Previously working x0x

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edm418
 
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Previously working x0x

Post by edm418 »

HI All, my x0x has been sitting unused for a couple of months.

When I went to switch it on the other day all LED's lit up and stayed lit.

There is no response from any of the controls, the LEDS stay lit, no response from random mode, keyboard mode or any other mode.

I checked voltage at J4 and its reading 5.27vdc. I cannot adjust TM6 to get 5.333vdc.

I'm really unsure of how to proceed from here but i imagine all problems are related to initial low voltages.

Can anyone suggest what to check next?

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antto
 
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Re: Previously working x0x

Post by antto »

you could try to reflash the firmware and see if that helps

edm418
 
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Re: Previously working x0x

Post by edm418 »

Hi Thanks for your reply, i was wondering about re-flashing the chip... but it wouldn't have anything to do with the low voltages in the PS circuit would it?

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antto
 
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Re: Previously working x0x

Post by antto »

i can't say why the voltage is low.. but having the sequencer working will be of help when troubleshooting, that's why i think it would be good to see if just reflashing the FW fixes it

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mmm
 
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Re: Previously working x0x

Post by mmm »

I don't believe that the low voltage is a problem here. The digital side is powered from a completely different +5V rail anyway; you might want to check this first (measure the voltage between pin 20 and 40 of the processor).

edm418
 
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Re: Previously working x0x

Post by edm418 »

Hi, sorry about late reply :(

Checking voltage between pins 20 and 40 of the micro controller gave a reading of 7.55vdc

When I switch the x0x on, I can hear a hiss from the headphones but no notes in any mode :(

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mmm
 
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Re: Previously working x0x

Post by mmm »

edm418 wrote: Checking voltage between pins 20 and 40 of the micro controller gave a reading of 7.55vdc
That's too high; and I'm not sure how this could come about. The digital +5V come from a separate 7505 regulator (IC20 on the IOboard). Please disconnect all cables (including the flat cable) between IOboard and mainboard and then measure the voltage between the metal tab of IC20 and its three legs. The middle one should not read any voltage.

edm418
 
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Joined: Mon Mar 09, 2009 12:11 am

Re: Previously working x0x

Post by edm418 »

Hi, thanks for your reply.

Voltages for IC20 are as follows:
( i/o board disconnected from main board, attached to power)

1) 13.30vdc (nearest to the White dot...)
2) 0vdc
3) 4.85vdc

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mmm
 
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Re: Previously working x0x

Post by mmm »

That looks ok; however it's the 4.85vdc that actually should power the processor.

Please recheck the voltage at the processor (you need to re-connect the flat cable). Double check if you've used the right pins. You can also check directly between the metal tab of the voltage regulator and pin 40 of the processor.

edm418
 
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Joined: Mon Mar 09, 2009 12:11 am

Re: Previously working x0x

Post by edm418 »

Hi, I went over both boards with a fine tooth comb and found a few issues with cold joints etc. I re-soldered them and now the b0x works as it always did :)

Thankyou for your help!

I will try to figure out why the tuning voltage is so low and sort that over the holidays.

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mmm
 
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Re: Previously working x0x

Post by mmm »

Two things to keep in mind:

Depending on your multimeter you may get different readings when measuring on pin 5 or pin 7 of IC23 (it's probably an impedance issue). Always check on pin 7 (or the connector between IOboard and mainboard).
There are different types of IC22. The two typically used are from Fairchild or from TI; however I believe the ones from TI have a tighter tolerance. Perhaps you're using a Fairchild?

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