6502.org

I really ought to get a hot plate - but ones big enough for 100x160mm eurocards ain't inexpensive.

(my experiments with a toaster oven were only partially successful, largely because one of the elements shorts to ground sometime after heating, and then the current trips turn all the lights out.)

Neil

Nice, it comes with an auto-off feature


I use one of the dodgy Chinese ones that I found on Amazon.

I ordered a 220V one but they sent me 110V one instead. When I tried to return it Amazon said the seller didn't accept returns - which is how I learned that was a thing sellers could just do.

One - very expensive - step down transformer later and it works fine. Is it a fire hazard? Almost certainly but it works fine.

I always think that anything that deliberately gets hot is kind of a fire hazard, but it's better than things that unexpectedly get hot!

Thanks for the suggestions. I was able to straighten the pins with flux, heating the pad, and using fine tipped tweezers to nudge the pins. Most of the pins looks respectable, except pin 22, but a continuity check says it's not shorted to the neighboring pad.

I then cleaned up the PCB with isopropyl, and twice ran a continuity check on all pad to pin connections. Everything says it's correctly soldered. Now the question.

Even though pin 22 says it's good, it looks really close to pad 23. Could this cause weirdness like stay capacitance or possibly a high resistance short? I'm tempted to leave well enough alone because I could make things worse by trying to fix a non-problem.

In any case I think this was a good learning experience with SMD soldering.

If it buzzes out short circuit between its pad and the top of the pin (where it goes into the plastic), and it buzzes open between there and pad 22, don't mess with it. I think it's only going to one of the IO blocks anyway, and you'll soon find out if it's got a short when you start using it

Neil

It looks decent enough that I would not try to fix pins 22, 23. Beside, they are power and ground, so you can check the resistance between power/ground.
Bill

Don't think they're power and ground, Bill; they're to the left - 14 and 15 maybe?

Neil

You are right, I’m looking at pin out of the 84-pin package.
Bill

Thanks for the feedback. I left those pins alone and started soldering the rest of the SMD components. While doing it I noticed a manufacturing defect in the D2 pad which abnormally small. It was only in this PCB and not the others, so bad luck that I picked this one to use. I was still able to solder the diode and verify continuity so no big deal.

While soldering the SMD resistors and caps I would occasionally have one stick to the tip of the soldering iron, rather than the solder and pad. Getting it off was tricky and I figured it was safer to assume the excess heating damaged the component and used a new one. I only have a few more to do, but I'm taking a break because it's fatiguing to solder them by hand.

I soldered the components required for a minimal system and cleaned the board. I applied power and got five volts in all the right places, but the power led doesn't work*. I hooked my scope up to the two clocks lines and saw healthy looking square waves. There's also activity on the serial out pin, so I think it's working.

But I have forgotten the baud rate for the w65c265 running at 3.68 MHz and Putty isn't helping me figure it out. I have tried 9600, 19200, 38400 but I am seeing gibberish. The WDC documentation isn't too helpful either.

Anyone know what it is?

* SMD led markings confused me and I think I have it reversed. If so I did it to all the LEDs.
Update: I found a way to check the power LED and it was reversed. I desoldered and installed a new one correctly.

Since you have a scope on the transmit, you can measure the shortest pulse width and figure out the bit per second that way.
Bill

I found in the documentation that it's supposed to be 9600 baud, but that isn't working. I used TeraTerm and tried all baud rates from 300 up to 115,200 with no luck. Although the USB dongle's data indicator is blinking.

My scope is an analog model that's seen better days. But I tried to estimate the w65c265's clock rate, and I think it's running slower than the target clock rate. I was careful about only installing one SMD component at a time to avoid mix-ups.

Update: I used my DMM to test the loading capacitors and resistors and I think they're correct. I then used my scope to estimate the clock frequency and came up with 4.5 MHz. But I suspect it is the scope that needs calibration and the oscillator is running at 3.86.

I regret not adding test points to the PCB to make it easier to attach scope probes. Live and learn on that.

Unfortunately, I have some things going on for the next week so I will have to back burner this after today.

The value of the loading caps is very small, on the order of 10pF, is that right? I'm not sure a DMM can reliably read a value that small (partly because of the capacitance of your hands gripping the probes, which would tend to increase the value "seen" by the DMM). Or perhaps that's not a legitimate concern. But -- just a suggestion -- if you choose instead to simply buy and install new caps then you can be certain things are right.

Speaking of ascertaining the correct parts, are your crystals the right type, I mean wrt series-resonant vs. parallel-resonant?
Alright, maybe you don't trust the scope to look at a pulse width from the SBC and determine a numerical value (which you can then correlate with, say, 300 Baud). But could you coax TeraTerm to output some 300 Baud, and then use the scope to compare those pulse widths with what your SBC is producing? IOW, don't bother with numerical values, and instead let TeraTerm generate a self-calibrated "yardstick" for you? Just an idea... but perhaps I've misunderstood the nature of the scope's shortcomings.

-- Jeff

A little known feature of TeraTerm is you can specify arbitrary baud number by typing whatever value instead of picking the default values in the drop down menu. The actual value is limited by granularity of prescaler, but at lower baud you have pretty good granularity. So take the best scope measurements you can and try a ranges of guesses at 5% increments.
Bill