Repair of Tektronix FG502 11 MHz Function Generator

[xrunner]

Just cosmetics updates. Front panel cleaned, dial polished, cracks repaired, aluminum panels cleaned. All knobs cleaned in ultrasonic cleaner. New LED installed (no it isn't nearly as bright as the camera makes it look).

Put a few of the pieces on the panel - looks like a new one coming off the assembly line. 

[tautech]

Real nice job on the front panel xrunner, it came out like new. 

Looking forward to seeing finished.

[Rerouter]

Your tempting me to rip my own ones down and make them look good as new,

dark times are ahead, I've already collected too many modules

my poor free time xrunner, you've doomed it.,
 

[Johnny10]

Are those BNC connectors new?

  Great Job,  I can see you are making me look bad already!

[xrunner]

Are those BNC connectors new?

Yep sure are. Got one installed (for the main output), but the rest are on hold until I get the insulated ground BNC. This because the nut can't be easily tightened on that one with the other parts in the way.

Great Job,  I can see you are making me look bad already!

I'm sure you will be able to out-class me Johnny10. No pressure, no pressure. Did you get the parts on order that you required?

[bitseeker]

Looking great there, xrunner! Any tips for restoring brushed aluminum face plates where some monster scratched it cross-grain trying to remove calibration stickers with a screwdriver ?

[David Hess]

If it is brushed aluminum then you can brush it again.  These Tektronix faceplates are silk screened and then anodized.

[xrunner]

Looking great there, xrunner! Any tips for restoring brushed aluminum face plates where some monster scratched it cross-grain trying to remove calibration stickers with a screwdriver ?

No not really. If it's got silk screened labels forget it. If it was clean aluminum you could brush it again with any number of materials but it wouldn't look exactly like the other panels, which may or may not matter.

The thing about those labels (cal stickers especially) is that you have to be patient with the removal (I know you know this). For example, on this project several places were so old that the old adhesive was more like petrified wood - rock hard. It literally took all night for the stuff to get soft, and then it took more than one application. But it will all come off eventually. If you get in a hurry then SCRACTH!  Fortunately the goo gone does not harm faceplates with painted labels.

Other things happen, for example on the FG 501A I wanted to remove the plastic dial for cleaning behind it, and it's held on by two little screws, just like this one. But one of the screws would not come out. It's steel into brass and they had been there from day one. I tried everything including penetrating oil but no go. I had to resort to drilling it out, and I was very nervous, but I succeeded.

I don't like the design of this older TM 500 plug-in frame, the second pass design is better. This one holds the front face plate to the frame with two screws each - top and bottom - going in from the front. Problem is the screws, once tightened, are then made inaccessible once the front face plate is on. If the plastic relaxes and makes it feel loose, you can't tighten it unless you take everything holding the face plate off which can be somewhat of a PITA. There's also a small screw that holds the locking mechanism for the frame once it's slid into the mainframe hidden behind there. So once you realize this you think man I need to make sure they are tight so I don't have to take it all apart again some day. Yea, but if they are too tight the plastic cracks, which I've seen now on most of them. So they have a fine line on how tight to screw them in.

And, the side shields are pressed in on the older design (the newer one has a securing screw and does not get warped trying to remove it). They can be warped because people have pulled on them when stuck, pulling too hard the wrong way trying to remove them. Instead of pulling up with your hand from the back try to pop each side out with a tool under the channel going along each side. A few I've gotten have side panels warped so bad I had to go into the garage with the panels and do unspeakable things to them with a hammer and block of wood. But it all comes out OK in the end

[David Hess]

The thing about those labels (cal stickers especially) is that you have to be patient with the removal (I know you know this). For example, on this project several places were so old that the old adhesive was more like petrified wood - rock hard. It literally took all night for the stuff to get soft, and then it took more than one application. But it will all come off eventually. If you get in a hurry then SCRACTH!  Fortunately the goo gone does not harm faceplates with painted labels.

I find that the same heat gun I use for heat shrink tubing does wonders for removing old labels even when the adhesive has dried out.

Other things happen, for example on the FG 501A I wanted to remove the plastic dial for cleaning behind it, and it's held on by two little screws, just like this one. But one of the screws would not come out. It's steel into brass and they had been there from day one. I tried everything including penetrating oil but no go. I had to resort to drilling it out, and I was very nervous, but I succeeded.

I keep some of the appropriately sized hex wrenches *without* ball tips (1) and cut the ends off when they get dull so they fit tightly.  If the set screw is worn so the wrench cannot fit tightly, then I take the next larger size hex wrench and grind the flats down to make one which fits very tightly.

(1) This was learned watching someone else break a ball tip off inside of a hex screw making it wisdom instead of experience.

[xrunner]

The insulated BNCs were to arrive today, all I got was this from tracking -

June 5, 2017, 10:59 am    Notice Left (No Secure Location Available)

 

The mailperson must be on crack. That's an insane message. There is no secure location? How about the  ... mailbox?

A notice? Must have put it up in a tree in my backyard, yea let me get a ladder and look fot it way up high in a tree.

Unreal.

[David Hess]

How was it shipped?  Nobody except the US Postal Service is legally allowed to use your mailbox.

[xrunner]

How was it shipped?  Nobody except the US Postal Service is legally allowed to use your mailbox.

I said mailperson, what do you think that means?

[David Hess]

How was it shipped?  Nobody except the US Postal Service is legally allowed to use your mailbox.

