Image Map Image Map
Tab Content
  • daver2's Avatar
    Yesterday, 05:04 AM
    >>> 6800: Wouldn't it have to be that Tektronix system with the incredible price tag? Yep, I would vote for the Tektronix 4051. I used one 'back...
    14 replies | 296 view(s)
  • daver2's Avatar
    September 20th, 2017, 05:20 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    U8 pin 10 would appear the logical choice. Unfortunately, U8 is not present on Falter's the board... U8 pin 9 appears the next logic choice - and...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 18th, 2017, 02:04 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    You've been busy doing other things :-)... Makes sense what you are saying. Need to chase pin 14 (the input) of the 'top most' 4049 next to see...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 16th, 2017, 11:53 PM
    daver2 replied to a thread ForthDOS? in Tandy/Radio Shack
    I see it has sold. Did anyone buy it from VCFED by any chance? Dave
    12 replies | 659 view(s)
  • daver2's Avatar
    September 15th, 2017, 06:27 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    I agree with Dwight about being careful with CMOS devices. You need an antistatic work mat and a wrist strap (with some antistatic storage for the...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 14th, 2017, 02:01 PM
    daver2 replied to a thread Quest COSMAC ELF in Other
    That makes sense. Dave
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 14th, 2017, 01:01 PM
    daver2 replied to a thread Quest COSMAC ELF in Other
    Pull-up resistors are not actually necessary. All of the 'control' switches are debounced by feeding them through two inverters connected back to...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 14th, 2017, 12:50 PM
    daver2 replied to a thread Quest COSMAC ELF in Other
    This may be worth a read... http://www.cosmacelf.com/publications/books/short-course-in-programming.html. I have a 'tame' obsolescence company...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 14th, 2017, 10:08 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    Hi RizThomas. I found your blog previously regarding your 1977 (re)build. Nice work. I tried to find a contact e-mail for Josh to see about...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 14th, 2017, 09:38 AM
    OK - so highly likely the character generator. Of course, you could download the file...
    21 replies | 508 view(s)
  • daver2's Avatar
    September 14th, 2017, 07:38 AM
    Hi Andreas, It's a bit tricky trying to catch the posts as they are moderated! Get a few more posts under your belt (10 I think) and it will be...
    21 replies | 508 view(s)
  • daver2's Avatar
    September 14th, 2017, 02:46 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    Well done that man! I suspect this is the first time this card has ever worked then... You may find this resource helpful...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 13th, 2017, 12:19 PM
    My thought exactly Dave... One possibility - some sort of problem with the "NO ROW" signal? Another is a partial character generator ROM fault...
    21 replies | 508 view(s)
  • daver2's Avatar
    September 13th, 2017, 10:16 AM
    As this is your first post, welcome to the forum... I agree with Andy - let's have a look at the 'modification' or 'fix' first. A close-up of...
    21 replies | 508 view(s)
  • daver2's Avatar
    September 13th, 2017, 07:10 AM
    daver2 replied to a thread ForthDOS? in Tandy/Radio Shack
    See post #7 (possibly) ... Dave
    12 replies | 659 view(s)
  • daver2's Avatar
    September 13th, 2017, 07:05 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    Hi Falter, Your visual representation is excellent. Basically, the arrangement of gates in the 4049 agrees very well with that published in...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 09:56 PM
    daver2 replied to a thread Quest COSMAC ELF in Other
    Well, U1 pin 3 HAS to be wired up somewhere! Can I suggest chasing the track back from U1 pin 3 to see where it ends up? If nowhere, then this is...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 12:52 PM
    daver2 replied to a thread Quest COSMAC ELF in Other
    If some LED's light - it is probably plugged in correctly... One possibility is that one of the blue wires has fallen off at some point that was...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 12:30 PM
    daver2 replied to a thread Quest COSMAC ELF in Other
    I may have found the source code for the 32-byte monitor (although it does say it is for the Super ELF) at...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 12:04 PM
    daver2 replied to a thread Quest COSMAC ELF in Other
    Ahh, the mists are slowly clearing now... I guess both U7 and U8 are missing from your board and these are where the blue wires are connected to...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 10:15 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    So, the switches look to be wired as we thought - don't use the centre position - just use the two far extremes. The LOAD switch appears to do...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 10:00 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    I forgot to say. Your display modification is in http://www.exemark.com/Microcontrollers/PopularElecwebc.pdf in Fig. 1 (9) on page 18. Obviously,...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 09:56 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    Thanks. Yes, pages 1 & 2 of the second part are the interesting thing... They are using the ROM loader here - so if the ROM has failed, you...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 08:58 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    I have just started to trace out the PCB (from http://www.astrorat.com/images/Quest_COSMAC_Elf_Original_Rev_2_1.pdf). I am now not sure whether...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 06:23 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    I assume your 'black' wire is actually positive and your 'red' wire is negative :-)! I see that you don't have the parts for the speaker driver or...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 04:33 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    The original ELF had a full-wave bridge rectifier and a protection device fitted. You are correct in that yours doesn't - so only feed DC (not AC) to...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 10th, 2017, 03:19 AM
    daver2 replied to a thread PDP-8/e key measurements. in DEC
    Yep, been to Vince's excellent site. Anyhow, my son turned up the other day with a 'tub full' of 3D printed paddles - and a thing of beauty they...
    11 replies | 531 view(s)
  • daver2's Avatar
    September 9th, 2017, 12:16 PM
    daver2 replied to a thread Quest COSMAC ELF in Other
    Yes, the LED 'values' will be a 'power of 2', so the LEDs will correspond to 8, 4, 2 and 1 respectively. Now which 'end' of the block of 4 LEDs is 8...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 9th, 2017, 01:48 AM
    daver2 replied to a thread Quest COSMAC ELF in Other
    The circuitry on the little daughter card (with the LED displays) effectively make two binary hex displays. The LEDs are arranged as two columns of...
    55 replies | 1422 view(s)
  • daver2's Avatar
    September 8th, 2017, 11:31 AM
    daver2 replied to a thread ForthDOS? in Tandy/Radio Shack
    I tried to send the seller a message. Unfortunately, they are not accepting messages. My plan was to see if they would ship to the UK - but that...
    12 replies | 659 view(s)
More Activity
About daver2

Basic Information

About daver2
Location:
UK - Worcester
Occupation:
SW/HW design engineer

Statistics


Total Posts
Total Posts
1,309
Posts Per Day
0.68
General Information
Last Activity
Yesterday 05:04 AM
Join Date
June 19th, 2012
Referrals
0

1 Friend

  1. Zetopan Zetopan is offline

    Junior Member

    Zetopan
Showing Friends 1 to 1 of 1