UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Reply
 
Thread Tools
Old 17th Sep 2019, 9:04 pm   #81
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 111
Default Re: Telequipment D75 scope.

Quote:
Originally Posted by MrBungle View Post
Unfortunately this one is beyond repair. The capacitors leaked in it. The seller did a respectable job of replacing them but the capacitor juice had wicked its way up the transformer leads and the have disintegrated.
That is sad to hear. I did not know electrolytic fluid could dissolve thick copper wires by creeping up the cable. That is more a thing of leaking batteries, according to my experience. And you cannot simply shorten the damaged parts of the leads and use new wires to connect them to the intended places?
Quote:
Originally Posted by MrBungle View Post
Thus if anyone needs any parts, let me know. All parts FOC - just postage cost.
If that D75 is really beyond repair I could make good use of quite some parts, when I finally get to repair my D755. That unit has, among other issues, broken stands at the back, a very damaged V4 front plate, a missing power cord and a messed up power connector plate, a scratched screen acrylic plate and a lot of potentiometers in horrible condition. Not speaking of the issues I have not yet discovered. If you are OK with it, I could put together a list of parts (only those which can be extracted without producing too much work on your side) once I finished repairing my D75.

Speaking of scratches on the screen acrylic plate: Does anyone know a secure and high quality method of removing scratches from these plates. Selectively sanding and polishing scratches often leaves ugly bumps on the surface that cause diffractive distortions. Scratches on the other side are non-transparent and additionally cast nasty shadows on the screen. I am reluctant to sand down and polish the entire plate surface because I could not achieve satisfactory results on a piece of acrylic glass that I experimented with.
Pinörkel is offline   Reply With Quote
Old 18th Sep 2019, 7:22 pm   #82
MotorBikeLes
Octode
 
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 1,661
Default Re: Telequipment D75 scope.

The mains lead has been "unobtanium" for 30 years. however, back then I had a few leads which were"wet and green". The HCl out of the PVC coating had been busy dissolving up the copper cores, and as well as looking green, it really did feel wet. Any cable you do get wants checking as it could be one of those early types. The last mains leads i got from TQ/Tek were only available with EU ends on them, and then they were no more.
What I would do was to remove the socket, cut a suitable piece of tufnol, drill it to take a restraint, and terminate that in the same way the socket was terminated.
Les.
MotorBikeLes is offline   Reply With Quote
Old 18th Sep 2019, 10:23 pm   #83
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 111
Default Re: Telequipment D75 scope.

I have a perfect quality EU (Schuko-Stecker) TQ mains plug for my D75. However, on my defective D755 this cable was missing and the former owner unfortunately drilled a hole in the back plate, put a through hole cable mount in it and then soldered the cable to the connector from the inside. A replacement plug should not be too difficult to make, since it consists only of an injection molded rubber substance around a piece of PCB. I already made a 3D-model of the plug for 3D printing, but I am still experimenting with the best way to integrate the PCB and the required contacts. On the original plug, the contacts are pressed against each other via the tension generated by the rubber material when compressed slightly on insertion of the plug. One way to produce a suitable plug could be to 3D-print the plug in multiple parts which can be put together around a suitable piece of custom cut PCB. Though I am not sure if PLA or ABS is a suitable printing material for insulating against 240V AC. Another way could be to print an injection mold form for the plug in which the cable and the custom PCB must be inserted before filling the form with liquid rubber or silicone. Of course, an original power cable would be much nicer to have.
Pinörkel is offline   Reply With Quote
Old 18th Sep 2019, 11:04 pm   #84
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,638
Default Re: Telequipment D75 scope.

Sorry didn’t get to reply to this before. A friend has taken the D75 off my hands to fix the D83 chassis i gave him so parts are off the menu. However he left the mains cable behind and wasn’t interested in that as the D83 he has is lucky enough an IEC socket. It’s in good condition so if anyone wants it let me know. I will cut the UK plug off it as it is quite frankly knackered however so cable and scope end of the mains lead.

