Amiga of Rochester

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Full credit goes to Zachary S. for his findings, I am just providing the information as I felt it would be valuable to someone.

A customer recently sent in a Mac 512k analog board that would start to get power but then die. It would repeatedly tick in fact with popping sound. I went through and checked all the diodes, nothing out of the ordinary. There was one backwards cap, but it was on the horizontal circuit so likely wasn’t “the” issue. Removed the cap, same issue persisted.

I put the board aside for a bit, then someone posted on a Facebook group that they had managed to repair their Mac 512k / Plus analog board. Here is a link to their video on the topic, I don’t want to take away anything from them and they deserve full credit for their findings, link.

Following their video, I checked the blue wire on the cable with the ferrite bead. Looking at the bead, you will see a “5A” and a line. This indicates there’s a fuse in the cable. Checking the blue wire…no beep. I think we might have found it! At the time of this post I have no tested the board but wanted to get this information to the world.

A customer recently shipped us an Amiga 600 that had no mouse movement. This was not a terribly difficult issue to resolve, but we had to check a few things as the board had a small amount of corrosion.

• Checked if the second joystick port worked, it did not.
• Verified the M0H and M0V traces were making there way from the far right side of the board to the Denise chip.
• Repeated the above with the M1V and M1V just in case.

At this point there was only one likely cause left, the 2:1 multiplexer; 74LS157. We went ahead and replaced this and success! We once again had mouse movement. We verified everything looked right in Amiga Tech Kit!

I was working on a Macintosh Classic II which had an interesting fault. It was the second time I had fixed it on one and thankfully had notes from the first time.

Symptoms:

When powering on the system you have either no sound or distorted sound. Pressing reset continuously makes it get “better” but never right.

Fix:

Check the resistance between pin 4 and 5 on the 34119, it should be 75k. If it’s say 1M or more, you have a bad connection. Likely due to corrosion. Add a jumper wire to fix.

A good customer sent us their Amiga 600 which was not booting. They had gone through reviewing various signals, like _RST, checked voltages and so on. They saw that the 555 was not putting out a proper signal, but couldn’t sort it out. That’s where we come in!

We started by confirming their issue, which we did; It would not start. Now sadly this post is going to be a bit short and not very climatic. I simply pushed down on the 555 and it immediately booted. I went ahead and applied flux and reflowed the chip, it continued booting without any intervention.

What should you check when your 600 does not boot?

• Look at the output of the 555, make sure it is properly changing output
• If the 555 is corroded, replace it
• If the 555 has dry solder joints, add flux and reflow.
• Using https://amigapcb.org or Amiga 600 schematics follow the path of the KB_RESET signal
• Look at the RESET signal on the CPU, also look at the HALT signal
• Q511, these can go bad due to capacitor leakage. This can be replaced with almost any NPN SOT-23 transistor.

This is a general process, if you’re unable to get your board to boot we’re available for repair.

I wanted to write about this Macintosh Classic as it stumped me for a bit. We had replaced UH6 which is a LS174 that handles timing for the CAS circuit. When booted, the system just showed a sad Mac with the error code 0000000e.

This error means there has been a data bus error. The last four numbers of second row are the 32 bits representing the failed bits. In our case, it’s all of the bits.

This could be caused by a number of things but generally it is related to the LS174. We verified all of the address lines were present and working. We checked the output pins and they were looking about what we expected. On a whim I checked the ground pin…no beep. Fixing the missing connection got the board working again. I haven’t traced to see where the failure is yet but I plan to.

Have boards you need worked on? Feel free to reach out to us! We work on more than Amiga as well. We’ve worked on PC motherboards, Xbox 360s and more! We can also do NESRGB installations! Let us know how we can be of service.

March is upon us, which means it is time for Marchintosh! Marchintosh is when we celebrate all things Macintosh. During the month of March we will be offering lower prices on our services. Not only that, we will be documenting as many jobs as possible. Making YouTube videos highlighting special boards we receive. This will allow others to learn and grow from the work we do. Of course we will be offering these same great deals to other jobs, not just Macintosh owners!

To find out how we can help you, reach out to us via our About Us page.

We were recently sent a TRS-80 for restoration. Here is a list of work done:

• Replace all capacitors
• Replace the old battery
• Clean up damage from two capacitors
• Fix any broken solder joints
• Ultrasonic the board

We’ve working with a client to get our hands on two boards they’ve had stored away. While stored away, a family of mice made it their home. Our goal is simple, clean the boards up and identify whether they can be fixed.

YouTube Channel: https://www.youtube.com/channel/UCJd7AlM-PULP61-2NCovIuA

We will be doing a series of livestreams and a documentary video. Below is a gallery of images that show the current conditions of the board.