Telequipment CT71 Curve Tracer - UK Vintage Radio Repair and Restoration Discussion Forum

Robert christi · 26th May 2006, 12:26 am

I have a CT71 Curve tracer with a Horiz Sweep problem. Does anyone have a schematic for this unit or experience with the same?
Thanks, Bob C

Biggles · 26th May 2006, 10:18 am

I think I may have a CT71 at home somewhere and I will look for any service info this weekend. I must admit I have never used it, and if I remember correctly there are a couple of "plug ins" on the front, presumeably for different component tests.

Biggles

Robert christi · 27th May 2006, 5:28 am

Hi Biggles,
I would appreciate you looking for any available data on the CT71. Thanks, Bob C

Biggles · 30th May 2006, 10:29 am

Sorry Bob, I've definitely got a CT71 but no manual. It is remotely possible that some of the circuits are similar to other Telequipment scopes of that era. If you need component identification etc I could have a look inside mine for you, although I can't be sure mine is working still, as it's not been switched on for a long time.

Biggles.

ppppenguin · 30th May 2006, 10:47 am

I've got a CT71 and the original manual. I bought it many years ago and have used about twice since then. Haven't got time to scan the whole thing at the moment but I'll scan the H amp schematic for you. If somebody wants to borrow the manual to scan I can give it to them at Gerry's on Saturday or Harpenden on Sunday.

Have you asked in the Tektronix forum? Somebody may have already done the job.

http://groups.yahoo.com/group/TekScopes/

Robert christi · 2nd Jun 2006, 8:21 pm

Its good to know that a manual exists for the CT71. I looked all over but could not find a copy. I also checked the Tek site you indicated but did not see anything on the CT71.
I opened up the curve tracer and saw all components were descrete and appeared to be those that were commonly used in designs in the early to mid 1960's. A scope indicated that the plus rail was approx 120vdc and the neg bias rail was -12vdc. Both probably OK. A schematic would be of great help in servicing the unit in that the problem appears to be ahead of the push pull deflection amplifier. If you could send the schematic that would be great or I could send a money order to cover postage to San Diego CA USA.

Dickie · 9th Jun 2006, 4:50 pm

We've got a CT71 at work and I've got these scans from the manual. Hope they are of some use.

Richard

JoOngle · 11th Aug 2006, 4:12 pm

Hi There,

I have a CurveTracer (CT71) with the same horizontal sweep problems (I think)
as it only shows either the X or Y curve on either Single-trace or step-trace (diagonal curve) but no curve-traces...

I suspect that someone before me have tried to repair it and used unoriginal
components so I'm looking for information on the components.

I've done extensive backtracing tests on the unit, but can't find any
components to be defective - so I'm a bit in the dark here.

Anyone got any tip, or input?

Thanks,
Tommy

JoOngle · 13th Aug 2006, 2:33 am

I'd really appreciate a scan of the Service Manual for this device.

I've fixed the step-generator, but the horizontal sweeper seems dead.
Funny thing really...this thing ain't got many components so its
fairly uncomplicated - but I still can't figure out how the
horizontal sweep works.

JoOngle · 17th Aug 2006, 6:27 pm

Many thanks Richard, very much appreciated.

Now I stand a chance at servicing this thing and restoring it to it's former glory
(I actually use these things to build stuff)

It even contains complete print-layouts so it's possible to reproduce the
actual prints themselves. The apparatus is so "non-complex" that it's
fairly trivial to build it ground up. Cool stuff.

JoOngle · 18th Aug 2006, 5:53 pm

Tricky stuff to fix, even with the schematics.

It seem to be the horizontal "sweep" that is completely done for,
the problem is I can't locate a single faulty transistor or diode whatsoever,
they all seem to check out just fine.

Even doing the fault finding tests indicate that all is well....just not on the display

What works:
---------------
The vertical stages seem to work just fine, steps work fine there too...it seem
to have some "curves" visible in the vertical line. I've measured the Collector
voltage ...it works like it should, waveform looks like it should (a half sine on AC)

The stepper seems to step just fine too, the more steps added..the more dots
appear (above eachother...again in one vertical line).

Horiz + veritcal position of the CRT works just fine.