I am super busy at moment so might be a couple of days for a reply.
MrBungle is offline   Reply With Quote
Old 19th Sep 2019, 6:03 am   #85
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 5,735
Default Re: Telequipment D75 scope.

"Of course, an original power cable would be much nicer to have. " Like this one? See attached. It's chipped on one side but works ok.

Andy.
Attached Thumbnails
Click image for larger version

Name:	Screenshot from 2019-09-19 06-59-27.jpg
Views:	87
Size:	36.4 KB
ID:	190473  
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Old 19th Sep 2019, 8:44 am   #86
ajgriff
Octode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 1,617
Default Re: Telequipment D75 scope.

That looks like a two pin connector from a Bush TV/Radio Andy. The Telequipment plug is quite different.

Alan
ajgriff is online now   Reply With Quote
Old 19th Sep 2019, 11:34 am   #87
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 5,735
Default Re: Telequipment D75 scope.

I'm pretty sure it's off one of the older TQ scopes I had Alan, though i thought from the description above it might not be the one the OP was after. That said it has no earth pin, so perhaps I'm mistaken.

Andy
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Old 19th Sep 2019, 6:44 pm   #88
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 111
Default Re: Telequipment D75 scope.

Quote:
Originally Posted by Diabolical Artificer View Post
"Of course, an original power cable would be much nicer to have. " Like this one? See attached. It's chipped on one side but works ok.
No, that is another design. The power plug of the D75 looks like in the attached image. The two gate like notches on the left and right side are for securing the plug in the connector by two screws.
Attached Thumbnails
Click image for larger version

Name:	20190919_203137.jpg
Views:	75
Size:	69.1 KB
ID:	190511  

Last edited by Pinörkel; 19th Sep 2019 at 6:57 pm.
Pinörkel is offline   Reply With Quote
Old 20th Sep 2019, 3:31 pm   #89
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 5,735
Default Re: Telequipment D75 scope.

Aha! Found this today, if any good drop us a PM.

Andy.
Attached Thumbnails
Click image for larger version

Name:	DSC01718.JPG
Views:	67
Size:	161.9 KB
ID:	190552   Click image for larger version

Name:	DSC01717.JPG
Views:	74
Size:	162.9 KB
ID:	190553  
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Old 20th Sep 2019, 4:41 pm   #90
ajgriff
Octode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 1,617
Default Re: Telequipment D75 scope.

That's the one Andy!

Alan
ajgriff is online now   Reply With Quote
Old 20th Sep 2019, 9:15 pm   #91
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 111
Default Re: Telequipment D75 scope.

I just did a little 3D printed design study regarding the TQ plug. For that, I modeled the plug geometry as two parts that can slide over each other. The part with the contacts contains a cavity for a printed circuit board with metal plug contacts which lead into the three sockets. Maybe I will try to do the contacts using flat plug sleeves or something similar. However, there is not much space in there. Once the cables are soldered or crimped to the metal contacts, the top part can simply slide over the lower part and makes a very firm connection via friction. The current part is, however, only a prototype not suitable for 240V, since it is made from PLA. The final part could be made from polypropylene filament.

@Diabolical Artificer:
Interesting, I did not know these were also produced with cross shaped holes.
Attached Thumbnails
Click image for larger version

Name:	20190920_225728.jpg
Views:	55
Size:	124.6 KB
ID:	190559  
Pinörkel is offline   Reply With Quote
Old 21st Sep 2019, 7:10 am   #92
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 5,735
Default Re: Telequipment D75 scope.

Nice work there, they look well.

Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Old 28th Sep 2019, 7:08 pm   #93
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 111
Default Re: Telequipment D75 scope.

