C64G short board shakeout

Disk drives, Monitors, SuperCPU etc.
banman
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Re: C64G short board shakeout

Post by banman »

Hi rmzalbar,

Thank you for that clarification on the grey dot bug.

I must admit I don't think I have consciously seen it.

How is your C64G coming on?



rmzalbar
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Re: C64G short board shakeout

Post by rmzalbar »

I'm still too busy with work to really get into it for now. I did take a few hours this weekend to make a composite video output for my Odyssey 2.

Wow the camera has trouble with CRT television screeens.

Image


Image

banman
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Re: C64G short board shakeout

Post by banman »

Hi rmzalbar,

No worries I know work sucks a huge portion of my time....

I like what you've done on your Odyssey2. :D

I actually got my self during the week 2 NTSC VIC 20's, They are pretty much bare boards not many chips left in the sockets,. No keyboards. I will spend a few hours on the week end seeing what I need to get for them.

:D

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Re: C64G short board shakeout

Post by rmzalbar »

I got a little time to work on the C64G.

- Replaced broken power jack
- Replaced DRAM with SRAM module.

As intended, replacing the DRAM with SRAM cured the VSP bug. VSP lab doesn't show any more errors and Super Mario Bros. 64 doesn't crash anymore. It didn't cure the gray dot bug nor the disk speeder bugs.

Desoldering from the short boards isn't much fun. The large power and GND fills go directly to small pads with no thermal relief, and the board delamination temperature is pretty low. I've been using solder wick to get the lion's share of the solder removed from the big fills, and using hot air to heat the fills and pins and ease the chips out after desoldering.

This is one area where they made a big improvement on the Amiga 500 motherboards - they seem to use the same process size for their PCB layout, but they have thermal reliefs on the pads.

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Re: C64G short board shakeout

Post by rmzalbar »

Okay!

Disk speeder issues:
- Not working with Warp Speed cart
- Not working with Fast Hack'em (Fastboot V2)

I thought these two problems were related; they aren't! Fast Hack'ems disk speeder doesn't work on PAL! I never thought to try it on one of my other PAL machines. I did; it doesn't work! IKARI put out a release of Fast Hack'em that is "PAL fixed." All they did was strip off the Fastboot V2 loader.

As far as Warp Speed is concerned, my cart is version 1.0. I found an Easyflash release containing Warp Speed 2.0, and that one works fine. Does anyone happen to have a Warp Speed 1.0 cart lying around and can try it on their C64C?

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Re: C64G short board shakeout

Post by rmzalbar »

Someone says their Warp Speed 1.0 works fine on their short boards, so it's still a mystery why it acts weird on mine.

Today I added joyport TVS diode protectors, and socketed the ROM in preparation for a Jiffydos wireless switcher. Getting better at desoldering from this board. Good practice for when - or if - I do the PLA.

Here's a shot of it right now. Visible: Eslapion's TOLB, Plazma's SRAM module which cured the VSP bug. Eslapion here makes a good one too, SaRuMan.
20200609_002759.jpg

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Re: C64G short board shakeout

Post by rmzalbar »

I thought I was on to something when I noticed the C64G does not reset the disk drive when using reset buttons that pull the reset line low, such as reset buttons on utility carts.

I was about to pull out the oscilloscope and take a look, but then read that 250407 was the last motherboard to run the common reset directly to IEC port, 250425 and onward do not - there is a a separate circuit just for the IEC port, buffered away from the internal reset line, so reset doesn't get to the IEC bus when the internal reset line is manually pulled low, i.e. by a button; it can only be initiated by the 555 reset timer, i.e. at poweron.

A side effect of this difference is that on the older breadbins only, when I press the RESET button on Jim Brain's uIEC/sd2iec daughterboard, it resets the entire C64, not just the sd2iec! :shock: I was not expecting that.

Tonight I assembled one of Plazma's switchless Jiffydos switcher kits. Pretty neat.. you drop a stake in RESET and another one in the RESTORE circuit, and you just hold down RESTORE during poweron or reset to select alternate ROM. No external switch needed.
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Last edited by rmzalbar on Wed Jun 10, 2020 8:09 am, edited 1 time in total.

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