test-drb November 2015

test-drb@ccmp.vtda.org

169 participants
223 discussions

by billdegnan＠gmail.com

Performed maintenance of my VAX 4000-200. Removed NiCad battery Replaced hard drive Made new image of system drive The how-to is all over the web, but I summarized a lot of the basic support tasks associated with a networked VAX 4000 here for anyone interested in a simple "for dummies" page http://vintagecomputer.net/browse_thread.cfm?id=608 The system is hosted here: vax4000.vintagecomputer.net -- Bill

8 years, 8 months

DEC 4260 transistors (MOS clock driver on LSI-11 CPU)

by spacewar＠gmail.com

Does anyone happen to know what the industry-standard equivalent for a DEC 4260 PNP transistors in the MOS clock driver circuitry on LSI-11 CPU is? Is it a 2N4260? Thanks! Eric

8 years, 8 months

VAX 4000-200 Maintenance

by mhs.stein＠gmail.com

----- Original Message ----- From: "Robert Jarratt" <robert.jarratt at ntlworld.com> Sent: Thursday, November 19, 2015 4:27 PM ... My to-do list has me doing the rounds of all my machines to check them all for the batteries. I'd like to replace rather than remove though, but that could get expensive at about ?10-12 pounds per machine for the cordless phone battery packs sold by Maplin. Maybe there is a better alternative, I should go and take a look. Regards Rob ----- Reply ----- Wow! I buy mine for $2 to $4 at the local 'Dollar' store... Or you could order from the usual place; e.g.: http://www.aliexpress.com/store/group/Battery/1191734_259040387.html m

8 years, 8 months

Todays Topic from Panelman

by rodsmallwood52＠btinternet.com

Hi Guys I think we are all only too well aware of the difficulty of getting parts for our old systems. This the more so for items that can been seen. Having got at least a half reasonable replacement front panel process my thoughts turned to toggle switches. In the case of PDP-11 this is already being addressed by another list member. So to PDP-8's. There's two parts to a PDP-8 toggle. The slide switch and the lever. The leaver is injection molded in a two part mold. The join line can clearly be seen. Clearly a mold is required to produce one or more at a time. These used to be very expensive but with modern CNC machines it might be worth finding out. In addition we now have 3D printing available To aid this have I have produced a drawing of the switch lever with views from three angles. From here it should be possible to: 1. Convert to 3D for 3D printing tests 2. Produce a drawing of the two part mold tool. Extruded PVC I'm familiar with having worked in the cable industry as a student. ABS which is what I think the leaver may be made of may be different (hot to cold shrinkage for example) Comments from list members with experience in the above areas would be of interest to us all. Now to the slide switches themselves. They are mounted by the screw hole lugs having been slid into a groove in two aluminum bars which in turn are attached to the PCB by pillars and screws. There are six connection pins on the bottom of each switch that go into holes in the PCB. (not all used) Switch replacement would be easy and a complete switch and lever sub module not too difficult. I hear a voice >from the distant past saying 'Micro switches' Thats all for to-day Rod

8 years, 8 months

Front Panels

by rodsmallwood52＠btinternet.com

Hi Guys Well the panel is here and I'm analyzing it to see what it tells us. So far it looks like I need to add a band of gray matte base to the front and a band of similar over the light ports on on the back. Looks like I have a new product. It's called an "Invisipanel" Its a clear plexiglas blank I use for checking alignments. Because its so clear I cant find it!!!! Rod

