AVT-8710 green screen error?
 

I have a green AVT-8710 (green case).

The unit stopped working. It’s showing Green lines instead of an image. Sending screenshots. It was working fine as of a few months ago. Not sure what is happening or if this is fixable. Photos attached. please help.

The first check power supply/replace with new. But remember - center pin is negative.

After a power supply swap, second thing to do is recap it.

I can likely refurb the unit for you (including full recap), but certain things aren't really fixable like if there happened to be static damage or damage to one of the unique ICs. It having worked fine a few months ago and now not kind of suggests capacitors since they can go bad just from non-use, especially surface mount ones like this has. If I'm unsuccessful, I'd charge less of course. PM me if interested.

So i guess i had lost the power and was using a regular 12v i bought on Amazon. at first it didnt turn on (it worked a few months before). But then i found the one it came with it it turned on! I was excited but then when i ran video through it, what i got was the green screen. (i feel foolish)

Don't feel too bad. Back in the 80s, I accidentally stuck my NES power plug into my Sega Master System, and got a smoke show. Oops.

The good news for the AVT-8710 is that it usually doesn't blow up or smoke from reverse polarity. But TBCs lack fuses, so damage is passed to the unit internals. For this mistake, the fault is likely not chips, but instead the power input or a capacitor, or both. Not guaranteed, just likely.

In addition to the above offer, Diopter_Doctor has experience with fixing TBCs. This is not an error I can address at this time, overbooked.

I can fix the board.

Can you explain what exactly you do to it?

I change all the capacitors and the transistors.

In my experience it's usually just the surface mount electrolytic caps which fail.

Yes, I have the same experience with my Cypresses. Bad caps and bad soldering quality. And the best removing method in this case - just turn with pliers (carefully, pushing down when turning) and snap off. Then use desoldering wick to remove remains. Board quality is not the best and traces can be lifted easily. So I would recap first and then start to look for a problem.

Be careful of cheap Chinese power supplies, I learned the hard way. Had a personal storage HDD that used with a cheap SATA to USB3 adapter, Although I had second backups around, there was some very important personal files that I hadn't made a backup of yet, The power supply failed and took the HDD with, It cost me $400 for data recovery, Luckily the HDD did not break, just data corruption, but still it cost me to get the files back. Now I have to do my homework twice before I buy an after market power supply.

From what you say it's possible the amazon bought power supply damaged the TBC. It probably needs checking by a skilled tech.

I just pulled out my AVT-8710 and its suffering from the same problem using the original power supply. I suspected caps given that this just randomly failed, and I'm likely right going by the responses here. I don't see any obvious leakage, but I suspect the two 220uF SMDs near the power jack are faulty.

OP, what is the serial number of your unit? I've suspected the first 4 digits was a year of production (mine is "2004"), but I could be wrong. I purchased this off of the forum back in 2010 and it certainly wasn't new then.

Played around a bit more with the unit. I am suspecting caps as the problem is intermittent. Sometimes all the LEDs pop on the control panel, sometimes I get no lights or random lights. The input ADC appears to be working as when the unit boots up correctly, the video system autodetect locks onto NTSC and I can faintly see video thru the green output.

I realize this unit has two revisions, this is the working "early" green version with firmware v2.0. I have the following cap list based on markings:

C52, C53:
220uF 25V

C56, C57, C58:
470uF 10V

C47:
10uF 16V

Anyone who has recapped their unit, can they confirm these values?

Also, I did some poking around of voltages. I think the problem may be the power supply. The stock "Everglow" unit is testing as outputting around 20V with no load. Testing points on the input side of the board reports around 17V going into the buck convertor (Sanken Electric SI-8033JD). The specs of the converter state 15VDC input (some sites say 6.3V to 40V unregulated is fine for this part) and 3.3VDC output. Testing the output I'm only getting around 0.7V! Hmm, seems that diode at D1 is bad too..... ugh.

I suspect the buck converter AND the power supply may be faulty too, but I still can't rule out capacitors.

Probably the quickest way to cook the converter is to reverse the power supply polarity. Unusually these AVT 8710's require centre negative at the plug and socket on the back. It's a shame this is not marked anywhere on the unit. Once you have the correct power supply, keep it with the TBC and dont be tempted to use anything else. On mine I have marked clearly on the back that centre negative is required.

Stock power supply was used. Luckily the power supply circuit in this thing mostly follows the example provided in the datasheet for the buck converter. Note my unit only appears to have a 3.3V unit in it so I'm guessing this design only uses 3.3V ICs.

I'm not looking forward to soldering this thing though. I might just bit the bullet and replace all the caps, the diode, and the transistor.