Test Equipment Anonymous (TEA) group therapy thread

[Vince]

That's very nice, would help me indeed ! 

For the QUAD 303 power amp I will have x4 2N5322 please :

https://www.mouser.fr/ProductDetail/610-2N5322

They cost an arm, 12+ bucks for these alone, before tax.

Then some Midget grooved light bulbs type #337 for the graticule of the Tek 7603 scope :

https://www.mouser.fr/ProductDetail/560-337

I will have 10 of them, gives a much better price per unit. So that's 5.51 dollars before tax.

So about 17+ bucks for these little things alone, crazy eh ?! 


If you give me a bit of time, I would need some specialty things as well... I just had an idea for a project, and I would need R-2R DAC resistor arrays. I don't think it's the kind of thing I would find locally... but mouser probably has some.

I would need one for 8 bits, which I guess must be very common, but also a 9 bit (or more) one, which I am not sure exists.... I bet you can only get these things for 8 bits maximum ?!....
I guess I could take an 8 bit one and add / calculate the required two extra resistors to add the ninth bit, worse case scenario... but an off the shelf one would be easier and tidier, if they exist.

I have never bought these things so if someone knows what search terms to use in the search engine, or have examples of brands or part numbers, I am all ears....

[ch_scr]

If you give me a bit of time, I would need some specialty thing as well... I just an idea for a project, and I would need R-2R DAC resistor arrays. I don't think it's the kind if thing I would find locally... but mouser probably has some.

I would need one for 8 bits, which I guess must be very common, but also a 9 bit (or more) one, which I am not sure exists.... I bet you can only get these things for 8 bits maximum ?!....
I guess I could take an 8 bit one and add / calculate the required two extra resistors to add the ninth bit, worse case scenario... but an off the shelf one would be easier and tidier, if they exist.

I have never bought these things so if you know what search terms to use in the search engine, or have example of brand or part numbers, I am all ears....

Vince, it's called a R / 2R DAC, because there are just 2 values. It get's even better, the second value is just double the first! All you need is a stock of decent quality resistors (like those metal film in the flat blue cardboard box, I also have some, you remember the type?) and you put one and then two in series; to make up your ladder, can go as long as you need! You can make it better, if you sort them, to all have the same value as close as you can get it - no need to buy anything! For 8 - 9bit, it'll be fine, especially if you pick them, to be 0.1% instead of the 1% they would have usually...

[Vince]

Yeah sure, but an off the shelf DAC would be much tidier, more compact and turnkey.... and probably very cheap, I assume ?! Has to be... it's just a resistor array...

If they are abnormally expensive or hard to get then yeah, I would have to resort to cobbling one together myself... but it's not the aim, if I can avoid it....

[ch_scr]

Yeah sure, but an off the shelf DAC would be much tidier, more compact and turnkey.... and probably very cheap, I assume ?! Has to be... it's just a resistor array...

If they are abnormally expensive or hard to get then yeah, I would have to resort to cobbling one together myself... but it's not the aim, if I can avoid it....

There should be an 8 bit DAC or two in the stuff I sent you? 5V positive logic this time, I promise!
"Just an resistor" starts to get really expensive, really fast, because it only makes sense, when the performance is better then "just doing it yourself" with "cheap" 0.1% resistors! If one does it with 0805 smd, it's quite small, too. You will find resistor networks most easily with (up to) 8 "uncomitted" same value resistors, than then can be arranged as needed - but stay away from the cheap thick film ones, they have worse long term drift, as all thick films. Such a "proper" network can be easily 5€ a pop - you'd need more than one, naturally. In almost all cases, it would be wasted on an 8 bit DAC, too. In the stuff I sent you, maybe there are some "thick-film, 8 single resistors"-networks, if you insist on that. Buying an off the shelf 8 bit dac will be the cheapest option anyway, but I'm not one to discourage tinkering!

[Vince]

Thanks for the info.

5 Euros is quite expensive... for that price I guess I can easily find a "normal" DAC.

According to my stock spreadsheet, I have only one single DAC, just one.... in a cool CERDIP package so it's probably from you 

It's an AD571. Conversion time is 40us if my notes are correct.

I need two DACs so I would need to buy at least one... so might as well buy two of them, so that they are identical.