What doesn't seem to work:
-----------------------------------
Horizontal sweeping. There's only a vertical line (or dot) period.... no
sweeping at all.

The funny thing is...I don't know wether the sweep occurs in the actual
CRT circuits (such as the horizontal amplifier circuit) or the Step-Generator.
The schematics doesn't indicate anything there.

Maybe my knowledge simply doesn't stretch far enough to reconstruct
how the "horizontal sweep" actually function, so I can't guess where it is.

Any help would be appreciated.

Robert christi · 20th Aug 2006, 6:23 pm

I sent Richard a private post indicating my email address where the CT71 manual info can be sent.
JoOngle, my horizontal problem was solved by replacing one of the two TO18 npn transistors with a plastic NPN part. I think I used a PN2222A. I later used a pair of PN2222A's as the input diff amp stage. When checking dc bias on the input stage, it was not apparent that their was a problem in the input stage. Signal tracing, with a small ac signal applied to the diff stage, did indicate the problem. Thats why I tried replacing the input stage amp. If I knew the correct part number for the input stage transistors, I would find a matched pair of something closer to use in the input stage. I should use TO18 devices since their is a cover over the transistors which is probably used to maintain the junctions at closer temperatures and to keep temperature gradients in the CT71 case from generating dc drift in the output of the diff stage.

Dickie · 20th Aug 2006, 8:04 pm

Robert,

You should recieve the data shortly.

Is there anyone out there who would like to take my scans, turn them into PDFs, and make them generally available on their site? I hadn't realised how popular this info. would be! I have had four requests so far.

Richard

JoOngle · 20th Aug 2006, 11:39 pm

Quote:

Originally Posted by Robert christi

JoOngle, my horizontal problem was solved by replacing one of the two TO18 npn transistors with a plastic NPN part. I think I used a PN2222A. I later used a pair of PN2222A's as the input diff amp stage. When checking dc bias on the input stage, it was not apparent that their was a problem in the input stage. Signal tracing, with a small ac signal applied to the diff stage, did indicate the problem. Thats why I tried replacing the input stage amp. If I knew the correct part number for the input stage transistors, I would find a matched pair of something closer to use in the input stage. I should use TO18 devices since their is a cover over the transistors which is probably used to maintain the junctions at closer temperatures and to keep temperature gradients in the CT71 case from generating dc drift in the output of the diff stage.

Interesting,

The Transistors you refer to are two BC-109C in TO-18 housing.
They are the originals, and the schematic refer to them as well.

Unfortunately (for me) changing these didnt change a thing, I moved a
few of the BC 109C's the apparatus have (everywhere) and exchanged
them around...no difference, and they measure just fine when checking.

Very puzzling...

Duke_Nukem · 21st Aug 2006, 8:14 am

Quote:

Originally Posted by Richard

Is there anyone out there who would like to take my scans, turn them into PDFs, and make them generally available on their site? I hadn't realised how popular this info. would be! I have had four requests so far.

Thought you'd never ask

Yes please.

TTFN,
Jon

Dickie · 17th Jan 2007, 7:57 pm

Courtesy of Jon, you can now find this manual here
http://www.thevalvepage.com/servdata...q/telequip.htm

woodstock · 23rd Mar 2012, 9:07 pm

Can anyone help?

I have a friend who has one of these but alas not a mains lead.

We are trying to sort out what is needed but he lives at the other end of the country and we communicate via eMail.

Any help would be appreciated.
Thanks.

NigelB
M0FOG.

MotorBikeLes · 24th Dec 2012, 7:11 pm

Hi Woodstock,

I bought some of these leads (Euro version) 25 or more years ago from Tektronics at Marlow I think. I could not find other sources, and I don't expect they are still available. I have a few SOCKETS still, but not leads. What I used to do was to remove the socket, and fit an aluminium plate over the opening, suitably drilled, and passed a mains lead through it with a plastic restraint to keep it in place. Tektronix used a little blue plate on some of their 'scopes or calibration fixtures which I used a few times, also then obtainable from Marlow. They were ready for a suitable restraint for the mains lead.

Les.

