Tektronix 570 Curve Tracer


David Simpson MM6ACI
 

Hello folks from a newbie. For a number of years I've been interested in vintage radio/electronics as a retirement pursuit. Particularly test equipment, and more particularly valve testers(mainly AVO VCM's & & the occasional Taylor or Mullard), and scopes(mainly Cossor, Solartron, & one or two wartime/post-war ones). Stemming back to my RAF T/Eq servicing/repairing days with CT160's, & Hartley, Solartron & HP scopes back in the late 60's/early 70's. Have also built my own DC Valve Tester. However, tabulating Ia & Vg & drawing up Gm curve results on hand drawn graph paper is laborious & tiring on old eyes. So a pal suggested I try & see if my skills are good enough to take on restoring a Tek570. Therefore would appreciate some help & advice from experts.
Yes - have been told its huge & weighs a cwt, has a multitude of valves & 5 T/F's, and internet wheeler-dealers have been asking megga$$$ or megga£££ for fully restored & calibrated ones, particularly in the USA. In the UK they seem to be as rare as rocking-horse manure. Speculators & Audio-Phools on eBay have already pushed AVO CT160's & VCM163's to horrendous prices in recent years, sadly for aspiring vintage enthusiasts.
Me - I'm not a mercenary wheeler-dealer, just a retired electronics technician who collects & restores old scopes.

Regards, Dave Simpson MIET BVWS & VMARS Member


Zentronics42@...
 

Dave,
Welcome to the group. In terms of the 570 I too would like to get one for the lab but there is also some other options. The 576 along with a tube tester that Dennis did a modification for can do tubes as well. The main difference for tubes in a 576 or 577 is the heater voltage taps off the transformer as well as some control grid voltages to keep the tubes from running away. The 576 has it own querks like the HV transformers dying as well as using a totally unique tube that is weak in a lot of units. The smaller 577 has proven to have more sustainability with rare parts. I know some people have spun up a small interface board and use external power supplies to drive the heater on the tubes to check say a 12ax7. I'll send you an email with a like to some curve tracer stuff off list. The TLDR is you are not limited to the 570 of you want to work with tubes. There is some adaption for the 576 and 577 as well but yes they are insanely heavy, the 577 being the lightest of all.

Zen

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of David Simpson MM6ACI
Sent: Saturday, August 21, 2021 9:07 AM
To: TekScopes@groups.io
Subject: [TekScopes] Tektronix 570 Curve Tracer

Hello folks from a newbie. For a number of years I've been interested in vintage radio/electronics as a retirement pursuit. Particularly test equipment, and more particularly valve testers(mainly AVO VCM's & & the occasional Taylor or Mullard), and scopes(mainly Cossor, Solartron, & one or two wartime/post-war ones). Stemming back to my RAF T/Eq servicing/repairing days with CT160's, & Hartley, Solartron & HP scopes back in the late 60's/early 70's. Have also built my own DC Valve Tester. However, tabulating Ia & Vg & drawing up Gm curve results on hand drawn graph paper is laborious & tiring on old eyes. So a pal suggested I try & see if my skills are good enough to take on restoring a Tek570. Therefore would appreciate some help & advice from experts.
Yes - have been told its huge & weighs a cwt, has a multitude of valves & 5 T/F's, and internet wheeler-dealers have been asking megga$$$ or megga£££ for fully restored & calibrated ones, particularly in the USA. In the UK they seem to be as rare as rocking-horse manure. Speculators & Audio-Phools on eBay have already pushed AVO CT160's & VCM163's to horrendous prices in recent years, sadly for aspiring vintage enthusiasts.
Me - I'm not a mercenary wheeler-dealer, just a retired electronics technician who collects & restores old scopes.

Regards, Dave Simpson MIET BVWS & VMARS Member


Michael W. Lynch
 

David,

Welcome Aboard! Following up on Zen's comments. Add the older Type 575 Curve Tracer to the list, as it is a viable option with the use of Dennis Tillman's VTCT Adapter. The 575 Mod122 is especially desirable. There is a solution for the HV Transformer failure on the 576. DM me for more details. The 576 and 577 both have their advantages. the 577 is well likes for its light weight and the 577 is available with a "storage" feature, which some people find quite useful. I have both 576 and 577, they are wonderful machines. One of these three instruments will be your best option, as the 570 is almost unobtainable at any reasonable price. Best of luck in your quest for one of these instruments.