The reasons I wanted to use a R-2R DAC are :

1) Beautifully simple, elegant
2) Most likely comes in a SIL package, so very compact and easy to try out on my breadboard
3) Cheap (I thought.... maybe not then...)
4) Analog... meaning I don't have to worry about conversion times, nor have to deal with control signals which will make the design phase more complex, longer, and dealing with these control signals probably will require some glue logic, hence more chips/complication/board space....

So an analog DAC, in all these regards.... was an amazingly attractive solution !! 

[ch_scr]

Maybe you're lucky and I was a bit too pessimistic: https://eu.mouser.com/ProductDetail/Bourns/4310R-R2R-103LF?qs=q1k7RwtO48gxHuVs5Nx%252BsQ%3D%3D

Edit: here are all the types: https://eu.mouser.com/c/passive-components/resistors/resistor-networks-arrays/?circuit%20type=R%2F2R%20Ladder

[factory]

Thanks for the info.

5 Euros is quite expensive... for that price I guess I can easily find a "normal" DAC.

According to my stock spreadsheet, I have only one single DAC, just one.... in a cool CERDIP package so it's probably from you 

It's an AD571. Conversion time is 40us if my notes are correct.

AD571 seems to be analog to digital, datasheet states it features "low cost monolithic construction" looking at the price on Mouser I would disagree.
I've got the opposite, digital to analog in the form of DAC08, no idea if I have ADCs as very little has been listed in my spreadsheet.

There is no rush to choose parts from Mouser, I'm not in any hurry to place my order.

David

[Vince]

Maybe you're lucky and I was a bit too pessimistic: https://eu.mouser.com/ProductDetail/Bourns/4310R-R2R-103LF?qs=q1k7RwtO48gxHuVs5Nx%252BsQ%3D%3D

Edit: here are all the types: https://eu.mouser.com/c/passive-components/resistors/resistor-networks-arrays/?circuit%20type=R%2F2R%20Ladder

Thanks for the links. 

I checked the first link before you edited your message. Looked at the datasheet and it says it's Thick Film which you said to run away from...
Also, datasheet says that tolerance is 2%.  That's atrocious in this day and age... and how can an 8 bit DAC even work with a 2% tolerance ?!

256 combinations, so each number is about 0.4% of full scale...

I guess I don't understand what they mean with their 2% "tolerance"... tolerance on what exactly ?

Maybe they talk about full scale ? So say if I feed the inputs with 5V logic chips, they mean that full scale might produce maybe 4,90V instead of 5V ?

If that's what they mean then I don't care, as the signal will be conditioned down stream anyway (scaled + adding an offset maybe, I don't know yet) .... what I care about is how well the resistors are matched, so that the linearity is acceptable for my application...

I will check your second link to see if I can find some 9 bit DAC in there.

But it's getting late so I will probably look into that tomorrow after work...

[Vince]

AD571 seems to be analog to digital

Geez you are right, made a mistake in my spreadsheet indeed ! 
ADC it is, not DAC....
OK so I have zero DAC in stock then, problem solved...

There is no rush to choose parts from Mouser, I'm not in any hurry to place my order.

Ah cool, thanks.
In this case I will take a few days to hurry up and start working on the project. A quick first pass, back of the envelope design so I can evaluate how complex it would be to implement a "normal" DAC.
If not too much trouble then might go straight for that and call it a day, but if it proves troublesome then I think I would just use cheap R-2R jobbies to just "get the job done"...
This would allow me to concentrate on the rest of the design, and once I have a working "proof of concept" board, I can always modify the design with a "proper" DAC later on, if really I deem the performance of the R-2R unacceptable after real world testing.

[Vince]

I don't want to disclose my project, it's a secret but... I guess to help you understand the situation here, I am trying to make my design run with only discrete logic chips, no CPU or MCU, hence why the use of a  "normal" DAC is not very easy at first glance, since these things are normally meant to interface with CPUs, not home made discrete logic....

Now it's time for some sleep..... 

[m k]

This a Tek 7504 scope.... from my big TE haul from a few months ago.
It's a parts unit in extremely poor shape...

So you lost a perfectly good sink wash demo possibility?

[TERRA Operative]

Annddd, now I have a Tek THS720 (with carry bag and charger) on the way... It has the usual burnt polarizer on the LCD, but it seems to work according to the pictures in the listing.

