillator under the board looks clean. Once you've cleaned it, check again to see if there are any breaks in the thin tracks.

Re-check the current and noise profile. Has anything changed? If so, it is worth testing again on the dish.

Good luck.

Following on from s-band if this helps a bit, iv'e had this problem like yours in the past in exactly the same place where it took out the tracks on both chokes. A multimeter continuity check between the output IF pin and the good side of the remaining choke could be done - if damaged perhaps try a hard wired link wire over the two damaged chokes.
Here's two CS plots from my two healthy 8002 & 8004 receiver boards, looking straight up into sky, not on satellite - current draw at 17.6 volts supply on both of my units are 84mA on the 8002, and 87mA on the 8004.
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

 

[Zapping]

Re-check the current and noise profile. Has anything changed? If so, it is worth testing again on the dish.

After a new careful cleaning nothing has changed, in these photos with better definition it is possible to observe that all the circuits + oscillator are in good condition except those two chokes that were completely burned, current probably doesn't pass from there.

iv'e had this problem like yours in the past in exactly the same place where it took out the tracks on both chokes.

Did you succeed in recovering the lnb or did you just throw it in the trash?

 

[John]

After a new careful cleaning nothing has changed, in these photos with better definition it is possible to observe that all the circuits + oscillator are in good condition except those two chokes that were completely burned, current probably doesn't pass from there.


Did you succeed in recovering the lnb or did you just throw it in the trash?

View attachment 151430

View attachment 151431

I didn't spend too much time trying to repair mine, i tried to do a repair on the actual choke's themselves but failed - it's micro surgery plus the fact that i don't possess the right equipment or skills level to carry it out. The underside of your board looks a bit suspect and in need of the cleaning procedure that s-band suggested to you.

 

[dreamsat]

The layout of this board probably consists of 3 to 4 layers. If I look at this board from the back, then there may be a lot more going on there. Dry, dry and dry again, like S-Band said

 

[Zapping]

Thanks for suggestions, the underside board looks bad but it's clean and apparently without any damage, those are age marks and part of them already existed when I bought Gilat.

I'm going to dry the board in the sun (it's 40 degrees here) and tomorrow I'll try again but I don't have big hopes.

 

[s-band]

I wouldn't worry about the corrosion on the large areas of plane on the underside.

I should have said that the current of around 120mA is with a 12V supply (it gets higher at lower voltage). Attached are my notes from a while ago showing voltages across the board. I'm surprised that that input track eroded enough to break the connection but re-making it with a bit of copper tape will be OK.

If the electrolytic action caused dendrites to form between the coupling elements in the LNA, it's possible that the FETs could be damaged. In that case, you'd see reduced output noise. Compare the voltages to mine. There will be small variations between FETs and be aware that the LNA may go unstable with the cover removed. This will affect the voltages a bit. However, the gates should all be slightly negative and the drains around 2V positive. Check that the synth is locked by looking at the voltage on the pin next to the IF out. It should be around 2.5V locked and will be zero when unlocked.

 

[Zapping]

I didn't have the skills or tools for a repair like this but I couldn't devalue your help here on forum and so I decided to get work.

It wasn't easy, I bought a multimeter, a soldering iron, watched a few videos on youtube and started measuring voltages, initially the values were always 0 and only when I skipped the first chokes and started measuring from the third onwards did I get results and guess what....? values matched exactly by the @s-band measurements.

I soldered a copper wire bridging the affected area and voila, the job wasn't perfect but the most important thing is that I have my Ka band back.
A thank you to all.

 

[John]

I didn't have the skills or tools for a repair like this but I couldn't devalue your help here on forum and so I decided to get work.

It wasn't easy, I bought a multimeter, a soldering iron, watched a few videos on youtube and started measuring voltages, initially the values were always 0 and only when I skipped the first chokes and started measuring from the third onwards did I get results and guess what....? values matched exactly by the @s-band measurements.

I soldered a copper wire bridging the affected area and voila, the job wasn't perfect but the most important thing is that I have my Ka band back.
A thank you to all.



View attachment 151493

View attachment 151494

Well done .