Building a Commodore 64 Diagnostic Test Harness

Let's build up and test Sven's (@svenpetersen191) Commodore Diagnostic Test Harness PCBs. They are used in conjunction with the Commodore Diagnostic ROM 586220 for complete testing of the C64 and most of the C128.
Sven's Github:
github.com/sve...
Download your own copy of the Diagnostic ROM 586220: (c64_diag_rev410.zip)
www.zimmers.net...
Mail Call #1 where I first featured the PCBs:
• Adrian's Digital Basem...

[@zenninom]

Adrian, the quality of your videos continues to increase and impress!

[@TheBananaPlug]

Camera makes a world of difference, great vid. as always.

[@Codeaholic1]

The production value of your videos is getting so much better. Keep up all the hard work!

[@doktor6495]

Hi Adrian, the C64 Diagnostic Test Harness is definitely one of my XMAS vacation projects! Greetings, Doc64!

[@Dorff_Meister]

I bought a harness from Etsy. Took forever to ship from Italy but it finally arrived last night and seems to work great.

[@BlackEpyon]

4:50 They're "solder tab" edge connectors. Normally you'd wire up a bus harness to them, soldering each wire manually, mount the connector in the frame, and insert the circuit board card (they were popular in the EARLY days of computing) but they work just fine for this.

[@DSP107]

That's what I was JUST about to explain to Adrian... 'Cause I'm also an "old times" electronics fan... 😉

[@BlackEpyon]

@@DSP107 It's no different from any PC bus, really, you just don't mount it to the PCB.

[@aitchpea6011]

Love these vids, and I have one tip: You wouldn't have miscounted the wires of your ribbon cable if you learned your resistor colour codes, and you wouldn't need your multimeter quite as often!

[@razterizer]

Exiting stuff. I always hold my breath when I do something like this with my c64. Even looking at this, especially when flipping the on-switch, makes me hold my breath as well. It is like disarming a bomb. Always a sigh of relief afterwards. Thanks for this awesome tutorial! I have realized it wasn’t just a matter of buying it.

[@RobertWCrouch]

Thanks for such a great channel! I finally have a workspace to repair my 20 year collection of C64s, Amiga and other items and your repair videos have been a great help. One thing I was missing was a solder roll holder and I saw your 3D printed one at 14:58; why didn't I think of that earlier!

[@stephenbruce8320]

Those harnesses are worth their weight in gold. I did not bother to make my own I purchased them already made from a vender in Texas who sells them on eBay. They are somewhat pricey but honestly like any good tool they pay for themselves in time savings. Less time at the bench the better.

[@spokehedz]

The pins on the cassette/user port were designed for use with wires. Back in the day, they would have been much closer together.

[@kneehighspy]

really appreciate sven’s hard work on all his projects.

[@TheXJ12]

These color ribbon cables use color code for resistors and capacitors : brown=1, red=2... so it's a smart idea to crimp the brown cable into pin 1. Using HE10 connectors will respect the rest of the color code automatically (unless inverted) but DB9 connectors won't.

[@tubeDude48]

Tacky, Tacky...order to correct values! YES, I knew your cables were to short!

[@jeffhalebopp]

Adrian, I'm a big fan of your videos. One thing that I'd like to mention is the contrast only detect auto-focus on all lumix cameras. I still use 2 of them. The GX85 and the G7. Love them, however, I never use full AF! Unfortunately it just kills video footage. I have them set up to touch focus then it locks and holds focus until I touch the screen again. I know this might be a big issue for your kind of video shooting since you don't want to be concentrating on focusing the camera all the time. But, your footage has constant focus hunting which just can't be avoided with a lumix camera in full auto-focus. It's constantly racking back and forth. Stopping down to a smaller aperture will help a little. I don't own one, but for full auto-focus, your best bet is probably a Sony a6400 since it has phase detect AF which is outstanding. Also it has no 30 minute video time limit and can be powered by the usb port. As always, thanks for the video.

[@MrSonic1953]

Excellent video! my friend. I wish I had paid more attention to my class when I took electronics right after high school (1970). It was actually Electronics, Radio, TV.

[@danielwilliams442]

Those little cutoffs also work good if you're resoldering a headphone jack. My dad would use them to take up the extra space around the jack pins to make it easier to solder without using so much solder.

[@dorinxtg]

Congrats for the new camera! If I may suggest 2 things: 1. You might want to buy a cheap 7" IPS monitor and connect it to the camera's HDMI port and put it on the table, that way you can see the framing, macro shots etc.. 2. Regarding the mic - yeah, it seems that you talked from one side of the camera so it didn't record the audio well. Perhaps you might consider purchasing the RODE micro mic and you can turn it to you when you speak. 3. Recording limit - yup, just like G85, G9 stops recording after 30 minutes. Happens also on Sony A6400 and other cams due to some old import/export rules.

