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[almcl]

I have broken my AstroEQ! (I think)

Had been using it with my grab-n-go set up and following invetsigations into a non-moving RA axis (which may have been down to a jammed stepper motor), I went to power up but got no response.  The power light comes on but the status light doesn't show any activity and attempting to connect via the Config utility (v 3.7.3) to update the firmware or configure the unit etc results in 'programmer not responding' message after 10 failed attempts to connect.

Any hints on diagnosing what's wrong would be welcome.

The unit is one of Tom's circuit board is V4.5

[TCWORLD]

Does the USB light blink?

[almcl]

Unfortunately, Tom, the USB LED succumbed to one of the accidental collisions with the concrete floor and Attempts to solder in a replacement merely demonstrated the inadequacy of my soldering skills and equipment, so I can't say. The controller was working OK without it for some months.

Thanks for the prompt response, as ever!

Al

[almcl]

Update.

Having spent the early afternoon with a soldering iron (and heart in mouth) I can now report that when the USB lead is connected the 'link' LED flashes quickly and continuously.  No flashing when power is connected or before the USB lead is plugged in. No sign of life from the status LED.

[TCWORLD]

Hmm. Might be a dead MCU.

Have you got an Arduino to hand? could wire up ArduinoISP to the ISP connector and see if the chip can still be programmed directly.

The other thing to try is connecting R15 and R16 together on the side of the silk screen legend. Then open a serial port utility (e.g. putty, hyperterminal, etc.) and see if you get an echo back (that will make sure the USB-Serial is working).

[almcl]

Not sure I understood all that!  But thanks anyway.

Don't have an Arduino nor an ISP for one, so dug out a copy of HyperTerminal and shorted the two resistors you indicated together (not without its challenges if you are as ham fisted and vision deficient as me :-). 

Typing AT in the HyperTerminal window shows the letters on screen when the two resistors are shorted together, but doesn't when they aren't, so does this mean the USB serial link is good?

And if so, does that mean I need to order a new main chip?

[TCWORLD]

USB looks good then.

Do you have a multimeter? If so, could you measure the voltage between pin 40 (+5V) and pin 20 (GND) of the ATMega? It's worth making sure that the 5V regulator is still working correctly.

[almcl]

Yes, multimeter readings are no prob (about the limit of my electronic ability!)

Pin 40 (on the opposite side of the chip from pin 1) shows 5.00 volts.

[TCWORLD]

In which case it is probably in need of a new main MCU.

Possibly a power surge from the motor being jammed has fried it. Hopefully the motor drivers are still functional.

[almcl]

Thanks, Tom.

I've ordered a replacement via the purchase page.  Fortunately, I still have a spare motor driver chip as I got through several of those a while back!

Al

[almcl]

Many thanks for the chips which arrived today.

Plugged the new ones in and all is working again, so, a great remote diagnosis for which many thanks!

Al