- vcf-midatlantic - lists.vcfed.org

Re: vcf-midatlantic Digest, Vol 13, Issue 9
by Jeff G 10 Jun '19

10 Jun '19

Where are you located? I have a tube tester (several actually) Jeff (aka Bags) On Mon, Jun 10, 2019 at 12:07 PM <vcf-midatlantic-request(a)lists.vcfed.org> wrote: > Send vcf-midatlantic mailing list submissions to > vcf-midatlantic(a)lists.vcfed.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.vcfed.org/mailman/listinfo/vcf-midatlantic > or, via email, send a message with subject or body 'help' to > vcf-midatlantic-request(a)lists.vcfed.org > > You can reach the person managing the list at > vcf-midatlantic-owner(a)lists.vcfed.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of vcf-midatlantic digest..." > > > Today's Topics: > > 1. Tube Testing - any recommendations (mwillega) > 2. Re: Tube Testing - any recommendations (Evan Koblentz) > 3. Re: Tube Testing - any recommendations (Chris Fala) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 10 Jun 2019 10:17:59 -0400 > From: mwillega <mike(a)willegal.net> > To: vcf-midatlantic(a)lists.vcfed.org > Subject: Tube Testing - any recommendations > Message-ID: <EF8D7552-F12A-490D-BB87-61C0CC3BAB15(a)willegal.net> > Content-Type: text/plain; charset=utf-8 > > Hi all, > > I?m about to embark on my first restoration of a piece of tube based test > gear. It?s an old Heathkit Oscilloscope from the early 70s. I am looking > for recommendations for approaches to tube testing. Do I seek out or > build a tube tester or just test in circuit. Anything else that I should > look out for, besides the usual concerns about high voltages on the > chassis, and old degraded components. > > Regards, > Mike Willegal > > ------------------------------ > > Message: 2 > Date: Mon, 10 Jun 2019 11:09:06 -0400 > From: Evan Koblentz <evan(a)vcfed.org> > To: vcf-midatlantic <vcf-midatlantic(a)lists.vcfed.org> > Cc: mwillega <mike(a)willegal.net> > Subject: Re: [vcf-midatlantic] Tube Testing - any recommendations > Message-ID: <664e3d37-3600-19ff-36c5-2c5367ce3f9e(a)vcfed.org> > Content-Type: text/plain; charset=utf-8; format=flowed > > > > Do I seek out or build a tube tester or just test in circuit. Anything > else that I should look out for, besides the usual concerns about high > voltages on the chassis, and old degraded components. > You might want to ask the NJ Antique Radio Club. They do this all the time. > > > ------------------------------ > > Message: 3 > Date: Mon, 10 Jun 2019 11:12:23 -0400 > From: Chris Fala <chrisjpf33(a)gmail.com> > To: vcf-midatlantic <vcf-midatlantic(a)lists.vcfed.org> > Subject: Re: [vcf-midatlantic] Tube Testing - any recommendations > Message-ID: > < > CAJCHokjMnpED5NSRON3fzk8BxG5oXJD3oUkvA+iJMDa0QWZUFw(a)mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > There is a Facebook group called Vintage Electronic Test Equipment and a > lot of the guys there post stuff about tube testers. Might be a good > resource for information > > > > . > > On Mon, Jun 10, 2019 at 10:18 AM mwillega via vcf-midatlantic < > vcf-midatlantic(a)lists.vcfed.org> wrote: > > > Hi all, > > > > I?m about to embark on my first restoration of a piece of tube based test > > gear. It?s an old Heathkit Oscilloscope from the early 70s. I am > looking > > for recommendations for approaches to tube testing. Do I seek out or > > build a tube tester or just test in circuit. Anything else that I should > > look out for, besides the usual concerns about high voltages on the > > chassis, and old degraded components. > > > > Regards, > > Mike Willegal > > > End of vcf-midatlantic Digest, Vol 13, Issue 9 > ********************************************** >

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Re: [vcf-midatlantic] Tube Testing - any recommendations
by Chris Fala 10 Jun '19

10 Jun '19

There is a Facebook group called Vintage Electronic Test Equipment and a lot of the guys there post stuff about tube testers. Might be a good resource for information . On Mon, Jun 10, 2019 at 10:18 AM mwillega via vcf-midatlantic < vcf-midatlantic(a)lists.vcfed.org> wrote: > Hi all, > > I’m about to embark on my first restoration of a piece of tube based test > gear. It’s an old Heathkit Oscilloscope from the early 70s. I am looking > for recommendations for approaches to tube testing. Do I seek out or > build a tube tester or just test in circuit. Anything else that I should > look out for, besides the usual concerns about high voltages on the > chassis, and old degraded components. > > Regards, > Mike Willegal

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Re: [vcf-midatlantic] Tube Testing - any recommendations
by Evan Koblentz 10 Jun '19

10 Jun '19

> Do I seek out or build a tube tester or just test in circuit. Anything else that I should look out for, besides the usual concerns about high voltages on the chassis, and old degraded components. You might want to ask the NJ Antique Radio Club. They do this all the time.

