Tutorial/tips on restoring vintage electronics - Page 1
Forum section: electronics / general

author: rvmeush
author_rank: Contributor
timestamp: March 28, 2013, 12:05:34 am
content: There is a thriving community of folks interesting in bringing vintage electronic equipment back to life. Often this equipment has laid around, unpowered for decades. I've seen some debate about the use of variacs to gradually re-power this equipment, as well as techniques for dealing with old components that may not have aged well. I'd like to get Dave's thoughts on working on some of these old gems, perhaps with a project to restore a specific piece of equipment.

author: c4757p
author_rank: Super Contributor
timestamp: March 28, 2013, 12:15:56 am
content: I don't think Dave cares much for vintage electronics. Not to speak for him, but I'm pretty sure I recall that he tends to think of them more as obsolete annoyances than anything. I like vintage stuff, but I can definitely understand that view.Quote from: rvmeush on March 28, 2013, 12:05:34 amUgh. I hate that method - so hamfisted. "Don't turn it on, take it apart!" I always open things up and carefully inspect for shorted resistors, open-circuit resistors, open tube filaments, conductive debris, etc. I even check that the tubes are the right type - I've seen one example where some dumbass must have thrown a random tube in an empty socket to make it look complete, but it was a completely different type that would have stuck the B+ straight up the filament. Then every single aluminum electrolytic capacitor gets removed from the circuit and tested for capacitance, dissipation factor and leakage at full rated voltage, and every non-aluminum large capacitor (oil, etc) gets replaced without question.Thenthe device is turned on.When I feel something behind my car tires, I don't back over it real slowly so it doesn't damage the paint, I get out and move it.

author: krivx
author_rank: Frequent Contributor
timestamp: March 28, 2013, 12:36:12 am
content: Variacs can certainly be useful for testing mains-powered equipment. Often you can't tell if any active device has failed until you apply power, and slowly increasing the supply voltage while monitoring the current drawn can prevent any further damage.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: March 28, 2013, 01:00:34 am
content: Being a vintage restorer myself, Variacs are completely useless at bringing up old equipment. Old dried out caps will blow now, or later. A variac will not fix these.I agree with c4757p, take it apart and inspect and replace the obvious. Starting with an overall inspection with a schematic. Then start with the power supply. That is where the first big bang is produced. If you just go for broke and plug it in, and fry the transformer, well you now have vintage parts.

author: c4757p
author_rank: Super Contributor
timestamp: March 28, 2013, 01:08:53 am
content: Quote from: krivx on March 28, 2013, 12:36:12 amWith tubes, they are useless. What kind of tube failure will cause it to draw way too much current, but not show up during pre-power tests? It's pretty much either "this shorted to that" (always something I check for), or "doesn't work at all". With either very high B+ or tiny signal tubes, an air leak can cause arcing, but you can see that by the color of the getter flash. And if it's semiconductor-based, it's not uncommon to see a circuit that will fry itself whenundervolted, so the variac is right out.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: March 30, 2013, 03:39:16 am
content: Aside from capacitors, I've heard of logic chips failing in some 70s/80s-era electronics, but that's more for arcade machines and video game consoles. Only way to really track those is to get a logic probe and turn the thing on (unless you start pulling chips for fun).

author: robrenz
author_rank: Super Contributor
timestamp: March 30, 2013, 02:23:17 pm
content: Warning! shameless self promotion aheadYou may findthis threadon my 7603 restoration interesting. There may be a few techniques not seen elsewhere.

author: SeanB
author_rank: Super Contributor
timestamp: March 30, 2013, 02:30:27 pm
content: Shameless self promotion is admired there! Can I send you mine to restore?

author: robrenz
author_rank: Super Contributor
timestamp: March 31, 2013, 02:01:41 am
content: Quote from: SeanB on March 30, 2013, 02:30:27 pmI know you are kidding but even If I did the restoration for free the shipping both ways would be more than a new digital scope. And from reading every post of yours since I joined the forum, you are more than capable of duplicating my results.

author: SeanB
author_rank: Super Contributor
timestamp: March 31, 2013, 05:07:02 am
content: True, but you do have the most amazing eye for small details. I know toll and die makers who would love to get tutored by you for a few weeks.

author: robrenz
author_rank: Super Contributor
timestamp: March 31, 2013, 01:50:10 pm
content: Thanks, I would like to get tutored by you for a few weeks on the electronic side of things. And I now bring this Mutual Admiration Society meeting to a close.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 07, 2013, 05:24:25 am
content: To the OP-----If the thing hasn't been used for years,& has been stored away haphazardly:-Open it up,remove the Redback/Black Widow Spiders,dead mice & Geckos,etc.Have a look at the electrolytic capacitors--if it is really old--50 years,or so,they will probably have oozed gunk out at some time or the other,so replace 'em!If it is a newer piece of gear,look for bulging tops,& replace 'em if you find this.If in doubt,replace 'em.If someone has tried to repair it in the past---beware!They may have been competent,but just ran out of time or patience,or they may be an idiot--in the latter case,look out for valves(tubes) plugged into the wrong sockets,completely inappropriate component substitutions,etc.Mechanical faults are another possiblity--a piece of equipment with an immensely complex slow motion dial may have been retired for that reason,& unless you are one of those people with almost infinite patience,you probably won't fix it,either.

author: SeanB
author_rank: Super Contributor
timestamp: April 07, 2013, 04:14:54 pm
content: Shoot, just got some boat anchors today........... in there is a nice HP spectrum analyser. Will get them out and apart sometime soon, hopefully nothing seriously wrong with them.