--
Michael Lynch
Dardanelle, AR


emissionlabs
 

Hello Dave,

I have had some 50 different tube testers in my collection. People sometimes think a curve tracer is useful for tube testing, but a curve tracer is not a tube tester. When the tube is definitely bad you will see that from the curves, but for the rest, Gm, gain, Ra, the use condition, and typical defects such as grid leakage, heater to cathode leakage, these things don't reflect in an optical way from the curves. But of course, it is great fun looking at tube curves, or curves of many other parts as well. For tube testing, VCM163 is one of the very finest testers ever made, and in the UK, you probably find one locally. I wanted to get a 570 myself too, these are so rare, you either pay 4000 Euro for a good one, or any lower price for one which you may end up having to restore it completely. But I do not want to repair other people's junk and mess any more. So I went for the 576, which can be found in good quality. These can do the same and a lot more, just it doesn't have a heater power supply and no G2 Voltage. I can do without G2, just test pentodes in triode mode. And if it becomes crucial to use G2, I can still take an external power supply. 576 can test at MUCH higher anode voltage than 570. I choose for the 576 because of the semi-digital read out. But 576 has really insane weight. For lifting it from the floor on the bench, you can not do this on your own. So at it's lighter weight, 577 is probably also a good one. But I can only speak for the 576, and I never regretted buying it. Here is a link to my 576: https://www.jacmusic.com/Tube-testers/TEK-576/Tek-576-1-General-Part.html


ChuckA
 

I bought a couple of Dennis's VTCT boards when he first produced them. I built a couple of crude adapters to use on my 576 which worked pretty well but were cumbersome to use.

I didn't like the use of a tube tester to get the required additions to make the adapter work so I decided to make a standalone unit to attach to the 576. After a couple of months and talking to Dennis about some issues I ran into, I came up with this:

http://www.myvintagetv.com/TEK576Tube.htm

Chuck

--
See Early TV at:

www.myvintagetv.com


Glydeck
 

Wow! Emissionslab, great page on the 576. Your repair notes will be super helpful. Great detail.

Chuck, Love your tube tester solution. Very nice documentation.

I’ve book marked both pages. For what it’s worth here is my solution using my 575;

http://glydeck.blogspot.com/2012/01/testing-dual-triodes-with-tek-575.html

http://glydeck.blogspot.com/2012/02/testing-miniature-pentodes-with-tek-575.html

The PDF files are on groups.io

https://groups.io/g/TekScopes/files/Tek575TestFixtures.pdf

https://groups.io/g/TekScopes/files/Tek575_TriodeTester.pdf

73s George KD6NEW

On Aug 22, 2021, at 7:40 AM, ChuckA <chuck@myvintagetv.com> wrote:

I bought a couple of Dennis's VTCT boards when he first produced them. I built a couple of crude adapters to use on my 576 which worked pretty well but were cumbersome to use.

I didn't like the use of a tube tester to get the required additions to make the adapter work so I decided to make a standalone unit to attach to the 576. After a couple of months and talking to Dennis about some issues I ran into, I came up with this:

http://www.myvintagetv.com/TEK576Tube.htm

Chuck

--
See Early TV at:

