Image Map Image Map
Page 5 of 8 FirstFirst 12345678 LastLast
Results 41 to 50 of 79

Thread: PET 4016 power in from transformer to Jumper 8

  1. #41

    Default

    Quote Originally Posted by Dokken View Post
    Attachment 59224

    for reference, my readings (the image size restrictions on this forum are harsh).

    so, where should i go next with this?
    Measure
    J8 9 to 8 AC Volts
    J8 1 to 3 AC volts
    J8 5 to 3 AC volts

    J8 2 to 3 or 6 DC volts
    J8 4 to 3 or 6 DC volts

    Dwight

  2. #42

    Default

    Quote Originally Posted by daver2 View Post
    Please tell me you haven't got 17.2 Volts across J8 pins 2 and 6 though!!!
    no, i think my labels are wrong for the connector. let me regroup and remeasure/relabel everything. i'll have some time off work this weekend.

    thanks everyone for your help and patience.

  3. #43
    Join Date
    Feb 2009
    Location
    Southern California, USA
    Posts
    2,821

    Default

    Quote Originally Posted by Dwight Elvey View Post
    Hi Dave_m
    Thanks for the clarification. The wiring makes sense now. I didn't look at the way they'd used the diode bridge.
    Commodore liked their documentation to be a bit confusing.

  4. #44
    Join Date
    Feb 2009
    Location
    Southern California, USA
    Posts
    2,821

    Default

    Quote Originally Posted by daver2 View Post
    I read approximately 8V AC from the centre tap (black wire) to each of the brown wires; and approximately 16.3V AC between the two brown wires.
    Daver,
    Is your DVM reading in AC rms or peak? I think my old voltmeter readings are peak and be higher. My data say 22 VAC across the brown wires of transformer. I'd better lay low as I may be confusing our OP who is working hard to fix his PET.
    -Dave

  5. #45
    Join Date
    Dec 2005
    Location
    Toronto ON Canada
    Posts
    7,291

    Default

    Quote Originally Posted by daver2 View Post

    It's all coming back to me now! J8 pin 4 is missing from the schematic in post #39 - which is why it is difficult to see how things work when you marry up the transformer/capacitor/J8 schematic with the main board regulator schematic. There is a wire missing from the schematic!

    Dave
    You're right; assuming you really meant post #28 the (red) wire connecting pin 4 to the capacitor+ (and then pin 2) is missing.
    Last edited by MikeS; February 20th, 2020 at 04:29 PM.

  6. #46
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    3,553

    Default

    I meant post #38 rather than #39 - but this same image has been posted multiple times in this thread anyhow.

    Yes, my multimeter would display RMS Volts when on the ac setting.

    Quite a number of companies either accidentally (or deliberately) introduced errors into their documentation. Honeywell were pretty good at this... I implemented a SIMH simulator from the manuals, but it didn’t work properly. Fortunately, Honeywell were pretty good at raising US Patents, so if you implemented the key instruction that didn’t work from the details presented in the US Patent, lo and behold - it works.

    Check and double check documentation...

    Dave

  7. #47

    Default

    Quote Originally Posted by Dwight Elvey View Post
    Measure
    J8 9 to 8 AC Volts
    J8 1 to 3 AC volts
    J8 5 to 3 AC volts

    J8 2 to 3 or 6 DC volts
    J8 4 to 3 or 6 DC volts

    Dwight
    Thanks Dwight, Dave, Dave, Mike, and others who have chimed in.

    first thing i'll check tonight is these voltages with the board connected to power, video cable disconnected, and post the results.

    Anything else i should look for to get to the next step? I'd kinda like to get a fresh baseline on where i stand.

  8. #48
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    3,553

    Default

    I have an 8032 on my bench at the moment I am repairing this morning.

    I have followed the same procedure that we are asking you to do this morning:

    Disconnect the monitor.
    Disconnect the power cable from the main board.
    Measure the AC Volts from the transformer windings - all OK.
    Connect the power cable to the main board.
    Measure the DC Volts from all of the regulators- all OK.

    These are the basics. If the power supplies are not good there is no point in moving on!

    I have a set procedure I then go through (which will be described next once we know your AC and DC Voltages are good).

    By following this procedure on my own PET, I have identified that the 16 MHz crystal oscillator is not working (to start with at least)! I am now trying to identify exactly which component is at fault - but that is a treat for another day...

    Dave

  9. #49

    Default

    Although, not truly relevant to this post, most meters do not read out true RMS. They rectify the AC signal and and take the peak multiplied by 0.7071 for the display. This only works for a perfect sine wave. I had a Fluke meter that one could buy a true RMS adapter. It was a $400 option, on a $500 meter.
    For the most part the signal is close enough but when you measure the AC side of a loaded signal going into a filtered rectifier, it can be 2 to 5% off what the true RMS really is. A square wave that goes + and - by 5V is a 5V rms signal. The typical meter would show 3.54V.
    Just useless facts to think about.
    Dwight

  10. #50

    Default

    Here are the voltage readings with the power connector to J8 on the board.

    J8 9 to 8 AC Volts = 17
    J8 1 to 3 AC volts = 9.0
    J8 5 to 3 AC volts = 9.1

    J8 2 to 3 or 6 DC volts = 7.5
    J8 4 to 3 or 6 DC volts = 7.5

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •