This Commodore Amiga 600 is arrived in laboratory in immaculate state still with the warranty sticker.

Immediately after the disassembly i have immediately noticed that were are several problems of acid released from the capacitors and dirty that affected this poor Amiga 600 and its Floppy Drive.

A decoupling capacitor it’s exploded with a pit on the PCB side, solved this problem i started to replace all the electrolytic capacitors and to clean the pcb with specific products.

After the replacement of the electrolytic capacitors, i have tried to turn on the amiga that apparently worked, shame about the distorted sound and the floppy drive that read 1 time of 100.

I had to replace the electrolyte capacitor on the Floppy Drive and soon after i looked for the fault of the audio problem that 99% is always the usual LF374.

In this case it was not only LF374 but also a 10ohm resistor that did not let the +12v to the LF374 and a short-circuited ceramic decoupling capacitor.

Components that have been replaced:

• IC LF374 substituted with a fully compatible TL084C (U15)
• 10Ohm resistor (R301)
• 330nF capacitor (C301)
• 330nF capacitor (C41)

Unfortunately the welding of the LF374 did not come very well how i like to do it but the pad are destroyed and corroded by the acid and they were about to detach, indeed the pad of the pin 2 of the LF374 was really detached, that’s why the pin 1 and 2 of the IC LF374 are connected together, they were connected via the pad.

I leave you to the photos and the video.

Gallery:

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Video:

The Commodore-SX64 keyboard after some time isnt’t responding anymore (all or some keys). In this case, the keyboard needs some cleaning and repair.

First of all you have to disassembly the keyboard housing, pay particular attention to the screws, this plastic is very old and not of a good quality, it breaks only if you look it.

Gently remove the membrane and clean with alcohol all the metal contacts on the keyboard pcb and also clean all the contact pads on the membrane without alcohol.

Next i took some graphite in cream (Keypad Fix) to reconstruct the pads on the membrane by simply applying a very fine layer of graphite on the contacts.

Gallery:

ARMSid (6581/8580 Replacement) by Nobomi.

I could not resist the temptation to try also this emulation of the SID 6581/8580 with the STM32F410 ARM Cortex M4, i’m talking about the ARMSid by Nobomi.

The fast shipping and the courtesy of Nobomi are certainly very well but also the packaging, the ARMSid is shipped in a plastic case to avoid any problem with the shipping.

The sound and the “audio” feeling are good like the SwinSID Ultimate but better, personally i would place the ARMDSid between the Original SID and the SwinSID Ultimate, Nobomi you have made a very good job. Congratulations.

Nobomi also wrote a software for Commodore 64 to configure the various ARMSid options and another software to update the Firmware.

Some information taken from the Nobomi site:

What is it ?:

• A new replacement of the MOS6581 and MOS8580 used in the Commodore C64. It is minimalistic (in simplicity of circuit and use, not in function and power).
• Real “plug & play” solution. Just insert instead of the original SID into the slot and it’s done.
• It determines (through supply voltages) which chip it replaces and starts the appropriate emulation (it can be changed later in software).
• No need to switch the PAL / NTSC version, the circuit uses directly the clock from the computer bus, always synchronous with the C64.
• It also emulates analog inputs (joysticks, mouse, etc. – POTX and POTY inputs)
• Analog output is sufficiently buffered, it is not necessary to change anything on the computer board for proper operation.
• Output sampling frequency is 1/16th bus clock of C64 (approx. 62kHz), real 12bit D/A converter, no pwm.
• Filters completely transferred to digital form, emulated by float point arithmetic.
• Significantly lower noise level and less interference from the power supply than the original :)
• Lower power consumption than the original.
• Firmware update possible inside the C64.
• Emulates all waveforms, and even “samples” (at least some of them, Ghostbusters laugh, Chimera screams at you).
• Full support of analog filters (LowPass, BandPass, HighPass, combination, Q quality control).
• Emulation of OSC3 and ENV3 registers (little delay, approximately 16 clocks of the C64 bus).
• Joysticks and mice work.

What is inside ?:

• A few resistors, capacitors, one stabilizer, one opamp and a processor. That’s all, parts only from one side.
• The only programmable circuit is the STM32F410, ARM Cortex M4 with HW float point arithmetic at 100MHz.
• Analogue output amplified via the AD8515 opamp.
• Stabilizer for the 3.3V processor, the processor itself has 5V tolerance inputs.

Firmware:

• New features in FW 2.6:
• Optimization for speed again (approx. 10ns more faster response to read registers, faster processing of writing registers).

• New features in FW 2.5:
• Again faster interrupt (approx. 10ns more faster response to read registers).

• New features in FW 2.4:
• Further optimization of the interrupt (approx. 20ns faster response to read registers).

• New features in FW 2.3:
• A part of source code (interrupt routine) has been rewritten in assembler and manually optimized.
• It makes a possibility to control the bus only through the CS signal (no need for O2 clock synchronization, so it can run on systems with a different CPU than MOS6502 now).
• Low frequency limit and filter strength settings and saving settings to permanent flash memory.

Gallery:

Download:

• ARMSiD Schematics (1287)
• Tester, Configuration Program & Firmware 2.6 (1099)

ARMSiD Video:

source: ARMSiD Homepage