www.myvintagetv.com






David Simpson MM6ACI
 

Many thanks Guys for the informative advice. Particularly regarding considering other models in the 57* family. As emissionlabs says, the AVO VCM163 is highly thought of here in the UK. Never owned one, but have owned a couple of CT160's in the past. Currently I use an AVO VCM MK3 which I restored, for "run of the mill" valve testing. (the CT160 is just a MK3/4 squeezed into a military grade clam-shell casing). But then, all of AVO's(and other UK manufacturer's, and Hickok's etc.) range of valve/tube testers all work using full-wave &/or half-wave mains frequency derived pulses on the working electrodes - Anode(Plate), Screen(G2) & Grid.
For several years I supplied a few folk in the UK vintage-radio fraternity with "Standardised" valves(ECC81's & 82's) using a hybridised CT160, but then some folk started to ask for standardised "power valves" - BT's & Pentodes. So, decided to build a fully DC Valve Tester which could determine mu & Gain "G" as well as just Gm. In addition, the bigger beasts - KT66's & 88's, etc., requiring matching of GM curves, could be supplied with A4 graphs.
Move foreward several years past "3 score years & ten" - getting older, eyes OK but they do get tired at times, wrist gets tired, and so on. Hence the thought of acquiring an item of vintage test equipment which could display a number of valve characteristics becomes rather attractive. From the pictures I've seen of a 570's CRT display, a decent digital camera or iPhone - should take some jolly nice pictures.
Again as "emissionlabs" says, buying an old clapped-out item is fraught with problems. For a 570, one would at least want the 5 transformers & the CRT working. Cosmetic & circuitry problems can be sorted with care and patience. I've already seen the strong warning in the 570's Manual about using the correct grade of solder, and soldering iron tips & temperature, when working on the ceramic tag strips. Back in the 60's & 70's I did work on RAF HP180A's, Collins 618T's, etc., so appreciate the high standard of US equipment.
Some folk might say ' why not buy something cheap & modern from China' using an LCD screen & a software package. No thank you. I'm just an old analogue guy with a 1960's, + or - ten years, mindset!

Regards, Dave


Zentronics42@...
 

In terms of current gear. The "modern" way of testing would be with 2+ SMU's depending on the number of dynamic voltages you want to sweep. You can get one up to 1Kv for the anode voltage but you would need at minimum 2 smu's + a computer and the software to script the test but you are starting to talk about $20K just to start as the smu's are in the 5-12K range in price. This is the "cheap" solution, the parameter testers are in the if you have to ask don’t buy category. They use 4X SMU's and an integrated computer they do C-I curves as well as V-I curves that that is cool but out in the 6 figure range. I do have a few SMU's on the list to acquire for the lab but there are pushed out a bit. I'll stick with my restored 57X's. If you go the 576 route at the current time a dead (weak) tube is a show stopper. But there are some who are working on getting over that hurtle. To stretch the tub as much as possible there is a 3d printable viewing window for the 576 this totally encloses the display in a dark area so the intensity can be kept as low as possible and still be viewable.

Zen

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of David Simpson MM6ACI
Sent: Sunday, August 22, 2021 12:22 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix 570 Curve Tracer

Many thanks Guys for the informative advice. Particularly regarding considering other models in the 57* family. As emissionlabs says, the AVO VCM163 is highly thought of here in the UK. Never owned one, but have owned a couple of CT160's in the past. Currently I use an AVO VCM MK3 which I restored, for "run of the mill" valve testing. (the CT160 is just a MK3/4 squeezed into a military grade clam-shell casing). But then, all of AVO's(and other UK manufacturer's, and Hickok's etc.) range of valve/tube testers all work using full-wave &/or half-wave mains frequency derived pulses on the working electrodes - Anode(Plate), Screen(G2) & Grid.
For several years I supplied a few folk in the UK vintage-radio fraternity with "Standardised" valves(ECC81's & 82's) using a hybridised CT160, but then some folk started to ask for standardised "power valves" - BT's & Pentodes. So, decided to build a fully DC Valve Tester which could determine mu & Gain "G" as well as just Gm. In addition, the bigger beasts - KT66's & 88's, etc., requiring matching of GM curves, could be supplied with A4 graphs.
Move foreward several years past "3 score years & ten" - getting older, eyes OK but they do get tired at times, wrist gets tired, and so on. Hence the thought of acquiring an item of vintage test equipment which could display a number of valve characteristics becomes rather attractive. From the pictures I've seen of a 570's CRT display, a decent digital camera or iPhone - should take some jolly nice pictures.
Again as "emissionlabs" says, buying an old clapped-out item is fraught with problems. For a 570, one would at least want the 5 transformers & the CRT working. Cosmetic & circuitry problems can be sorted with care and patience. I've already seen the strong warning in the 570's Manual about using the correct grade of solder, and soldering iron tips & temperature, when working on the ceramic tag strips. Back in the 60's & 70's I did work on RAF HP180A's, Collins 618T's, etc., so appreciate the high standard of US equipment.
Some folk might say ' why not buy something cheap & modern from China' using an LCD screen & a software package. No thank you. I'm just an old analogue guy with a 1960's, + or - ten years, mindset!

