Toshiba RC-K1 Clock Radio

[davegsm82]

I'm trying to find a schematic for the aforementioned clock radio, being VFD I have more of a hankering to save it rather than it's LED counterparts.

It works but some of the buttons on the strange circular clock-set arangement don't work. I think I've traced it to an input on the main Clock IC (T6589 - No info) which has suddenly become an output.

There's a copy of the schemtaic on Radiomuseum but I don't have an account there, so I know at the very least that it exists.

Can anyone help? Before I strip out the mains TX for another project?...

Thanks, Dave.

[Mark Hennessy]

You don't have to be a member to download from there these days. Click on the schematics and fill out the form - it will arrive via email.

[davegsm82]

I'm still sort of at a loss, I can't see a form to fill out, clicking 'I need this schematic' from the second dropdown box just takes you to a login page. My membership long since expired and it looks like the only way to sign up is to 'Earn' or 'Pay'.

Or perhaps I'm missing something?...

[Mark Hennessy]

I just Googled the model number, followed the first result to RM.org, clicked the schematic on the top right, then clicked the schematic on the left of that. Up pops the window with the form...

The attached screen shot shows what I did.

   

I'm not logged on to RM.org on this PC, so you should see what I see.

[davegsm82]

Ohhh. Oh, thank you, I see what you mean now. My crumby internet here is has caused me to miss that pop-up box when it opened.

I've applied for the schematic, thanks again!

Dave.

[davegsm82]

Have received the schematics from Radiomuseum, sadly looks like it will be curtains for this unit, the 'A' line from the keyboard is most definitely an 'Input' on the T6589 clock IC, however it's suddenly become an 'Output' and is stuck high at about 200k-Ohms but only when powered up. When switched off it's just like all the other pins, about 0.5MegOhms.

I suspect the T6589 IC is a special and only used in this unit. Shame!

Thanks for all the help.

[Mark Hennessy]

Ah well...

I trust you'll be re-deploying the VFD though

[davegsm82]

I'm not sure, after re-examining the circuit it looks like the voltage I'm seeing on the collector of a transistor doesn't make sense but is true to the manufacturers data. So it looks like it MIGHT be right, but it just doesn't work properly.

If I do scrap it then I'll be keeping the mains TX as I need it for another vfd project,  not so bothered about the tube itself.

[Mark Hennessy]

It's not the most obvious circuit. It doesn't help that it's across multiple PDFs that I don't fancy trying to stitch together.

What's the deal with the switches with 3 contacts? Are all 3 shorted when the switch is pressed? I'm guessing that must be the case - it looks like you have to hold either "ALARM ADJ" or "TIME ADJ" for the buttons in the circle to work?

I can't see why the collector of Q801 is at 15V when the base and emitter is at 14.5V. So that suggests that it is lifted up there by "A". I guess a 'scope on the collector might reveal a pulse or similar. Obviously the pin could be both an input and an output, depending on how it's scanning the keyboard. Wonder why they didn't go for simple X-Y scanning? 34 switches, 6 times 6, so 12 pins (earth and +V not needed), and conventional SPST switches. But I guess the IC designer had some other idea...

[davegsm82]

Hi Mark,

You're following the same line of reasoning as me regarding the 'A' line. You'll notice that R802 is referenced to ground, so it would reason that the A line is an input to the micro, however when I lift the inter-board connection for A, the micro side stays solid at about 16V, whereas the voltage on R802 falls to zero, only coming up to ~15v when Time ADJ and one of the buttons assosciated with Q801 is pressed.

The 3 contact switches are odd, they threw me for a while, before I had the diagram I was wondering why I seemed to get 3 different voltage readings on the same set of contacts!

I've looked for pulses and found none, this whole thing works on logic 1/0, just at unconventional voltages.

It's time is short....