Re: 1526 printer - repair(able) or not?

From: Pete Rittwage <>
Date: Wed, 9 Apr 2014 16:11:30 -0400 (EDT)
Message-ID: <>
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.


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
> (
> Cheers,
> --
> Ville
> 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
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>> ========================================
>> Message du : 06/04/2014 17:41
>> De : "Ville Laustela " <>
>> A :
>> 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:
>> - 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
>> > 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

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Received on 2014-04-09 21:00:37

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