[@DouglasFish]

Thank you for all these videos. I only recently found you, but I'm strangely interested in all of this

[@8_Bit]

12:31 Are there STILL ants escaping from that 64C that lived in a field for 10+ years?? :)

[@tuff_lover]

Ah yes, the long forgotten C64, powered by MSI...i'll take two, please!

[@JasonSimpson1966]

When soldering the DIN connectors, it helps to plug them in to an opposite connector to hold them in place so that you don't overheat them and even if you do, when they cool they remain in position.

[@dantootill]

Surprised to see this. Sven's documentation is so darn good, you don't really need a tutorial video!

[@fierodoug58]

New camera looks great!

[@borismatesin]

Just took a look around the schematic for the 250407 board to see what that U28 (4066) does. Apparently, it buffers the POTAX/POTAY/POTBX/POTBY lines, the analog inputs from the joystick ports. Turns out - those aren't handled by the 6526 CIAs (like the digital directional and fire lines are), but by the SID! More interestingly, since the directional/fire buttons are multiplexed over the keyboard inputs (again, handled by the CIA), I don't know if the Dead Test Harness could detect a joy port is dead, since the keyboard loopback would probably just keep sending A-OK signals. The poor SID might get blamed even if it's a connector's fault.

[@danielmantione]

The diagnostics program will likely send signals from the user port to the joystick ports. By putting all keyboard lines in input mode, you can prevent signals being sent through the keyboard harness.

[@atkelar]

YT just suggested this older video... and I did use one of these harnesses when I fixed up my SX-64 in 2018; it came ready made though, found it somewhere on e-bay. The funny thing was, everything showed up as working, until the "iteration count" went over a certain number; I forget what, but it might have been 5... something rahter odd. The counter went from one normal digit like 0004 to some odd character like 000x and then to 0010 with the next iteration. When I popped in a replacement CPU it worked. So something inside the original one broke in the ALU it seems. Very odd failure mode; I recommend running serveral iterations for that reason ^^

[@8_Bit]

I've never tried it, but I've heard that sticking those DINs in a potato before soldering the pins is a really good solution. It might have even been Sven that told me that trick.

[@FPVphilly]

Love the way you assemble the test harness... very enjoyable and interesting video.

[@parrottm76262]

Love this! Amazing what must be done to diagnose the old tech. Back in the day, it took days to debug my old Trs-80 Model 1.

[@BlackEpyon]

debugging it manually was half the fun!

[@turgin9098]

Haven't even finished watching yet but just wanted to say the video quality is superb with the new camera and lights!

[@Melmelbaton]

*to the tune of the Pink Panther theme* that ant, that ant, that ant that ant that ant that ant that aaaaaant

[@SteveStoltz]

The first thing I noticed is the great video quality.

[@bobsbarnworkshop]

The user port and cassette connector tabs were meant to have wires harnesses soldered to them, not a PC board.

[@Lee_Adamson_OCF]

If I ever meet you in person, I'm gonna buy you a beer.

[@braydenwegner288]

Same.

[@PhobosTK]

5:09 - Good to know. I've just got my first vic-20 and I want to make some pcb for it... although I need to make a psu and video cable first.

[@DanBowkley]

For crimping flat cables, try a Harbor Freight radiator hose pinch off pliers. Item 99704 at $12.99. It works exactly the same as the original tools from the big connector manufacturers and unlike the originals costs less than a new car.

[@The.Doctor.Venkman]

Excellent quality and color balance, Adrian!

[@johnfinn1570]

New camera quite nice, colour and detail are great

[@Sheevlord]

Oh yeah, the new camera is a big improvement. Looks a lot better

[@DaarkCloud]

Omg the lights make things even better than before! Love it!

[@tubeDude48]

At 17:01, look at the end of the *DB-9* in the *Blue* *plastic.* It's labeled their!

[@luther99flame]

Adrian, look for a tool called an IC lead setting tool. I used them all the time when I worked in the electronics industry. They perform much better than bending the legs on the table but it helps if your chips are all of the same DIP package in width, length it doesn't matter. Basically it's a bar the chip straddles and it has a couple of ball bearings either side to "set" the legs straight. Useful for new and recycled chips.

[@steffenbrix]

The audio on the new cam is better! Keep going ❤

[@bobblum5973]

You didn't mention that the rainbow flat ("ribbon") cables use the same 0-9 color code as resistors, repeating in that pattern for each successive group. So a 50-conductor cable would repeat the pattern five times. Something an inexperienced person might not realize, while an experienced one barely thinks about it. Good video overall.

[@wolvenar]

Cool been waiting for this video. Wanted to see how those cables actually work. I never had them either .

