Grass Instruments Polygraph / EEG / Lie Detector Machine Teardown

[dexters_lab]

while i was picking up my latest junk item to teardown i took a quick look at this interesting item, it's a Polygraph machine, well it's actually two of them, with the chart recorders

i was surprised by the build quality, you wont see that from the pictures but there is a stainless frame with aluminium plug-in modules, all the control knobs etc are machined aluminium, it must have been very expensive when it was new, i didn't have time to start poking around properly

it's an unusual item to see, but i am not sure about taking it for teardown, the seller will take a deal on it but it's going to be a load of mostly identical amplifiers, filters and stuff so i dunno. It's way more £ than i would normally do for a teardown... what do people think?

[PA0PBZ]

I agree that it looks like more of the same², but man that is an impressive piece of hardware!

[Kjelt]

It was probably used in a hospital for EEG,s since the number of probes and units exceed normal polygraph usage. Would be interesting to have a look inside to get a date of build.

[Paul Moir]

Would be interesting to have a look inside to get a date of build.

The Canadian patent listed as pending was issued in 1957 to Albert M Grass, so it must be from about that time.
I'll bet it would be entertaining to see what they thought was adequate isolation between HV supplies and electrodes wired into someone back then.  But I can't imagine the entertainment would be worth much money.  Better things to do with it.

[Mashpriborintorg]

Awesome looking piece of Equipment  ! What is the teardown item you picked up, by the way ?

[dexters_lab]

right well i might let it slip then.

Must admit i really dont have the space for it, i need Dave's workshop!

SWMBO would go nuts if it turned up in the kitchen or lounge!

Awesome looking piece of Equipment  ! What is the teardown item you picked up, by the way ?

it's a Teac RD-111T PCM Data Recorder (records 8 channels of data onto tape)

[Kjelt]

SWMBO would go nuts if it turned up in the kitchen or lounge!  

Logistic issue, first get awsome machine in tha house, second get the SWMBO and fake back complaints.

[dexters_lab]

SWMBO would go nuts if it turned up in the kitchen or lounge!  

Logistic issue, first get awsome machine in tha house, second get the SWMBO and fake back complaints.

"of course it will be gone in a couple of days darling, i cant be untruthful to you, it's a lie detector!" 

[Macbeth]

Just tell her she doesn't have to drag you on to The Jeremy Kyle Show now! Of course this won't help with the paternity testing so you may still have to endure the baying unemployed chavs in the audience for that 

[dexters_lab]

Just tell her she doesn't have to drag you on to The Jeremy Kyle Show now! Of course this won't help with the paternity testing so you may still have to endure the baying unemployed chavs in the audience for that 

lol, Jeremy Kyle, car crash tv of the highest order

[crispy_tofu]

Those square-looking knobs though... 

[dexters_lab]

well i managed to pick this item up for a reasonable price so we have a couple of polygraph & EEG machines to take apart. I wasn't that interested in it but the price made it worthwhile or at least it's a 'free' teardown that shouldn't cost me anything once i have chopped in the metal.

[Mashpriborintorg]

Beware, prices of scrap metal are currently quite low. Maybe you can also retrieve some money by selling  duplicate modules and parts on eBay.

[dexters_lab]

Beware, prices of scrap metal are currently quite low. Maybe you can also retrieve some money by selling  duplicate modules and parts on eBay.

so long as it covers most of my costs i'll be happy... plus thankfully i sell my metal to a specialist company that makes alloys and not to a scrap metal dealer/middleman

[SeanB]

Multiturn dials and the 10 turn pots behind are worth a bit if you sell them. You should have some nice precision opamps there as well, and they likely will all be socketed as well. At least the ones I took apart were, still have the Tek scope out of one that i must recap and turn into a component curve tracer, though the other one with the Tek storage scope in it is likely dead, though the tube might still be usable.

Should pull it off the top shelf and take a few pics of it sometime.

[Towger]

I was watching the price dropping. You could rent it out as a B movie prop.
So what does the SWMBO think of it?

[Delta]

Dex, that is an EXTREMELY cool piece of vintage machinery!  Far too good to be chopped up for scrap!

I'd even buy it off you if the logistics were possible.

You may well find that producers of TV programmes and films set in the 60s & 70s would be interested in it as a prop.

Please don't scrap it!

[dexters_lab]

I was watching the price dropping. You could rent it out as a B movie prop.
So what does the SWMBO think of it?

lol, she has not seen it yet, my storage is about 20km from home

Multiturn dials and the 10 turn pots behind are worth a bit if you sell them. You should have some nice precision opamps there as well, and they likely will all be socketed as well. At least the ones I took apart were,

indeed, yea there are quite a few of the multi-turn dials

Dex, that is an EXTREMELY cool piece of vintage machinery!  Far too good to be chopped up for scrap!

I'd even buy it off you if the logistics were possible.

You may well find that producers of TV programmes and films set in the 60s & 70s would be interested in it as a prop.

Please don't scrap it!

sadly i dont have the room to keep it! In fact it needs to be gone within a couple of weeks as i will be parking up our classic toyota in my container for the winter

it would have been scrapped if i had not bought it, at least this way we can look inside and salvage those beautiful control knobs and other goodies!

[mikeselectricstuff]

There must be an analogue synth nut out there who would wet themselves over that thing!

[krivx]

There must be an analogue synth nut out there who would wet themselves over that thing!

Yep, people use Grass gear for music, just not the traditional analogue synth crowd. Dexters_lab, I've PM'd you about this 

[dexters_lab]

There must be an analogue synth nut out there who would wet themselves over that thing!

Yep, people use Grass gear for music, just not the traditional analogue synth crowd. Dexters_lab, I've PM'd you about this 

i guess those amplifiers could be used for a few different things

[SeanB]

Interested in getting some of those multiturn knobs and pots Mark.

[owiecc]

Wow. Wonderfull piece of equipment for something that never actually worked.

[Towger]

The Yanks appear to believe in polygraphs! Or at least that's the impression given in movies.

[dexters_lab]

Interested in getting some of those multiturn knobs and pots Mark.

no worries i have a growing list of things to put to one side for people