Color Classic analog board trouble

[JDW]

Thanks for the extensive testing and photos.

The 1N5237B (DF2) seems to be a 1/2W 8.2V Zener. And from your Flir hot-spot test, I see that DF2 is getting quite hot, along with RF11.

Also is interesting to see that your massive 5V RL62 replacement still rises to 90.6°C. I agree that RL22 (100Ω) should be swapped out with a 5W and raised up on its legs if it is really 167°C. Yikes!

 

[Paolo B]

I’d be extremely cautious at taking the flir values as absolute ones. Those cameras work magic, but my professional experience is telling me that there are so many variables affecting each reading… Anyhow, surely they highlight extremely high temperature for the hot components, the charred board speaks clearly (mine, too, I also have raised them for allowing some more venting… Or maybe flush mounting allows the board to act a a big heat sink?).

 

[JDW]

I’d be extremely cautious at taking the flir values as absolute ones. Those cameras work magic, but my professional experience is telling me that there are so many variables affecting each reading… Anyhow, surely they highlight extremely high temperature for the hot components, the charred board speaks clearly (mine, too, I also have raised them for allowing some more venting… Or maybe flush mounting allows the board to act a a big heat sink?).

A type-K temperature sensor attached to a multi meter would be able to verify the temperature measurements made by the Flir. The metal tip on the wire of the temperature sensor with need to be strapped onto the resistor using a wire tie.

Although circuit boards are used as heatsinks all the time, that’s only true in the case of surface mount components which directly solder onto large areas of copper. In the case of this analog board though, the components are merely resting on the circuit board where there is no copper, and that area winds up scorched or even burned with a partial hole in it.

The best “heat sink“ for those resistors is a physically larger resistor that stood up on its legs for better airflow around it.

 

[Paolo B]

A type-K temperature sensor attached to a multi meter would be able to verify the temperature measurements made by the Flir. The metal tip on the wire of the temperature sensor with need to be strapped onto the resistor using a wire tie.

Although circuit boards are used as heatsinks all the time, that’s only true in the case of surface mount components which directly solder onto large areas of copper. In the case of this analog board though, the components are merely resting on the circuit board where there is no copper, and that area winds up scorched or even burned with a partial hole in it.

The best “heat sink“ for those resistors is a physically larger resistor that stood up on its legs for better airflow around it.

Totally agree!

 

[JDW]

I left RF11 alone for now because it measured 363Ω. The discoloration looks like it may have come from the outside.

If indeed @Branchus is correct about RF11 being 390Ω (which means the stripe which looks Yellow in his video is in fact White), then with a Gold 5% tolerance, your measured resistance should lie between 370.5Ω & 409.5Ω. But you measured 363Ω, which perhaps indicates that burned resistor is showing signs of having been compromised by excessive heat.

---

We have established that DF2 is a 500mW 1N5237B Zener. I found the following two 1.3W replacement candidates; but the case size is the same, so the only advantage of swapping out DF2 would be to raise the new part up on its legs for better airflow and cooling around it:

1. BZV85-C8V2
2. BZX85C8V2

 

[YMK]

But you measured 363Ω, which perhaps indicates that burned resistor is showing signs of having been compromised by excessive heat.

It's very possible, so I'll replace that one too. There's a 5W 8.2V Zener from the same series as the 18V part I used: 1N5344B.

 

[JDW]

For CC owners who want to upgrade their own Analog Boards, here's the Replacement Parts List compiled thus far...

• RL62: 47Ω 5W 5% Axial Resistor — DigiKey | Mouser
• DL21/22: Remove 2 stock parts and replace with 1pc of 1N5355B 5W 18V Zener — DigiKey | Mouser
• RL22: 100Ω 5W 5% Axial Resistor — DigiKey | Mouser
• RF11: 390Ω 5W 5% Axial Resistor — DigiKey | Mouser
• DF2: 8.2V Zener, currently untested, so here are 2 wattage choices which both are better than the 500mW 1N5237B original (Izt=20mA):
  • 1.3W (Izt=25mA): BZV85-C8V2,113 — DigiKey | Mouser
  • 5W (Izt=150mA): 1N5344B-TP — DigiKey | Mouser

All of these parts get hot, so they should be stood up on their legs with the body rising above the PCB (not in contact with the PCB), for better airflow and cooling.

