MCE2VGA composite CGA and monochrome mode not working

Posted on 2021-04-15, 14:11

by

by keenerb

in Marvin \ Video

in Marvin \ Video

I've picked up an MCE2VGA adapter and it works wonderfully with generic CGA/Tandy/EGA modes. I can't get it to interpret CGA composite which was supposedly added as a feature, and the monochrome mode is not working properly. For the CGA composite I read that hitting the "reset" button would enable …

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Re: Tiny Vortex86-based DOS gaming PC - weeCee

Posted on 2021-04-13, 13:24

by

by keenerb

in Marvin \ System Specs

in Marvin \ System Specs

also your open-source carrier link doesn't seem to have any files or documents or anything, just a picture of it?

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Re: CRT monitor whine; what causes it, ways to mitigate it, do some display types suffer from it more than others?

Posted on 2021-04-02, 00:53

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I will keep the cga monitor as primary but picked up a 9 pin switch box I will use to swap over to a small lcd vga panel with mce2vga adapter if the kids are in the bonus room.

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Re: CRT monitor whine; what causes it, ways to mitigate it, do some display types suffer from it more than others?

Posted on 2021-04-01, 20:21

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That's what I was just pondering, must be the lower CGA frequency. I'll probably switch to a VGA monitor with mce2vga rather than CGA to make them happy...

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CRT monitor whine; what causes it, ways to mitigate it, do some display types suffer from it more than others?

Posted on 2021-04-01, 20:03

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I can't really notice it myself having lost that range of hearing year ago, but my kids tell me that my CGA monitor is MUCH louder/more annoying than the handful of VGA crts I've been tinkering with. Is CGA more likely to be noisy in this way than VGA/EGA/etc? Is there anything that can be done to …

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Re: Tandy Nano - 3 Voice Soundcard ISA - Lowprofile

Posted on 2021-03-26, 16:30

by

by keenerb

in Marvin \ Sound

in Marvin \ Sound

OK so it IS working, it's just EXTRAORDINARILY quiet compared to the Pearce board. I pulled the PIC completely and I can barely hear the default SN76489 noise and music playing with speakers turned all the way up, which is ear-splitting when using the Pearce board. Maybe the variable resistor …

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Re: Tandy Nano - 3 Voice Soundcard ISA - Lowprofile

Posted on 2021-03-26, 03:55

by

by keenerb

in Marvin \ Sound

in Marvin \ Sound

OK so it IS working, it's just EXTRAORDINARILY quiet compared to the Pearce board. I pulled the PIC completely and I can barely hear the default SN76489 noise and music playing with speakers turned all the way up, which is ear-splitting when using the Pearce board. Maybe the variable resistor thingy …

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Re: Tandy Nano - 3 Voice Soundcard ISA - Lowprofile

Posted on 2021-03-26, 03:00

by

by keenerb

in Marvin \ Sound

in Marvin \ Sound

I've finally put one of these together and I can't get any audio from it. My early prototype Pearce tandy sound card works fine but this is just dead silent. Is it possible the little PIC controller wasn't programmed? Is there a TSR to unmute it or something? *edit* I realized my programmer can read …

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Re: Unknown Unisys 8-bit card, need help with identification

Posted on 2021-03-24, 03:34

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

COuld that be an AUI connector, the 15-pin one?

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Re: Unknown Unisys 8-bit card, need help with identification

Posted on 2021-03-23, 02:45

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Early caching scsi controller?

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Re: Unknown Unisys 8-bit card, need help with identification

Posted on 2021-03-23, 00:26

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Two 50 pin headers; scsi? Jumper blocks labeled IRQ, STP, 2, 3, ADR STOP, A C D E, X21, 282 (partially obscured)

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Multimeter reads continuity between +12v and -12v on PSU connector; is that rational?

Posted on 2021-03-15, 23:51

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That doesn't seem right to me. I don't have another AT power supply handy to check. The system in question suffered a serious short between +12v and -12v on the motherboard that burned a hole through it, so I'm questioning whether the PSU itself is damaged...

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Can a UV EPROM eraser be used to de-yellow small parts?

Posted on 2021-02-23, 18:42

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I picked up a QUV-T8 at a garage sale for a dollar, and it seems to be functional. I was contemplating using it to bleach some small parts like floppy drive fronts, yellowed keys, etc. etc. Is this something that would be possible? I'd think it should be much quicker than leaving the yellowed parts …

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Re: (SOLVED - defective FPU) How hot should an 8087 FPU be at idle? I'm getting 55-60 deg C... And other 8087 questions

Posted on 2021-02-23, 11:33

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I am no math processor expert but it seems to me it's connected to many or all of the same data lines as the main processor. If it's defective it may be putting data into the bus when it's not supposed to be?

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Apex Turbo XT motherboard repair first steps...

Posted on 2021-02-11, 17:45

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've picked up a nice almost working Apex 200(?) Turbo XT complete system (system unit, monitor, keyboard, mouse) but it's suffered from a bad battery, like so many other systems of this era. In addition to that, it has a blown tantalum capacitor and the +12v and -12v rails shorted and burned a 1/8" …

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Re: Troubleshooting 1000SL: Power supply runs when not connected to motherboard, no PSU activity when connected to boar

Posted on 2021-02-11, 02:25

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

ANy idea what type of capacitor this is? 106k seems to be a ten microfarad capacitor, and it's probably not HUGELY important what type I use, but I'm curious as to which type this is regardless. Filename capacitor.JPG File size 125.98 KiB Views 48 views

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Re: Troubleshooting 1000SL: Power supply runs when not connected to motherboard, no PSU activity when connected to boar

Posted on 2021-02-11, 00:59

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Looks like your advice was spot on. Audio daughtercard C20 appears to be shorted, and sl boots fine with daughtercard removed! Interestingly, it looks like someone rebuilt the audio daughtercard at some point in the past and not very well, so I think they knew there was a problem with it of some …

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Troubleshooting 1000SL: Power supply runs when not connected to motherboard, no PSU activity when connected to board

Posted on 2021-02-10, 17:56

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Possible short to ground/overload? What should I look for here?

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Re: Memory card with "stacked" dram chips: I don't understand how this works

Posted on 2021-02-09, 02:13

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

imi wrote on 2021-02-09, 00:52: they're probably two slightly different chips It is a different part number on the top chip vs. the expansion daughtercard. Maybe you're right.

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Memory card with "stacked" dram chips: I don't understand how this works

Posted on 2021-02-09, 00:29

by

by keenerb

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've come across a decently rare combo parallel port and memory upgrade card, and I'm confused. The main board has 128kb of memory on it, using "stacked" dram chips, soldered directly on top of one another: ram_pins_2.JPG ram_pins.JPG I'm not well versed in the sorcery of DRAM address decoding and …

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