Regards, Dave


John Griessen
 

On 8/22/21 9:38 AM, Glydeck via groups.io wrote:
here is my solution using my 575;
http://glydeck.blogspot.com/2012/01/testing-dual-triodes-with-tek-575.html
http://glydeck.blogspot.com/2012/02/testing-miniature-pentodes-with-tek-575.html
Thanks George KD6NEW,

I like the practicality of your adapter and using inexpensive 575 CTs! Is the 400V mod something you can add easily to a normal 575?

--
John


 

Adding to the discussion, my setup of a 576 with a Metrix U61 (tube analyzer (as heavy as the 576). Its perhaps the most versatile analyzer around. I just had to plug the base voltage into G1 and the collector voltage in the anode circuit. Had to take shielded cables, otherwise I got oscillations. The operation of the Metrix remains identical.

See the pic here... https://groups.io/g/TekScopes/album?id=267344 - nice to watch, indeed, analyzing an EL38.

cheers
Martin


John Griessen
 

On 8/22/21 12:53 PM, Martin wrote:
my setup of a 576 with a Metrix U61 (tube analyzer (as heavy as the 576). Its perhaps the most versatile analyzer around. I just had to plug the base voltage into G1 and the collector voltage in the anode circuit. Had to take shielded cables, otherwise I got oscillations. The operation of the Metrix remains identical.
Seems much better than using the analyzer meters alone. Does your analyzer tell all the parameters of the DUT?


 

Hi Jon,

"all" the parameters certainly not... ;-)
There is an add-on to the U61, as large as the unit itself, allowing to measure transconductance.

The U61 has 5 meters allowing measurement of voltages for heating, G1, G2, G3, Anode and current for Anode, G2 and G3.
All voltages are stabilised internally (no rheostats as in most other instruments).

The U61 has output plugs for all voltages. G1 is of high impedance, so I can plug the 576's step generator in parallel as it is capable of delivering current. The anode output can be used as input if you take out a bridge normally used for inserting a resistor in the anode circuit. That gives a clean and simple setup... so far I only used it for fun, to echo what "emissionlabs" said in an earlier post.

My main use of the U61, right now, is to identify tubes that have lost their labels.

cheers
Martin


 

Hi Martin,
this looks really well made. I'm having trouble imagining why it works
- I'm not the most acquainted with how the 576 works or how tube
testers work. Would you mind explaining the function of your bridge a
little bit deeper?

Thanks and best regards

On Mon, Aug 23, 2021 at 9:03 AM Martin <musaeum@arcor.de> wrote:

Hi Jon,

"all" the parameters certainly not... ;-)
There is an add-on to the U61, as large as the unit itself, allowing to measure transconductance.

The U61 has 5 meters allowing measurement of voltages for heating, G1, G2, G3, Anode and current for Anode, G2 and G3.
All voltages are stabilised internally (no rheostats as in most other instruments).

The U61 has output plugs for all voltages. G1 is of high impedance, so I can plug the 576's step generator in parallel as it is capable of delivering current. The anode output can be used as input if you take out a bridge normally used for inserting a resistor in the anode circuit. That gives a clean and simple setup... so far I only used it for fun, to echo what "emissionlabs" said in an earlier post.

My main use of the U61, right now, is to identify tubes that have lost their labels.

cheers
Martin







 

The bridge ist perhaps better called a Jumper. Its a large jumper with banana plugs that is in the output line of the anode supply. There are 3 types of jumpers, each with different resistors in it (0, 5k and 100k). When I take the jumper out the anode supply is cut from the rest of the instrument, so I can connect the collector supply of the 576.

