V1.x Assembly Notes

If you want to assemble a V1 or V1.1 card, please read the following notes carefully or you might destroy your SID chip.

First of all, please note that all V1.x PCBs are exactly the same from an electrical point of view. The only differences are in the top silkscreen layer, which reports a few different values for a few components, namely:

• R8 -> 3.3 Ω
• C15 -> 100pF
• L1 -> 100uH

These values were fine-tuned during the development of V2 (which will be released soon) and will place the switching frequency of the step-up voltage converter way out of the audio band, greatly reducing the output noise.

Since there are no changes in the PCB you are strongly recommended to use (or switch to) the new values with any V1.x board. If you have an 8580 SID, changing R8 alone should already improve things dramatically.

Then, be aware that the values of some components depend upon the SID model:

MOS 6581

• C1/C2 = 470pF
• R3 = 1k
• R9 = 11k 1%: CAREFUL!
• SW1/RV2/R6 = Do not mount

MOS 8580

• C1/C2 = 22nF
• R3 = Do not mount
• R6 = 180k
• R9 = 7.87k 1%: CAREFUL!
• SW1 = Mount normally
• RV2 = 1M

Be VERY CAREFUL with R9: it is this component that decides whether the auxiliary supply voltage of the SID will be 9V or 12V. The 6581 requires 12V, but if you provide an 8580 with that you are likely to destroy it. In fact, the 8580 requires 9V, if you provide a 6581 with that it will probably output distorted sound or no sound at all, but SHOULDN'T get damaged. In any case, I recommend measuring the voltage between pins 14 and 28 of the SID socket before you actually plug your precious SID into the board. Consider yourself warned.

Also note that CN3 shorts AUDIO_IN to GND in order to avoid noise, when no input jack is inserted. If you don't like that, cut JP1 open. I guess this is a good idea (= do it!) if you are using a DigiBlaster add-on.

Integrated Circuits

You should be careful when choosing some of the ICs to be installed on the card:

• U2 is a binary counter IC, it MUST be of the "simple CMOS" type, NOT a high-speed variant, i.e.: a CD4520B is fine, a CD74HCT4520 is NOT, for instance. If you can, look at the pictures of the SIDcards originally manufactured by Solder and try to get one of those exact chips.

• U4 is a GAL that is used to generate the SID Chip Select signal: this one should be as fast as possible (10-15 ns). I have used an ATF16V8B-15PU with good results. Be careful with second-hand pulls from China: they generally work but they are very often relabeled parts, so you might have a -15 chip that is actually a -25...

  Being a Programmable Logic Device (PLD), U4 has to be programmed before use. The necessary .jed file storing the GAL configuration is provided among the release files. The sources can be found in the gal directory and can be compiled with Atmel WinCUPL (which is Windows-only and full of bugs, sigh...). To program the chip with the configuration provided, you need to use a programmer, like the ubiquitous TL866 (all versions should be fine). In alternative, you can build one yourself thanks to the afterburner project. There is also a simpler variant of the afterburner device which is sufficient and can easily be built on a breadbord. A tutorial on how to do this is available here.