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  1. H

    Replacing the power supply in a Commodore PET 8032

    Picked up a CBM 8032 with a bad transformer a few years back. Posted about how to fix here http://www.vcfed.org/forum/showthread.php?65594-Converting-CBM-8032-PET-to-switching-power-supplies and finally got around to cleaning up the wiring and permanently mounting the parts. Here's the parts...
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    Recreating the Ferguson Big Board

    As part of a recent estate sale, my son and I ended up with two Big Boards, one built, and the other almost completely bare. Stripped the bare one down, took a couple of scans on a large format flatbed and started doodling in Sprint Layout. Doesn't look to bad to replicate if anyone is...
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    Converting CBM 8032 PET to switching power supplies

    It's alive! It's alive! Ghetto rigged it all up. +21V DC feeding the monitor through the rectifier bridge and rest of the buck converters. +16V DC feeding the +12V regulator through the rectifier bridge. +9V DC feeding the +5V regulator directly, bypassed the rectifier bridge since...
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    At VCF Midwest, dragged along some SBC6120 RBC full kits and FD50to34 Adapters

    Everything you need to build one, including the HD1-6120 chip and preprogrammed ROM's and GAL's. https://www.retrobrewcomputers.org/doku.php?id=boards:sbc:sbc6120-rbc-edition:start The ultimate Adventure game platform. $120 Also have some of NF6X's excellent 50 to 34 pin adapters (8 inch...
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    Converting CBM 8032 PET to switching power supplies

    Picked up a 8032 with bad transformer a while back, my son posted about it here. http://www.vcfed.org/forum/showthread.php?55630-Commodore-CBM-8032-Transformer-Problem&highlight=8032 Primary winding is open circuit, didn't see a thermal fuse anywhere. Bottom line is fixing the transformer...
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    SBC6120-RetroBrew Computers Edition - KiCAD, Gerber PCBs & Partial IC Kits

    Finally found some time to get mine assembled. Came up right away once I figured out the IDC to DB9 cable was not wired correctly, initially it was just throwing garbage on the terminal screen.
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    WTB FD50TO34 adapter card

    I've got a few extra from a batch I built with cheap Chinese non-latching connectors. Say $10 and whatever postage is to you? Shoot me a PM if interested.
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    Zenith Z-90 repair log and schematic request

    Success! After replacing the shorted 4.7uf tantalum on the terminal board and repairing another burnt and lifted trace (the -18V supply between pins 1 on P514 and P515) I've got an H: prompt and working memory test. After swapping the jumper shunts between my two drives (I've got another burnt...
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    Troubleshooting a Kaypro II power supply

    Picked this up from a neighbor awhile back, didn't power on at the time and the 12V line showed 0V under load, no load it showed almost 12V. Unplugged everything except for the logic and video boards, did a quick check on the boards and didn't find anything pulling the 12V line down, so just...
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    Zenith Z-90 repair log and schematic request

    Thanks for the link. All my logic board tants that I replaced look like 2.2uf 20V. The ones on the terminal board on the same voltage rails (-18V, +18V) are 4.7uf 50V, including the one that is shorted (but did not blow like the logic board).
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    Zenith Z-90 repair log and schematic request

    My son recently acquired a Z-90 that would start-up, but only displays a cursor, no H: prompt. Seems like the CPU board is not starting. A quick tear down and right away here's a problem, blown tantalum cap and lifted traces all the way back to the power input on the +12V area of the CPU...
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    Issue with FreHD Boot ROM in Model 4 Student Station

    Getting closer, got a 254 with the FreHD attached and powered. Still no boot menu though, tried both a 2GB and 4GB SD card. Does FreHD support SDHC? I'm using the SD-CARD contents starter files from Ian's download page.
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    Issue with FreHD Boot ROM in Model 4 Student Station

    BASIC commands didn't work. Got a 255 from the second line, and the final line returned a SN Error (tried the whole sequence twice with a power cycle in-between). Keep in mind I have no idea if the FreHD I built is fully functional yet. It seems to work as expected (solid LED's on first...
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    Model 4 Screen Brightness Issue

    I have the RCA board, not seeing an INT-BRT pot either on the board or in the schematic (Model 4 Technical Reference Manual). The three pots I do see control size and hold. The TCE board does show INT-BRT as VR303.
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    Model 4 Screen Brightness Issue

    Once the CRT on my Model 4 warms up, this is what my screen looks like, even at minimum brightness. The front brightness 500K pot tests OK, and it appears minimum brightness happens at the zero ohm end of the scale. Sprayed it with contact cleaner and even jumped the contacts to force zero...
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    Issue with FreHD Boot ROM in Model 4 Student Station

    Stock U70 is a 2716 EPROM
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    Issue with FreHD Boot ROM in Model 4 Student Station

    Keyboard is back together, BASIC program is entered, and the dumped ROM set is attached. Looks like the included receiver program has some bugs (was accumulating bytes faster than the TRS-80 was sending), and I didn't have a C compiler handy, so I just captured the output in TerraTerm and...
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    Issue with FreHD Boot ROM in Model 4 Student Station

    I've got a Model 4 Student Station (Model 26-1059) that's a diskless 64KB machine. It has an 8048364 in U68, so I'm using the Gen 2 ROM image from Ian's page. http://ianmav.customer.netspace.net.au/trs80/downloads.htm Without the FreHD connected, I'm getting garbage screens on boot or...
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    Success creating new Model II disks with ImageDisk 1.18 and an FDADAP adapter

    Just wanted to share my experience with this. Things went better than expected and my son now have a number of new disks to play with in the Model II. I have the later rev drive controller card, so I simply unplugged the 50 pin connector from the TRS-80 card, and plugged in into the FDADAP. I...
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