 

[YMK]

5W (Izt=150mA): 1N5344B-TP

If this ends up being a problem, there's also the 1N5345B (8.7V@150mA). I'll order some just in case.

Also, there are indeed two DL21/DL22 Zeners in the photo I uploaded, but I had removed one and can confirm this has no effect on the picture.

There's no harm in using two if you'd like.

 

[Cam]

If this ends up being a problem, there's also the 1N5345B (8.7V@150mA). I'll order some just in case.

Also, there are indeed two DL21/DL22 Zeners in the photo I uploaded, but I had removed one and can confirm this has no effect on the picture.

There's no harm in using two if you'd like.

Which part did you end up going with? I have two ABs I'm looking to refresh.

 

[YMK]

Which part did you end up going with? I have two ABs I'm looking to refresh.

The 8.2s arrived today. I'll try one tonight.

 

[YMK]

The 1N5344B works well for DF2, no picture adjustments needed.

I've used the full lead length and stood it up off the board.

Shown here, at 111.9°C:

 

[Cam]

Thanks for all the information you've shared in this thread!

 

[JDW]

@YMK
Thanks for the detailed info. I have the aforementioned parts on order to upgrade my own CC Analog Board.

Just to confirm, how long did you have your CC switch on before you took the Flir temperature measurements? And were you running anything processor intensive or just letting it sit idle?

 

[YMK]

Just to confirm, how long did you have your CC switch on before you took the Flir temperature measurements? And were you running anything processor intensive or just letting it sit idle?

After three hours of idling at the desktop with the cover off, 109°C was the highest I measured today.

 

[YMK]

In your photo, the stripes, from right to left, look like: YELLOW, GRAY, BLACK, GOLD, BROWN

I finally found the bag. They are 47Ω, but only 500mW:

https://www.mouser.com/ProductDetail/Xicon/273-47-REEL-RC?qs=HzxXYqKzAP3PjyF6RC6fPA==

(don't buy these)

 

[JDW]

I finally found the bag. They are 47Ω, but only 500mW:

https://www.mouser.com/ProductDetail/Xicon/273-47-REEL-RC?qs=HzxXYqKzAP3PjyF6RC6fPA==

(don't buy these)

I bought this 5W 47Ω resistor as an RL62 replacement...

https://www.digikey.jp/en/products/detail/koa-speer-electronics-inc/MOS5C470J/15276085

I also bought a Uni-T brand UTi260B thermal camera from Banggood (I also bought their UTZ002 macro lens for it) and am waiting for it to arrive. That way I can do a video of the components in question, showing BEFORE/AFTER temperatures too, and give you all the credit, @YMK ! I'm really excited about this. Seems like it will be a great Analog Board upgrade for every Color Classic owner!

 

[YMK]

I can't take all the credit. Thanks for compiling the convenient parts list.

Mouser was out of the 100Ω, so I ordered ROX5SSJ100R.

 

[JDW]

@YMK
Here's part of my video work on this topic, covering my Thermal Camera readings of the machine with the stock analog board components, with only the power switch at back on (the CC is shutdown).

I now need to check the heat with the machine booted and running. After that, I can change the parts we talked about and then recheck temperatures.

 

[retr01]

@JDW, that is cool! So, what about the CPU and the Apple IIe Card?

 

[JDW]

@JDW, that is cool! So, what about the CPU and the Apple IIe Card?

Doing thermal measurements on the motherboard will prove much harder because there is no way for me to keep the motherboard outside the chassis while at the same time keep it connected. I can do that with SE & SE/30 motherboards, but not a motherboard in a Color Classic.

This video is about upgrading the Analog Board, and that is a board which is exposed (with the back case off), which is how I can take thermal measurements. Tomorrow, I will continue this work by taking measurements with the machine booted. The will give me a frame of reference. I can then swap the Analog Board components discussed earlier in this thread and then take measurements again to see if the larger and higher wattage components resulted in better cooling. Sadly, it won't impact power consumption though. As you can see from my video, 8.5W to 9W is a lot of power draw when the machine is totally shutdown.