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Sega STV repair (Need help)

HardAzRockz

HardAzRockz

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I've had the broken STV board for a couple years. It had some physical damage to the CPUs and couple resistor arrays and caps. I decided to work on it today. I replaced the CPUs, caps and arrays, The system boot with or without the the DS Multi cart.to an error message. 1673911942662.png. I then hit the service button and the STV logo plays. 1673912034811.png. I then hit the test button and do a ram test which is demonstrated in the video.
View: https://youtu.be/zZzMPID7Gkc
It says IC10(HM514260CJ7)is bad but doesn't finish the ram test . I would appreciate any help or advice. thanks
 
I’d start replacing IC10 then see if it pushes things along in the test. If not, I’d replace IC24 and go down that path…
 
djsheep said:
I’d start replacing IC10 then see if it pushes things along in the test. If not, I’d replace IC24 and go down that path…
Click to expand...
I plan on replacing the bad ram(potentially). I'm about to burn the multi bios and test again. I don't expect and different results.
 
You could try reflowing those IC’s and seeing if they magically come back to life, or even flexing the board gently.
 
Anyone else have the issue where the ram test doesn't complete? I would expect it to complete the ram test showing all potential bad rams.
 
My answer may sound silly but did you try cleaning the contacts them sometimes happens like on nes consoles or SNES Ect..

It could also be a broken solder or changing the EPROM in the socket.
 
Last edited:
HardAzRockz said:
Anyone else have the issue where the ram test doesn't complete? I would expect it to complete the ram test showing all potential bad rams.
Click to expand...

In MAME, after testing IC11, it looks like it moves on to test IC24 and IC25 simultaneously. Since it's freezing at that step on your board, it's likely that either or both IC24 and IC25 (or the connections to them) are bad.

Screenshot.png
 
Adrick said:
My answer may sound silly but did you try cleaning the contacts them sometimes happens like on nes consoles or SNES Ect..

It could also be a broken solder or changing the EPROM in the socket.
Click to expand...
I cleaned the cartridge slot and reflowed the ram.
 
Hold the service button on boot (gives you a diff service menu) and check the CPUs.

If you run the test and one is bad grab a heat gun and reflow the legs of the 2 cpu chips.
They have a tendency to bend legs out when you put carts in the board.
 
Well, we got really good experts here. Definitely checking the RAMs and their connections and the other service menu to check the CPUs are they 2 compulsory tests IMO.

Good luck! Let us know how it goes.
 
Rukas said:
Hold the service button on boot (gives you a diff service menu) and check the CPUs.

If you run the test and one is bad grab a heat gun and reflow the legs of the 2 cpu chips.
They have a tendency to bend legs out when you put carts in the board.
Click to expand...
I just found this somewhat hidden menu earlier and the dual CPU test and it says the salve CPU is bad. i tested all 144 pin and no bridges and everything seems connected. I went over it again. same bad slave message. These aren't the original CPUs. I bought them from UTsource couple years ago and I believe they were used. there's a possibility the CPU is just bad. the original CPUs were physically damaged like someone drop something on top and and multiple pins missing. I will remove the CPU and have a look. I soldered these on two years ago and haven't touched it since..
 
Darksoft said:
Well, we got really good experts here. Definitely checking the RAMs and their connections and the other service menu to check the CPUs are they 2 compulsory tests IMO.

Good luck! Let us know how it goes.
Click to expand...
Ya those damn CPUS! Worst design ever. I have 2 working STV boards this is my 3rd. and Its a back burner project i finally got around to look at. it after two years. Might need to harvest a CPU from a junk Saturn.
 
HardAzRockz said:
I just found this somewhat hidden menu earlier and the dual CPU test and it says the salve CPU is bad. i tested all 144 pin and no bridges and everything seems connected. I went over it again. same bad slave message. These aren't the original CPUs. I bought them from UTsource couple years ago and I believe they were used. there's a possibility the CPU is just bad. the original CPUs were physically damaged like someone drop something on top and and multiple pins missing. I will remove the CPU and have a look. I soldered these on two years ago and haven't touched it since..
Click to expand...

The reason those other ICs are stalling there is usually because CPU2 is bad or testing blank. Try the CPU swap before doing the ICs again.
I have done a few boards in the last year with the same issue.
From memory you can use the sega saturn cpus as they are the same however im not 100% sure.
 
Rukas said:
The reason those other ICs are stalling there is usually because CPU2 is bad or testing blank. Try the CPU swap before doing the ICs again.
I have done a few boards in the last year with the same issue.
From memory you can use the sega saturn cpus as they are the same however im not 100% sure.
Click to expand...
That makes sense. I bought a couple broken Sega Saturns with the intent to harvest the CPUs . Ended up fixing both and couldn't bring myself to harvest parts on a working systems. I will have to find another to harvest. Thanks for the help
 
Well I harvested a CPU from a Saturn and Im still getting a Bad Slave CPU.
1673992418472.png
I tested all the traces under and around the CPU. No bridges or loose pins. It must be something else.. I went back and swapped the MAIN CPU and same result. Not sure where to go from this point.
 
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