I said mailperson, what do you think that means?

That is just weird then unless the package would not fit into your mailbox although that has never stopped them here.

[bitseeker]

It is unfortunate that the plastic part of the front plates are held on so tightly with screws that they end up fracturing. Alas, manufacturers weren't really considering what would happen to their gear this long after they were made. It, like former-owner sticker damage, can aggravate the OCD. 

[xrunner]

That is just weird then unless the package would not fit into your mailbox although that has never stopped them here.

No excuses for them David. They continually leave mail too big for my mailbox (yes I really do have a secure mailbox) on the porch. They simply ring the bell and run back to the truck. I was sitting right in my lab right by the window. Nobody came to the door, nobody left a "notice". A bag with two connectors in it will fit in my mailbox as has much bigger things for many years.

Most seem incompetent and/or like they'd rather be cleaning porta potties than doing the job they have. They've proven it time and again. They had the deliveries mixed up and instead of notating that in the tracking someone put in a false and irrational claim that no secure location was available and a false claim that a notice was left. That's a bold lie. That's total and complete BS. It was in another mailperson's route. Somebody just wanted to go home for the day and not drive out of their route to deliver it. But they don't want to actually say that. All those USPS commercials you see on TV, claiming they are the best delivery for business, don't believe it for a second.

They just don't have their act together. I'll have to go to the post office and get it (who knows if it's actually there), and present them with the tracking notes from their own system that are just non-sensical. All I'll get from the clerk is a blank stare because they don't care what happened, and they don't care if it happens again.

End of ranting.

It is unfortunate that the plastic part of the front plates are held on so tightly with screws that they end up fracturing. Alas, manufacturers weren't really considering what would happen to their gear this long after they were made. It, like former-owner sticker damage, can aggravate the OCD. 

Yes, although it was top quality test gear in the day it certainly wasn't considered especially valuable or "collectable". As I said I used this exact Tek gear in the aerospace industry and it got used & abused, that's just the way it was. It was just expendable equipment supplied by the Company, if it broke, just send it back to the cal lab for repair or salvage, go get another one from the storage room. It wasn't like "Man I really want to have one of these 20 years from now!". 

Now that I think about it I have an idea for reinforcement of that screw area. I have some very thin plastic strips for modelling, the same kind of plastic that melts together with MEK. What I should have done (and will do next time) is make a reinforcement for each of the four screw areas. Like a square with a hole in the middle. Then glue it to the back of each screw hole. I bet that would really help. Let me see if I have another old case type that I can get the front off of easily. Maybe I'll make a thread showing that kind repair, but I've put too much back together on this one for now.

[David Hess]

It is unfortunate that the plastic part of the front plates are held on so tightly with screws that they end up fracturing. Alas, manufacturers weren't really considering what would happen to their gear this long after they were made.

The plastic bezels on the TM500 series are a known weak point of their design.  The plastic becomes brittle with age and broken off corners are common.

[xrunner]

Picked 'em up at the post office. I took the tracking info and asked the clerk to read it. She was rather befuddled. She said "That doesn't make any sense".

 

I said "Yea, I know that it doesn't make any sense, since I was sitting right there at that time, there was no note on my door, and there is a secure mailbox at the street, can you go back there and see if you can find it?"

She came back with it. She said "Oh it just arrived here today!"

"What do you mean? It was out for delivery from this post office yesterday."

I said "Look I have a repair thread on the EEVBlog that's been stopped in it's tracks because this part is MIA. This is important! 

I just quit asking questions at that point and left. But it's the right part, NOS made in 1989. 

[bitseeker]

Yeah, who does the postal service think they are, suspending a repair thread like that!

[xrunner]

Yeah, who does the postal service think they are, suspending a repair thread like that!

LOL. 

Well I have to tell ya - this little gem is lookin' really good. I still have a few more things to put back on, but I expect to have an unveiling in the morning. 

[xrunner]

Here it is all put back together. Project is basically done except for some additional data I will be posting, which will include scope screen captures from selected test points and associated schematics with notations. Perhaps somebody in the future will be able to make use of the data for their own repair project.

[Johnny10]

Beautiful unit!

I am out of town so won't be working on mine again till next week.
But I don't see a way for any better looking unit from me.

Glad you are posting waveforms.

[bitseeker]

xrunner, now you've done it. I'm afraid it looks too good to use!

[kayvee]

Nice job xrunner.  Love those shiny BNCs!  That FG is looking somewhat shabby next to it.

I scored two of these babies in pristine condition in a batch of modules I was after.

This thread reminds and inspires me that I need to make a repair attempt on the FG 504 that was in the batch.

[xrunner]

Thanks for the kind comments. I'm working on a set of scope captures and associated schematics. I also got a little graphics pad I'm going to try out to notate the schematics. Takes some getting used to as compared to a mouse. I'm going to highlight the adjustment points in addition to inputs/outputs and active devices.

I also have an idea for a way to repair/reinforce the plastic corners of these older units, where it cracks at the screw attachment points. I'll put it in a little thread by itself (if I'm satisfied it's viable). I do have a guinea pig available ... 

[xrunner]

Waveforms - Triangle Generator

Comments:

Serial # B037759. Some alignment instructions pertain to certain serial number ranges, consult your particular S.N.

Note step 8 "Adjust Triangle Peak", C287 had very minimal effect on this unit.