Black screen and drive problems with NTSC-J Model 2 Saturn

[Eidolon]

Hi again,

my next problem relates to a newly-bought "Skeleton Saturn" ("This is cool!" model).
I hope - with the community's help - I'll be able to revive it.

Hardware info:
- Model HST-3220
- Mainboard: Seems to be a VA15? (PCB info: Sega 171-7462B PC BD Saturn VA15, Made in Japan, 837-13137 IC BD Saturn Main VA15 JPN, (c) Sega 1997)
- CD Drive: Assy CD Unit Sat Jvc EXL-P608, Made in Japan

The symptoms are:
- it only shows a black screen when powered up
- the CD drive does not spin up the disc. The laser unit however moves (e.g. if pushed to the outside, during power-on it moves to the center) and tries to focus the laser on the disc (move up/down of the lens visible)

What I already did is:
- switch the CR2032 battery to a new one
- clean the flat cable between CD drive and mainboard on both ends with Isopropyl alcohol
- measure the voltage coming out of the power supply board on Pins 3 and 4 when Saturn is powered on. Both are fine (?) with 5,05V.

My questions:
- What can I test to evaluate further and pin-point the problem?
My lab-at-home is equipped with soldering station, multimeter, logic tester, so I can use all of these to hunt down the error in either device (3D controller or Saturn)

Thanks in advance - any help appreciated!

[Eidolon]

I got hold of the Saturn VA13 Board Service Manual now. Luckily, there are some similarities between a VA13 Board and my VA15 Board Saturn.

So, I could do some measurements against the specs, without having a clue how to interpret the results now.
Looking forward to ideas/tips on how to proceed!

Measurement power supply onboard circuitry
- CF1 = 5,05V (VCC)
- CF2 = 5,03V (VCC2)
- L8 = 5,03V (AVCC3)
- L9 = 5,03V (AVCC2)
- IC42 Pin 3 = 3,33V (LVCC)
Measurement CD Unit Power supply
- CN7 Pins 1/4 = 5,05V (CD Drive Connector)
Measurement A/V Out Circuit ICs
IC21
- Pin 12 = 4,92V (VCC1)
- Pin 19 = 4,93V (VCC2)
IC22
- not possible to measure for me, because difficult to reach below power supply board
Measurement IC9 (Sega 315-5744)
- Pin 16 = 4,84V (VCC)
- Pin 15 = 4,79V (Reset) !!!!! potential problem?! - stays high
--> maybe IC35 (S-80723AN-DL) defective? Here Pin1 (CS=Reset) stays high
- Pins 13/14 = ~50Hz (X1/X2 32768kHz) --> probably my multimeter can't measure this correctly
- Pins 10/11 = ~50Hz (OSC1/OSC2 4MHz) --> " "
Measurement IC17 (Sega 315-5965)
- Pin 124 = low (Resetn)
- Pin 116 = 5,05V (Vcc)
Measurement IC14 (Sega 315-5964)
- Pin 78 = low (Reset)
- Pin 85 = 4,95V (AVCC)
- Sample VCC: Pins 10/151 = 5,03V (VCC)
Measurement IC5 (Sega 315-5966)
- Pin 100 = high 5,05V (Reset=SYSRES) !!!! potential problem?! stays high - what could be the cause of this?
- Sample VCC: Pins 208 = 5,03V (VCC)
Measurement IC37 (Sega 315-5962)
- Pin 115 = low (Reset=CDRES)
- Sample VCC: Pin 7 = 5,03V (VCC)

[dj898]

it's likely the laser module is busted. Try to replace the laser module and see it works - shouldn't cost ya more than $25 from eBay

[zyrobs]

Jun 22, 2016 1:51:15 GMT dj898 said:

it's likely the laser module is busted. Try to replace the laser module and see it works - shouldn't cost ya more than $25 from eBay

That won't help when the machine gives a black screen on boot. A working model 2 board should boot to the bios even with the entire cd drive removed.

I'd just find the most yellowed, dirty, and cheapest model 2 unit with a matching VA15 board on ebay, and swap it out with the skeletons.

[dj898]

then it's likely the PSU was busted and although it might have been replaced some other parts on MB was/were damaged?

[Eidolon]

Jun 22, 2016 1:51:15 GMT dj898 said:

it's likely the laser module is busted. Try to replace the laser module and see it works - shouldn't cost ya more than $25 from eBay

No, I think the CD drive is ok. the laser lens slide moves, it tries to focus on a CD, and it shows a red laser. Also, the spin motor is principally functioning, which I tested by attaching a 1,5V battery directly to the motor (it spins then).
Plus, what zyrobs said. It shouldn't cause a black screen.


Posted by dj898
then it's likely the PSU was busted and although it might have been replaced some other parts on MB was/were damaged?

That's what I am trying to find out with diagnostics & measurements according to the VA13 schematics (even though the Skeleton is a VA15 board - there are many similarities).

With good luck, it is just a standard component which has failed and can be replaced easily.
With bad luck, it's one of the Sega custom ICs which can't be replaced.

The hard part is to analyse and diagnose without having a diagnostics manual and parts list, just the schematics.

I guess I have three options now:
1. Wait patiently until real Sega hardware diagnostics gurus find this post and can give guidance on analysis/diagnostics to pinpoint the root cause
2. Buy a working VA15 Saturn as a reference device to compare measurements, try pinpointing the root cause myself
3. What zyrobs said. Forget the board, buy a new one(, keep the power supply board and CD drive as spare parts).

[fillernet]

Olá, eu tenho o mesmo problema com a mesma placa, VA15, model 2 JPN, Power Suply C, eu já troquei todos os capacitores e nada, foi quando cheguei no IC21 - "CXA 1645M", que pode ser substituído tranquilamente pelo
"BH 7236AF", esse CI faz o encoder de vídeo RGB. Já vi alguns vídeos que esse CI entra em curto cortando o vídeo. Amanhã vou fazer a substituição do CI para ver se consigo ressuscitar o meu Sega Saturn, foi bem agora que consegui encontrar os esquemas para converter qlqr controle de qlqr console no Saturn,, inclusive estava projetando um controle Arcade qndo me deixou na mão. Me desculpem mas escrevi esse comentário em português pq meu inglês ainda está pobre, kkkk façam igual a mim qndo não consigo entender o POST de vcs, jogam no Google tradutor Vlw

[davyk]

Sometimes it's a simple thing....how is this connected up to the TV and what type of TV are you using? Some modern displays just won't work with a Saturn.