RESTORATION of TEK 7603 Scope w 7A18 amp + 7B53A timebase  - Page 1
Forum section: electronics / testgear

author: robrenz
author_rank: Super Contributor
timestamp: December 16, 2012, 08:20:07 pm
content: This is my restoration of my first scope from 32 years ago. The story of getting it back 32 years later isthis threadIt had very little use during the roughly 30 years it was not in my possession but was very dirty inside and out yet was fully functional.The main cosmetic issue was serious corrosion under the nickel plating on the front and rear frame bezels. The main covers were just dirty and needed some body hammer work from heavy items that gently bowed the tops in the perforated areas and some light dents. Magic sponges and simple green were extremely effective at removing the dust that very firmly attached itself to everything. Armor all was used on all the exterior plastic and vinyl parts. The plastic CRT filter needed a wet sand and plastic polish treatment to remove some mild scratches.The main functional issues were the very dirty and corroded bnc connectors and the normal scratchy pots and switches. I disassembled the pots that were bad and ultrasonic cleaned all the parts in IPA. Then cleaned all the contacts and wipe areas with Deoxoit D100L on a soft wood stick. Clean with IPA again and lube the gold wipe areas with Deoxit G100l and the actual pot wiper with Caig Faderlube. The mechanicals were lubed with Triflow grease. The gang switches were flushed with IPA and then Deoxit D100L was blasted thru them with compressed air. The drum switches in the amplifier and timebase were disassembled and all the gold finger contacts were individually cleaned with D100L on paper pulled thru the contact area, cleaned with IPA and lubed with G100L. I also replaced the power cord that was pretty stiff.I have many more pictures but I am trying to restrict this thread to things that are not in your typical restoration. I will start with just before and after shots and then post more details following.Front before, the poor(er) photo quality was not intentional.Front AfterTop right beforeTop right afterRear beforeRear afterbottom afterAfter top and handleAfter left topAfter topAfter side

author: david77
author_rank: Frequent Contributor
timestamp: December 16, 2012, 08:31:58 pm
content: Great! I was looking forward to reading your restoration on this scope. As soon as I can find one in reasonable shape and at reasonable price I'll get one.A small electronics shop here has a couple of them for sale, in unknown condition without plugins for 550,00 EUR a piece non negotiable - I think not.

author: robrenz
author_rank: Super Contributor
timestamp: December 16, 2012, 10:00:02 pm
content: More before and after shots. All the knobs went into the ultrasonic with waterbase cleaner. Front panels were removed cleaned and replaced. Armor all got rid of oxidation on the black portions of the knobs and the AC-GRND-DC switches.Finshed back.Since I had to refinish all of the frame I was able to match the bottom extrusions to the front and rear bezels at the bottom.Very dirty 7A18 vertical amp.Crusty bnc connector.After 7A18Very dirty 7B53A timebaseAfter 7B53A timebase

author: Unknown
author_rank: Unknown
timestamp: December 16, 2012, 10:49:21 pm
content: Very impressive results!

author: robrenz
author_rank: Super Contributor
timestamp: December 16, 2012, 11:56:32 pm
content: The Frame bezels are nickel plating over a copper flash on the base aluminum die casting. I thought I could just glass bead blast it off but the plating thickness varies greatly because of the current density variations in the plating bath. So all the sharper corners are plated thicker. So I had to file all the nickel off on all the areas that are exposed when assembled. After all the body work and sanding of the exposed areas it went into my glass bead blast cabinet for that uniform frosty finish. The frame and CRT bezel were then washed in solvent and sprayed withPermalacsealant. Very high performance stuff with a price to match. All this work may seem extreme but I think the final results are worth the effort.Heavily corroded spotGeneral peelingGeneral funkFiling thru the corner. Nickel then copper flash then the base aluminum.Precisely filing all the nickel off. Several hours of work followed by several more hours of contour filing and sanding.220 wet or dry silicon carbide paper glued to a cast iron surface plate. This allows me to flatten the face of the bezel.I put black marker on the face to check when it is all cleaned up. I am about half done, have to sand until all the black is gone.This is the bare aluminum with a glass bead blast finish and sealed with the Permalac.The CRT bezel fortunately was not plated so it only needed some filing, sanding and bead blast before the Permalac

