VOGONS


Reply 80 of 87, by Benedikt

User metadata
Rank Member
Rank
Member

Turns out my soldering iron cleaner/holder is useful for more than one thing:

db25_desoldering_lifehack.jpg
Filename
db25_desoldering_lifehack.jpg
File size
39.96 KiB
Views
250 views
File license
Fair use/fair dealing exception

#lifehacks 😎

Reply 83 of 87, by Paralel

User metadata
Rank Member
Rank
Member

The community really owes you a major thanks for your work on reversing the SoundJr. Despite not being as well known, it's capabilities are significant. It is something that a lot more people would use if they were aware of its capabilities and it was easier to acquire (at least I'd like to think so).

One of these days I hope to get up the gumption to do a little disassembly on mine and nail down the values for those couple little bits were there was a little guess work.

Reply 84 of 87, by Benedikt

User metadata
Rank Member
Rank
Member

Cloudschatze's photos and measurements were also very helpful. The SoundJr reverse engineering certainly would not have been possible without them.

The only components of which the value still remains unknown are the two 0805 ceramic capacitors on the back side of the board.
Unless you want to desolder and measure them, comparing the frequency response of the original device and the replica should be the most pragmatic approach.
The effect of the transistor substitution on distortion etc. would be interesting, as well.

But first things first: The next logical step is to add the proper short circuit protection resistors to the FTL Sound Adapter replicas.
Unfortunately, I lifted a pad here and there when I removed the Sn99Cu1 solder joints at 400 °C. It should all be repairable, though.

Reply 85 of 87, by Benedikt

User metadata
Rank Member
Rank
Member

Follow-up post:

The replacement resistor packs went in in mid-November and by the looks of it I was able to fix the only seriously damaged pad, but final measurements and tests have been pending, since.
While I was at it, I also made another two Speech Things from surplus PCBs.
There are PCBs for another two FTL Sound Adapter replicas, as well, but I didn't have enough DE9 connectors.

Reply 86 of 87, by Benedikt

User metadata
Rank Member
Rank
Member

The evaluation of the joystick ports on the FTL Sound Adapter replicas has been complicated further by the recent realization that my only suitable joystick appears to be broken.
If the appropriate pins on the adapter's DE9-connector are bridged with jumper wires, the software on the PC-side will however detect the change, accordingly, which means that the adapter itself is now indeed fine.

Evaluation of my only readily assembled SoundJr replica turned out to be surprisingly easy, though, because Modmaster in Covox Speech Thing mode does not touch the parallel port control port that the SoundJr uses for volume control.
You simply write a value to the control port register and start the player afterwards.

The following table lists all possible control port values and the respective volume levels:

Ctrl 3..0 | Volume level
----------|-------------
0000 | undefined (weaker 8)
0001 | undefined (weaker 6)
0010 | undefined (weaker 7)
0011 | undefined (weaker 5)
0100 | 8
0101 | 6
0110 | 7
0111 | 5
1000 | undefined (weaker 4)
1001 | undefined (weaker 2)
1010 | undefined (weaker 3)
1011 | muted, if data 1..0 = 0
1100 | 4
1101 | 2
1110 | 3
1111 | 1

It is derived from the schematic and appears to be accurate.