It's very common for those pins to get stuck. I would poke at it a bit with some machine oil and see if it will loosen up. -Pete On Wed, April 9, 2014 1:03 pm, Ville Laustela wrote: > > Hi again, everyone. > > I have now assembled the printer and I am happy to report that it is > working! > > There was quite a lot of cleaning and lubricating required (some parts > were even rusted) and fe. the mechanism that tightens the ribbon during > printing was jammed and it kept rotating in both directions (=loosening > the ribbon into the printer!). Also several screws were missing. The > ribbon itself is not too bad, actually. There is still one fault: all the > letters are missing a dot on the top of the character. The flat cable > between the print head and the PCB might have a bad contact or there is a > pin stuck in the print head. Also I am still wondering about the > transformer if it could be re-wired for 230V. > > Some more pictures (and couple short videos) added > (https://www.dropbox.com/sh/j1n1kplrdy0w3ky/nGg0CoBbMN#/). > > Cheers, > > -- > Ville > > > > email@example.com kirjoitti 7.4.2014 kello 0.47: > >> Ville, >> >> You're saying : "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?" ==> Definitely, if you can confirm a >> permanent low level at reset's CPU pin, there must be a trouble around >> there and nothing can start. >> >> From service manual's schematics, this line is driven by U1C (74LS14). >> From this line (74LS14 pin 4), you have together (6504, pin 1), 6522 >> (pin 34 TBC), both 6532 (pin 34), and U8B (LM555 pin 4). Reset line is >> also driven by extrenal reset pin of serial port on U1C pin 1. To go >> deeper on this option, I would sugest you to remove U1C or to isolate >> (cut trace) for either (in preference order) pin 4, 3, 6, 5. From there >> you should be able to manage manually the reset line. >> >> Another approach could be to remove (agin !) all socketed ICs >> (CPU/6522/both 6532) to confirm that reset line remains low everytime >> [if not, then one of our 4 ICs is guilty/dead - if yes, we're still in >> troubles ==> remains U1C or U8B or transistors / Zeners in between] >> >> The LED is driven by 6532 pin 13 (U5D). >> >> Regards - Hervé >> >> >> Tous vos emails en 1 clic avec l'application SFR Mail sur iPhone et >> Android - En savoir plus. >> >> >> ======================================== >> >> Message du : 06/04/2014 17:41 >> De : "Ville Laustela " <firstname.lastname@example.org> >> A : email@example.com >> Copie ŕ : >> Sujet : Re: 1526 printer - repair(able) or not? >> >> >> >> 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 list >> > > Message was sent through the cbm-hackers mailing listReceived on 2014-04-09 21:00:37
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