I'll upgrade it to a THS720P and update the firmware if needed. Might even try and see if the TDS210 to TDS220 upgrade hack (Tell the scope it is the higher model then run the appropriate adjustment routine before rebooting it) will work to upgrade this THS720 to a THS730. ([EDIT] Just looked at the schematics, might be a case of swapping resistors and maybe one or two other parts to make the upgrade)
Probably end up doing the LED backlight mod, and building a new battery pack while I have it in pieces.

Will be handy for working on the car and for the youtubes, easier to lay on the bench under the camera than the TDS220..


Should provide a few hours of fun giving it a bit of love on the healing bench.

Oh so you are expanding your old Tek scope expertise to this line of prodcuts as well ?!

GREAT !.... because I really like them and would get one one day.
Very low on my priority list money wise, so it's only a remote idea.
But just in case, get whatever model is the top of the range, give it all the mods it can take, polish it up, and stack it on that TDS 784D that's marked "Vince".
It should not increase the price of shipping all that much I would think...

Ha, I'll keep an eye out for another one.




Tonight's work was replacing the typically snapped off 'Left Right' toggle switch on the 177 test fixture for my Tek 577 curve tracer.
Got a switch from Mouser (they cost way too much for what they are, but such is life) and pulled the toggle lever out and replaced the broken one in the switch in the fixture.
You can't buy the whole switch in the test fixture configuration, but as the switch is part of a series using common parts to build up the needed configuration, there are many common parts, so swapping the lever was just a simple matter of knocking out a pin to extract the lever, then performing open heart surgery with a little rocket science to reinstall in in the test fixture.

While I was there, I replaced the carbon composite resistors with equivalent metal film (gotta order a 22Meg 1/2W still) and it all went rather painlessly.
Now to find some replacement knobs for the front.

Next I'll have to lug the 577 onto the bench and figure it out. I know there's at least one shorted tant in it so far...

But before that, I'm waiting on parts to build my calibration and retro gaming PC, and I have a TM5006A mainframe to finish repairing, and a toaster to fix, and a shitty 30MHz scope to get the triggering working, and, and, and.....

[ch_scr]

AD571 seems to be analog to digital

Geez you are right, made a mistake in my spreadsheet indeed ! 
ADC it is, not DAC....
OK so I have zero DAC in stock then, problem solved...

There is no rush to choose parts from Mouser, I'm not in any hurry to place my order.

Ah cool, thanks.
In this case I will take a few days to hurry up and start working on the project. A quick first pass, back of the envelope design so I can evaluate how complex it would be to implement a "normal" DAC.
If not too much trouble then might go straight for that and call it a day, but if it proves troublesome then I think I would just use cheap R-2R jobbies to just "get the job done"...
This would allow me to concentrate on the rest of the design, and once I have a working "proof of concept" board, I can always modify the design with a "proper" DAC later on, if really I deem the performance of the R-2R unacceptable after real world testing.

Hi Vince, I've looked and IMHO you "might as well buy a few of these" . Yeah, thick film, 2% but at the price they are well worth it to "have a play", at least!
Don't forget what comes "before and after" - the logic buffer to drive the bits (it's output transistors in particular) influence dac performance - make sure to go CMOS, TTL won't cut it. Also, you probably want to buffer the DAC output - take care that you would need either an opamp with "rail-to-rail in and output" or a negative supply to make it "go to zero". Good luck!

[Vince]

This a Tek 7504 scope.... from my big TE haul from a few months ago.
It's a parts unit in extremely poor shape...

So you lost a perfectly good sink wash demo possibility?

I don't know what that is 

[Vince]

Hi Vince, I've looked and IMHO you "might as well buy a few of these" . Yeah, thick film, 2% but at the price they are well worth it to "have a play", at least!
Don't forget what comes "before and after" - the logic buffer to drive the bits (it's output transistors in particular) influence dac performance - make sure to go CMOS, TTL won't cut it. Also, you probably want to buffer the DAC output - take care that you would need either an opamp with "rail-to-rail in and output" or a negative supply to make it "go to zero". Good luck!

Yes I will probably do that.
I checked all the ladders on mouser.... they don't have that many all in all, and you quickly realize that they really only have one brand and one series... Bourns series 4000, same datasheet for all, all 8 bits or nothing. The choice is more about value and package type.