author: robrenz
author_rank: Super Contributor
timestamp: December 17, 2012, 01:31:38 am
content: Much to my dismay the screen printed text on the rectangular push buttons wiped off with just water. So I pondered many other bad fix methods before realizing I could engrave the buttons and fill them with black epoxy.Engraver set up with quick fixture to repeatably locate the buttons. Ratio is set to match the original text size.Quick fixture made with toolmakers vise and parallels glued to the vise to nest the button.It just so happens the engraver font I have is the same as the button text.I sharpened the engraver cutter to a narrower than usual included angle so I could get some substantial depth without the cut getting too wide. This cut is about .01" deep.These have the original text still on and I have used the same engraving cutter to cut the horizontal line in these buttons.Mixing 20 min epoxy with carbon black to fill the engraving. The milligram scale allows precise ratio mixing of very small quantities.Epoxy was spatula-ed into the engraving and cured under the luxo lamp.All the buttons have been filed and then wet sanded on 6 micron diamond film. This also removed all of the yellowing of plastic on the buttonsButton after polish with Meguires plastic cleaner on woven nylon metalographic pad.At normal viewing distance I don't think anyone is going to know these are not original.

author: T4P
author_rank: Super Contributor
timestamp: December 17, 2012, 03:20:25 am
content: Extreme machining comes into practice here - Great work rob!

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2012, 05:34:49 am
content: Very nice work there, looks better than when it left the assembly line all those years ago.

author: Shuggsy
author_rank: Regular Contributor
timestamp: December 17, 2012, 06:38:11 am
content: Amazing looking work robrenz. Did you have to replace any parts or was it all "just" (BIG quote marks there, a LOT of work involved!) cleaning? Those buttons look particularly great. Tek should have made them that way!

author: firewalker
author_rank: Super Contributor
timestamp: December 17, 2012, 07:50:11 am
content: Awesome!!!Alexander.

author: muvideo
author_rank: Frequent Contributor
timestamp: December 17, 2012, 10:11:16 am
content: Wow, hats off to you, wonderful work !Fabio.

author: Soertier
author_rank: Contributor
timestamp: December 17, 2012, 12:03:08 pm
content: Awesome restoration!!

author: TerraHertz
author_rank: Super Contributor
timestamp: December 17, 2012, 12:32:51 pm
content: I'm speechless! Awe and envy at your skills. Beautiful work.(So *that'* how to shine up dirty BNCs. I never was able to do even that terribly well.)

author: robrenz
author_rank: Super Contributor
timestamp: December 17, 2012, 02:45:14 pm
content: Thanks All for the kind words. It is easy to do when it is a labor of love.Quote from: Shuggsy on December 17, 2012, 06:38:11 amThe only replacement was the red center knob on the timebase dial and I broke one switch on the timebase circuit board. (I had another timebase to rob from)Quote from: TerraHertz on December 17, 2012, 12:32:51 pmSpeaking of BNC connectors,Never dullis what I used on the outside of the connectors. This stuff is a cotton wadding that is very damp with some magic cleaner/polish.This is the secret to the super clean BNC insides. I mount avery hardfelt cylinder in a Dremel tool running at 5000 rpm. In "manual lathe mode" take an exacto knife and bore a hole in the felt that clears the teflon insulator of the BNC. Also turn down the outside diameter of the felt to be a snug fit into the BNC. This can be a very dangerous thing,apply all your wood turning skills here. Soft felt won't work, it will fly apart before you get the shape you need.Wet the outside of the felt with Gaig Deoxit G100L and slide into the BNC and then turn on the Dremel at 5000 rpm. Oscillate the felt and apply light side pressure in a full circle. The whole thing will be done in about 3 seconds.The inside of the center connector is cleaned with aMicrobrushin the Dremel at 5000 rpm. I wet the Microbrush with G100L and insert it into the BNC before turning it on so it doesn't throw all the Deoxit off.I wrap a kimwipe or a piece of toilet paper around a 1/4" dowel so that its outside diameter is a snug fit in the BNC. Wet that with IPA and clean all the residue out. The paper needs to extend past the dowel far enough that it reaches the bottom of the BNC. Clean all the BNC's this way and then use a fresh wipe and repeat until the wipe stays clean after doing all the BNC's Then a flush of IPA in the center connector and a air blast to remove all the IPA. Finally a light coat of Deoxit G100L outside and inside.This was the worst of the BNC's, beforeAfter (OK not the same BNC but the same amp, this is channel 1)

