IBX100 sound components - revision A

[Mark Leman]

Hello Ralph, a few comments to your helpful posting :

>C9 appears to be in parallel to L1 ???

I think C9 is from the analogue end of L1 to GND, in parallel with C12.
Probably a 100nF decoupling cap.

>C5, C3 1uF +  += from ESP board

Are you sure? The PCB footprints are small (0805 size), not many 1uF caps
come in that size and the Philips app note shows 1nF!

>R3, R(not marked?) 10k +
>R6, R(not marked) ?? (these are not fitted on my ESP board)

There are two not marked parts between R3 and R6, I think it is safe to say
they are R4 and R5 because I cant find them any where else on the board and
the labelling is quite 'ordered'.

So that gives us R3 and R5 as 10K and R4 and R6 as unknown. They must be
small values, probably to match the load impedance of the destination -
guess 1k or less ? any bigger and the 10k load resistors would start affect
the level. I'll fit 0R to start with :-).

>X2 11.2896Mhz +
Bugger forgot that :-)

>R20 ?? series resistor for xtal oscillator
else where on the board they have used 220R (R81 for X6) to damp the clock
line, I don't expect the value is critical, I'll try 220R or 100R to see.

Regards, Mark Leman





-----Original Message-----
From: bush-hacking-admin@earth.li [mailto:bush-hacking-admin@earth.li]On
Behalf Of Ralph Barrett
Sent: 13 February 2002 21:39
To: bush-hacking@earth.li
Subject: IBX100 sound components - revision A


In response to Marl Leman's enquiry, I've spent some more time mapping
out the IBX100 sound circuit, and comparing artwork to my ESP RiscPC
16-bit sound card.

Warning - there are bound to be some mistakes in the following. Use with
care. This is Revision A of this list and is incomplete. No doubt a
correct definitive list will be posted in the future (do a search - do
not rely on this list).

I still believe that IC2 is a TDA1545A DAC. IC2 and IC3 share the same
filtered power feed that appears dedicated to the analogue sound
circuitry. IC1 uses the digital +5v. This implies that IC2 is the DAC
and IC3 is the op amp. I reckon IC1 is a flip flop (J-K type) ??

On IC1 :-

pin 6 (out) is BCK to IC2 pin 1
pin 3 (out) is DATA to IC2 pin 3
pin 9 (in) is SDCLK from ARM7500
pin (in) 10, 12 is reset
pin 13 (in) is SDO from ARM7500

So all we've got to do is find a 74ACT series TTL using these pins in a
sensible manner (or perhaps take the lid of my RiscPC and have a look!).

I've checked through the artwork and I am now pretty sure that IC2 is
the philips DAC. Remember that some of these ICs are the wrong way
around. Also that IC2 and IC3 do not use the normal digital +5volt
(VDD?).

Here is my first take of a suggested components list :-

IC1 74ACT78 ?? or 74ACT108 ?? (confirmation to follow)
IC2 TDA1545A or equivilent
IC3 TAA1308 or equivilent

L1 inductor filter for analogue sound supply +5v
C12 10uF capacitor filter for analogue sound supply +5v
C2 100nF *   *= recommended components from TDA1545A data sheet)
R8 22k *
C10 1uF *
R7 33k *
C5, C3 1uF +  += from ESP board
R2, R1 3.9k +
C6, C13 100uF 16v +
R3, R(not marked?) 10k +
R6, R(not marked) ?? (these are not fitted on my ESP board)
X2 11.2896Mhz +
R20 ?? series resistor for xtal oscillator

C9 appears to be in parallel to L1 ???
C14 does not appear to be part of the sound circuit ?

Er that's it for now. Comments welcome.

Ralph