21st Feb 2020, 12:19 am | #121 |
Dekatron
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Re: Commodore PET 3016
You may also get louder sound out from your Arduino sounder if you drop the value of your series resistor to a lower value, try 470 ohms or 1K instead of 10K.
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21st Feb 2020, 8:07 am | #122 |
Hexode
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Re: Commodore PET 3016
Thank you for all of this! I shall give it a go!
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21st Feb 2020, 10:26 pm | #123 |
Hexode
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Re: Commodore PET 3016
Hi guys, I think I’m going to have a panic attack!
I was messing about with sound and now it’s all gone haywire! I type in BASIC commands and it returns ?SYNTAX ERROR. I think I’ve done something seriously wrong to it! Help! |
21st Feb 2020, 10:57 pm | #124 |
Hexode
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Re: Commodore PET 3016
I found this on the web:
SYNTAX ERROR on every command and screen scrolling problems: I read of a case where on every command entered the system reacted with a "SYNTAX ERROR". Also when scrolling the screen, some characters change. This is a problem when the main CPU reads the video screen. When a command is entered, it is read from screen, not from some buffer memory. Also when the screen is scrolled, the data is read from the screen and written back to it. So both problems came from the same source, the bus driver that separated the video RAM from the CPU bus. It had a broken driver in one of the lines. Any use? |
21st Feb 2020, 11:31 pm | #125 |
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Re: Commodore PET 3016
I think to get to a position of sanity you are really going to have to get those sockets changed first because the behaviour of the machine was unpredictable to begin with.
When you asked about trying out your sound add-on I did almost say that when making modifications or adding things to any sort of system you really need to start with the system in full working order, otherwise if something weird happens, you don't know whether it was your mod / add-on that caused it, or whether it was going to happen anyway. Try to be patient, get those sockets replaced and if there are still outstanding problems after that then at least they will be consistent and you should be able to fault find it more logically. Almost all of the connections on the user port connector go back to the second 6520, so if you really feel your experiments have caused this latest behaviour try changing the second 6520 to see if that makes a difference. It might, but at the present time there's no way of knowing whether it is the chip or its socket which is causing this behaviour. |
21st Feb 2020, 11:46 pm | #126 |
Hexode
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Re: Commodore PET 3016
You are quite right. I’m getting them changed next week!
I swapped on of the 2114s actually. Seemed to do the trick but as you say-who knows!! Thank you for saving my sanity! |
22nd Feb 2020, 11:09 pm | #127 |
Hexode
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Re: Commodore PET 3016
Whilst I’m waiting for the sockets to be replaced I would like to start thinking about the sound issue though. Although I can download from a tape it doesn’t seem to be saving them. I’ve tried 2 different commodore tape machines-both allow the PET to download software but not save programs I’ve written. Could the problem be connected since they are sound problems? Just thinking ahead!
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23rd Feb 2020, 2:40 am | #128 |
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Re: Commodore PET 3016
The CASS_WRITE signal on pin E5 of the cassette connectors JP3 and JP6 and on pin 7 of the user port appears to originate from the 'user port' 6520 pin 13 (PB3). You could try checking that the connection between that IC pin and those three connector terminals is intact, as it should be.
I'm not familiar enough with PETs to know whether the CASS_WRITE signal is a digital data stream which is converted into audio tones inside the cassette unit, or whether the CASS_WRITE signal is TTL-level audio tones. Does anyone know? |
23rd Feb 2020, 8:21 am | #129 |
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Re: Commodore PET 3016
Cass_write is essentially a TTL level signal that drives the record head (after a bit of simple analogue processing). The cassette unit is very simple inside.
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23rd Feb 2020, 10:13 am | #130 |
Hexode
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Re: Commodore PET 3016
Thanks guys. Is the 6520 likely to be the one furthest away from the keyboard connector? I call that the first one!
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23rd Feb 2020, 11:23 am | #131 |
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Re: Commodore PET 3016
Yes, but from what Tony says you are looking for a data signal from CASS_WRITE rather than an audio signal.
