Amiga of Rochester

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

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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.

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This Amiga 600 came in as the owner wanted to replace the IDE header. Through the consulting process we helped acquire the new headers.

Here is a complete overview of work performed :

• Header removed
• Pads were cleaned with Amtech flux and soldering braid
• Sony audio chip was cleaned with flux and fresh solder applied.
• Header replaced.

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A close friend of mine Paul sent over 4 boards for repair. I’ve successfully got 3/4 booting with the 4th one needing a new Agnus socket. Many of them only needed simple things like a new CPU socket (we’ll definitely do more!) I’ve done my best to take detailed photos of the renovations.

Board 1

This board was pretty straight forward, it only needed a new CPU socket. This board is not done, we will update the post once we’ve completed it. This is just the start, we will replace capacitors and clean the battery terminals before we’re done.

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Board 2

This board, like the previous one only needed a new CPU socket. At Amiga of Rochester we don’t just fix the main issue but perform preventative maintenance where necessary.

In this case we did the following:

• Replaced the CPU socket
• Replaced the Kickstart socket
• Cleaned the board with alcohol
• Removed and cleaned components near the keyboard connector
• Replaced electrolytic capacitors around the corrosion area

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This Amiga 1200 was sent in to get some loving. We removed the old naughty capacitors and replaced them with happy little capacitors.

This board overall was pretty clean, not much needed. However there were a few bad capacitors, one 10uf by the composite out and one over by the floppy port. They were starting to damage the pads and traces around them and by the smell, were leaking for a little while. I went a head and cleaned the pads before placing the new capacitors and made sure no future damage could occur.

All capacitors are Nichicon, Panasonic or Rubycon. All ultra low ESR.

There will be another update with photos of the second board.

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