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V4 Assembly Notes

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Giorgioggì edited this page Oct 10, 2025 · 14 revisions

Prerequisites

  • Read the V4 Configuration page, make sure you understand it and make your choices.

First Steps

  • If you decided for real ESD filters, install U91-U95, it's much easier if you do it first thing.

  • Add CN8, C100, C103, F100 (with 1.5A fuse), SW1, C101, C102, C104, C105, C106, C107, C109, R96.

  • Connect your power supply, take your multimeter and take some measurements inside the following rightmost points of the LF100 footprint:

    • DC mode between GND (black) and +5V (red): you must read a steady 5.0-5.2 V. If reading above that, change your power supply.
    • AC mode between +9VAC and -9VAC: you must read 9-12V. Readings above those shouldn't happen, anything below might still work.

  • Now you know your power supply is good, take it out and add LF100. 20240223_231143

  • Add all components in the CLOCK GENERATOR box (hint: be careful with R3!) OR the discrete oscillator alone.

  • Connect your power supply, turn SW1 on, take your 50MHz-or-better oscilloscope and check that you have a steady 17.734475 MHz signal on TP1 (14.31818 MHz for NTSC, center pin of Q2 is also a good test point if you want to clip your probe), at least 4 V peak-to-peak. If you went with the whole clock circuit, you can use CT1 to tweak the frequency in order to get as close as possible. While not recommended, if you don't have a good scope, do this later, when you have a video signal, and turn CT1 until you get color on your screen.

    (Note the following picture was taken before X1 was introduced) 20240223_232239 20240223_232200

Main Assembly

  • Install U1, U2, U3/U4/U90 (according to chosen ROMs configuration), U5, U9, U10, U12, U13, U14, U15, U17, U18, U19 (needs programming), U26 (needs programming), U30.

  • Install ALL components that are NOT in a box.

  • Install components in the VIDEO OUTPUT AMPLIFIER box according to your chosen configuration.

  • Configure JP5/6/7/8 and JP13 according to chosen ROM configuration.

    The board should start up to the BASIC screen at this point, showing 60671 bytes free, and most functionalities should be there, including floppy drives BUT NOT the Datassette.

RAM Expansion

  • Add U6, U25, U28 (needs programming), U29.
  • Use siz's RAM testing program to make sure that 256 or 512 kB are detected according to JP4 and that no errors occur.

User Port

  • Add all components in the USER PORT box according to your chosen configuration.
  • Make sure JP12 is in the UP position.
  • At this point the Datassette should work.

SID

  • U21 and U25 should have already been added.
  • Add all components in the SID box (Again: BE CAREFUL!)
  • Use RV3 to tune the amount of SID sound that gets mixed with the TED sound to your liking.
  • If using an 8580, use RV4 to tune the volume of samples.

3rd joystick Port

  • After you have completed the SID section, add all components inside the JOY3 box.
  • Wire a male DB9 port to a female IDC connector using a 9/10-wire cable and plug it into CN14, taking care of correct orientation, and leave it hanging out the case through the tape or userport holes.

Keyboard

On a C64C case with original metallic keyboard frames, there is a significant risk of short-circuiting the unused surface mount pads for U93/U94/U95. Metallic frames are outright unusable if these are installed instead of the through-hole diodes for electrostatic discharge protection.

In addition, U17 and U18 sit too high on the board if socketed and an original metal frame is used. RP2 also doesn't allow the metal frame to sit correctly.

Image

To work around this, install U17 and U18 directly to the board and modify the metallic frame, or modify the frame further to allow more clearance for socketed U17 and U18. Use electrical tape around the mount point to prevent shorting against the pads for U93-95. Alternately, a 3D-printed plastic frame for a C64C keyboard may avoid this entirely.

Image

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