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23rd Feb 2020, 1:20 pm | #132 |
Hexode
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Re: Commodore PET 3016
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23rd Feb 2020, 1:21 pm | #133 |
Hexode
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Re: Commodore PET 3016
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25th Feb 2020, 9:14 am | #134 | |
Hexode
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Re: Commodore PET 3016
Quote:
Pin 13 - cassette 5 = 110 Pin 13 - User port 7 = 110 Pin 13 - User port M - 110 Not sure what this tells me but you will know I am sure! J |
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25th Feb 2020, 1:12 pm | #135 |
Hexode
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Re: Commodore PET 3016
Interesting, seems I can save afterall. I am also getting sound again now but intermittently - seems to be fading in and out but with a constant buzz in the background now which it didn't have before. Let's hope the new sockets will sort it out!
J |
25th Feb 2020, 1:55 pm | #136 |
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Re: Commodore PET 3016
As you're now so close to getting those sockets replaced I think it best to let that go ahead before attempting any further diagnosis since the machine seems to be randomly rewiring itself, making logical fault finding challenging.
See how that goes first, and then we'll look at any outstanding problems you still have after that. It's always easier to hit a static target than one which is constantly moving. |
5th Mar 2020, 11:37 am | #137 |
Hexode
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Re: Commodore PET 3016
Hi, I have had the sockets replaced. A couple of things:
1. Plugged it in last night and all seemed to work fine. Didn't try the sound though. 2. Switched in on this morning and nothing! I swapped the 6520s around and it worked! I don't think it's got anything to do with them though. 3. I'm running it now to see how it is performing and all seems well. However, I tried loading a program I saved before the sockets were replaced and although it loads the program, the pet hands a the 'Ready' prompt and I have to switch it off and on. It will load however, ready prepared software e.g. I am playing Space Invaders right now and it loaded first time etc. It all seems to be working well. I tried the sound again this morning and same isssue. Can you help with the next step? Infuritaing thing is - the sound was working from CB2 well! Could it be a damaged resistor or capacitor somewhere?? Best wishes, John |
5th Mar 2020, 11:38 am | #138 |
Hexode
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Re: Commodore PET 3016
There's also a tiny video wobble which I got before anyway so I'm not worried by that.
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5th Mar 2020, 5:09 pm | #139 |
Hexode
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Re: Commodore PET 3016
Just by way of an update. I've had the PET working in DEMO mode on Space Invaders most of the day. Have now just tried to play the game and it's stuck in demo mode - seems to be looping that part of the program!
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5th Mar 2020, 7:40 pm | #140 |
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Re: Commodore PET 3016
Earlier you said that a program which you had written, presumably in BASIC, and saved, and then loaded back in did not automatically run, although other software which you had did automatically run.
This behaviour would be my default assumption, on most computers of that age if you saved a BASIC program and then loaded it back in it would take you to the program listing, and you'd have to RUN it to make it do something. Commercially written software provided on tape is likely to be machine code and will usually be configured to start automatically once loaded. However, my knowledge of how to actually use a PET is near zero, so I think you'll need to enlist the help of someone who knows these machines better in that respect. It's probably worth checking the supply voltages now (with power on, and your meter on volts of course). For example, what voltage do you have (with respect to 0V) on pin 16 of the 74LS145? I'm assuming your meter volts range goes up in steps of 2V / 20V / 200V, if so use the '20V' range for this measurement. Only check the low voltages please, don't go anywhere near the mains side voltages unless you are absolutely confident that you know what you are doing. With regard to the sound problem, what are your symptoms again? It was working to your satisfaction and then something happened, and now the sound is not what it was? What value of series resistor are you now using with the sounder? If you ever used the sounder in an Arduino project, does it still work with that Arduino project? Space Invaders and demo mode: Unfortunately I'm not familiar with this software but the 'demo mode' was often provided so that the machine could be left running in 'attract mode' in a shop. It may not have encouraged anyone who took an interest to start playing on it (Expensive machine: Keys easily broken). |