Test Equipment Anonymous (TEA) group therapy thread

[xrunner]

Well, at a recent recycler auction were some lots that contained old test gear. I've got too much in my clean/verify/repair/adjust queue already and am suffering some of the burnout that Rob mentioned. So, I didn't bid in earnest, but I had to bid something, right? Otherwise, I wouldn't be a proper TEA member and a good bit of old kit would end up in a landfill or shredded and melted down as a result of getting no bids (i.e., PETA).

Yay more stuff!

Speaking of which I just got the sacrificial TM500. First thing I did was to see if any contacts were burned. They all look OK but check out the picture. Do you see it, back there in the High Power compartment? It's the same problem with the PS503 as mine had, and somebody fixed it by putting a piece of foam tape in the exact spot where it would push back on the switch. 

[bitseeker]

Is that backplane bent too?

[msraya]

More Stuff... That I not need...   
GO GO GO...

Manuel

[xrunner]

Is that backplane bent too?

It's not bent, but slightly pushed back. The top is pushed back more then the bottom. The top always gets pushed back farther than the bottom because there are four transistors mounted on the bottom that extend from the circuit board to another aluminum panel (see pic of the one awaiting a new connector). These transistors keep the bottom from moving, although they shouldn't be subjected to that duty. 

The only thing keeping the whole kit and caboodle behind it (the circuit board) from going backwards when a module is pushed in is that metal cross-brace that you see the tape on, and which was bent on mine.

It appears that due to repeated forces being applied over many years the two bolts on either side were not enough to keep the brace where it should have stayed. There is not a hole but a slot that the bolt goes through, probably to allow for slop during assembly. The bolt holds it if it's tight, but if it gets loose the panel will be able to move backwards.

When I re-assemble my first one I will use a 90 deg triangle to make sure it's perfectly straight, and put a drop of removable loctite on the threads as well. Tektronix clearly didn't plan well enough on that part of the design.

[bitseeker]

Yeah, it all sounds a bit fragile.

[xrunner]

Yeah, it all sounds a bit fragile.

Ha! I just found another funny thing on this one, if you're interested I'll show you. 

Please say yes or I'll go nuts ... 

[GreyWoolfe]

Yeah, it all sounds a bit fragile.

Ha! I just found another funny thing on this one, if you're interested I'll show you. 

Please say yes or I'll go nuts ... 

yes.  Or is it time to 

[xrunner]

The top of this one had been dented, right along where it caused the top metal cover to touch some fuses on top of the circuit board. You can see where in the distant past a thoughtful person ran a strip of kapton tape all along underneath the cover so the thing wouldn't flame-out due to a massive short circuit.

Only one thing wrong with that idea - those fuses up there are spares. They are not only shorted out by the storage traces, the traces are also ground. They are just grounded lugs that don't do anything. 

I guess beating the cover back flat with a large metal tool wasn't given a consideration. 

Man I love the history this old stuff presents!

[AF6LJ]

The top of this one had been dented, right along where it caused the top metal cover to touch some fuses on top of the circuit board. You can see where in the distant past a thoughtful person ran a strip of kapton tape all along underneath the cover so the thing wouldn't flame-out due to a massive short circuit.

Only one thing wrong with that idea - those fuses up there are spares. They are not only shorted out by the storage traces, the traces are also ground. They are just grounded lugs that don't do anything. 

I guess beating the cover back flat with a large metal tool wasn't given a consideration. 

Man I love the history this old stuff presents!

Amazingly poor engineering for Tek...
I cannot believe what I am seeing.
I would have expected this from Heathkit......

[xrunner]

Amazingly poor engineering for Tek...
I cannot believe what I am seeing.
I would have expected this from Heathkit......

Yea they could've done better ...

Hey how is your HP spectrum analyzer coming along? I really want to see pics of that thing running!

[mmagin]

The top of this one had been dented, right along where it caused the top metal cover to touch some fuses on top of the circuit board. You can see where in the distant past a thoughtful person ran a strip of kapton tape all along underneath the cover so the thing wouldn't flame-out due to a massive short circuit.

Only one thing wrong with that idea - those fuses up there are spares. They are not only shorted out by the storage traces, the traces are also ground. They are just grounded lugs that don't do anything. 

I guess beating the cover back flat with a large metal tool wasn't given a consideration. 

Man I love the history this old stuff presents!

Amazingly poor engineering for Tek...
I cannot believe what I am seeing.
I would have expected this from Heathkit......

IMHO, after about 1970, the mechanical engineering of Tek stuff is too small and fiddly and fragile compared to their earlier reputation.

