Test Equipment Anonymous (TEA) group therapy thread

[0culus]

Do any of you fine TEAers happen to have (or know where I can purchase) the rear panel bumpers for HP 8568/66 spec analyzers? I only have 3 of them between all the units I have, and only one of the ones that clamp the RF unit and the display unit together on the back. I'm happy to paypal a reasonable cost + shipping. Thanks!

[beanflying]

Not rockin' my socks.

Then there's eBay ... Do I dare?

Let me know. These two were socketed pulls from an Xray power supply.

[beanflying]

Do any of you fine TEAers happen to have (or know where I can purchase) the rear panel bumpers for HP 8568/66 spec analyzers? I only have 3 of them between all the units I have, and only one of the ones that clamp the RF unit and the display unit together on the back. I'm happy to paypal a reasonable cost + shipping. Thanks!

What do they look like? Job for 3D printing maybe?

[0culus]

Do any of you fine TEAers happen to have (or know where I can purchase) the rear panel bumpers for HP 8568/66 spec analyzers? I only have 3 of them between all the units I have, and only one of the ones that clamp the RF unit and the display unit together on the back. I'm happy to paypal a reasonable cost + shipping. Thanks!

What do they look like? Job for 3D printing maybe?

Here's an example. Those plastic things at each corner, and the ones in the middle screw together to secure the halves.

[Brumby]

Yeah, but the 7442 is like the 7404... a $2 chip retail.

You would think...  but the trick is finding one.  It might have been a lot easier 30 years ago.

Perhaps I should look at variants - but which, if any, could substitute for regular 70's TTL?

[beanflying]

Here's an example. Those plastic things at each corner, and the ones in the middle screw together to secure the halves.

Not the same but similar https://www.thingiverse.com/thing:2492594 yours could certainly could be done with 3D printing.

[0culus]

Thanks! I know a guy with a 3D printer...might be worth a look. The parts that are more important to me are the middle ones that screw the two instruments together. Those are proving the hardest to locate unfortunately.

[beanflying]

Thanks! I know a guy with a 3D printer...might be worth a look. The parts that are more important to me are the middle ones that screw the two instruments together. Those are proving the hardest to locate unfortunately.

Depending on theirs or your skills drawing up the first one will take a bit of time mirroring the design should be easy after that. Material costs under $1 each 

[0culus]

Thanks! I know a guy with a 3D printer...might be worth a look. The parts that are more important to me are the middle ones that screw the two instruments together. Those are proving the hardest to locate unfortunately.

Depending on theirs or your skills drawing up the first one will take a bit of time mirroring the design should be easy after that. Material costs under $1 each 

Well, I do have one of the clamp ones so that makes reproducing it easier!

[bitseeker]

Successful property auction haul today. Grabbed another HP spectrum analyzer display (contemplating doing the LCD upgrade to it) which hopefully eventually will go with the 8568B RF unit I'm repairing. And got another 3455A voltmeter. And I spent less than $100 so that was a win. A number of other things were for sale that I kind of wanted, but they got bid way out of my price range.

For both? Cool.

[0culus]

Successful property auction haul today. Grabbed another HP spectrum analyzer display (contemplating doing the LCD upgrade to it) which hopefully eventually will go with the 8568B RF unit I'm repairing. And got another 3455A voltmeter. And I spent less than $100 so that was a win. A number of other things were for sale that I kind of wanted, but they got bid way out of my price range.

For both? Cool.

Yeah, I was happy. There was a lot of good stuff for sale. Sadly my pocketbook and current lab space said no... 

[bitseeker]

Yeah, but the 7442 is like the 7404... a $2 chip retail.

You would think...  but the trick is finding one.  It might have been a lot easier 30 years ago.

Perhaps I should look at variants - but which, if any, could substitute for regular 70's TTL?

Yeah, I don't know what specs are critical for substitution and I wouldn't buy them from random eBay vendors. I remember someone here (bean maybe?) mentioned that they got some ICs from LCSC and they worked fine.

https://lcsc.com/product-detail/74-Series_TI_SN74HC04N_SN74HC04N_C2886.html

[BravoV]

I feel you. Have several "must-do" projects on at the same time right now; not a lot of time for the "fun". Even the PC modding thing... which is usually fun for me... is turning into a chore due to time pressure and the fact I need stuff off that PC.   

mnem
 

Not to mention the finicky fan that need to be taken care of if I managed to fix it  , thanks for your excellent details posts in the 2465B thread about that evil fan. 

[beanflying]

uncertainTEA will they be 10,000mAh as claimed  On a positive note taking a 1A charge without going kaboom 

Who said Aluminium held together with clamps was a bad conductor kwality job

[Brumby]

I mean... you're talking about a lot more than $8 and 40 minutes worth of hassle between the two, and if you're going for 2 parts, it seems worth it even just for troubleshooting.

Part of the effort is for troubleshooting - but part of it is the challenge of doing it.  The 7400+7400=7404 is a simple exercise - but the Arduino emulator is more interesting.  If I get some tri-state gates, I can program it up for a single module to be a (sort of) pin-compatible substitution for hundreds of chips.

Just a bit of fun - but one that can help me progress the troubleshooting of the 5381 with items I have on hand ... and maybe identifying other chips I need.


Edit: Doesn't meant I won't say "stuff it" and just fork out some pesos to save me the hassle.   

[bd139]

Propagation times are shit and the electrical interface is different if you stick an arduino in there. Be careful with timing sensitive circuits and things that expect TTL.