I just did some frequency dependent testing on both channels of the D75. The horizontal calibration so far matched nicely with the square and sine waves from my directly connected function generator. However, I observed something strange regarding the amplitudes, I have no explanation for. I applied a 5 Vpp sine wave and varied the frequency over the full range of my function generator from 0 Hz to 30 MHz. From 0 Hz to approximately 1 Mhz the amplitude on both channels was spot on at 5 divisions. From then on, on channel 1, the amplitude lowered to 4 divisions at 30 MHz. This is something I kind of expected, because of the bandwidth limit of the scope. The manual says, that a 5 division display at 50 kHz should lower to no less than 4.2 divisions at 50 MHz. From that, I conclude that my channel 1 performs not optimal with respect to bandwidth. Now, on channel 2, the amplitude did something that I did not expect. From 1 MHz to approximately 25 MHz, the amplitude increased from 5 to 5.8 divisions and then lowered to 5.6 divisions at 30 MHz.

Since the issue affected the amplitude, I suspected the attenuator being involved. So I probed the issue depending on the attenuator setting and found out that it did not directly depend on the input voltage but on the Volts/Div setting. It only occurred on channel 2 for Volts/Div settings of 0.5, 1, and 2, being the strongest at the 0.5 setting. An issue linked in this way seems logical, since the Volts/Div rotary switch activates linked circuitry for each triplet of .5, 1 and 2. So, to me it seems likely that the issue is located in the attenuator, which is bad, since screwing around with the attenuator could affect a lot of things I can not recalibrate at the moment. The ringing may hint at some uncompensated inductance. So maybe an off-valued resistor?

Coincidentally I also noticed that a square wave had a significant rising edge overshoot including some ringing specifically for these three settings (see attached two images of channel 1 and 2). This can not be compensated with attenuator calibration via C906. I am not sure if these two issues are connected and how to further track them down without making things worse. Maybe there is something that oscillates with a resonance frequency of around 25 MHz, which also gets activated by signal edges with a rise/fall time near that frequency? Has anybody a good idea how to narrow these issues down?
Attached Thumbnails
Click image for larger version

Name:	_MG_0872_ch1.jpg
Views:	34
Size:	61.5 KB
ID:	190998   Click image for larger version

Name:	_MG_0872_ch2.jpg
Views:	37
Size:	72.1 KB
ID:	190999  

Last edited by Pinörkel; 28th Sep 2019 at 7:15 pm.
Pinörkel is offline   Reply With Quote
Old 28th Sep 2019, 10:33 pm   #94
MotorBikeLes
Octode
 
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 1,661
Default Re: Telequipment D75 scope.

For frequency bandwidth checking, you need a constant output signal generator, normally with a 50 ohm input connection (which is what the constant amp sig gens are usually designed around).
The only way to draw sensible conclusions is after you set up the main amp (with the calibration unit), then set the individual plug ins according to the manual. It is quite explicit, but fairly time consuming. If there are any problems with the rotary switches (dirty), you can get all sorts of silly things happening.
Whenever I sold one of these, I always did a full calibration check. Not financially rewarding these days, but 35 years ago, worthwhile.
Les.
MotorBikeLes is offline   Reply With Quote
Old 21st Dec 2019, 10:05 pm   #95
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 111
Default Re: Telequipment D75 scope.

My ebay monitoring was partially successful. I shot a set of TQ calibration units, namely the 067-0672-00 and the 067-0673-00, unfortunately without side covers. Haven't had time to check if they are okay, but for about 10 bucks there is no reason to complain, even if not.

To improve available documentation on the D75 and the calibration units, I made some high resolution photos of my D75, my D755 OPT 66, the contained V4 and S2A and S2C units, and the calibration fixtures. For each, I included shots of all interesting sides with and without cover to show all detail on the circuit boards. In addition to that, I extended the textual information in the Tekwiki for all units. All images can be accessed via the Tekwiki page of the D75 http://w140.com/tekwiki/wiki/Telequipment_D75. Since it does not contain any potentiometers, the 067-0673-00 unit should be easy to reverse engineer. I will provide the serial numbers of the transistors later.
Pinörkel is offline   Reply With Quote
Old 22nd Dec 2019, 10:02 pm   #96
MotorBikeLes
Octode
 
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 1,661
Default Re: Telequipment D75 scope.