Is that clear enough? I have not set it up right now, otherwise I would take some more pics.

cheers
Martin


Keith
 

re: 575 tidbits

First, if you haven't already - I recommend you check out the 575 Tek Wiki at: https://w140.com/tekwiki/wiki/575

An incredible wealth of info there in those document links on the right, including a complete set of instructions for converting a regular 575 to Mod122C. I suggest you look at it, as it will give you an idea of what's involved. Not for the faint of heart, though the 400V part is doable. Look and you'll see how they accomplished it without swapping transformers. Very clever, those Tek designers. :-) My advice is this. If you choose to go with a 575, do try to get one with 122ModC already installed. Worth the few extra pounds (or is it Euros?) to get one already in there, IMO.

Note that there are quite a number of other factory updates recommended for a 575 over its 15 year manufacturing life. Make sure you do them. Especially the fuses that are part of the silicon rectifier update. Save that mains transformer!

There are about 40 valves in the 575. So, get ready to shell out extra bucks if you need certain valves - like those four 6AN8 - which unfortunately are used in certain currently popular HH Scott Hi-Fi receivers. We all know what THAT means! :-/ There's no easy substitute for a 6AN8 (or the 6BW4 rectifiers, though thankfully those are fairly common and not too expensive.)

575 have a fair number of can type electrolytic caps, but from my reading of the experiences of others, and from my own 575 experience, many are often still serviceable. In my one experience, after replacing a single dead horse, my 1962 instrument's PSU made spec for ripple after a simple variac power up.

Speaking of bad can caps, if when you power up your 150 volt or 300 volt is wonky, then IMO the first thing to check is C244. That is a single section 350V 150uF capacitor - it is the only one WITHOUT the can insulating plastic shield installed. It is rather unfortunately located right next to three big heat emitters - First, a 6080 pass tube and second a trio of big and HOT ceramic resistors right under the chassis near the base of C244. Third, as an added bonus, the 575 fan blows the waste heat from that 6080 right onto the entire can cap assembly, especially C244. :-/ Not optimum, IMO.

I vote C244 as "most likely to fail" capacitor in the 575 power supply. Just my opinion.

Speaking of valves, pay attention to the condition and match of the horizontal and vertical amplifier Tek 157-0050-00 "special" 12AU6 pairs. Understanding this part and how to finesse it will make your calibration life easier.

Another tidbit: Verify that your 575 is correctly wired with switched and fused hot. (Apparently, some weren't?) Tek informs us that getting those backwards can induce a bunch of coupled AC noise through the secondary shielding of one of the transformers...again somewhere in those additional documents on Tekwiki.

Also, verify that your 575 has a bottom panel in place. It DOES matter, both during calibration and use. See Tek literature for "installing a temporary bottom panel with hole" for calibration purposes. Without a bottom, you won't get sufficient isolation of the HV CRT oscillator circuit, and all kinds of noise bits will leak into places you don't want. BTW, the 575 panels are unique, as they are 18 3/8 long, which is 2" shorter than the other 500 series scopes.

Be equipped and prepared to check the accuracy of the "precision" resistors on the various step controls. I replaced about a dozen out-of-spec carbon comp "precision" resistors on mine. The carbon comp are the worst - and to that end Tek suggested that they be replaced with 1% metal oxide type - again, somewhere in their upgrade docs. (I just read it a couple days ago) Not hard to do, but a bit tedious.

FWIW, once you get it up and working Mr. George Lydeck's elegant and simple solution to supplying B+ to G2 in a pentode works well, as does his 1K resistor jumper to drive additional V- bias to the grid via the current section control of the base step generator. Definitely worth the look.

IMO, Dennis Tillman's VTCT setup is a good thing too. I'm building one myself, though it is not done yet. It is more complex than George's setup, but has more total feature horsepower as well. Since it has transistors in it, I am out of my league, as I barely understand how those little bugs work. :-) Dennis assures us that it does indeed work, and his writeup on it is a good read as well. Thank heavens for people like Dennis and George!

Finally, if you do go with a 575, note that a 575 CRT is no easy thing to find these days either, so be just as careful with your 575 CRT as you would be with a 576!