So if even Mouser has only 8 bits ones, no need to waste my time trying to find 9 bit jobbies, they either don't exist or can't be bought by a hobbyist.  So I will have to make one myself using an 8 bit one and adding a couple 0.1% resistors to extend it and make up the ninth bit. I checked the price of such resistors on Mouser (so I can order everything from the same place...), and they are freaking expensive in leaded / through-hole type, but way, way cheaper in SMD packages. In 0805 (easy to solder) 1/8W (same power rating as the ladders), they are 35 cents a piece from Bourns, and only 17 cents, less than half price, in 10 quantity.

https://www.mouser.fr/ProductDetail/Bourns/CRT0805-BY-1002ELF?qs=h2IHEVivlqCjNQtH%252BVLkLw%3D%3D

As for buffers, hopefully I don't need any. Won't be using TTL for the reason you said.

Basically, what I want to do is have binary counter chip, 74HCxxx, drive the DAC.
So I thought, if I use a 10K or 100K ladder, it should not load the 74HC outputs enough to cause trouble.
At any rate, even if it did, every output would behave the same, so it should not affect the linearity of the DAC should it. Might affect the output voltage, I would get a bit less than 5V full scale, but I could not cat less in my application.
All I want is a DAC, any DAC... just convert the counter output to analog and that's it, no fuss. I am not designing a metrology grade instrument to say the least.... I guess anything would do.

Buffering the output of the DAC, might no even be necessary, it will drive 1Mohm loads.
And again even if the voltage dropped, I don't care, I can adjust full scale deviation afterward, no big deal.

I will post somewhere on the forum to gather suggestions about DACs that can be used without a CPU, maybe there are some out there that exist, or maybe not. The experts will tell me...

[ch_scr]

Hi Vince, I've looked and IMHO you "might as well buy a few of these" . Yeah, thick film, 2% but at the price they are well worth it to "have a play", at least!
Don't forget what comes "before and after" - the logic buffer to drive the bits (it's output transistors in particular) influence dac performance - make sure to go CMOS, TTL won't cut it. Also, you probably want to buffer the DAC output - take care that you would need either an opamp with "rail-to-rail in and output" or a negative supply to make it "go to zero". Good luck!

Yes I will probably do that.
I checked all the ladders on mouser.... they don't have that many all in all, and you quickly realize that they really only have one brand and one series... Bourns series 4000, same datasheet for all, all 8 bits or nothing. The choice is more about value and package type.

So if even Mouser has only 8 bits ones, no need to waste my time trying to find 9 bit jobbies, they either don't exist or can't be bought by a hobbyist.  So I will have to make one myself using an 8 bit one and adding a couple 0.1% resistors to extend it and make up the ninth bit. I checked the price of such resistors on Mouser (so I can order everything from the same place...), and they are freaking expensive in leaded / through-hole type, but way, way cheaper in SMD packages. In 0805 (easy to solder) 1/8W (same power rating as the ladders), they are 35 cents a piece from Bourns, and only 17 cents, less than half price, in 10 quantity.

https://www.mouser.fr/ProductDetail/Bourns/CRT0805-BY-1002ELF?qs=h2IHEVivlqCjNQtH%252BVLkLw%3D%3D

As for buffers, hopefully I don't need any. Won't be using TTL for the reason you said.

Basically, what I want to do is have binary counter chip, 74HCxxx, drive the DAC.
So I thought, if I use a 10K or 100K ladder, it should not load the 74HC outputs enough to cause trouble.
At any rate, even if it did, every output would behave the same, so it should not affect the linearity of the DAC should it. Might affect the output voltage, I would get a bit less than 5V full scale, but I could not cat less in my application.
All I want is a DAC, any DAC... just convert the counter output to analog and that's it, no fuss. I am not designing a metrology grade instrument to say the least.... I guess anything would do.

Buffering the output of the DAC, might no even be necessary, it will drive 1Mohm loads.
And again even if the voltage dropped, I don't care, I can adjust full scale deviation afterward, no big deal.

I will post somewhere on the forum to gather suggestions about DACs that can be used without a CPU, maybe there are some out there that exist, or maybe not. The experts will tell me...

Don't want to pee in your coffee, but where will the 5V for the buffers come from? If they drift, your "full scale" (or any divided part of it) will drift accordingly! All I'm saying is, maybe get a few TL431 as well, and maybe use one just to power the buffers - If you do, get the specific Onsemi one's linked (TL431BC) as they're pretty good (lowest noise).

