Anyone diagnose a "poorly" Vic-1010?

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eslapion
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Re: Anyone diagnose a "poorly" Vic-1010?

Post by eslapion »

Mayhem wrote:UA7 is indeed 74LS00PC on the chip.
Thanks for checking.
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mrr19121970
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Re: Anyone diagnose a "poorly" Vic-1010?

Post by mrr19121970 »

So what is the most likely logic chip causing this issue ? 74ls245 ?

Why would you say replace them all? If mayhem has an ic tester and a ic clip he can test them on the board in seconds.
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Re: Anyone diagnose a "poorly" Vic-1010?

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Big use of the word "if" there :lol:

I'll connect her up and see what happens with DK and Lunar Leeper first.
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Re: Anyone diagnose a "poorly" Vic-1010?

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mrr19121970 wrote:So what is the most likely logic chip causing this issue ? 74ls245 ?
The VIC-1010 has 2 different types of buffer chips unlike the VIC-1020 so it's impossible to tell.
Why would you say replace them all?
Because modern equivalents from the HCT family consume less than 1/10th the amount of power taken by 74LS family chips and its usually less trouble than trying to troubleshoot.
If mayhem has an ic tester and a ic clip he can test them on the board in seconds.
You can't check an IC when it is still attached to a board where other ICs can send disruptive signal - connecting an IC tester will power all the chips.
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Re: Anyone diagnose a "poorly" Vic-1010?

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Sorry for not coming back to this yet, real life and all. Hopefully soon!
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Re: Anyone diagnose a "poorly" Vic-1010?

Post by Kakemoms »

mrr19121970 wrote:So what is the most likely logic chip causing this issue ? 74ls245 ?

Why would you say replace them all? If mayhem has an ic tester and a ic clip he can test them on the board in seconds.
Assuming the 1020 schematics is the same as the 1010 (I don´t have a 1010 schematics), the CRW line seems to be unidirectional and going through U1 twice (NOT+NOT). I am not sure why, but in the case the U1 chip isn't working, the RAM expansion would not work. If the 74LS244 or 74LS245 didn´t work, ROM would´t have worked either.

That being said its not that many chips and they are rather cheap, so I would have replaced them all. Check the board between each desolder/resolder to see if it fixed things. You may even put in sockets to make it easier to swap chips in the future?

PS: Before desoldering a chip, try melting the solder of all the chips. The most common error is a cracked solder which does not show but results in a broken circuit. I would do that with the U1 first.
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Re: Anyone diagnose a "poorly" Vic-1010?

Post by eslapion »

Kakemoms wrote:Assuming the 1020 schematics is the same as the 1010 (I don´t have a 1010 schematics), ...
The schematics for the VIC-1020 are here: http://sleepingelephant.com/denial/wiki ... ic1020.gif

If you look at the photos at the beginning of the thread, there are much more chips on the VIC-1010 so the schematics are definitely not the same.
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Re: Anyone diagnose a "poorly" Vic-1010?

Post by Kakemoms »

eslapion wrote:
Kakemoms wrote:Assuming the 1020 schematics is the same as the 1010 (I don´t have a 1010 schematics), ...
The schematics for the VIC-1020 are here: http://sleepingelephant.com/denial/wiki ... ic1020.gif

If you look at the photos at the beginning of the thread, there are much more chips on the VIC-1010 so the schematics are definitely not the same.
The 1020 has 5 IC's. The 1010 has the same 5 IC's plus two additional 74LS365 hex buffers. Since we don't have the schematic, we can only guess at their use. The most obvious is to buffer the non-buffered lines on the 1020.
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Re: Anyone diagnose a "poorly" Vic-1010?

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Kakemoms wrote:The 1020 has 5 IC's. The 1010 has the same 5 IC's plus two additional 74LS365 hex buffers. Since we don't have the schematic, we can only guess at their use. The most obvious is to buffer the non-buffered lines on the 1020.
When you assume you make an a55 of U & Me...

Sorry... this one was too easy. But I would say this; there is no way to tell if the buffers are connected to different lines in a manner remotely similar from one device to the other.
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Re: Anyone diagnose a "poorly" Vic-1010?

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Sorry, just been so busy with a bunch of other things, I haven't had a chance to get back to this. Hopefully soon, at least to see what happens when I try to run those double bank games.
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Re: Anyone diagnose a "poorly" Vic-1010?

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When I get some moments, I really am going to get back to this! :P
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