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  1. Yes, it looks like you have an alternating data...

    Yes, it looks like you have an alternating data bit fault. The bad/good indicates page 0. The video display indicates screen memory. Unless you have two faulty RAMs? The other alternative is an...
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    >>> birth of our first grandchild ...

    >>> birth of our first grandchild

    Congratulations...

    Dave
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    So, the two switches I like are these: ...

    So, the two switches I like are these:

    https://uk.rs-online.com/web/p/toggle-switches/7347101/

    https://uk.rs-online.com/web/p/toggle-switches/7347129/

    The first one is for the switch...
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    We'll try and keep the momentum going... Just...

    We'll try and keep the momentum going...

    Just been to the post office to pick up my bag of IC's for the project (mainly from Unicorn Electronics). Only a couple of devices to find - and I have a...
  5. Nope. PDP-8 and PDP-11 are my thing (along...

    Nope.

    PDP-8 and PDP-11 are my thing (along with Nascoms and Zilog machines to name but a few).

    Dave
  6. I am planning to go down for Saturday 7th as a...

    I am planning to go down for Saturday 7th as a day visitor though.

    Too much work on at the moment to even think about taking anything with me...

    Dave
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    I have managed a good run at soldering in the IC...

    I have managed a good run at soldering in the IC sockets in today. Done everything apart from the 12 off RAM sockets now. Unfortunately, business trip time again... Components should arrive this...
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    CUP == CPU... That's Roland typing too fast. Hi...

    CUP == CPU... That's Roland typing too fast. Hi Roland :-)...

    Elsewhere you are stating problems with bank 0 - you need to fix that first...

    As Roland states - you need to get a CPU and memory...
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    The switch settings should only affect the...

    The switch settings should only affect the BAUDRATE. You stated that you monitored pin F of the BERG connector but saw nothing. This is the transmit line itself, so should have had some activity even...
  10. Nice job Glitch. My son has done a 3D...

    Nice job Glitch.

    My son has done a 3D printable model for the DEC handles. He has 'tweaked' the holes to suit Vince's PDP-8 flip-chip PCBs for the straight-8 (someday I will build it...).

    I did...
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    That's correct. By understanding the CR network,...

    That's correct. By understanding the CR network, you can choose to output or not the bit to the keyboard and decide at the rate at which you send the data to the keyboard.

    You may also decide that...
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    http://www.douglas.com/index.php/off-the-shelf-sol...

    http://www.douglas.com/index.php/off-the-shelf-solutions/bread-boards-by-function/board-extender.html

    You can purchase the extender cards with the appropriate connector fitted.

    Dave
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    Practically, you would either use a statistical...

    Practically, you would either use a statistical testing method or break the problem down into smaller 'blocks' assuming that the blocks didn't interact too much (if at all).

    For example, if you...
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    Hi GT - how are you? The circuitry is quite...

    Hi GT - how are you?

    The circuitry is quite basic that drives the speaker (a flip flop, a transistor and a speaker) - although it does have an interesting CR (capacitor/resistor) timing network in...
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    Assuming the hardware is set-up OK, the HLT...

    Assuming the hardware is set-up OK, the HLT should have permitted the character to have been transmitted.

    There must be something wrong with the configuration of the card or the power supply...
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    Started to solder in the IC sockets now... I had...

    Started to solder in the IC sockets now... I had a bit of time today because of the rain (I was going to do some gardening but...).

    Just placed an order for most of the ICs...

    Dave
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    It depends what you mean by 'hacking' in this...

    It depends what you mean by 'hacking' in this context of course. Do you mean an unmodified keyboard?

    All the information you should require is in the technical manual and schematics on bitsavers....
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    Try here...

    Try here http://www.6502.org/users/sjgray/projects/

    Those frequencies look ok to me - so I suspect your PET is working (video wise) it is just that the monitor you are using won't lock onto the...
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    You have an oscilloscope, so you have all the...

    You have an oscilloscope, so you have all the test equipment you need to repair the PET.

    So, first off, what is the horizontal and vertical synchronising frequency or period?

    Measure (say) the...
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    So, how come R50 was missing? This is one of...

    So, how come R50 was missing?

    This is one of the major clock lines into the video circuit, so with R50 not present it was never going to work...

    Has this machine been 'worked on' previously?
    ...
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    Another nice job Roland! Dave

    Another nice job Roland!

    Dave
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    Yep, that's set the bar! Dave

    Yep, that's set the bar!

    Dave
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    He he! The hard part is finding any time :-)!...

    He he!

    The hard part is finding any time :-)!

    I need to retire...

    Have a good weekend yourself.

    Dave
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    That's all the decoupling capacitors soldered in...

    That's all the decoupling capacitors soldered in :-)!

    IC sockets next...

    Dave
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    The strange branch instruction is a result of...

    The strange branch instruction is a result of compiling a 16-bit application with a 32-bit compiler - and getting a sign extension. I assume the original code for PDP11DASM was written years ago when...
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