[@rdoetjes]

Thanks and especially thanks Sven :) I was looking for a edge cartridge with solder eyes of the user port pcb layout for eagle. I couldn’t find one and was coming to terms of drawing one. Now I have it :)

[@adriansdigitalbasement]

The beauty of OSH right??

[@JasonB483]

I liked the old school look on the old camera

[@tonanornottonull7132]

I had a good laugh when I saw those resistors. See that's also nice to see -- thinking quick in a pinch

[@104d_3rr0r_vince]

Hey Adrian, 22:40 You can use a female too connected to the one you solder. It will act as a heat sink plus as a driver and the pins will stay in place.

[@tomgeorge3726]

Hi, the terminations on the back of the blue connectors are meant for individual wire connections, hence the hole in them. Old school termination.👍😊 I'm surprised the PCB's didn't have A and K on the silkscreen for the LED orientation. The DB9 has the pin numbers on the front of the connector in the blue plastic, you can see the outlines at 17:00.

[@wbfaulk]

The rainbow cables aren't colored that way (just) for fun. The colors match resistor color codes so that you can identify which wire is which number without having to count. You've failed to follow this convention for at least one of your cables. (19:25)

[@VintageTechFan]

22:45 .. just plug it into a mating receptable while soldering. That stops the pins from moving even if the plastic gets soft and does cool the front part a little, making melting less likely, too.

[@jsf4star891]

"Okay, I'm gonna try some dual camera here with my old crappy camera"........Old crappy camera promptly dies.

[@diondoran]

I LOVE your new camera! a gazillion times better.

[@twocvbloke]

Well, I guess that ant didn't see that coming, that's one way to work out the bugs when soldering... :P

[@coryengel]

Nice vivid colors.

[@chrismorley5393]

You should buy a set of assorted E12 range axial resistors. Then get a ringbinder and some 9 pocket photo sleeves. Sort the resistors into the pockets and label with dymo/sticker/paper pushed into pocket. Perfect DIY resistor book make pulling 1 or 2 resistors for a project trivial.

[@timpsensky5181]

One thing I'd like to add. If you run an aftermarket SID chip like I do (such as the SwinSID nano); It will show errors on U18 (SID) and I believe both control ports as well due to lack of analog paddle support.

[@svenpetersen1965]

Thank you for featuring my harness. I have obtained all information for it from the World of Jani blog. Jani also provides some enhanced version of the Diagnostic 586220 software, that deals with other versions of the kernal rom like JiffyDOS etc. blog.worldofjani.com/?p=164

[@CrossedCoder]

I was wondering why your harnesses userport, datasette port and joystick ports are connected to each other, while harnesses from other makers aren't. Also what are the IC's for on the userport?

[@svenpetersen1965]

@@CrossedCoder The schematics of the harness is always the same. You can put the ICs on the User Port dongle, the cassette port or a possible control port dongle. The control dongles have one problem. You would have to match the distance of the connectors perfectly, which is not possible. It results in excessive sideways forces, which might lead to contact problems and false bad. Sawickipedia has experienced something like that. So, I decided to put it on the user port PCB. It could be on a cassette pcb too, but that offers less space. Many hobbyists do not like SMD parts. The connectors are cheap and the cables are easy to make. At present, I am working on a new version of the harness, which switches off the keyboard dongle while testing the control ports, BTW. With an inserted keyboard dongle, the control ports are not properly tested.

[@bobsbarnworkshop]

Can you give us specific details where to order this? I have a serial number C64 ~5.7meg, 250425 MB and I get black screen. I ordered the dual diagnostic cartridge and new IC sockets and ram for it, seeing that usually is the cause. I also ordered the unbranded IC tester going around to test the other logic chips. I know I'm spending more money than it's worth but I enjoy fixing things like this. THX, great videos, I watch them start to finish! (I was in EE over 35 years as a career, Westinghouse, Kodak and a leading university!)

[@moth.monster]

For the dual camera action, you may want to get a color calibration card, so you can get things looking seamless.

[@crapcbm]

in forum64 in germany we had the check64, all electronics in the expansion module, only wires to the posts also there are 2 different connectors for the serial port, for 64 and 128

[@mharding1258]

May I suggest for propping up PCBs when soldering, I have a big blob of white-tac (dont know what it'd be called in N.America but thats what it is in the UK) in my workshop that I pull the right amount from when I need to shape something to hold perfectly. It sounds odd but trust me, its sometimes better than professional tools for the job!

