Conversation

Notices

1. Embed this notice
   Bernie (codewiz@mstdn.io)'s status on Thursday, 23-Jan-2025 21:53:42 JST Bernie

   Yesterday I received a donation of #Commodore hardware from a childhood friend, including this lightly used #Plus4 in its original box, with perfectly preserved manuals.

   #vintagecomputing #retrocomputing

   • Embed this notice
     Bernie (codewiz@mstdn.io)'s status on Thursday, 23-Jan-2025 22:13:35 JST Bernie

     in reply to

     In spite of its excellent conditions, this #Plus4 does not power up at all 😭

     The AC fuse in the PSU and the DC one on the motherboard aren't blown, so my next suspect is the "wedge" power-supply.

     These PSUs made by #Commodore in the '80s are known to fail often. Sometimes, they even output higher voltages on the +5V line which powers ALL the chips on the board! 😱

     But this isn't the case: the power LED is steady off, and I measured near 0 volts on VCC pins.

     #electronics #vintagecomputing

   • Embed this notice
     Bernie (codewiz@mstdn.io)'s status on Thursday, 23-Jan-2025 22:18:04 JST Bernie

     in reply to

     • root42

     @root42 The CPU is indeed a 6501R1, with a conspicuous "OK" drawn on it in purple. How do they die?

     Anyway, the PSU appears to be broken (I'll post more details on the main thread).

   • Embed this notice
     root42 (root42@chaos.social)'s status on Thursday, 23-Jan-2025 22:18:05 JST root42

     in reply to

     @codewiz love it. Is it still alive? If not: check the CPU. If 8501R1, it’s most probably dead. The power brick is also dangerous. You can replace the square power jack on the plus/4 for a C64 one and use a modern C64 PSU.

   • Embed this notice
     Bernie (codewiz@mstdn.io)'s status on Thursday, 23-Jan-2025 22:31:49 JST Bernie

     in reply to

     Last night I carefully opened the #Commodore wedge PSU with flat screwdrivers, but the interior is filled with a potting resin which is stuck to the box.

     I measured +5V after the regulator, but it drops as soon as I connect the #Plus4 board.

     If the board was shorted, the fuse would have blown. So I guess the regulator is unable to source more than a few milliamps.

     I couldn't make further progress without tools. I'm literally working from my mother's kitchen! 🤓

     #electronics #vintagecomputing

   • Embed this notice
     Bernie (codewiz@mstdn.io)'s status on Thursday, 23-Jan-2025 22:45:41 JST Bernie

     in reply to

     • root42

     @root42 Aha!

     By the way, I found schematics and service manuals for the Plus 4, but couldn't find gerbers or pictures to help follow traces on the board. Know where to look?

   • Embed this notice
     root42 (root42@chaos.social)'s status on Thursday, 23-Jan-2025 22:45:42 JST root42

     in reply to

     @codewiz another candidate is a corroded power switch. Can lead to „no power“ symptoms.

   • Embed this notice
     Bernie (codewiz@mstdn.io)'s status on Friday, 24-Jan-2025 05:49:08 JST Bernie

     in reply to

     • root42

     @root42 Even these C64 -> Plus4 adapters cost a lot, like 15 EUR + shipping.

     Ok ok, I guess spending 2 hours repairing a PSU would cost more, but... isn't it more fun? 😂

   • Embed this notice
     root42 (root42@chaos.social)'s status on Friday, 24-Jan-2025 05:49:10 JST root42

     in reply to

     @codewiz yeah I guess the regulator is borked. Ditch the old PSU, buy a round DIN socket for the Plus/4 and use a modern C64 PSU. Sad that the PSUs are all potted. Otherwise one could easily repair them.

   • Embed this notice
     Bernie (codewiz@mstdn.io)'s status on Monday, 27-Jan-2025 21:24:34 JST Bernie

     in reply to

     I detached the #Plus4 keyboard to test the power LED with a battery: it works.

     I cleaned the contacts with isopropyl and plugged the flat cable back on the board and now... IT WORKS! 🎉

     Was it just an oxidized contact? I'm not sure.

     Anyway, the tuner video signal is very noisy. I wrote this short program to test sound output.

     First time I play with the BASIC V3.5 multimedia commands, and it's awesome! :commodore:

     #commodore #retrocomputing #vintagecomputing