author: grenert
author_rank: Frequent Contributor
timestamp: December 17, 2012, 03:32:25 pm
content: Wow, this should be stickied as the "Ultimate Instrument Restoration Techniques!" Very, very impressive. Those restored buttons are done similar to the old HP calculator buttons (don't know if they used the same technique in their instrumentation).Two questions:What are magic sponges?Where do you get those tiny, tiny brushes for the BNC connectors?

author: robrenz
author_rank: Super Contributor
timestamp: December 17, 2012, 03:52:16 pm
content: Quote from: grenert on December 17, 2012, 03:32:25 pmMagic sponges are Melamine foam. A brand name is Mr Clean magic eraser (most expensive way to buy them). google magic sponge for lots of sources. They wear out quickly but one sponge did this whole restoration. They really are magic!There is a hyperlink (underscored blue text) right in the thread that will take you to the Microbrush site.

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2012, 04:03:10 pm
content: Links are inline in the text for the Eshops. Lovely work there, I normally just use brass polish liquid ( leave it in the tin for a week so it settles out from the abrasive) and a cloth. Learnt that from cleaning ceremonial uniform brassware so it would shine, I also made a sheet plate to act as a cloth protector for the buttons, so I did not have to remove them every week to polish. I did pay to send a set in to be gold flashed, never needed to polish them again, but they were for special parades only.

author: robrenz
author_rank: Super Contributor
timestamp: December 17, 2012, 04:22:16 pm
content: For some reason Tek did not provide power for the illuminated pushbuttons on the 7603. I followed the instructions from the update kit PDF for installing a LM309K to provide the 5V to the main interface board that the plugins plug into. I made up the mounting bracket out of aluminum angle.The EMI shield strips were all pretty dull with a heavy oxide layer. These things are very thin material and easily kinked. So I sanded down a paint stir stick to precisely match the shape of the EMI strip so it would be a press fit.I usedAstonish cleanerto polish these because it is a fairly aggressive abrasive as cleaners go. (don't use on BNC's it will remove the nickel if you polish very long). I used a felt pad and I could bear down on the strips since they were fully supported by the custom wooden mandrel.Before (an especially corroded example)AfterI have lots of other pics of the internals but It would be the same stuff as other rebuild threads on here so not much point in posting.The End.

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2012, 05:15:45 pm
content: Any reason for using the TO3 part over the TO220 other than it matches the rest of the unit construction? Lovely finish on that angle there, you probably got better surface finish than the original heatsinks have.

author: ModemHead
author_rank: Frequent Contributor
timestamp: December 17, 2012, 05:35:23 pm
content: Truly awesome work. Thanks for sharing your techniques with us. It reminded me that I have some of that wadding polish, I had forgotten about it and never thought to use it on things like BNC connectors. Interestingly mine is called "Ever Brite" as opposed to "Nevr Dull".

author: mamalala
author_rank: Unknown
timestamp: December 17, 2012, 05:41:48 pm
content: Wow, fantastic work! I seriously envy you for you handicraft. Me, i'm rather unable to do much mechanical work. Give me a file and a piece of metal, and you get back a flat file and an unchanged piece of metal.Again, really fantastic what you are doing there. This takes the word "refurbished" to a whole new level.Greetings,Chris

author: robrenz
author_rank: Super Contributor
timestamp: December 17, 2012, 05:48:05 pm
content: Quote from: SeanB on December 17, 2012, 05:15:45 pmNone other than that is what I had on hand. That reg is left over from the original project from 32 years agoI have an obsession about deburring and chamfering,I like very precise chamfers and well rounded corners that will pass the aerospace white glove tests. Abrasive sponges really do a nice job on blending corners and the glass bead finish can make anything look good.