[@RDJ134]

Hmm this is very interesting to see, should be in the arsenal of every one that owns a C64 or want to buy one to check out if it works correctly

[@Muldrf]

I like that it has voltage test points. I like how that is all designed there, nice and easy to build. I am wondering if the LED on the Cassette port comes on when the signal is received by it. I was wanting to try that with the Cassette port to see when the signal was applied, but didn't get around to looking into it. The 120k is what the original schematics have, and are a voltage divider for the POT lines on the Joystick ports. I am pretty sure 100k resistors would be perfectly fine in that use, considering 5Volts across 240k Ohms vs over 200k Ohms shouldn't be a problem (0.00002 A vs 0.00003 A...).

[@johnsonlam]

The Panasonic camera sure a lot better, just put an external mic around the shelf to improve the vocal more.

[@sumplais]

Oooohh....a Compaq Portable! Thanks for the video.

[@DerMartexus]

Hey Adrian, you should be able to seperate the audio of the new camera's videos from the actual video part with some demux software. Perhaps you can also find the right setting of the camera and record the two signals seperately and edit the sound in Audacity.

[@alisterbh]

Sometimes 'sketchy will get ye' where you need to be!

[@crapcbm]

cassette port is only on the 128D "CR" on the right side (sold in USA somewhere...) We in Europe hat the plastic 128 first and has all ports like the c64

[@foffplease3944]

I like the old audio better.

[@hernancoronel]

Video quality is outstanding! I am not even sure I am that much interested hehe but the video quality makes me stay :-)! Just joking, thank you for the great video!

[@jameswestwood]

Great Camera and sound.

[@bb-ov3pi]

In my time the use of a 0-ohm resistor is to act as a fuse. because it will change color when it overheats it is a visual way of see a problem.

[@hansu-nihon]

Hi Adrian! Good camera quality, but when you zoom in a few times during real close up (6:10 for example) it gets blurry/unsharp. So please no zoom like that. 😉

[@kriswillems5661]

Great new camera.

[@199854a]

i lold when the ant got soldered

[@timmbacher]

Retrobright those cases Adrian!!!

[@orangeActiondotcom]

Looking fantastic!

[@drakepirate]

12:37 Hugh, did you toast that poor Ant?

[@NicoDsSBCs]

Hi Adrian. I'm watching KZbin on single board computers(now the NanoPi M4V2). They can't handle 1080p 60fps, only 1080p 30fps. It can handle up to 2560x1280@30fps(1440p from LTT) . So I need to watch in 720p 60fps on big 4k display. I wonder why do you render to 60fps? I've never seen a difference except in fast moving pictures. And it doubles the render time too. Just friendly curious. I also make KZbin videos about single board computers. And I edit and render them on the SBC's. I render to 1440p 30fps. Works great on them. I do have to watch my youtube in 1080p, but can watch up to 4k video files. Hope this will improve soon for SBC's. I'd like to also be able to watch 4k youtube on my 4k display. My aging pc can only output up to 1080p, so any SBC is bettter than that :) Thank you for the great content. Greetings, NicoD

[@woodengamer]

Death of ant by soldering iron.... love it! oh.. and great video as usual! hehe

[@tmbevtfd]

Did Commodore have a test rig like that for factory diagnostics? If they did I’m surprised if nobody’s got one of those out there. Just curious.

[@micv2]

Thanks 👍

[@svenfromgermany]

The ant comes back for the filedfound c64 nest

[@richardhead8264]

_Ant gets soldered at _*_12:37_**_._*

[@pauldeane8369]

Where would one in North America get a PCB made? is there a preferred/recommended website?

[@SuperVstech]

You point out the ant, then chase it down with your iron! Did James get it?

[@nrdesign1991]

17:58 do NOT open the connectors. Just slide the ribbon in and crimp it shut. The little latches are designed not to be opened ever again.

[@ExStaticBass]

Commodore code is usually backwards compatible in my experience. Do you suppose that would work on an Amiga 500 or a 1000?

[@Tonkotsu2k10]

" You will hear it click.." " I didnt hear it click" hehe

[@adventureoflinkmk2]

Nice Jerry rigged 120k ohm resistors.. LMFAO

[@maniatore2006]

Great work, and thank you for the video :)

[@newtom80]

Adrian, it would help a lot if you'd share some aliexpress links or at least search queries for the connectors.

[@nikelquint]

for the zero ohm resister , why couldn’t the trace just be connected if you are able to bridge it with a leg like that?

[@osgeld]

to answer your question about the blue connectors they would have been screwed down with a hole cut in the base material and soldered point to point with wire edit I want a 128D so bad

[@donnied8127]

Can you give us a link what connectors that we need to buy? There are so many on offer on Aliexpress. Many Thanks

[@DDT2005]

Some footage is out of focus.

[@nickwallette6201]

Welcome to the Lumix club! :-D

[@basvanharen2904]

LOL ! 12:36 you actualy fry one hahaha