[bitseeker]

Only one thing wrong with that idea - those fuses up there are spares. They are not only shorted out by the storage traces, the traces are also ground. They are just grounded lugs that don't do anything. 

I guess beating the cover back flat with a large metal tool wasn't given a consideration. 

Man I love the history this old stuff presents!

LOL! Know thy tools.

[AF6LJ]

Amazingly poor engineering for Tek...
I cannot believe what I am seeing.
I would have expected this from Heathkit......

Yea they could've done better ...

Hey how is your HP spectrum analyzer coming along? I really want to see pics of that thing running!

It's coming along, pictures will be posted tomorrow baring any unforeseen interruptions.
Stay Tuned.

[mtdoc]

Amazingly poor engineering for Tek...
I cannot believe what I am seeing.
I would have expected this from Heathkit......

Yea they could've done better ...

On the other hand, the fact that so many of these modules are still in service after 30-40+ years is testament to the fact that they did something right.  I guess from a mechanical failure standpoint perhaps they did not consider that they would need to withstand the stresses of being in service that long.

[AF6LJ]

Amazingly poor engineering for Tek...
I cannot believe what I am seeing.
I would have expected this from Heathkit......

Yea they could've done better ...

Those modules are very cool, one of these days I want to assemble a little test set with some of them.

On the other hand, the fact that so many of these modules are still in service after 30-40+ years is testament to the fact that they did something right.  I guess from a mechanical failure standpoint perhaps they did not consider that they would need to withstand the stresses of being in service that long.

[dimkasta]

Soooooo....

Is this a support group?
Or are just enabling each other?

[xrunner]

Xrunner- Would this be a suitable replacement for those card edge connectors?  It looks like it may be. 

Got the new part today - virtually identical.  Thanks for searching for that! 

Soooooo....

Is this a support group?
Or are just enabling each other?

It's group therapy - you know - therapeutic 

causing someone to feel happier and more relaxed or to be more healthy:
I find gardening very therapeutic.

http://dictionary.cambridge.org/dictionary/english/therapeutic

Like today when I got my new connector, to fix my TM500, I felt happier because Housedad's find was very therapeutic. 

[bitseeker]

Is this a support group?
Or are just enabling each other?

We support each other by enabling safe, therapeutic acquisition of otherwise unloved test equipment and associated paraphernalia.

[mmagin]

I have two GR 1862-B megohmmeters.  I thought one had an internally arcing transformer and had given up on fixing it, just using parts from both to make one nice one.  Recently I saw the "bad" one sitting around and I just said "F--- it" and decided to instead of bringing it up gently on a variac to just put it on 120VAC and see what happens.  Well, it seems like the noise I was hearing was actually the panel meter buzzing.  Seems like I have an electrical problem, but likely not the transformer!  (It's been recapped, all but the one mica domino)

Though after I fix it up I should sell it/give it away, since I have way too many ways to measure high resistances now.

[Housedad]

Got the new part today - virtually identical.  Thanks for searching for that! 

Anytime.  Glad it is going to work out for you and less frustration. 

[AF6LJ]

Soooooo....

Is this a support group?
Or are just enabling each other?

Yes

[dimkasta]

Soooooo....

Is this a support group?
Or are just enabling each other?

Yes

Answering an "or" question with yes Message received

[bitseeker]

Welcome aboard!

[xrunner]

Tales from the Crypt continues ...

I just received a DC504 Counter plug in. The other two plug ins I have are in the best of the two TM500 power units (the one I repaired with the new connector). So, to test the DC504 I naturally plugged it into the unit with the other two operating plug-ins to test it. I did so and turned the power on, and the other two plug-ins came on - but the DC504 did not.

I tried all the slots and it did not work in any of them, but the other plug-ins do work in any slot one or both at the same time. So I figured the guy sent me a bum DC504. But just for fun I took the DC504 over to the second TM500 I got for parts (but is basically functioning although it's in the process of getting cleaned up). The DC504 did come on when I tried it in that TM500, in any slot. Also, the other plug-ins I have all work OK in both TM500s in any slot.

 

I'm going to stop for a while and think about this one, any ideas are gratefully accepted at any time as always ... 

[mmagin]

I managed to avoid acquiring more equipment upon realizing that my Keithley 610b is quite usable as a DC VTVM.  They even provide a tip in the manual that you can set it to the 10^-7 amp position and use the multiplier for the voltage range, giving yourself a 10M input impedance voltmeter.  It also has the ability to be in a center-zero mode which was a useful feature of many old VTVMs.

I've been thinking of building an improvised resistor-in-a-probe for measuring DC voltages (with some division ratio) without loading sensitive circuits with the cable capacitance.  (Similar to the probe built-in to the HP 410B in DC mode.)