8 years, 8 months

Testing bus transceivers

by jnc＠mercury.lcs.mit.edu

> From: Guy Sotomayor > A number of data books have circuits that were used to measure the > parameters .. so you might want to look at some of them Thanks for the tip! Alas, I don't know of any data books with circuits like that - any pointers? (And it's only the leakage current I need to check; the other 3 key DC parameters I have already managed to check.) > From: Mark J. Blair > Do you have any sort of precision, regulated, adjustable lab bench > power supply that you could use to vary input voltage? Well, I have some Lambdas, but I'm not sure they are 'precision' (any more - the pots are kind of dirty/flaky, so they jump when you turn them). > If not, using a potentiometer as you mentioned would also work. Yeah, that's what I did - running a 500 ohm pot from ground to +5V provided a nice input, and I was able to verify the 'maximum 0 input voltage' and the 'mininum 1 input voltage' quite easily. I also realized that in a system with 'normal' single QBUS box with termination, one has a 330 ohm pull-up in the CPU's termination, and 180 ohm pull-up in the BDV11 terminator, which adds up to 42 mA into the transceiver when pulling to low voltage; if one adds another 180 ohm pull-up, that adds another 28 mA, getting me to the required 70 mA for the 'maximum 0 output voltage' check. Since the QBUS specs allow another termination, if you have a second box, that's probably why they spec it at 70 mA, actually. > Also, how many of these did you buy? Umm, like 400? :-) (Dave Bridgham and I are winding up to produce a QBUS card which uses SD memory cards along with an FPGA and micro-controller to emulate a range of DEC disk systems - RK11, RP11, etc - and we wanted to assure a goodly supply of our selected transceiver chip before we spin out a PC board.) > If it's something like a dozen, manual testing will be practical. If > it's something like a hundred, then automating the testing might be a > good idea, and a fun project all by itself if that sort of thing > interests you. Well, not really, to be honest (I'm not an analog person), plus to which I have a zillion other projects (e.g. a bunch of UNIBUS machines to refurbish, plus other non-computer things) which are backlogged, the last thing I need is another one! ;-) Also, you might be able to automate the _testing_, but one still has to plug the chips in and out, which is a certain amount of work, so it's not like automated testing would allow me to trivially check really large numbers of chips. Which is why I've adopted the 'test randomly selected units for meeting specs' approach (remember, I'm just trying to make sure these aren't counterfeits), and for that, manual testing works fine. Noel

8 years, 8 months

PDP 8a transformer capacitor replacement?

by thebri＠gmail.com

Having read all sorts of bad things about these older oil filled capacitors, I decided to replace the one on my 8a. I got what I think is a replacement - 6 microF, 660VAC, 50/60Hz, "NO PCB's" - but it is physically about 1/3 the size as the original. Did the tech for these get that much better? What purpose does this serve? It's hanging off the transformer. I see lots of links about motor start capacitors, but nothing relating to transformers. http://www.mouser.com/ProductDetail/Cornell-Dubilier/SFA66S6K288B-F Thanks, b

8 years, 8 months

Wanted: 9-track tapes.

by tomjmoss＠googlemail.com

Does anyone have any 9-track tapes for sale, preferably in the UK/EU? I'm getting tired of ordering NOS tape from the US just to find they've got sticky-shed... I'd also like one of those early IBM style reels, the red/blue ones with the three "viewing holes". Doesn't have to work. -Tom

8 years, 8 months

Could someone make the list do the thing in the subject line?

by COURYHOUSE＠aol.com

OR UC ONLY BEEHIVE TERMINAL! NOTHING LIKE 'RIDIN THE 'HIVE AT MIDNITE! In a message dated 11/18/2015 4:24:14 A.M. US Mountain Standard Time, ard at p850ug1.demon.co.uk writes: > > COMBINE THEM THEN JUST ADD TWO LETTERS AND A DASH AS THUS > > CC- > > SOMEONE SUGGESTING THIS AND USING CAPITALS ONLY PROVES TO BE A MAIL NOOB > ;-) Or is using a Model 33 ASR (or KSR) :-) -tony =

8 years, 8 months

Could someone make the list do the thing in the subject line?

by COURYHOUSE＠aol.com

good point Ethan that is one of the main reasons as if it has a list designator I would defiantly look at it then.Ed# Tue, 17 Nov 2015, ethan at 757.org wrote: > By any chance could someone configure the mailing list to add or [cc] or > [cct] into the beginning of the subject line? Not looking to filter, just not > looking to delete messages.

8 years, 8 months

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test-drb November 2015