26th May 2006, 12:26 am	#1
Robert christi Retired Dormant Member Join Date: May 2006 Location: San Diego CA USA Posts: 4	Telequipment CT71 Curve Tracer I have a CT71 Curve tracer with a Horiz Sweep problem. Does anyone have a schematic for this unit or experience with the same? Thanks, Bob C

26th May 2006, 10:18 am	#2
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: Telequipment CT71 Curve Tracer I think I may have a CT71 at home somewhere and I will look for any service info this weekend. I must admit I have never used it, and if I remember correctly there are a couple of "plug ins" on the front, presumeably for different component tests. Biggles

27th May 2006, 5:28 am	#3
Robert christi Retired Dormant Member Join Date: May 2006 Location: San Diego CA USA Posts: 4	Re: Telequipment CT71 Curve Tracer Hi Biggles, I would appreciate you looking for any available data on the CT71. Thanks, Bob C

30th May 2006, 10:29 am	#4
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: Telequipment CT71 Curve Tracer Sorry Bob, I've definitely got a CT71 but no manual. It is remotely possible that some of the circuits are similar to other Telequipment scopes of that era. If you need component identification etc I could have a look inside mine for you, although I can't be sure mine is working still, as it's not been switched on for a long time. Biggles.

30th May 2006, 10:47 am	#5
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: Telequipment CT71 Curve Tracer I've got a CT71 and the original manual. I bought it many years ago and have used about twice since then. Haven't got time to scan the whole thing at the moment but I'll scan the H amp schematic for you. If somebody wants to borrow the manual to scan I can give it to them at Gerry's on Saturday or Harpenden on Sunday. Have you asked in the Tektronix forum? Somebody may have already done the job. http://groups.yahoo.com/group/TekScopes/

2nd Jun 2006, 8:21 pm	#6
Robert christi Retired Dormant Member Join Date: May 2006 Location: San Diego CA USA Posts: 4	Re: Telequipment CT71 Curve Tracer Its good to know that a manual exists for the CT71. I looked all over but could not find a copy. I also checked the Tek site you indicated but did not see anything on the CT71. I opened up the curve tracer and saw all components were descrete and appeared to be those that were commonly used in designs in the early to mid 1960's. A scope indicated that the plus rail was approx 120vdc and the neg bias rail was -12vdc. Both probably OK. A schematic would be of great help in servicing the unit in that the problem appears to be ahead of the push pull deflection amplifier. If you could send the schematic that would be great or I could send a money order to cover postage to San Diego CA USA. Last edited by mikelect; 3rd Jun 2006 at 9:51 pm. Reason: remove e-mail address

9th Jun 2006, 4:50 pm	#7
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	We've got a CT71 at work and I've got these scans from the manual. Hope they are of some use. Richard Attached Thumbnails

11th Aug 2006, 4:12 pm	#8
JoOngle Retired Dormant Member Join Date: Aug 2006 Location: Odense, Denmark Posts: 7	Re: Telequipment CT71 Curve Tracer Hi There, I have a CurveTracer (CT71) with the same horizontal sweep problems (I think) as it only shows either the X or Y curve on either Single-trace or step-trace (diagonal curve) but no curve-traces... I suspect that someone before me have tried to repair it and used unoriginal components so I'm looking for information on the components. I've done extensive backtracing tests on the unit, but can't find any components to be defective - so I'm a bit in the dark here. Anyone got any tip, or input? Thanks, Tommy

13th Aug 2006, 2:33 am	#9
JoOngle Retired Dormant Member Join Date: Aug 2006 Location: Odense, Denmark Posts: 7	Re: Telequipment CT71 Curve Tracer I'd really appreciate a scan of the Service Manual for this device. I've fixed the step-generator, but the horizontal sweeper seems dead. Funny thing really...this thing ain't got many components so its fairly uncomplicated - but I still can't figure out how the horizontal sweep works.

17th Aug 2006, 6:27 pm	#10
JoOngle Retired Dormant Member Join Date: Aug 2006 Location: Odense, Denmark Posts: 7	Re: Telequipment CT71 Curve Tracer Many thanks Richard, very much appreciated. Now I stand a chance at servicing this thing and restoring it to it's former glory (I actually use these things to build stuff) It even contains complete print-layouts so it's possible to reproduce the actual prints themselves. The apparatus is so "non-complex" that it's fairly trivial to build it ground up. Cool stuff.