[Vince]

No worries, you can't pee in my coffee because I don't drink the stuff, I hate it 

You are complicating things... it's not looking simpler to use a "proper" DAC.

As I said I only need a crude DAC, don't care about full scale value or stability, could be +5V or -17V or +27.34V, doesn't matter.

Now I think of it, I remember some gizmo available for sale, that does something similar to what I want to do, and it uses just a SIL ladder connected to the I/O pins of an MCU, nothing else, and it works perfectly...
So I guess I am again guilty of overthinking things...

Hell maybe I will reconsider my position and use an MCU instead of discrete logic chips. Would make the design more compact and easier to modify/fine tune.
I will check the timing requirements of my project and see if an AVR MCU could cope with it or not.
Only reason for discrete logic initially, is to try to fo more with less... it's more satisfying and elegant. But at the end of the day I want this project to come to life, I kinda need it as stepping stone for a larger project, so if an MCU makes more practical sense then I can't rule it out...

I don't want to disclose my project, so I will PM you so you can understand the situation better.... but you will have to sign an NDA first ! 

[m k]

This a Tek 7504 scope.... from my big TE haul from a few months ago.
It's a parts unit in extremely poor shape...

So you lost a perfectly good sink wash demo possibility?

I don't know what that is 

Yes, probably means nothing in selected language.

I remember you were not very comfortable with Tek's washing method.
“We no longer consider it necessary to remove the CRT, shields, vacuum tubes, etc. to do a thorough cleaning job. Experience has shown that warm water and detergent under pressure penetrates these areas adequately without completely exposing them.”

If you don't have a tub just flip your old refrigerator on it back.
Assuming here that for now you're at least on a brink of replacing it.

[Vince]

Oh, OK ! 

Washing that 7504 did not occur to me.... it's not hollow-state technology, it was not dirty to begin with either, and it was so far gone that restoring it never ever even remotely crossed my mind....

No tub here, and my fridge is doing just fine thank you ! 

OK I need to replace the thermostat (still runnong on my home made electronic timer for now... works like a charm), and the door lock of the freezer compartment at the top, does not close anymore... so I can't buy any frozen food.
But, other than than it works like a champ ! It's only 30/35 years old, and my dad replaced the compressor 25 years ago with a top quality one, a Swedish brand. He said back in the day that brand made top notch compressors...   
So I will probably keep it until the compressor dies, because I know that if I buy a brand new fridge it will come with a crappy compressor that will give up the ghost in just a few years.

[m k]

Washing that 7504 did not occur to me.... it's not hollow-state technology, it was not dirty to begin with either, and it was so far gone that restoring it never ever even remotely crossed my mind....

My mental image also included a belly up machine handled from the frame with long yellow gloves, a brush resting aside and Bobby Darin rolling on the turntable.

[Vince]

You have too much imagination.... I would just use a high-pressure washer at full blast....

[Robert763]

No worries, you can't pee in my coffee because I don't drink the stuff, I hate it 

You are complicating things... it's not looking simpler to use a "proper" DAC.

As I said I only need a crude DAC, don't care about full scale value or stability, could be +5V or -17V or +27.34V, doesn't matter.

Now I think of it, I remember some gizmo available for sale, that does something similar to what I want to do, and it uses just a SIL ladder connected to the I/O pins of an MCU, nothing else, and it works perfectly...
So I guess I am again guilty of overthinking things...

Hell maybe I will reconsider my position and use an MCU instead of discrete logic chips. Would make the design more compact and easier to modify/fine tune.
I will check the timing requirements of my project and see if an AVR MCU could cope with it or not.
Only reason for discrete logic initially, is to try to fo more with less... it's more satisfying and elegant. But at the end of the day I want this project to come to life, I kinda need it as stepping stone for a larger project, so if an MCU makes more practical sense then I can't rule it out...

I don't want to disclose my project, so I will PM you so you can understand the situation better.... but you will have to sign an NDA first ! 

Hi Vince, There are LOTS of simple to use parallel input DAC chips out there. anything from 8 to 12 bits are common. Most don't need any "support" logic, not even a clock. Parallel binary in voltage out. A "multiplying" type will even take a variable voltage in (AC bipolar for many) and multiply the voltage (by a value of 0 to 1) according to the digital input. For example 2V in and 128 (binary for an 8 bit  DAC) inputs will give 1V out.

