Featured
Latest
Forums
Electronics
In The Workshop
Test Equipment
Simple LOPT ringer
 
Share:
Notifications
Clear all

Forum 141

[Sticky] Simple LOPT ringer

 
Test Equipment
Last Post by Boingy 6 years ago
1 Posts
1 Users
1 Likes
851 Views
Boingy
 Boingy
(@boingy)
Posts: 136
Estimable Member Registered
Topic starter
 

Hello all,
Whilst in the process of repairing my little GEC TV, it was suggested that I check the LOPT to make sure it was OK. As usual, I prefer to build these things, than buy them, so I set about designing a LOPT ringer.
Seeing as there were a few 555 timer ICs in the parts box, I chose to utilise one of these.
My design has a diode protected (and limited) output. After some experimentation, I settled on 100us pulses spaced at 50ms intervals. Anything more than a pulse of about 150us and the LOPT would react to the initial rise of the pulse and create a fair old bit of hash on the waveforms.
The old Veroboard came in handy again, so I won't bore you with the details of that!
So, below is the circuit diagram for the LOPT ringer of Boing!

Schematic LOPT ringer of Boing Sheet 1 20180903224329

Here's the waveform of the initiator pulse, 50us and 200mv per division.

Ringer 100us pulse

Here's the pulse train, 10ms and 200mv per division.

Ringer 50ms pulse

Lastly, here's a waveform of a known good LOPT (it's the one on my little T-9 portable). [Edit: 50us and 200mv per division]

T9 LOPT

If anyone finds this useful, then all the better 🙂
As usual, if you have any comments or questions, please don't hesitate.

All the best,
Tony

 

Standards are like toothbrushes. Everybody needs them, but nobody want to use yours!

 
Posted : 03/09/2018 10:38 pm
6.3volts reacted
Forum Jump:
  Previous Topic
Next Topic  
Share:

You may have missed

Forum Free Registration Closed 148

Forum Free Registration Closed

crustytv April 15, 2024 94
Granada Television Brochure, 1970s 150

Granada Television Brochure, 1970s

crustytv March 19, 2024 233
Long Gone UK TV Shops 152

Long Gone UK TV Shops

crustytv January 16, 2024 1124
Memories of a Derwent Field Service Engineer 154

Memories of a Derwent Field Service Engineer

crustytv December 28, 2023 929
PYE Australia Circa 1971 156

PYE Australia Circa 1971

crustytv November 11, 2023 689
Radios-TV VRAT 158

Radios-TV VRAT

crustytv November 7, 2023 742
Fabulous Fablon 160

Fabulous Fablon

crustytv October 14, 2023 520

Thorn TX10 Chassis

crustytv August 27, 2023 800
Crusty-TV Museum, Analogue TV Network 162

Crusty-TV Museum, Analogue TV Network

crustytv August 22, 2023 1211
Philips N1500 Warning! 164

Philips N1500 Warning!

crustytv July 23, 2023 1560