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Sl1200 Stuck On 45rpm

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Sl1200 Stuck On 45rpm

Postby diyaudio » 19 May 2011 11:50

Hello all,
I'm a tech working on my first SL1200. Found it cheap at a thrift store and I'd love to get it working to use with my music. Here's the issue:

I did a bunch of repairs on it as the power supply section blew and sent +38 to +42v down TP5 (the main power input). This blew the 10v NPN and some resistors and caps. I've replaced everything and now I'm feeding it a 20v PSU separately (couldn't get the onboard power supply working again but that's another story).

It runs smooth now but on start it' on 45rpm and I have to physically hold down 33 to make it do that. It' definitely not the buttons and I think it's a problem with the AN6680 since the speed select pins read ~6.5v on pin 6 and ~7.8v on pin 7. This is definitely way off judging from the service manual.

I replaced every electrolytic cap on board, but does anyone have any other ideas on what I could replace or what could be causing this? or could someone explain how the speed select works in a more normal operation? I'm thinking maybe 10k pull down or pull ups might trick into working but I rather get to the bottom of the problem.

many thanks in advance!
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Joined: 19 May 2011 11:40
Location: CA

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