Although one of the things I did many years was using a PIC to emulate logic:

; set up ports
mainloop:
; read ports
; do logic
; write ports
goto mainloop

That was it!

Edit: took less power than original 74 / 74LS logic as well.

[Zucca]

Clearly a TEA brother:

https://www.eevblog.com/forum/projects/your-stupidest-mistakes/msg1110679/#msg1110679

[Brumby]

Propagation times are shit and the electrical interface is different if you stick an arduino in there. Be careful with timing sensitive circuits and things that expect TTL.

Already noted:

Yes, the propagation delay will be poor, but in some applications that won't matter at all - and in the ones that do matter, I'll just have to take that into account.  .....  Maybe use my stash of 7400's for input/output buffering.

Remember, this is only to aid troubleshooting.  No way I'd put something like this in as a permanent solution.  Yuck!

[bd139]

Got my head in the 465 last night. Some progress:

1. Put the spare timebase IC in - that's working nicely now.
2. Cleaned the vertical pots. All good. Actually exceptionally good now!
3. Put new graticule lights in.
4. Added missing button surround.
5. Added some better condition feet.
6. New graticle blue plastic thing on it
7. Swapped a button out for one the legend hasn't worn off on.

Still one issue remaining however. The channel 1 vertical attenuator is being a dick. I've eliminated all mechanical problems from it now so what remains must be related to the PGA after the attenuator. Fun fun fun.

Edit: just to mention, I had problems with this before. The PGA was not working correctly and artificially injecting a 50% voltage loss. It was due to components touching the ground plane. Hmm.

[nixiefreqq]

The only thing THAT BAD I can think of off the top of my head would be to rob it out of a 24xx family Tek... 

mnem
I don't bite. Well, not without permission. 

No, nothing so cannibalistic.

I might as well just say it.... An Arduino based emulator.  Yes, the propagation delay will be poor, but in some applications that won't matter at all - and in the ones that do matter, I'll just have to take that into account.  The main purpose is to enable function of a dead chip so the rest of the circuit can be checked out, ideally making my purchase of proper replacement chips a one-stop shop.  The good thing is that you can turn it into any chip you like.  Maybe use my stash of 7400's for input/output buffering.

The 7404 I will do with 7400's, but the 7442 is a definite candidate for emulation.

Yeah, but the 7442 is like the 7404... a $2 chip retail. Jaycar doesn't have them too? I mean... you're talking about a lot more than $8 and 40 minutes worth of hassle between the two, and if you're going for 2 parts, it seems worth it even just for troubleshooting. Especially if you can online order/pick up in store and add some resistors, caps, etc to get the online price break. 

mnem
It's a sad day when I'm the voice of reason... 

ya know.....I can never remember if its mnem or nmem or or mnen.   BUT TVOR.....I can remember TVOR.

[mnementh]

Source	7404	$ (ea)	7442	$ (ea)
Jaycar	Y	3.95	N	-
Altronics	N	-	N	-
Mouser	Y	2.96	Y (non stocked)	Call for quote
Digikey	Y	2.94	Listed, No stock	Obsolete
RS Components	Y	3.3	N	-
Wagner	Y	1.5	N	-
Element 14	Variants: HC, AC, AHC, AS, F, HCT, AHCU, LS, HCU	$0.43 - $2.15	HC variant only	2.43
Octopart	Yes, various	From $1.55	LS and HC varieties and nothing in DIP	From $0.89

Not rockin' my socks. Then there's eBay ... Do I dare?

https://www.ebay.com/sch/i.html?_from=R40&_nkw=7442+ic&_sacat=0&LH_TitleDesc=0&_sop=15

Oh fuck... right, you're in oz. Not like it is over here, where 74xx are like potato chips: Plentiful, if a little greasy.

I think you should take bean up on his offer. I know it was genuine; just look at it as a chance to Pay It Froward.   

mnem
*School timE*

[med6753]

Got my head in the 465 last night. Some progress:

1. Put the spare timebase IC in - that's working nicely now.
2. Cleaned the vertical pots. All good. Actually exceptionally good now!
3. Put new graticule lights in.
4. Added missing button surround.
5. Added some better condition feet.
6. New graticle blue plastic thing on it
7. Swapped a button out for one the legend hasn't worn off on.

Still one issue remaining however. The channel 1 vertical attenuator is being a dick. I've eliminated all mechanical problems from it now so what remains must be related to the PGA after the attenuator. Fun fun fun.

Edit: just to mention, I had problems with this before. The PGA was not working correctly and artificially injecting a 50% voltage loss. It was due to components touching the ground plane. Hmm.

465? Don't you actually mean 475? 

[bd139]

No I've got a 465 as well

Currently have a 475A, 465, 2235 and TDS210

[med6753]

I feel you. Have several "must-do" projects on at the same time right now; not a lot of time for the "fun". Even the PC modding thing... which is usually fun for me... is turning into a chore due to time pressure and the fact I need stuff off that PC.   

mnem
 

Not to mention the finicky fan that need to be taken care of if I managed to fix it  , thanks for your excellent details posts in the 2465B thread about that evil fan. 

And since your new acquisition has the GPIB and probe power options your teardown will be a slightly less complex version of this:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1861713/#msg1861713

You won't have the DMM up top nor the CTT (Counter Trigger) board underneath but you will have the Buffer Board directly under the top plate and attached to that the GPIB board.

[med6753]

No I've got a 465 as well

Currently have a 475A, 465, 2235 and TDS210

You haven't got a 465B junker there with a good attenuator switch do ya?