Tektronix 7603/7613 Repairs

[timb]

Very clever solution, but one question: Do all four of the ground pins actually need to be connected from the cap to the board? The only reason I can see for that is if Tek used the caps to hook separate ground runs together.

.. and that is exactly what is happening on the rectifier board in the 76x3 scope. The cap is used to bridge 2 parts of a ground plane together so that a track may run underneath. I have seen other repairs where wire links were installed to make the bridge. I think the PCB solution looks neater 

Ah hah, gotcha! I figured that must be what's going on; just wanted to make sure. Does look a ton nicer!

You know, I recently opened a small triple output HP power supply from 1984. It used smaller diameter versions on those 4-terminal caps, only they were 5-terminal! Two positive and three common ground terminals; they were actually two separate capacitors in one can!  (One was a 1000uF/300uF, for example.)

They also used the three ground terminals to bridge two ground planes. I was actually going to make up little adapter boards just like yours; only they would have allowed you to put two capacitors on them. (In the end, all the caps tested fine, so I figured it was more trouble than it's worth.)

I think I'll have some of your PCBs made up though as they're cheap enough and it seems like I'm always fixing a TM500 series mainframe! (It's a better solution than just wedging a two lead snap in cap down. I just did a TM501 last week, and there wasn't quite enough horizontal clearance for the new cap. This would have been the ideal solution.)

What kind of pins are those you have on the bottom of the boards? They don't look like standard headers to me.




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[krivx]

What kind of pins are those you have on the bottom of the boards? They don't look like standard headers to me.

Yeah, I'm also curious about this. I want to make some boards to plug into vacuum tube sockets and these look close...

[Tothwolf]

What kind of pins are those you have on the bottom of the boards? They don't look like standard headers to me.

To me they looked like they might be feed-thru turret terminals with the head clipped off.

http://www.keyelco.com/category.cfm/Terminals-Turret-Rivet-Types/Feed-Thru-Terminals/p/512/id/759

[krivx]

The original cap is on the right, replacement with adapter on the left. PCB was made by iTead (US$1 per board) and the mounting pins are from Harwin (p/n H2101-01).

I should have paid more attention...

[dom0]

One plug-in I commend highly is the 7A13. It's incredibly useful for many things, and allows insanely accurate measurements, even in comparison to top-of-the-line digital scopes.

A storage mainframe (e.g. 7623) is pretty neat to have, because the various storage modes, mainly FAST and VAR PERSIST, allow to filter noise very effectively. This is especially handy for low-level measurements e.g. with a 7A22.

(Maybe we should make a thread for general 7000 series discussion? On the other hand this might drive prices up even further )

[DC912]

I recently purchased a 7633 storage scope and would appreciate some guidance on getting the vertical placement of the readouts on the screen adjusted.

The location of the upper readouts are fine.  The lower readouts need to be raised up towards the top of the screen because the bottom half of the characters are not visible.  Will a row adjustment on the readout board take care of that, or is there something else that ought to be adjusted?

Thanks.

[dom0]

Colum and row match adjust the analog level used to index the ROMs, if the characters are displayed properly these are already correct.

Take a look at R2291 (vertical separation). If you can't get a good display, check for drifted resistors in the vicinity of U2284.

[MarkL]

One plug-in I commend highly is the 7A13. It's incredibly useful for many things, and allows insanely accurate measurements, even in comparison to top-of-the-line digital scopes.

A storage mainframe (e.g. 7623) is pretty neat to have, because the various storage modes, mainly FAST and VAR PERSIST, allow to filter noise very effectively. This is especially handy for low-level measurements e.g. with a 7A22.

(Maybe we should make a thread for general 7000 series discussion? On the other hand this might drive prices up even further )

Too late.  Prices on 7A13 plugins just jumped 20%.

Let's hope Dave doesn't mention them in a video.

[timb]

The original cap is on the right, replacement with adapter on the left. PCB was made by iTead (US$1 per board) and the mounting pins are from Harwin (p/n H2101-01).

I should have paid more attention...

Whoops. Serves me right for posting while half asleep!

OP, can you post the Gerbers somewhere? I know you said you'd make them available, but I didn't see a link or anything.


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[dave_k]

I posted them earlier in this thread. 

https://www.eevblog.com/forum/testgear/tektronix-76037613-repairs/msg804009/#msg804009

[MickM]

see reply # 12 for the two zips

[miguelvp]

One plug-in I commend highly is the 7A13. It's incredibly useful for many things, and allows insanely accurate measurements, even in comparison to top-of-the-line digital scopes.

