Attempting the repair of Telequipment D75 - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

pixeltwisted · 26th Jul 2020, 9:19 pm

Hello again Les stumbled across a post you took part in back in 2012:

https://www.vintage-radio.net/forum/...d.php?p=582394

There you suggest a number of alternatives including the BFW10/11's you mentioned earlier.

Another user posted to the thread in 2013 with the infomation that Tek 151-1036 part is a
dual 2N4393. These are readily available and pretty cheap.

Only question is do they need to be plastic encapsulated so they can be tightly connected
for thermal conductivity? or can I get away with metal can for testing?

Gavin

pixeltwisted · 27th Jul 2020, 9:24 pm

Swapped TR601 and TR603 today and the problem swapped aswell. Looks like replacing
them is inevitable.

Just in case it helps someone else in the future below is a link to a PDF with information
about the Tektronix (Telequipment) dual n-channel JFET 151-1036-00. It gives invaluable
information about the 2N4393's hiding inside.

Regards G.

https://w140.com/tekwiki/wiki/151-1036-00

pixeltwisted · 18th Aug 2020, 5:19 pm

Hello everyone hope you are safe and well.

Just wanted to update this thread with some major success.
I now have a fully functional D75 scope, rock solid excellent bright and
crisp traces. (images attached)

After my short circuit of -24 and 30v rails I needed to replace multiple
transistors which took a while to arrive install and test.

Also I replaced the bulged C202 electrolytic in the S2A plugin, insulated the
power lamp holder and tested with no magic smoke.

Due to my poor troubleshooting previously I was sure that the Dual JFET's
in the V4 plugin were damaged during the short circuit so I tried using
two 2N4393's to replace the two packages.

I could get a trace when I pressed Trace Locate but otherwise all other
signals I applied produced nothing. Until I tried the 300mV calibration signal
only the bottoms of the square wave showed on the CRT?

I reinstated the Dual JFET's and luckily they work perfectly!

So maybe the JFET's installed in my scope are not 151-1036-00 as indicated
by the manual. Would have been better off trying BFW10/11 JFET's suggested
by Les in an earlier post as the 2N4393's do not work as replacements.

Anyway cannot thank everyone enough for their advice and help.

Kindest Regards,

Gavin

Pinörkel · 18th Aug 2020, 8:41 pm

Congratulations on your repair.

Optically, your D75 seems to be in very nice condition. No scratches and no missing labels on the front panels and all plastics, the grey knobs and the transparent one must have seen only minimal amount of sunlight and fingertouches in the past.

pixeltwisted · 18th Aug 2020, 9:41 pm

Thankyou Pinörkel for all of your help and your work on the Manual.

Can confirm that everything looks pratically unused considering the units age.
The blue case is a different matter though but with some cleaning it will
hopefully look OK. I have not done any cleaning so far so the front panel and
knobs are all as purchased.

Have been very lucky.... which is a new experience for me.

Anyway good luck with restuffing the capacitors I sent to you.

Regards

G.

26th Jul 2020, 9:19 pm	#41
pixeltwisted Triode Join Date: Jul 2020 Location: Redhill, Surrey, UK. Posts: 28	Re: Attempting the repair of Telequipment D75 Hello again Les stumbled across a post you took part in back in 2012: https://www.vintage-radio.net/forum/...d.php?p=582394 There you suggest a number of alternatives including the BFW10/11's you mentioned earlier. Another user posted to the thread in 2013 with the infomation that Tek 151-1036 part is a dual 2N4393. These are readily available and pretty cheap. Only question is do they need to be plastic encapsulated so they can be tightly connected for thermal conductivity? or can I get away with metal can for testing? Gavin

27th Jul 2020, 9:24 pm	#42
pixeltwisted Triode Join Date: Jul 2020 Location: Redhill, Surrey, UK. Posts: 28	Re: Attempting the repair of Telequipment D75 Swapped TR601 and TR603 today and the problem swapped aswell. Looks like replacing them is inevitable. Just in case it helps someone else in the future below is a link to a PDF with information about the Tektronix (Telequipment) dual n-channel JFET 151-1036-00. It gives invaluable information about the 2N4393's hiding inside. Regards G. https://w140.com/tekwiki/wiki/151-1036-00 Last edited by pixeltwisted; 27th Jul 2020 at 9:34 pm.

18th Aug 2020, 5:19 pm	#43
pixeltwisted Triode Join Date: Jul 2020 Location: Redhill, Surrey, UK. Posts: 28	Re: Attempting the repair of Telequipment D75 Hello everyone hope you are safe and well. Just wanted to update this thread with some major success. I now have a fully functional D75 scope, rock solid excellent bright and crisp traces. (images attached) After my short circuit of -24 and 30v rails I needed to replace multiple transistors which took a while to arrive install and test. Also I replaced the bulged C202 electrolytic in the S2A plugin, insulated the power lamp holder and tested with no magic smoke. Due to my poor troubleshooting previously I was sure that the Dual JFET's in the V4 plugin were damaged during the short circuit so I tried using two 2N4393's to replace the two packages. I could get a trace when I pressed Trace Locate but otherwise all other signals I applied produced nothing. Until I tried the 300mV calibration signal only the bottoms of the square wave showed on the CRT? I reinstated the Dual JFET's and luckily they work perfectly! So maybe the JFET's installed in my scope are not 151-1036-00 as indicated by the manual. Would have been better off trying BFW10/11 JFET's suggested by Les in an earlier post as the 2N4393's do not work as replacements. Anyway cannot thank everyone enough for their advice and help. Kindest Regards, Gavin Attached Thumbnails

18th Aug 2020, 8:41 pm	#44
Pinörkel Pentode Join Date: Jun 2019 Location: Dortmund, Germany Posts: 161	Re: Attempting the repair of Telequipment D75 Congratulations on your repair. Optically, your D75 seems to be in very nice condition. No scratches and no missing labels on the front panels and all plastics, the grey knobs and the transparent one must have seen only minimal amount of sunlight and fingertouches in the past.

18th Aug 2020, 9:41 pm	#45
pixeltwisted Triode Join Date: Jul 2020 Location: Redhill, Surrey, UK. Posts: 28	Re: Attempting the repair of Telequipment D75 Thankyou Pinörkel for all of your help and your work on the Manual. Can confirm that everything looks pratically unused considering the units age. The blue case is a different matter though but with some cleaning it will hopefully look OK. I have not done any cleaning so far so the front panel and knobs are all as purchased. Have been very lucky.... which is a new experience for me. Anyway good luck with restuffing the capacitors I sent to you. Regards G.