- cctalk - classiccmp.org

by Rob Jarratt

(sending again from a different email address as I don't think my first email got through, apologies if this is a duplicate) I have a VT100 that I was working on a while back and then set aside for a bit. I have started to look at it again. I have noticed that the Video Shift Register, a 74S299, gets very hot, I can smell the heat and the chip gets almost too hot to touch, reaching almost 40 celsius. I have a working VT102 for comparison and the same chip there does not get so hot (it reaches about 30 celsius). I have already tried replacing the chip, but the new one gets equally hot. I looked at the signals the chip is receiving and the one that stands out as different is the CLK input (pin 12). It looks like this: https://rjarratt.wordpress.com/wp-content/uploads/2024/04/vt100-74s299-clk-s ignal.png. On the VT102 it looks like this: https://rjarratt.wordpress.com/wp-content/uploads/2025/11/vt102-74s299-clk-s ignal.png. It is much spikier on the VT100 and I was told at one point that this could be the cause of the hot running for the chip. Is that a reasonable assumption? Assuming the spikes are the cause of the hot running. I am trying to see why there is a difference. I have noticed that on the VT102 there is a 68R resistor between the DC011 which produces the signal and the 74S299. You can see this as R86 in the VT101 printset https://bitsavers.org/pdf/dec/terminal/vt101/MP-01066-00C_VT101_Family_Field _Maintenance_Print_Set_Apr82.pdf (p47 of the PDF). The VT100 printset dated Feb 82 https://bitsavers.org/pdf/dec/terminal/vt100/MP00633_VT100_Schematic_Feb82.p df shows an inductor L8 being used (PDF p17), but my VT100 does not have this and so must be described by the March 80 printset https://bitsavers.org/pdf/dec/terminal/vt100/MP00633_VT100_Mar80.pdf (PDF p17). Could the absence of L8 explain the spikier DOT CLK signal and the hotter 74S299? Incidentally, I suspect that the flyback transformer on my VT100 has failed. If anyone has a flyback transformer going spare, especially in the UK, then I would love to hear from you. Thanks Rob

1 month, 4 weeks

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Conductive material in rubber dome

by me＠scifidan.com

I just acquired a TRS-80 model 102, my first of that model. Everything is great other than three keys. The 2 keys works intermittently, q, and [ don't work. Having checked the schematic, the keys have no commonality on the circuit. Before I pull the cap off the switch, I know that the rubber dome inside has material on the inner part that meets with the silver contacts to complete the circuit. I'm told this material will wear out or lose conductivity. I reflowed the solder joints on the pcb and this didn't help. Other people have simply replaced the rubber dome from another dead 102's keyboard. But, I'd rather attempt applying new material inside that dome. I'm hoping there is an inexpensive and mainstream solution I can buy at home depot or something. Any tips? Daniel sysop | Air & Wave BBS finger | calcmandan(a)bbs.erb.pw

2 months

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leave

by Ralph M. Hockens

leave

2 months

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Re: leave

by junk myalternateemail.com

Shoes? Heck, I have to put pants on first.

2 months

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BDV11 programming information

by Peter Ekstrom

Does anyone know if there is any programming information about the BDV11 card? I have disassembled the ROM files for it and I see they do various operations with the registers on the card, but it is not clear to me exactly what they are doing. - Peter

2 months

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OT Scotch Type 871 Tape Reel?

by Holm Tiffe

Hi all, I'm trying to sell an old Scotch tape reel on Ebay Kleinanzeigen here in germany. It's box is labeled 871-1-3600 R41 which I think means Type 871, 1 Inch and 3600 ft, Don't hve an idea about R41. Stock No: 84-9800-5294-2 I've bought that myself in a error..needed an Data tape to this time. Now one asks if that is an vintage video tape for the philisp EL3400 Recorder.. Has someone an idea what kind of tape that may be? Thx, Holm -- Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, Goethestrasse 15, 09569 Oederan, USt-Id: DE253710583 info(a)tsht.de Tel +49 37292 709778 Mobil: 0172 8790 741

