Hello, I'm looking for a bit of information regarding old terminals. My New England Digital Synclavier II (an old computer based music synthesizer) has the option of having a terminal connected via RS232, and the manual specifically mentions the following three terminals: VT100 VT640 ADM-3A Am I correct in understanding the first two are by DEC (Digital Equipment Corporation) and the third one is by Lear Siegler? How common were and are these three terminals? I'd like to get hold of one for use with the Synclavier, just wondering what views people hold on them, both from a popularity point of view and in terms of usability. Presumably you get a slightly different experience using all three, at least in terms of build quality, display type, keyboard type etc, if not in terms of supported terminal modes as well. Curious to hear what people think. If you're interested, there's a video of me demonstrating the Synclavier on YouTube. http://www.youtube.com/watch?v=ZuUh4eIE3-k Richard

Although the manual might mention three specific terminals, use of those terminals for the synthesizer is actually RARE. Most computers have some sort of terminal emulation software available, which usually CLAIMS VT100 emulation. If you are looking for the LOOK of those terminals, VT100 terminals are not very hard to find. Does the iMac have software to emulate an ADM3A ?

The VT100 is, indeed a DEC terminal. It's very well-known and not too hard to fidn, but equally there are people who want them. You might also consider a VT101, which looks the same but has more limited intenral expansion (and an easier-to-fix PSU). I don;t think DEC ever made a VT640. The VT640 I know of was made by a company called soemthing like 'Retrographics'. It was a VT100 (genuine DEC) with an extra board added to give a graphics mode (I think the '640; in the mdoen mumber was the horizontal resolution). This board intercepted the RS232 lines between the host machine and the VT100 logic, DEC kidnly provided a connector for his purpose. For text-only operaiton the VT640 and VT100 are indentical AFAIK. FWIW, I think most later DEC ternminals (VT220, VT3xx, etc) will eessentially emulate a VT100. And just about any terminal emulator program offers VT100 emulation. Of coruse this doesn't help if you wanm the real thing. I'e never used a ADM-3A, so I can't comment o nthat one. VT100s were very common. I can see 2 from where I am sitting (and a VT105 too, which is a VT100 with a DEC graphics module). However, soem DEC enthusiasts also like to have the origianl type of terminal for their PDP11s and VAXen, so these terminals may or may not be easy to find now. The VT640 is not common. I've only ever seen one, that was some years aog. I didn't; get it, a friend and I were colelcting old DEC 'junk'. He got the VT640, I got a VT55 (complete tiwth the built-in electrolytic printer). I think I made the right choice.... As to faults : The VT100 logic is very reliable. There are 2 custom chips in the video ciruitry, but they tend not to fail (I dont think I've ever replacved one). The keyboard uses the same contact system as the VT52, TI99/4A, origianl TRS-80 Model 1, HP85, HP9816, etc. The keyboards can have contact trouble, but it's gernally fixable. The VT100 PSU is a switcher. It's a relatively friendly swithcer iwt hthe cotnrol circuitry o nyhe isolated side (powered by a little linear supply), but it still cah have problems. The VT101 has a simpler suppy lwith a big mains transformer which might be easier to repair The video monitor can have problems. Flyback transformers fail (and are non-trivial to get now). Diodes o nthe video board also fail, this cna kil lthe flyback transfoemer. The CRT can also lose emission, but do clean the screen ebfore thinking about relpalcign it (yes, I fell for that once). The genuine VT100 has a white phosphor IIRC, but the VT640 I say had a green phosphor CRT fitted. -tony

On 01/22/2012 02:29 PM, Tony Duell wrote: Yeah I was thinking the same thing. :-( I'd love to have a P112. -Dave -- Dave McGuire New Kensington, PA

On Sun, 22 Jan 2012, Andrew Lynch wrote: That's really weird. I never got that impression from Dave Brookes. How did you arrive at the conclusion that cloning the P112 is illegal? -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

On Sun, 22 Jan 2012, Andrew Lynch wrote: The way my involvement with the P112 started was that I asked David Brookes if I could make more. He said, "yes" and handed over the design files. I'm looking around for the emails now. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

On 22 Jan 2012 at 19:29, Tony Duell wrote: Many hobbyists seem to be deathly afraid of soldering SMT, particularly fine-pitch (0.5 mm) QFPs. It's not that bad, even with a regular soldering iron, but a microscope or other aid to visually inspect the result helps a lot. At some point, someone offered adapter cards with, for the want of a better term, employed a "trench" for each lead, so that misregistration was almost impossible. I don't know if they're still made or even how difficult it would be to fabricate such a thing on a circuit board--but it might bear investigation for future kits. --Chuck

Do you believe I do love doing that?! :)

On 01/22/2012 07:54 PM, David Riley wrote: I suggest getting a good liquid flux (I use a flux pen from MG Chemicals, with rosin flux, very nice) and absolutely drown the area with it. Decrease the solder feed rate. If you find that you have a hard time feeding the solder slowly enough to avoid bridging, switch to a smaller-diameter solder. Oooh. Umm, yes. I use a Metcal SP200. One of the best investments I've ever made, and I was lucky enough to get it cheap. It, plus a good liquid flux makes all the difference. With that, I can use the "drag" technique to solder all 36 pins of a 144-pin QFP in one pass with somewhere between 0-3 bridges in about 8-9 seconds. (just did a bunch of those a few days ago) 0402s are definitely tougher; you have to be very quick with the iron. 0603s aren't much different from 0805s though. (0805 is the "standard" size that I use in my designs unless the it calls for something else) Oh neat, I will check those out. That price sounds pretty good. -Dave -- Dave McGuire New Kensington, PA

