Music 500 mod

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pau1ie
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Music 500 mod

Post by pau1ie » Wed Jul 11, 2018 8:40 pm

I obtained a music 500, but I only have a Master, so decided to try doing the mod to make it work.

I looked at the photo at the end of thedark's useful post, and decided to go for it, looks pretty simple. I cut the track, soldered on the resistor, but when I measured across it, it was a 0 ohms. I took the resistor off, but it is still 0 ohms. Is there something the matter with it, or am I missing something? It seems pointless putting a resistor across a short circuit.

I measured both ways round, so it isn't a diode. Because of the connector it is hard to see where the tracks go. I am willing to put some effort into solving this, but I am not really sure where to start. Any ideas? Is there a schematic? (Not that it would help me that much!)
I'm working on http://bbcmicro.co.uk

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danielj
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Re: Music 500 mod

Post by danielj » Wed Jul 11, 2018 8:58 pm

That's fine - you're just pulling/biasing/somethingerising a line. I remember doing this and thinking it shouldn't be measuring zero, but it was, and it was and it was fine that it was :)

d.
Last edited by danielj on Wed Jul 11, 2018 8:58 pm, edited 1 time in total.

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hoglet
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Re: Music 500 mod

Post by hoglet » Wed Jul 11, 2018 9:23 pm

Obvious questions, but:

a) Are you sure the track was properly cut?

b) What resistance range was your multi meter on? (Or is it auto ranging)

Dave

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1024MAK
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Re: Music 500 mod

Post by 1024MAK » Wed Jul 11, 2018 9:29 pm

Also, where exactly were you measuring from and to? And I trust that the power was disconnected and the 1MHz bus connector was not connected at the time.

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pau1ie
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Re: Music 500 mod

Post by pau1ie » Wed Jul 11, 2018 9:56 pm

danielj wrote:
Wed Jul 11, 2018 8:58 pm
That's fine - you're just pulling/biasing/somethingerising a line.
Thanks. Based on that, I went ahead.
hoglet wrote:
Wed Jul 11, 2018 9:23 pm
a) Are you sure the track was properly cut?
Yes, it is open circuit across the cut.
hoglet wrote:
Wed Jul 11, 2018 9:23 pm
b) What resistance range was your multi meter on? (Or is it auto ranging)
Auto ranging. 0.00 Ohms
1024MAK wrote:
Wed Jul 11, 2018 9:29 pm
Also, where exactly were you measuring from and to?
I measured across the resistor, or where the resistor would have been when I took it out. (It is in again now after DanielJs reassurance)
1024MAK wrote:
Wed Jul 11, 2018 9:29 pm
And I trust that the power was disconnected and the 1MHz bus connector was not connected at the time.
Yes, it was all disconnected.

I will try firing it up tomorrow.
I'm working on http://bbcmicro.co.uk

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