Many many years ago (Blimy nearly 40) I designed an analog gauge for an aircraft that had a complex calibration curve in a ROM. I took 0-10V input. This fed a ADC with free-running clock, Data output connected to the address inputs of the ROM. The data outputs connected to the inputs of a DAC and the output of the DAC drove an analog meter. Not a microprocessor in sight. I didn't even have a PROM progrmmer. It was hand programmed with a bunch of toggle switches. To simplify the PCB layout (hand laid with transfers and tape) to fit it in the case on a single sided PCB I laid the chips side by side and pin to pin. This "scrambled" both the address and data lines Enigma style
So I just scrambled the wiring to the switches in the programmer the same way. Years later I was asked to update the calibration because they had changed the airframe. I had to make up a de-scramber adaptor to go between my progammer and the PROM. I've still got it somewhere.

Robert.

[German_Engineer]

Yet another 5334B frequency counter OCXO and prescaler retrofit. The OCXO is a rather inexpensive board from aliexpress (TZT store, 2525 OCXO board, BG7TBL, 20USD), since I did not want to spend the money for an original hp part. The board fits nicely and needs only a 7805 to connect to the the always-on 15VDC supply of the counter. I have been watching a 1MHz signal from a GPS receiver for a few weeks now and the OCXO is very stable - only "lots-of-zeros" on the display. Recommended.

[Vince]

Hi Vince, There are LOTS of simple to use parallel input DAC chips out there. anything from 8 to 12 bits are common. Most don't need any "support" logic, not even a clock. Parallel binary in voltage out. A "multiplying" type will even take a variable voltage in (AC bipolar for many) and multiply the voltage (by a value of 0 to 1) according to the digital input. For example 2V in and 128 (binary for an 8 bit  DAC) inputs will give 1V out.

Many many years ago (Blimy nearly 40) I designed an analog gauge for an aircraft that had a complex calibration curve in a ROM. I took 0-10V input. This fed a ADC with free-running clock, Data output connected to the address inputs of the ROM. The data outputs connected to the inputs of a DAC and the output of the DAC drove an analog meter. Not a microprocessor in sight. I didn't even have a PROM progrmmer. It was hand programmed with a bunch of toggle switches. To simplify the PCB layout (hand laid with transfers and tape) to fit it in the case on a single sided PCB I laid the chips side by side and pin to pin. This "scrambled" both the address and data lines Enigma style
So I just scrambled the wiring to the switches in the programmer the same way. Years later I was asked to update the calibration because they had changed the airframe. I had to make up a de-scramber adaptor to go between my progammer and the PROM. I've still got it somewhere.

Robert.

Thanks for the story, I always love them ! 

Good news on the DAC front then... do you have suggestion of brands and models / series that are easily available these days ?
I guess I will want a couple 9 or 10 bit ones.
Problem is that the parametric search on Mouser probably does not allow to filter for "CPU-less" DAC sadly.
So unless I know what models to look for, I could spend my life checking thousands of datasheet one by one....
However as you said, at the least, a multiplier DAC would fit my needs, and maybe it's not unreasonable to expect the parametric search to have a "multiplier" keyword somewhere.... let's see...
Then sort by price, package type, stock/availability....

You were brave programming that EPROM by hand with switches... hopefully it was not a 27C4000....
You were young and motivated I guess 
Sounds like the kids back then who programmed their Altair computer the same way.... sure takes some love....

[srb1954]

Good news on the DAC front then... do you have suggestion of brands and models / series that are easily available these days ?
I guess I will want a couple 9 or 10 bit ones.
Problem is that the parametric search on Mouser probably does not allow to filter for "CPU-less" DAC sadly.
So unless I know what models to look for, I could spend my life checking thousands of datasheet one by one....
However as you said, at the least, a multiplier DAC would fit my needs, and maybe it's not unreasonable to expect the parametric search to have a "multiplier" keyword somewhere.... let's see...
Then sort by price, package type, stock/availability....

Search for a suitable DAC using "interface type = parallel".

This will quickly narrow down the search to types that can be easily interfaced without a micro. You can then refine your search further selecting resolution, voltage or current O/P etc