Tektronix 214 restoration - Page 1
Forum section: electronics / repair

author: Mysion
author_rank: Regular Contributor
timestamp: August 23, 2015, 05:55:50 am
content: I just got hold of a dead 214 for 30$. Sold as not working. I hoped the battery's would be the main issue but sadly I was not that lucky.It's a sick looking puppy. There's too much of it to be battery leakage. It look like it was stored upside down and suffered water damage, and with all the build up salt water. At least I hope it's salt, could be a combination of chemicals from a flooded basement. The saving grace is the bottom board is more delicate and it was upside down.Powered it up from my bench supply and nothing. If put into store mode the CRT glows but that's it. Not surprised in the least.The other obvious issue was a dead 1uF 50v tantalum. Replaced it with a 2.2 uF 50v electrolytic. No change.Power draw is withing range, 150-250 mA at 12 volts. So how the heck do I clean that... blue crap. Tried a tooth brush and wire brush, neither worked that well. To add salt to the wound every single transistor and IC is in a fruity low profile socket. Tried to take a picture of it but my phone had issues getting close enough.Should be fun, hope he is savable. Such a cute little scope.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: August 23, 2015, 09:19:51 am
content: For an Alkaline leakage (batteries and possibly capacitors) you need to use a mild acid such as white vinegar or possibly CLR (not corrosive to copper). For an acid leakage you need to use a base such as baking powder. Using the wrong neutralizing agent will only exacerbate the problem! You then need to clean with isopropyl alcohol and distiled water and go over it with a nylon bristle brush, then dry it. If the PCB is one of reasonable quality the solder mask will be made from polyimide which is a relatively chemically stable polymer so there shouldn't be any real damage to the board itself. But the pads and pins oxidizing on each of the components is going to be a issue you are going to have to deal with and maybe broken traces.

author: tautech
author_rank: Super Contributor
timestamp: August 23, 2015, 09:43:44 am
content: Looks like a major project, good luck.I'd do a full disassembly and clean, starting carefully with a stiff plastic scraper to dislodge as much corrosion as possible. Then the usual cleaning procedures, brushing, washing, IPA, etc. Get it spotless.Check the Restoration thread on this Repair board for ideas.Every socketed device and connector will need to be pulled and leads/pins checked for corrosion.Presets and pots, even switches may be stuffedmark the setting on each one, remove and check for correct resistance and estimated wiper resistance, exercise wiper if necessary and replace presets as required.Inspect ALL with good light and magnification for ANY faults: traces, solder joints, cableing, inter-connects etcTake plenty of photos.Expect anything, this project might be a REAL test for you.Again, good luck.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: August 23, 2015, 09:44:42 am
content: You will have to clean the corroded solder pads and leads. You going to need a good temperature iron with good thermal recovery, this is key and you will need to remove components and clean the solderpads with a desoldering desoldering wick/braid, the good quality with flux already in it, or as they call it "No-Clean Wick", it works miracles on cleanup jobs like this. You will need also plenty of flux for cleaning up and retinning the pads. Look also for any broken traces as you go and take your time and be careful, as you can damage traces easily.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: August 23, 2015, 10:05:29 am
content: That actually from the battery, wasn't water damage. Worked on project of stuff like this all the time. The fumes also will corrode and affect areas.

author: SeanB
author_rank: Super Contributor
timestamp: August 23, 2015, 11:30:52 am
content: With NiCd batteries best neutraliser is first wash with a weak organic acid. I use citric acid, as I can get it at work, and it is both mild and chemically pure. Follow with multiple rinses in deionised water and then a dry cycle, and remove anything in sockets as well before the acid wash. After drying you can go with the alcohol wash to get more off, then see what is eaten away.

author: Mysion
author_rank: Regular Contributor
timestamp: August 24, 2015, 12:55:12 am
content: Old school the pcb's don't have any solder mask. Well the particularly damaged one used to but it was in the process of flaking off. Still no broken traces though. I assumed the battery to be the source of the damage at first too but it doesn't compute. Neither battery has external evidence of leakage. There is nothing trickling down the side and you can't see or feel any sort of leakage path. Must be water damage.Tautech I took your advice in cleaning the boards. got it pretty clean. One of the labels on it smeared but that's a small issue. Still unsure on how to clean the sockets. I think I'll have to revisit it with a needle and scrape at them.SeanB I don't have the needed acid on hand right now but if the sockets prove trouble some I'll have to try it.I'll get some new pictures up after the boards finish drying.

author: tautech
author_rank: Super Contributor
timestamp: August 24, 2015, 01:36:28 am
content: Replacing IC sockets won't be a problem if needed, however some of the transistor ones might.But you can always ditch the sockets and just solder components in.Often PCBs can be washed in warm soapy water, rinsed and left to dry. Sealed components like pots need good time to dry so don't hurry this process. A couple of days on a window will in the sun..….. that sort of thing.

author: Mysion
author_rank: Regular Contributor
timestamp: August 24, 2015, 03:37:35 am
content: Good point. Soldering is always an option. The service manual looks good so hopefully I can narrow down problem sockets.I did some basic trouble shooting to figure out why the power LED wasn't lightning. Turns out it's dead, both status LEDs are dead. 2.7 volts on it and nothing. I isolated both LEDs and it's puzzling.... I put another red LED in it's place and it worked as expected. Maybe 1970 era LEDs just didn't age very well. Could also be a bad connector, I'll cut into it tomorrow.

author: Mysion
author_rank: Regular Contributor
timestamp: September 02, 2015, 01:09:52 pm
content: Small update. School started so things are going to slow down. I tested the main voltage rails coming off the isolated smps. Chased a red hearing for a while as I read a 3 as a 5 on the schematic. Not the best quality print, gota be careful with reading it.