TI Program Recorder schematics

[David994a]

Hello,

I'm wondering if anyone has the schematic for the TI cassette recorder.  I recently purchased a TI-99/4A bundle here in the UK and it came with the cassette recorder.  I plugged it in and popped in a cassette to see if it still worked.  Well, it turns out it was the USA 110V version and not the UK 240V version even though I bought it from a UK seller and the actual TI-99/4a PSU was the UK 240V version.  It actually worked for a brief period before starting to smell and then it stopped.  Looking inside it looks quite simple (late 70s mostly analogue tech) so I'm going to take a crack a fixing it.

 

Thanks,

David

[+arcadeshopper]

2 hours ago, David994a said:

Hello,

I'm wondering if anyone has the schematic for the TI cassette recorder.  I recently purchased a TI-99/4A bundle here in the UK and it came with the cassette recorder.  I plugged it in and popped in a cassette to see if it still worked.  Well, it turns out it was the USA 110V version and not the UK 240V version even though I bought it from a UK seller and the actual TI-99/4a PSU was the UK 240V version.  It actually worked for a brief period before starting to smell and then it stopped.  Looking inside it looks quite simple (late 70s mostly analogue tech) so I'm going to take a crack a fixing it.

 

Thanks,

David

just sent you this on facebook..  

 

[Ed in SoDak]

Have you tried it on batteries? Perhaps the doubled voltage only fried the AC power supply.

[+acadiel]

10 minutes ago, Ed in SoDak said:

Have you tried it on batteries? Perhaps the doubled voltage only fried the AC power supply.

Or replacing the transformer - could very well be that's all that got fried.  Some ICs in there (amplifier, diodes, etc) might have gotten collateral damage as well.  

[Ed in SoDak]

Yet another option is to use an external 240AC to 6vDC wallwart since there's a jack for that as well. For that matter, small plug-in adapters are cheap to convert US 120AC to Europe 240AC. So you're not necessarily limited to only using 240AC components.

 

I'd try either batteries or wallwart first, just to make sure the recorder itself wasn't damaged, meaning only the power supply took the hit. No sense fixing the built-in AC supply if the recorder itself is toast, although it might be easily repairable. But this test would at least show where to look.

 If something got smelly, it could be the transformer which may or may not show any discoloration, a multimeter should show if the windings are either shorted or opened. Any other fried parts might show heat damage.

[+acadiel]

Yep, likely the transformer might have had a fuse in it, and probably protected everything else.  (Or at least, you would hope it did.). The output of the transformer is likely 6VAC.  More when it’s not under load.  Try what Ed says - batteries first.  If those work, verify your rectifier or diodes past the transformer that turn the voltage from AC to DC are ok - if they are, then replace the transformer with a small 240V to 6V one.  (They’re usually on a small board next to the transformer.)