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Commodore PET CBM 4016 ASSY 8032080 RIFA burn and more

1 high
2 10 khz squarish
3 1 mhz squarish
4 high
5 10khz squarish
12 10khz squarish
13 high
11 1 mhz squarish
9 complicated stuff see photo
10 high
IMG_9763.jpeg
 
UB1 was featured in #101 . the image is the pin described as complicated
 
But UB1/9 should be connected (via a PCB track) to UC1/2.

In post #104 you say that both pins are LOW and in post #101 you state that there is a signal on UB1/9...

Both statements can't be true...

Dave
 
yes i just tried to redo the measurements from #101 and they are different - intermittent fault ? wtf - these are the measurements now

1 high
2 low
3 1 mhz squarish
4 high
5 low
12 low
13 high
11 1 mhz squarish
9 low
10 high

remember there was some variation with power cycle
 
with all those pins i didnt even realize getting two different reads on ub1/9... when measuring i dont have the screen connected so i wouldnt see if suddenly stuff shows up. well at least we seemed to have exactly observed failed and maybe nonfailed states
 
Are you turning the machine OFF and ON when taking a new set of measurements by any chance?

UB1/2 comes from the CRTC controller.

You are finding 'funny' signals on the CRTC pin 40 (none at all) whereas pin 39 has a signal. The implication being that either the CRTC is being programmed correctly - but generating the wrong signals (i.e. the CRTC is faulty) or it is being programmed incorrectly (i.e. the problem is either the Kernal or EDIT ROM or something between the CPU and the Kernal or EDIT ROM).

Are you serious about continuing with this fix or are you going to give up?

I am just asking because I don't want to invest too much of my time in this repair if you are out of your depth and are not willing to invest in some additional test tools (e.g. a NOP generator, ROMulator or my PETTESTER).

Dave
 
yeah i turn the machine on/off between measurements, but it never chirped. yeah if pettester is an option lets go this way. i am not sure if i can bake my own or have someone mail one.

thanks for your time. i feel tracing this backwards is too tedious.

i just appreciate 5150 post error messages a lot more now.
 
DrAlis said:
I got a tll 866ii plus eprom burner and apparently if you crank up vpp to 21v with a bench power supply it can do the trick. it is just opening another can of worms that id rather avoid - if positive reinforcement is staying absent i will likely just sell the pets without board - should work ideal for mini 40 or such as keyboard monitor and case are almost mint. i actually own a pro log m900 eprom burner from the 70s based on a 4004 (for sale to fund my other retro invests) but i got no way to get the data on that heavyweight. i am missing the actual eprom ics and a uv light. and i am not very interested to learn how to compile assembler as of right now.
Click to expand...
You might be right about cranking the voltage up to 21V, sometimes these Uveproms can give trouble unless they are the correct versions for the correct programming voltage , generally the eproms with the "A" suffix are the 21V versions. You don't have to bother buying a UV eraser if you buy NOS eproms that have never been programmed.

Your idea to sell the PETs without their broken original boards is a really bad one.

A person would much rather buy the PET in the original condition with its original board (many enthusiasts can fix these boards themselves). Also, there is the repair support here with the major contribution from excellent teachers like @daver2, but for this to work, the student has to be motivated and patient and willing to learn.

For example I know one person with an original PET housing with the PET mini board in it and they are disappointed with its performance (some issue with the screen pixels not visible on the L) so they are trying to build another, but they want an original PET board !

My advice is, leave the original boards in your PETs , not only will it increase their sale value, but it preserves their history.

In the future it pays to keep one thing in mind. (this same applies to all vintage electronics). Most people interested in buying this stuff don't expect that it will be working 100% or at all. And they expect they will have to do some restoration and fault finding, it is part of the fun of vintage computing.

I think most buyers would much rather buy something original and untouched from a seller.

If the seller is inexperienced in repairs, lacks the correct diagnostic equipment and workshop equipment and skills, and tampers with the circuitry, that really puts people off, because they know this sort of thing introduces more faults and damage, especially pcb damage where parts are unnecessarily removed and replaced with poor de-soldering skills. Or say running a CRT for too long with a bright spot and no beam deflection, it damages the phosphor. No repair is a lot better than a botched repair.

One other example of this is in the field of vintage transistor radio collecting. Many sellers do things like re-cap the transistor radios in an attempt to get them working, and a lot of the time they "get lucky" and the radio works, as they are quite simple devices. However if I see one the seller has re-capped, I never buy it, or even consider it, because these radios have very delicate phenolic pcb's. It requires special de-soldering techniques and exact soldering temperatures not to lift the pcb's foils and damage the vintage germanium transistors too. Every seller re-capped version I have seen has damage, so I avoid them like the plague and only buy un-touched radios, working or not. The sellers probably don't know they are putting some buyers off.
 
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Ok so a gent from UK can burn the ROM... (actually, why don't you have a webshop, Dave?) To avoid a useless ROM, could you please check the edit ROM number to see if the ROM will work? I have no clue about ROMs, don't even know what file type he needs... Also no assembler compiler on my machine etc... Thanks!
 
@Hugo Holden actually agree on all your points. I also dislike recaps and other mutilations. I also avoid solderwork on orignal PCBs. I.E. some frequently broken tantals can be just cut off and left off in 5160 which is an insight i have from -0degrees. On a different note, I do have some phenolic boards (casio 1969...) and was wondering if you have a source on how to solder on those or could tell me more.
 
DrAlis said:
. (actually, why don't you have a webshop, Dave?
Click to expand...

I think Dave is too busy with his job and what free time he has helping people out of the goodness of his Heart. He is an altruist and a true teacher. I doubt if a web shop would appeal to him at all.

When people buy things from a "shop" even for tuppence (you might not know the Mary Poppins reference), that would barely buy a bag of food for the Pigeons, they expect the world. Dealing with customers is painful and time consuming and most Scientists, like Dave, cannot be bothered with that.

But I wouldn't want to put words into his mouth, he may give you a better explanation.
 
If I had a webshop I would be obligated to support people...

This is a hobby for me (and many other people on VCFED) so we all (largely) do this for interest. I have a full-time job and I am involved in the audio/visual work at our Church (design, support, training, operation) and that takes up time also.

Perhaps when I retire...

I have enough 'fun' dealing with some of my 'customers' and 'suppliers' at work!

If you read the source code I supply with my PETTESTER you will see that you do not require an assembler to be installed on your machine. I use an online assembler (at asm80.com). All you have to do is to create a new file for a 6502 CPU and copy and paste the source code into the window. Hit the SAVE button and then the COMPILE button - job done. I provide the source code so that people can learn and modify it to suite their needs.

The ZIP file also contains a binary and HEX file - both of which should be supported by any reputable EPROM programmer. Hence, no assembler is generally required to use my PETTESTER.

Colin has already produced a 40 column CRTC version of my PETTESTER (see post #595 of https://www.vintage-radio.net/forum/showthread.php?t=201990&page=30). Thanks for the link Colin.

To be on the safe side, get an EPROM made of my 'standard' PETTESTER and Colin's modified version. You have both available to you then (if you are planning on fixing a range of PET computers).

To reiterate, Bitfixer and Nivag have incorporated my PETTESTER into their ROMulator products.

Dave
 
Thanks Dave & Colin, i fetched the 2 bin files. I did notice that Dave's is 2k and Colin's 4k. I assume the part above 2k is ignored anyway by the PET. For the Bitfixer, I just saw a soldering kit and no ICs... I'll just get the ROMs
 
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