How To: Craig W460 switchable AUX input hidden in Dolby pushbutton

[Rhye]

I'd like to share a solution for Craig AUX input that I've never found published anywhere before - correct me if I'm wrong. My idea uses a Dolby pushbutton & LED to switch the AUX input on and off any time you want when in FM or AM mode - no additional switch is needed. Both AM and FM tuners are switched off when the AUX input is on. AUX input is disconnected when either of tuners or a tape is on (so there's no interference between them). All radio and tape functions, including Dolby filter, remain unaffected by this modification. I've also modified power antenna circuit so it will retract when in AUX or tape mode.

You can use the AUX input by simply connecting it to any audio device. There's also a potential to use a bluetooth transmitter connected to AUX input - it can be hidden somewhere (in a glove box, for instance) so there's absolutely no impact on car's interior look.

I've tested this mod successfully on early-style Craig but I guess it will work exactly same on later-style W460 with clock. And since I'm a bit far from a professional electronics engineer, there's a little chance that my solution might have some shortcomings I've not taken into account or I've not noticed - I'm sure there are electronics experts among you to give an opinion. Anyway, for those brave souls who want to try, DIY manual is attached. Enjoy.

W460_hidden_AUX_by_Rhye_v1.0.pdf

[DMCMW Dave]

I'd like to share a solution for Craig AUX input that I've never found published anywhere before -.
W460_hidden_AUX_by_Rhye_v1.0.pdf

I'm amazed that there is enough room in the radio to add two relays. It's amazingly tight in there! Nice work on the write-up.

[Mark D]

Wow this is a fantastic how to! It really makes me want to attempt this mod... Hopefully this summer I'll have some time

[cdouch]

Love this! Working on doing mine at the moment. Although, I'm wondering if it's possible to get the display to read AUX. I'm think that maybe the unused half of the second relay could send a current to the right connections of the LCD screen. Just a question of working out which are the right ones. What do think?

[Ron]

[Rhye]

Yes, I've even made some research into displaying AUX when preparing this mod, but decided not to do it 'cause it's quite a lot of additional wiring. Besides, I thought that a single dolby LED is just enough for indication - just my "less is more" approach .

The spare relay contact can be used of course. Try to use a wiring diagram to find the correct connecting points. Don't forget to use a separating diodes for powering/grounding the segments. And mind the voltage/current limitation of LED's when deciding the power source! It's easy to destroy one.

I can prepare some simplified how-to for this option within a week or so, but all the tests will be completely on your side (don't have time for that at the moment, have to focus on my project cars before the warm season is over).

[Rhye]

One important correction/clarification to my post above: you can only display single letter (or a set of 3 identical letters - which is useless :| ) using the method I've described! I'd suggest to make an "A" letter in place of one of the digits. Sorry for confusing you - several months have passed since my last "contact" with W460 and I totally forgot that our display works in multiplexing mode, which means that segment inputs are common for all digits. :| Displaying "AUX" obviously requires installing additional 7-segment display driver (no way to use the existing uPD1701c-013 FM/AM synthesizer), but it will be a bit tricky (if not impossible) to force a standard one (digits only) to display the letters we need, so probably more advanced IC would be needed here - I'll try to check it out soon...

[Rhye]

OK, so here is my very rough idea on displaying "AUX" letters:

AUX_display_driver.jpg

The circuit consists of 2 IC's, 9 transistors, 10 diodes, 17 resistors and 3 capacitors. PCB would need to be designed and some space inside the radio housing would have to be found. The CD4553 provides sequential grounding for 3 digits, as well as powering for some segments through a simple array of diodes switched by a 3 pairs of polarity inverting transistors. Those segments which are common for all 3 letters are powered constantly. NE555 servers as a square wave generator for 4553.
Quite a lot of hassle for such a simple and quite imperfect effect ("X" will actually appear as "H"). If anybody is still interested, I can develop it further. I'd also appreciate if someone more experienced than myself can propose a better/more simple solution, or at least can point out all my mistakes.

[Rhye]

I've got one important note to share with all do-it-yourselfers - please take a look at the front PCB layout from page no. 2 of my manual:

front_panel.JPG

All those circled areas look like PCB pads bridged together - they're in fact LED symbols! Some of you may find it confusing when troubleshooting the mod.
I'm attaching an updated manual with LED's erased for clarity (that's how this side of PCB actually look like). Many thanks to Bikercmbc for pointing this out!

W460_hidden_AUX_by_Rhye_v1.1.pdf