2 months

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Someone is letting go of a Data General Eclipse S/20 in Missouri

by Christian Liendo

This is not my ad, but I saw this and I figured someone would be interested and reach out. https://www.reddit.com/r/VintageComputers/comments/1oxu9h5/data_general_ecl…

2 months

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WINdows-1985

by Murray McCullough

According to history Windows 1 was introduced to the world on Nov. 20, 1985, 40 years ago, minus 2 days. Prior to this Windows was first announced in 1983(vaporware) but…An even earlier development was Interface Manager. What we have now is much more and ‘better’ but for classic computing I still prefer WIN 3.1. Happy computing. Murray 🙂

2 months, 1 week

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Depraz Mouse, Type D 83 / P, Excellent Condition, Looking to Establish Value and Sell

by microprint314＠gmail.com

I found a Depraz mouse the other day (Type D 83 / P) while going through moving boxes. I used to - long time ago - make things out of broken or disassembled computer gear. There was the most amazing store in Dover, NJ called Second Byte where I spent too much time and money (according to my ex-wife). I purchased this mouse 30 years ago with no particular project in mind, and it has just stayed packed away. I'm looking to sell it but I admittedly don't know what it's worth. I see two of them on eBay for $20-$30K, but don't see any Sold Items as a reference. Those sale prices sound largely aspirational. The mouse is in pretty amazing physical condition, with only basic scuffing on the red surface. The larger spots you see are reflections. The cable has scuffs but no fraying at all. The ball turns when the mouse is rolled. No pins are bent on the connector (RS-232 / DB9?). The three buttons click. Any insight - or offers - is welcomed. Thanks.

2 months, 1 week

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Re: Seagate half high hard drive face plate & cables

by Peter Ekstrom

Mike, Where are you located? I am in the US in Georgia. I have several of each of those connectors. - Peter On Fri, Nov 21, 2025 at 3:42 PM Mike Katz <bitwiz(a)12bitsbest.com> wrote: > 20 and 34 pin edge (2 each) and 20 and 34 pin female dual in line (1 > each). I have the ribbon cable and the tool > > Thank you > > On Nov 21, 2025 12:19 PM, Peter Ekstrom <epekstrom(a)gmail.com> wrote: > > Mike, > > Which connectors is it you need? > > -Peter > > On Fri, Nov 21, 2025 at 1:08 PM Mike Katz via cctalk < > cctalk(a)classiccmp.org> wrote: > > > Paul, > > The connectors are about $5 apiece and I would need 7 connectors. I > have the cable and tool. > > My goal for asking was to see if anyone had a spare cable or two and > save them from eventually going in the land fill. > > Thank you for your help, > > Mike > > On 11/21/2025 11:17 AM, Paul Koning via cctalk wrote: > > For that matter, since the connectors are insulation displacement type, > you can assemble your own: buy the connectors and a length of table, cut > pieces to size, and assemble the connectors onto the cable. A press is > normally used for that, but a vise should do the job too. > > > > paul > > > >> On Nov 21, 2025, at 11:03 AM, Paul Koning via cctalk < > cctalk(a)classiccmp.org> wrote: > >> > >> General comment on cables like that: in the past I have obtained flat > ribbon cable assemblies from Digikey. If you're dealing with a cable > that's simply a ribbon of width N and a connector at each end, companies > like that can supply them easily and cheaply, in any length you want. > >> > >> paul > >> > >>> On Nov 20, 2025, at 9:40 PM, Mike Katz via cctalk < > cctalk(a)classiccmp.org> wrote: > >>> > >>> Does anyone out there have a spare 1/2 high 5 1/4" Seagate MFM hard > drive face plate (ST-221, ST-251, etc.) that they can let go cheap? > >>> > >>> And also a 34 conductor dual drive cable and a single 20 on single > drive cable? > >>> > >>> Thank you. > >>> > >>> Contact me off list at bitwiz(a)12bitsbest.com > > >

2 months, 1 week

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