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Tube Testing - any recommendations
by mwillega 10 Jun '19

10 Jun '19

Hi all, I’m about to embark on my first restoration of a piece of tube based test gear. It’s an old Heathkit Oscilloscope from the early 70s. I am looking for recommendations for approaches to tube testing. Do I seek out or build a tube tester or just test in circuit. Anything else that I should look out for, besides the usual concerns about high voltages on the chassis, and old degraded components. Regards, Mike Willegal

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Museum report
by Evan Koblentz 08 Jun '19

08 Jun '19

A bunch of visitors to InfoAge today, but mostly for the military stuff because they had a D-Day 75th anniversary event. Highlight for us was a guy in his 30s who is part of the 2600/HOPE community. Between visitors I did some cleaning in the workshop + replied to VCF emails. Evan Koblentz Executive Director, Vintage Computer Federation evan(a)vcfed.org / (646) 546-9999 www.vcfed.org @vcfederation

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Festivus December 7 & 8, 2019
by Jeffrey Brace 07 Jun '19

07 Jun '19

Mark your calendars. The infamous VCFestivus party has been scheduled. Signup here: < https://docs.google.com/spreadsheets/d/1x0oSxqZXh8tmqqbUsP3KS3OywiNsEAOOmtq… > -- ========================================= Jeff Brace Vice President Vintage Computer Federation <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campai…> Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campai…> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

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Re: [vcf-midatlantic] PDP-11/10 PSU Repair/Warning
by systems_glitch 07 Jun '19

07 Jun '19

Apparently some of the other DEC power supplies include a fuse on the AC input for the 5411086 board! I guess they discovered the problem in the field, too. It is a little ironic that the board that generates power fail blew up :) That's why I'd suggested the analog circuit that generates AC LO/DC LO -- both of them had gone away on the backplane. I also find it interesting that DC LO really has nothing to do with the output of the various independent regulator modules. You'd think since DC LO is open collector, each module would be able to pull it down and it'd only be released when all modules were stabilized. That is of course one of the issues with memory write-protect lockout on nonvolatile RAM on S-100: you have to wait til all three supplies stabilize, and then factor in enough time delay for each board to also have stabilized before releasing *PRESET and/or memory write lockout. I guess that's why they built a signal in for just that purpose on IEEE-696! The current draw through the connector should be 2-3 A, the combined output from the 5411086 board's +15V and +8V supplies isn't supposed to exceed 4A and is fused at 5A. It's switchmode (albeit kinda weird early switchmode, using a uA723) so current out should be less than current in, even accounting for efficiency losses. A 1A load on the +15V supply didn't register on the (granted, somewhat insensitive) power meter I was using on the AC transformer primary side. I plan to include a 0-15A AC current meter on the "actually in a box" version of my AC test supply, for finer measurement of module consumption at given loads. I've also seen various old computers and other machines with fuses bypassed, or something that's not a fuse in the fuseholder (cut off pieces of bolt or rod are common). Not a good choice! I did once see a military computer power supply with "battle fuse" switches -- the switches bypassed the power supply fuses, presumably so that you didn't lose computer power in a critical situation from a fuse breaking due to concussion from a shell hit or something. Thanks, Jonathan On Fri, Jun 7, 2019 at 11:29 AM Herb Johnson via vcf-midatlantic < vcf-midatlantic(a)lists.vcfed.org> wrote: > This caught my eye, so I looked at the schematic. Ironically, the > shorted full-wave rectifier is shown on the "power-fail" circuit > drawing. But the rectifier supplies all the unregulated DC voltage. > Unfortunately the fuse F1 is *after* the rectifier and not before. Thus > adding a fuse before the rectifier is wise. > > Bypassing the now-destroyed edge-connector pins is also wise. Did you > determine the normal AC current on those pins? I suspect a few amps, > thus those pins are at risk anyway. > > Thanks for calling this repair out. It's a cautionary tale about vintage > power supplies in general; look for AC-side fuses, install if not. I"m > looking at an IMSAI; the prior owner bypassed the AC fuse holder! ;( > > Shocked, > Herb > > > -- > Herbert R. Johnson, New Jersey in the USA > http://www.retrotechnology.com OR .net >

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PDP-11/10 PSU Repair/Warning
by Herb Johnson 07 Jun '19

07 Jun '19

This caught my eye, so I looked at the schematic. Ironically, the shorted full-wave rectifier is shown on the "power-fail" circuit drawing. But the rectifier supplies all the unregulated DC voltage. Unfortunately the fuse F1 is *after* the rectifier and not before. Thus adding a fuse before the rectifier is wise. Bypassing the now-destroyed edge-connector pins is also wise. Did you determine the normal AC current on those pins? I suspect a few amps, thus those pins are at risk anyway. Thanks for calling this repair out. It's a cautionary tale about vintage power supplies in general; look for AC-side fuses, install if not. I"m looking at an IMSAI; the prior owner bypassed the AC fuse holder! ;( Shocked, Herb -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net

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PDP-11/10 PSU Repair/Warning
by systems_glitch 06 Jun '19

06 Jun '19

full writeup here: http://www.glitchwrks.com/2019/06/05/pdp1110-psu-repair I finally fixed the power supply in my PDP-11/10S, it turned out to be a shorted bridge rectifier on the 5411086 board, which provides +15 VDC, LTC, and AC LO/DC LO. Unfortunately, when it failed, the rectifier burned up the edge connector traces for the AC input to the board. I ended up cutting the edge connector traces away (what was left) and soldering on a pigtail to connect to the Mate-n-Lok coming from the AC transformer. I added a 15A inline fuse, in the repair. For those who have original 5411086s that haven't failed yet, you might want to make up a little pigtail with an inline fuse holder. It'd be easy to make up such that it could plug into the existing harness without permanent modification, and it'll save your edge connector traces if the rectifier shorts. It can happen in the other regulator modules too, but they use a Mate-n-Lok instead of an edge connector, so any damage would be repairable. Anyway, the PDP-11/10S is back up and running! Thanks, Jonathan

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Museum report
by Evan Koblentz 05 Jun '19

05 Jun '19

It was slow-ish at the museum today. Visitors included a man who last saw our exhibits a few years ago, and a family of five (three middle-school kids) who took a solid tour and asked smart questions. Wednesdays always get busy in the summer when school is out and families come to the shore on vacation. I'm looking forward to that. Docent days are more fun when there are lots of visitors.

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