author: lewis
author_rank: Frequent Contributor
timestamp: December 18, 2012, 03:05:26 am
content: Sir, that is absolutely awesome. Truly a labour of love. It's great to see classic instruments brought back to showroom condition. Extremely impressed

author: FenderBender
author_rank: Super Contributor
timestamp: December 18, 2012, 03:23:34 am
content: Fabulous work! I think I know what I'll be doing with my 465 this Christmas break.

author: BravoV
author_rank: Super Contributor
timestamp: December 18, 2012, 04:26:31 am
content: Thank you so much for sharing this, one the best thread about old scope restoration !Thread bookmarked, and 5 stars rating given (geezz.. c'mon folks, why I'm the 1st who clicked the 5 stars rating) %-B

author: robrenz
author_rank: Super Contributor
timestamp: December 20, 2012, 03:17:54 am
content: Thanks again all for all the kind words,It looks like I have some more work to do:The readout system is giving bogus readings as the timebase reads 1000 faster than it realy is and the vertical amp is good down to 1V/div then is off by 100 on all settings below.The beam intensity on intensified trace is too high relative to the unintensified trace. Also seems to be some noise riding on the intensified section.Fortunately I have the original service manuals for all the pieces.

author: casinada
author_rank: Frequent Contributor
timestamp: December 20, 2012, 06:51:46 am
content: Too much polishing made the electrons go much faster

author: robrenz
author_rank: Super Contributor
timestamp: December 23, 2012, 08:47:47 pm
content: After exchanging all the IC's on the readout board with ones from a working readout board, the readout still off. So I just exchanged the whole readout board from the other 7603 (I know that's cheating but its working now). I can try to figure out whats wrong later.I checked all the supply voltages and they were in spec. including ripple. I still see what looks like a very faint Z axis modulation on the traces. It is barely noticeable but I wonder what is causing it? Any help gladly acceptedI did the proper Z-Axis DC levels adjustment per the service manual but the intensified trace was way too bright compared to the normal trace. So I just adjusted the CRT grid bias until I got a normal difference between the intensified and normal sweep.anyone know if this will be an issue?

author: wkb
author_rank: Super Contributor
timestamp: December 23, 2012, 11:00:05 pm
content: Very impressive!It is now better than new!

author: grumpydoc
author_rank: Super Contributor
timestamp: December 24, 2012, 12:13:20 am
content: Rob, that is utterly brilliant work - you don't know how much I hate you right now

author: casinada
author_rank: Frequent Contributor
timestamp: December 24, 2012, 05:39:16 am
content: Rob,The best place for help with the 7603 is the Tekscopes group at yahoo. I have a tek 7603 myself. I got it at a Junk yard 24 years ago and it still works very well. I only had to clean it. It even came with the coverOne of this days I will open it to clean it again.

author: Unknown
author_rank: Unknown
timestamp: December 24, 2012, 09:09:58 am
content: well done! impressive!you just remember me to clean my oscilloscope...

author: saturation
author_rank: Super Contributor
timestamp: January 03, 2013, 12:20:32 pm
content: Most amazing results! robrenz procedures should be of help to all, the photos show it all. I've highlighted the key equipment used.Quote from: robrenz on December 16, 2012, 08:20:07 pm

author: billclay
author_rank: Regular Contributor
timestamp: January 04, 2013, 08:17:30 pm
content: I always look forward to your posts and videos. Your work is superb, as is the presentation and explanation of the process. Can't wait to see your next project!

author: felixd
author_rank: Regular Contributor
timestamp: October 05, 2015, 12:50:08 pm
content: :scared:AMAZING !

author: e-doc
author_rank: Contributor
timestamp: April 04, 2016, 09:13:07 pm
content: Very impressive!

author: luudee
author_rank: Frequent Contributor
timestamp: October 10, 2022, 09:28:49 am
content: I know this thread is 10 years old, but I enjoyed it very much, answered some questions I had.By the way, I use small brushes and sponges that my wife buys at beauty shops. Specially allthose things they sell for eye and lashes, are particularly useful to get into the small center holeof the BNC connector, for example ...Cheers,luudee