Hello, and thanks, Martin, Hervé and Olaf. I was positively suprised to have received this many ideas so quickly. As I have very little space to work, I had just a quick look on the board today. I had the board on my desk without the printer mechanics so all indicator I had was the paper advance button with the LED. Today's experiments: - Into the primary side of the transformer goes three wires: brown, white and black. White is neutral (directly from the mains connector) and black is the live wire (comes thue the fuse and the power switch). Without modifying the wiring I was able to measure that between the black and brown wires there was 100V AC voltage. If some of you who have a 220V version could have a look on the PSU to see how it is wired? The case of the transformer is apparently fixed in place and I can't see where the wires go. - I pulled out, checked for bent pins and reseated all chips - no change - I found another copy of the service manual (as PDF) in here: http://www.commodoreman.com/Commodore/Library/Man/1526_MPS802_4023_ServiceManual.pdf - On page 24 the manual explains that the board accepts 24 or 28 pin ROMs, jumpers J1-J4 (next to the ROM socket) are used to set which size is used. In my board they are set correctly. I have no equipment to check the ROM. I have been thinking of getting an EPROM burner (mainly to read some older ROMs for backup and sharing), but can't decide on the model. A quick search on eBay gives just about only two choises: TOP853 and G540, both USB and cheap chinese units. Reviews on both units are not especially good (bad manuals, unstable software, only 32-bit drivers...). Still some say that they are just fine. Perhaps either of these would be just fine for me? Being able to burn Kickstarts for Amigas would be a plus, but not a necessity. Finally I checked the /RES signal on the 6504 (at last I had some use for my eBay-bought logic tester!). It seems that the /RES signal is being constantly held low. Would this indicate bad ROM or a fault in the reset circuit? I pulled the 6504 out and bent the /RES- pin out of the socket. This had no visible effect (I manually pulled it low after applying power to the unit), at least judging by the front-panel LED. Please ask if I explained something badly, I am still very new to this level of fault-finding. Again, thanks for your support, guys. -- Ville > You can measure the voltage between the brown wire and the other wires. If > the transformer has a 230V connection you must measure to one other wire > 115V and to the other one 230V. So you can use the wires where you measure > 230V for input with 230V. Then if you look at the wire with 115V, you must > find a junction for two wires out of the transformer. The 115V / 230V > transformer has two 115V coils. One i used for 115V input, both are used for > 230V input. > Have you checked the /RES signal for the CPU? At the picture i see an EPROM. > The content of an EPROM can be non-permanent over more than ten years. You > can compare it! > > The CPU needs RAM. This RAM is into the 6532. There are two 6532. Swap these > chips! The 6532 have no internally programming! > I would first double check that all socketed ICs are 1) at good location 2) facing the good direction 3) no blent pin. I would then try to force a reset (pulling low the relevant pin). I would also confirm that reset is not low every time ... Also, I would confirm clock operation and or data/address bus activity. As a last try, I would try to confirm status of the eprom (good/bad ?). > > The board looks quite nice and the ribbon should not be an issue even if dried. > > I wish you great pleasure trying to repar this ! The service manual is very nice, I must a pair or 4023 around there if you wish that I have a look at something. > Interesting that you report about that just at this moment. > I have an MPS-802 (which is pretty much the same thing, going by the > pictures) which also doesn't power up. It is a 220 V model though. > > I haven't done any measurements inside since the connections on the > transformer expose 220 V if the enclosure is taken off. I'll want to do > something about that first. > > My ROM next to the 6504 is shorter than the socket, just like in the > reference above (and unlike your dropbox picture). Message was sent through the cbm-hackers mailing listReceived on 2014-04-06 16:00:02
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