Well, I wouldn't classify myself as "deathly afraid of" surface-mount. But I don't like the little of it I've done, and that is the voice of experience, albeit only minor experience, not "no foundation in reality". I'm sure that with proper tools and a fair bit of practice I could be fine, but I definitely prefer through-hole. (My current tools aren't really _bad_ for the job - I'm not talking a half-inch chisel tip on a 45W open-loop iron - but they're hardly ideal.) Strictly, I suspect that it's not through-hole versus surface-mount but 0.1" versus 0.5mm; through-hole 0.5mm, if such a thing exists, would probably aggravate me at least as much as 0.5mm surface-mount, and I wouldn't expect 0.1" surface-mount to be any worse than 0.1" through-hole. Component size matters too. I've seen surface-mount parts that are about four times the size of a typical grain of sand; I'm not fond of the idea of dealing with such a thing at all. (It'd be better with through-hole simply because the leads provide some mechanical mounting which surface-mount doesn't have, but still not great.) /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mouse at rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

On 23 Jan 2012 at 0:01, Dave McGuire wrote: Heh. Must be a generational thing. I remember many years ago, my late father wanting to recapture some of his experiences and construct his own receiver. So he went to the local electronics dealer and came back with some 14AWG bus wire, a spool of 24AWG magnet (enambeled) wire, a 1G4G and an Eby surface-mount octal socket (he was upset when he discovered that UV201s were no longer made), a No. 6 dry cell and a couple of 45V "B" batteries. He'd already selected and shellacked a nice pine board and was working on fabricating his own book-type "condenser". It worked, and I suppose it was a real work of art, but I thought the use of bare #24 wire was *so* retro and campy, compared my up-to-date use of point-to-point using hookup wire and tie strips... We're fast coming to a time, I suppose when through-hole PCB construction will seem just as dated--and 5V logic will seem curiously power-hungry although RTL was 3V, so at least we've been here before. --Chuck

On Jan 23, 2012, at 12:44 AM, Dave McGuire wrote: If I had proper tools (which, once we make this move which will hopefully be the last one for a while, I will start doing), I'd probably like SMT more. As is, I've had good luck with the toaster oven method (which isn't *that* different from the industrial reflow process, just a little less controlled) and there wasn't much cleanup with leaded solder. I enjoy soldering, though. I feel like it's been a productive day when I can't get the smell of burnt rosin out of my nostrils. It's a smell that brings back as many fond memories as the smell of burnt gunpowder, which just smells like mischief. :-) - Dave

I think I still prefer through-hole work (maybe becasue I've had more expeirence of it, or becuase you can easilly socket DIL pagkages to make debugging easier, or becuse through-hole prototpying boards are easier to obtain). but I certainly don't worry aobut SMD stuff. -tony

On Sun, 22 Jan 2012, Chuck Guzis wrote: I can probably deal with QFPs, but BGAs are just nasty, particularly when combined with the wrong sort of solder. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

On 01/22/2012 11:29 PM, Chuck Guzis wrote: It's pretty easy to do that with vias. -Dave -- Dave McGuire New Kensington, PA

On Sun, 22 Jan 2012, Chuck Guzis wrote: As someone else mentioned, those are made by Schmartboard. I asked on a homebrewed PCB mailing list how or if trenches like that could be made on a homebrewed or professionally-made board. The answers ranged from "maybe" to "yes, but very expensive" to "no". -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

On Sun, 22 Jan 2012, Chuck Guzis wrote: That sort of thing is precisely why I had the boards pre-stuffed with the surface-mounts. The boards were fabbed and stuffed a few miles from Portland Oregon by Sunstone Circuits and Screaming Circuits. I'd gladly use their services again. Soo.... anyone want P112 kits? Two are sold. Five more are left. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

On 01/23/2012 08:01 AM, David Riley wrote: I use Advanced Circuits regularly; I'm expecting a shipment of PCBs (for work) tomorrow. They're a bit pricey, but they are top-notch. I've never used Advanced Assembly, though they keep sending me spam. I do small production runs myself. -Dave -- Dave McGuire New Kensington, PA

Ture, but the way to overcome these fears is to have a go. You wil lnever learn new skills if you don't try things. If all kits haev the 'difficult' bits done dor you, you'll never learn to do it. What do toy do if you've build a P112 kit and one of the SMD devices fails? You're goign to have to desodler it and solder in a new one then, I guess. I rememebr the first SMD device I fitted. It wwas the I/O contorlelr IC in a Ahrp PC1500 pocket computer, at a time when the PC1500 was not a 'classic computer'. It had failed, and I managed to buy a replacement form the sercvice agents. I worried a lot about doing it, until I tried. Then I foudn how easy it was. of course threre's SMD and SMD, some compoennts being larger and/or have a coarser lead pitch than others. But jsut about anything (otehr than BGAs) can be hand soldered. -tony