18th Aug 2006, 5:53 pm	#11
JoOngle Retired Dormant Member Join Date: Aug 2006 Location: Odense, Denmark Posts: 7	Re: Telequipment CT71 Curve Tracer Tricky stuff to fix, even with the schematics. It seem to be the horizontal "sweep" that is completely done for, the problem is I can't locate a single faulty transistor or diode whatsoever, they all seem to check out just fine. Even doing the fault finding tests indicate that all is well....just not on the display What works: --------------- The vertical stages seem to work just fine, steps work fine there too...it seem to have some "curves" visible in the vertical line. I've measured the Collector voltage ...it works like it should, waveform looks like it should (a half sine on AC) The stepper seems to step just fine too, the more steps added..the more dots appear (above eachother...again in one vertical line). Horiz + veritcal position of the CRT works just fine. What doesn't seem to work: ----------------------------------- Horizontal sweeping. There's only a vertical line (or dot) period.... no sweeping at all. The funny thing is...I don't know wether the sweep occurs in the actual CRT circuits (such as the horizontal amplifier circuit) or the Step-Generator. The schematics doesn't indicate anything there. Maybe my knowledge simply doesn't stretch far enough to reconstruct how the "horizontal sweep" actually function, so I can't guess where it is. Any help would be appreciated.

20th Aug 2006, 6:23 pm	#12
Robert christi Retired Dormant Member Join Date: May 2006 Location: San Diego CA USA Posts: 4	Re: Telequipment CT71 Curve Tracer I sent Richard a private post indicating my email address where the CT71 manual info can be sent. JoOngle, my horizontal problem was solved by replacing one of the two TO18 npn transistors with a plastic NPN part. I think I used a PN2222A. I later used a pair of PN2222A's as the input diff amp stage. When checking dc bias on the input stage, it was not apparent that their was a problem in the input stage. Signal tracing, with a small ac signal applied to the diff stage, did indicate the problem. Thats why I tried replacing the input stage amp. If I knew the correct part number for the input stage transistors, I would find a matched pair of something closer to use in the input stage. I should use TO18 devices since their is a cover over the transistors which is probably used to maintain the junctions at closer temperatures and to keep temperature gradients in the CT71 case from generating dc drift in the output of the diff stage.

20th Aug 2006, 8:04 pm	#13
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	Re: Telequipment CT71 Curve Tracer Robert, You should recieve the data shortly. Is there anyone out there who would like to take my scans, turn them into PDFs, and make them generally available on their site? I hadn't realised how popular this info. would be! I have had four requests so far. Richard __________________ Regards, Richard, BVWS member

17th Jan 2007, 7:57 pm	#16
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	Re: Telequipment CT71 Curve Tracer Courtesy of Jon, you can now find this manual here http://www.thevalvepage.com/servdata...q/telequip.htm __________________ Regards, Richard, BVWS member Last edited by Dickie; 17th Jan 2007 at 8:21 pm.

23rd Mar 2012, 9:07 pm	#17
woodstock Retired Dormant Member Join Date: Mar 2007 Location: Meir Park, Stoke-on-Trent Posts: 4	Re: Telequipment CT71 Curve Tracer Can anyone help? I have a friend who has one of these but alas not a mains lead. We are trying to sort out what is needed but he lives at the other end of the country and we communicate via eMail. Any help would be appreciated. Thanks. NigelB M0FOG.

24th Dec 2012, 7:11 pm	#18
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Telequipment CT71 Curve Tracer Hi Woodstock, I bought some of these leads (Euro version) 25 or more years ago from Tektronics at Marlow I think. I could not find other sources, and I don't expect they are still available. I have a few SOCKETS still, but not leads. What I used to do was to remove the socket, and fit an aluminium plate over the opening, suitably drilled, and passed a mains lead through it with a plastic restraint to keep it in place. Tektronix used a little blue plate on some of their 'scopes or calibration fixtures which I used a few times, also then obtainable from Marlow. They were ready for a suitable restraint for the mains lead. Les.