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Posted By
Charlemagne
on 2019-01-17
11:46:44
|  Re: What can be wrong?
gerliczer: WoW, thanks a lot, I'll try it...
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Posted By
MMS
on 2019-01-17
11:56:52
 | Re: What can be wrong?
The still working PLAs can be used in a Plus/4 also the newer type od memories.
So it is ON 
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Posted By
siz
on 2019-01-17
12:45:56
| Re: What can be wrong?
>The still working PLAs can be used in a Plus/4 also the newer type od memories.
C64 and 264 series PLA-s are not compatible so they cannot be used in a plus/4.
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Posted By
MMS
on 2019-01-17
16:10:39
| Re: What can be wrong?
then it is OFF, sorry... SID chip? partially ON
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Posted By
siz
on 2019-01-18
03:17:52
| Re: What can be wrong?
> SID chip
Only if you have a very rare SIDCard that accepts 6581.  Most of them capable of using a 8580 only.
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Posted By
gerliczer
on 2019-01-18
03:52:40
| Re: What can be wrong?
6581
Then, AFAIK, it is not a C64C (or C64G), but an original one. Either Charlemagne found the wrong illustration or at least one of his C64Cs has its mainboard replaced.
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Posted By
Charlemagne
on 2019-01-19
07:58:46
| Re: What can be wrong?
Yes, gerliczer is right again because I found a wrong illustration on the net, but the first site (I mentioned before) says: "The Commodore 64C was simply the original C-64 repackaged in in a beige C-128 style case.", so the difference can be a little, on the other hand now when I take them apart, turning out that these are C64E...
The first one is made in Hong Kong (initial screen and no cursor), the second is made in China (blank screen).
There are three ICs which are easy to take out and put in:
8565R2 - VIC-II Video (U7)
8580R5 - SID Sound (U9)
8701 - MOS Clock generator IC (U20)
So I tried:
1.: MOS-Clock to Hong Kong: initial screen and no cursor
2.: VIC-II to China: blank screen
3.: VIC-II, SID, MOS-Clock to China: blank screen
4.: VIC-II, SID, MOS-Clock to Hong Kong: initial screen and no cursor
Well, these ICs are good...
Some strange things:
- There is no MN2114-2 (U19) in the Chinese one, only a diode.
- There are different capacitors (the 9 pieces on the right side)
- There are plus two diodes in the Chinese.
After having a closer look at the ICs:
- 64 x 4 D-RAM (U11) is very hot in the Chinese.
- and maybe the problem is around the oscillator (PAL / NTSC) or keyboard multiplexer.
One of my friend take the two motherboards with him and will try to exchange other fixed ICs, too.
Thank you for responses.
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Posted By
theruler
on 2019-01-19
13:21:39
| Re: What can be wrong?
You can check the c64 pictorial fault guide.
https://derbian.webs.com/c64diag/
Unfortunately Black screen can be due to a wide variety of faults. And C64C have very few chip socketed.
You can start removing the SID and check if it boots. C64 can operate without a SID chip installed (obviously without sound).
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Posted By
Charlemagne
on 2019-01-20
08:18:02
| Re: What can be wrong?
In the meantime... I rehashed my old computers and checked them...
I have found:
- 2 Commodore Plus 4
- 2 Commodore 16 (one of them: gave a black screen, but now it works again, see below)
- 2 Commodore VIC 20 (one of them: some keys work hard, so they need clean, I think)
- 2 Commodore 64
As you can see there are a lot of "easy-to-replace" (socketed) ICs in a Commodore 16, so I started to change CPU (8501), TED (8360) and then I tried 3584...
...what is this??? I cannot find anything about it... After replacing this (3584), the Commodore 16 revived and works well again!
theruler: Thanks. OK, I will try it.
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Posted By
gerliczer
on 2019-01-20
09:30:32
| Re: What can be wrong?
Well, that 3584 is a date code not a type code. The code you must be looking up is 251641-02 or you could have checked U16 in the schematics. That is the PLA. It's in the top 3 both in importance and frequency of breaking.
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Posted By
MMS
on 2019-01-20
12:14:51
| Re: What can be wrong?
I knew it
(BTW little OFF
just yesterday I read a blog from a guy made a lot of adventures, and was involved in the revival of an adventure game creator engine, unknown till today, called DAAD (from the same Gilsoft as the legendary PAW and QUILL adventure editors on Spectrum, C64, CPC, etc), and can work from Microsoft Visual Studio Code with a plugin). It has a kind of similarity to LUMYDCTT, but less general, and little less user friendly).
https://www.msx.org/news/en/multi-platform-daad-adventure-writer-v2-r2-released
http://8-bit.info/infinite-imaginations-aventuras-ad/
ON: He bought some almost mint condition C64s in Germany, and the PLA ICs (only this) died in two of these almost pristine quality Commodores after short period of use. So maybe in C64 PLA is the Top1, in out case Top3 (after CPU and TED).
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Posted By
MMS
on 2019-01-20
14:50:56
| Re: What can be wrong?
I was just kidding...
But had a "stomatch feeling" on the matter after reading that blog I mentioned.
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