A storage mainframe (e.g. 7623) is pretty neat to have, because the various storage modes, mainly FAST and VAR PERSIST, allow to filter noise very effectively. This is especially handy for low-level measurements e.g. with a 7A22.

(Maybe we should make a thread for general 7000 series discussion? On the other hand this might drive prices up even further )

Too late.  Prices on 7A13 plugins just jumped 20%.

Let's hope Dave doesn't mention them in a video.

I'm glad I was able to get mine earlier this year, $36 for all three shipped. The one on the left is really an 7A11 but the pull tab was missing so I used a broken single channel plug-in as the donor for the pull tab.

[timb]

I posted them earlier in this thread. 

https://www.eevblog.com/forum/testgear/tektronix-76037613-repairs/msg804009/#msg804009

Sorry, I think my Tapatalk app is eating posts. I just looked at the thread on the website and saw your original post that talks about bridging the ground planes, has the pin part number and post 12 with the links. So basically every one of my posts in this thread is redundant.

I'm not illiterate, I swear!


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[AF6LJ]

This is great work.

[dan3460]

Thanks Dave, I think I place the order correctly, we'll see what I order when it arrives.

[scopeman]

Dave,

This is ingenuous! Tek Aficionado and legendary analog guru  Jim Williams would have been impressed!

7K series are great scopes!

They are dirt cheap for what they are at hamfests these days.

All the best.

Sam
W3OHM
Owner/Moderator of the LeCroy_Owners_Group on Yahoo! Groups

[scopeman]

Okay .. I'll post them here

Dave,

When I try and load these Gerbers in Gerbv or Sprint I either can not get the drill file to line up or the layers do not contain traces. I don't know what is happening here. Any chance you could also post the original CAD system files and perhaps the drill file in standard 2.4 Excelon trailing format?

Thanks,

Sam

[scopeman]

Okay .. I'll post them here

Dave,

When I try and load these Gerbers in Gerbv or Sprint I either can not get the drill file to line up or the layers do not contain traces. I don't know what is happening here. Any chance you could also post the original CAD system files and perhaps the drill file in standard 2.4 Excelon trailing format?

Dave,

I may have figured this out by using a couple of CAD systems. I have one board done in SprintLayout 6.0 and will post the Sprint and Gerber files probably tomorrow (it's probably near 1 am now). If you post the original files it might be easier.

Thanks,

Sam


Thanks,

Sam

[dave_k]

The next item of work on the first 7603 scope is cleaning up the horizontal output PCB.
It is looking rather crusty and dirty. 


Particularly around the output drive transistors.


After removing all components, the amount of crud left behind is visible. Some repair work has been done to this board in the past with solder that left behind lots of ugly flux.


A combination of careful solder removal with wick and copious cleaning with IPA has made a significant improvement. Despite the scorch marks on the board not one track has lifted. This is a very well made PCB!


Now I am half-way through reloading the board. The wipe-contact IC socket was replaced with a machine pin version. 4 out-of-tolerance resistors and 1 capacitor have been replaced so far..

[AF6LJ]

This looks good, this has become one of my favorite threads.

[dave_k]

Rebuild of horizontal amp is complete 


Compare the finished board ...


.. to what it originally looked like.


Components rejected for being out of tolerance or damaged.


Next on the agenda is to remove the HV power supply for re-capping.

[dom0]

Soon you'll be making repairs as elaborately as Ralf does..did them (www.amplifier.cd) :-)

[Radio Tech]

Very good job on this. Cannot wait to see more.
 

[SeanB]

You replaced a silver mica capacitor with a ceramic one, I would not do that, the ceramic cap is very poor as against the silver mica, which I onlyt see fail as open circuit or blown apart from overvoltage.

As well space the hot resistors off the board a little so you can have airflow around them, and they do not contact the board and scorch it.

[AF6LJ]

You replaced a silver mica capacitor with a ceramic one, I would not do that, the ceramic cap is very poor as against the silver mica, which I onlyt see fail as open circuit or blown apart from overvoltage.

As well space the hot resistors off the board a little so you can have airflow around them, and they do not contact the board and scorch it.

Generally speaking I would agree, the SM is most likely more stable, I would trust the ceramic to be of the proper voltage but may not age as well as the SM cap.