Hello everyone,
I wonder if I might ask if anyone could render some kind advice? On my A2Pi thread I posted how I wanted a Mockingboard sound card for my Apple IIe, price and availability being the main stumbling blocks so I decided to hand wire (ugh!) my own from the v1a schematic.
It seems said schematic has some errors and given my lack of knowlwge of such things I have struggled to dope out what the fixes should be... if anyone feels like lending a hand feel free to post on that thread.
Well in a fit of madness I got ticked off, decided I could do better (famous last words), downloaded Eagle, and had a go:
I must say what a total b**l ache Eagle is to use if you've not used it before. Oh well, crack on... I present my MockingChick Mockingboard clone. I believe just about as cut down as you can get and have something that functions about right.
No mixing for the motherboard speaker. Sorry, but easy enough to patch in if wanted.
An amp will be needed. I very much doubt it will drive speakers by itself.
So, the advice?
I'm absolutely pushing beyond the limits of my knowledge with this one. If anyone feels like doing a reality check to see if there are any obvious errors I'd be most grateful.
.sch and .brd files in a .zip file above
pictures of schematic and PCB layout for anyone interested.
Area(s) of specific concern:
My version on this theme comes from a simplified design I found that uses two DIP40 AY-3-8910s. I ditched those in favour of two DIP24 AY-3-8913s as they are nearly pin compatible for the purpose, much smaller (potential PCB cost), and it's what I've got.
The 'nearly' is what has me concerned...
The AY-3-8910 has two 'selection' lines: BCR1 and BCR2, while the AY-3-8913 only has BCR1. BCR2 exists internally, pulled high. I don't *think* this is important here... famous last words..?
The AY-3-8913 also has a line the AY-3-8910 does not in the shape of BDIR.
Well, after some thought I basically wired up my AY-3-8913s as AY-3-8910s subsitiuting the 'missing' BCR2 line for the BDIR... This alteration has been deliberately left obvious on the schematic.
My other (lesser) concen regards the AY-3-8913s two GND pins. I only wired up PIN19 and left the other floating... naughty, but as far as I understand both pins are internally connected and given how I packed this board (again with an eye on cost) Eagle had some issues routing the PCB. For the same reason I've left a good few unused pins elsewhere floating and the (only?) two power rail caps are quite deliberately nested one on the other.
Also in the interests of component count and availability I played a bit fast 'n loose with the mixing resistors on the output. Near enough is good enough?
So:
How many obvious mess up's..?
Suggested fixes..?
D'ya think my chick could fly..?
Many thanks in advance.
I wonder if I might ask if anyone could render some kind advice? On my A2Pi thread I posted how I wanted a Mockingboard sound card for my Apple IIe, price and availability being the main stumbling blocks so I decided to hand wire (ugh!) my own from the v1a schematic.
It seems said schematic has some errors and given my lack of knowlwge of such things I have struggled to dope out what the fixes should be... if anyone feels like lending a hand feel free to post on that thread.
Well in a fit of madness I got ticked off, decided I could do better (famous last words), downloaded Eagle, and had a go:
I must say what a total b**l ache Eagle is to use if you've not used it before. Oh well, crack on... I present my MockingChick Mockingboard clone. I believe just about as cut down as you can get and have something that functions about right.
No mixing for the motherboard speaker. Sorry, but easy enough to patch in if wanted.
An amp will be needed. I very much doubt it will drive speakers by itself.
So, the advice?
I'm absolutely pushing beyond the limits of my knowledge with this one. If anyone feels like doing a reality check to see if there are any obvious errors I'd be most grateful.
.sch and .brd files in a .zip file above
pictures of schematic and PCB layout for anyone interested.
Area(s) of specific concern:
My version on this theme comes from a simplified design I found that uses two DIP40 AY-3-8910s. I ditched those in favour of two DIP24 AY-3-8913s as they are nearly pin compatible for the purpose, much smaller (potential PCB cost), and it's what I've got.
The 'nearly' is what has me concerned...
The AY-3-8910 has two 'selection' lines: BCR1 and BCR2, while the AY-3-8913 only has BCR1. BCR2 exists internally, pulled high. I don't *think* this is important here... famous last words..?
The AY-3-8913 also has a line the AY-3-8910 does not in the shape of BDIR.
Well, after some thought I basically wired up my AY-3-8913s as AY-3-8910s subsitiuting the 'missing' BCR2 line for the BDIR... This alteration has been deliberately left obvious on the schematic.
My other (lesser) concen regards the AY-3-8913s two GND pins. I only wired up PIN19 and left the other floating... naughty, but as far as I understand both pins are internally connected and given how I packed this board (again with an eye on cost) Eagle had some issues routing the PCB. For the same reason I've left a good few unused pins elsewhere floating and the (only?) two power rail caps are quite deliberately nested one on the other.
Also in the interests of component count and availability I played a bit fast 'n loose with the mixing resistors on the output. Near enough is good enough?
So:
How many obvious mess up's..?
Suggested fixes..?
D'ya think my chick could fly..?
Many thanks in advance.
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