Interesting coincidence! I just read this posting. Yesterday afternoon I finally completed the circuit for the vertical cal unit (I did the H one a while ago) and sent a message to Mark who you may recall said he would compare with his. I posted the circuits to him maybe one hour ago. If he agrees with my circuit, they can be posted here (or maybe a separate thread) when I hope one of the TEK/TQ engineers from 40 years ago, or some other sage, will comment on how to calibrate a calibration unit. Only needed for the Vertical unit I think.
I looked at the Tek wiki, but no manuals listed there.
Les.
MotorBikeLes is offline   Reply With Quote
Old 22nd Dec 2019, 10:10 pm   #97
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 3,907
Default Re: Telequipment D75 scope.

Quote:
Originally Posted by Pinörkel View Post
unfortunately without side covers.
I don't believe they came with covers. Certainly, mine do not have them.

Congratulations on winning a bargain. That's an excellent price, given the rarity.

Your pictures on the Tekwiki are excellent. I'm comparing your vertical unit to my one, as it is right in front of me now, and they look very similar indeed. I suspect that R1015 might be a replacement, given that it's a different type to R1012. Otherwise, all looks good to me.

I still think it will be difficult to figure out how to calibrate these. Given the warning in red text on the front panel, I suspect that Telequipment never published information about this.
mhennessy is offline   Reply With Quote
Old 23rd Dec 2019, 2:26 am   #98
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 111
Default Re: Telequipment D75 scope.

Quote:
Originally Posted by MotorBikeLes View Post
Interesting coincidence! I just read this posting. Yesterday afternoon I finally completed the circuit for the vertical cal unit (I did the H one a while ago) and sent a message to Mark who you may recall said he would compare with his. I posted the circuits to him maybe one hour ago. If he agrees with my circuit, they can be posted here (or maybe a separate thread) when I hope one of the TEK/TQ engineers from 40 years ago, or some other sage, will comment on how to calibrate a calibration unit. Only needed for the Vertical unit I think.
I looked at the Tek wiki, but no manuals listed there.
Ah, I just started making notes and searching a good circuit diagram software. Looks like I can skip that. I also never found a manual for the units, which is why I stuffed the Tekwiki with good quality images of the units.
Quote:
Originally Posted by mhennessy View Post
I don't believe they came with covers. Certainly, mine do not have them.
That may be true. My assumption of them having covers was based on an image on the Tekwiki that shows a 067-0673-00 with covers.
Quote:
Your pictures on the Tekwiki are excellent. I'm comparing your vertical unit to my one, as it is right in front of me now, and they look very similar indeed. I suspect that R1015 might be a replacement, given that it's a different type to R1012. Otherwise, all looks good to me.
Thanks for the compliment. I tried to make the images as good as possible. Yes, R1015 might be a replacement one. However, to me, TQ seems to have had a habit to not always use the same components, but the stuff the currently had a supply of. You can see this when you compare my images of circuit boards of the S2A and S2C plugins (http://w140.com/tekwiki/wiki/Telequipment_S2).
Quote:
I still think it will be difficult to figure out how to calibrate these. Given the warning in red text on the front panel, I suspect that Telequipment never published information about this.
Regarding the calibration: maybe we can find a way to measure and compare the output signals of our units to get clues on how to calibrate them.
Pinörkel is offline   Reply With Quote
Old 23rd Dec 2019, 10:41 am   #99
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,638
Default Re: Telequipment D75 scope.

My calibration fixture had covers.

Honesty after that last D75 I never want to see another vintage scope
MrBungle is offline   Reply With Quote
Old 23rd Dec 2019, 10:55 am   #100
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 111
Default Re: Telequipment D75 scope.

Quote:
Originally Posted by MrBungle View Post
My calibration fixture had covers.
Maybe covers were optimized away over time to save money.
Quote:
Honesty after that last D75 I never want to see another vintage scope
Aww, too bad. I still love stuff that challenges me to triumph over the insidiousness of the object.
Pinörkel is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 2:04 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.