Speaking of 575 CRT, IME, they don't ship well. If you have a complete 575 shipped to you, I STRONGLY recommend that you consider having the CRT removed and separately shipped. I know this will sound like overkill, but if it were me, I would go to the trouble of finding and using original type Tek packing materials for a 5" round CRT if at all possible. In my four attempts to get a working 5" round shipped to me, I experienced a 50% breakage rate. Tek packing material = both perfect, anything else = broken. That was my experience anyway.

Just a few notes from my recent and ongoing 575 restoration.


Cheers!



Keith
coolblueglow
Full Disclosure; I'm the dumbest and least educated Tek user on this forum.


 

OK, am I getting this right, so on the tube tester you have those
small jumpers that configure the pinout of the tube base, and you
remove the anode supply jumper, and instead connect the collector
supply output of the 576?

What about the rest of the connections to the 576?

Thanks!

On Mon, Aug 23, 2021 at 1:35 PM Martin <musaeum@arcor.de> wrote:

The bridge ist perhaps better called a Jumper. Its a large jumper with banana plugs that is in the output line of the anode supply. There are 3 types of jumpers, each with different resistors in it (0, 5k and 100k). When I take the jumper out the anode supply is cut from the rest of the instrument, so I can connect the collector supply of the 576.

Is that clear enough? I have not set it up right now, otherwise I would take some more pics.

cheers
Martin







 

OK, am I getting this right, so on the tube tester you have those
small jumpers that configure the pinout of the tube base...
No, its not that one. Its the general one that cuts the anode voltage supply before the pinout-levers.

Have a look at any U61 on internet: its the one on the top right of the unit's frontplate.

cheers
Martin


 

Gotcha. So how are the base and emitter connected? I'm still confused
about those. Thanks

On Mon, Aug 23, 2021 at 5:26 PM Martin <musaeum@arcor.de> wrote:

OK, am I getting this right, so on the tube tester you have those
small jumpers that configure the pinout of the tube base...
No, its not that one. Its the general one that cuts the anode voltage supply before the pinout-levers.

Have a look at any U61 on internet: its the one on the top right of the unit's frontplate.

cheers
Martin





David Simpson MM6ACI
 

Once again, many thanks for all the extra input folks, most appreciated. For folk with a strong interest in semiconductors, the later 57* models of transistor curve tracers are exceptional by the look of things.
I certainly was very interested in reading emissionlab's "jacmusic" link. I'll certainly echo his praise of Hameg scopes & their component tester facility. I've a couple of HM605's & an HM203-5. When I have my DC V/T fully set up for testing valves, for the "Gain G" test I use the 203-5 to monitor a P-P Grid input of 1KHz and the 605 to monitor the Anode(Plate) P-P o/p, this is then compared to the RMS metered(using a Marconi TF1041C VTVM which is built into the V/T) calculation of G. Belt & braces I guess, but mostly obtain results within 5%.
I'm not really needing any more T/Eq for Transistors & semi-conductors. Apart from the Hameg's facilities, I've a Peak Atlas DCA55 for quick testing, and an AVO CT446 MK2 Transistor Analyser for in-depth measurements.
Back to the 570 :- Have noted advice on shipment of Tek scopes & the vunerability of the CRT's. If I do get wind of one, I'll certainly consider asking the seller to ship the CRT seperately. Mind you, here in the UK, those of us who are members of the UK Vintage Radio Repair & Restoration Forum, have an excellent FCS - - Forum Courier Service, which is well supported. Certainly for me, living in the North of Scotland, I've used our FCS for transporting items over a few hundred miles, to or from England or Wales, and have never suffered damage to anything.
By the by, my cousin in Waynesboro, PA, has learn't of a Tek Scope enthusiast in Ohio called Dick Anderson, who is heavily into 570's. Does anyone have an email address for him, please ?

Regards, Dave


Roy Thistle
 

On Sun, Aug 22, 2021 at 09:22 AM, David Simpson MM6ACI wrote:


I supplied a few folk in the UK vintage-radio fraternity with "Standardised"
valves
Hi Dave:
If you have a chance: what is a "Standardised" valve. (A valve is a vacuum tube.)

--
Roy Thistle