Help repairing Sony Betamax SL-2500

[blue lander]

Hi,

I recently bought a Betamax SL-2500 from a thrift store and it wouldn't turn on at all, no display on the clock either. Upon opening it I found two problems:

1: The backup battery had leaked onto the board below it. I removed the battery and cleaned up the motherboard. I removed the components around the leak and repaired the damaged traces

2: I was only getting about 3v on the 12v rail. I replaced the two caps on the 12v rail in the power supply and now I'm getting 12v and 5v.

Even now that I have power, there's still no signs of life. The guy in this video had the exact same problem, but he decided it was more effort to fix than it was worth.

https://www.youtube.com/watch?v=ZVoJHQMbNes

I also found this post describing a similar problem, and he mentions that you should measure 12v on the test cable coming out of the clock module. I'm only getting 5 volts on both pins.

https://www.freelists.org/post/techa...ta-Dead-NO-FIX

Does anybody have an idea what the problem could be? Or is there a service manual availble for this unit? I found one for the SL-2700 and the SL-C9 (UK version of the player) but they're both significantly different internally.

[kf4rca]

I'd check around on the system/servo (SS) board for voltages. Check the connectors at the board's edge for voltage. If you have a scope check for clock oscillations on the main chip. You can look up the chip's number to find out which pins are clock.
You might still have problems in the area you did the repairs.

[Popester]

You also might check Mr Betamaxweb site. Might have posts on your symptoms you have.

[Popester]

mrbetamax.com is the website. Sorry I forgot to leave it on previous post.

[Oldperson1]

Since you’re only getting 5V instead of 12V on the test cable from the clock module, it could mean the clock module itself isn’t powering up properly or there’s an issue with its internal voltage regulator or connections.

[djfivos]

Hello. Sorry for the late reply. Did you ever succeed in finding the problem? I have a pdf of the SL-2500 service manual and I have three SL-C9s in my collection with good power supplies (two of them fully work) so I might be able to help. On these models the clock/timer must be operational before the rest of the unit can turn on (the power button triggers the POWER CONT signal in the timer CPU and then the timer CPU operates the relay in the power supply to turn on the switched voltages). One of the most common faults with the C9 is failure of the DC-DC converter module that supplies power to the tuner and the clock display (I repaired one of those). On the 2500 there is a DC-DC converter for the clock display too but it's slightly different and less prone to failure. What happens with the US/Canadian model is the timer CPU itself fails. You can bypass the timer to allow the machine to be constantly powered on.