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 > General Vintage Technology > Components and Circuits

Notices

Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

Closed Thread
 
Thread Tools
Old 31st Jan 2016, 7:03 pm   #1
Tyso_Bl
Hexode
 
Tyso_Bl's Avatar
 
Join Date: Jul 2014
Location: Magor, Monmouthshire, Wales, UK.
Posts: 436
Default Burst Selenium rectifier substitute

Trying to work out what to replace this with, its a multi disc selenium jobbie, lookis like the encapsulation dissolved or otherwise failed from the spring tension.
Its a type FSY7093A , 120V rating. I can't find out anymore about its properties, such as its forward voltage drop, reverse leakage, forward resistance, etc.

Any thoughts? I'm going to do the obvious and try a silicon part, see what happens...
Attached Thumbnails
Click image for larger version

Name:	20160116_232153.jpg
Views:	210
Size:	80.0 KB
ID:	119319  
__________________
Adapt, Improvise, Oh Bother.....
Tyso_Bl is offline  
Old 31st Jan 2016, 7:29 pm   #2
evingar
Octode
 
evingar's Avatar
 
Join Date: Oct 2003
Location: Newbury, Berkshire, UK.
Posts: 1,770
Default Re: Burst Selenium rectifier substitute

If you are using silicon, stick a limiting resistor in series with it. Difficult to know what value to suggest without data for the selenium part - When I "Googled", the only reference I got was your post

Anyway, best to start with a high value and monitor the voltage rail it supplies- reduce the value of the resistor to suit.
__________________
Chris
evingar is offline  
Old 31st Jan 2016, 7:38 pm   #3
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: Burst Selenium rectifier substitute

1N4007 and a 200 ohm resistor is the usual rule of thumb advice. If you use two diodes in series you reduce the voltage stress and will survive one failing short circuit. The resistor value isn't critical.
paulsherwin is offline  
Old 4th Feb 2016, 10:22 pm   #4
Tyso_Bl
Hexode
 
Tyso_Bl's Avatar
 
Join Date: Jul 2014
Location: Magor, Monmouthshire, Wales, UK.
Posts: 436
Default Re: Burst Selenium rectifier substitute

Thanks for the suggestions, I've studied the circuitry round this rectifier, and it purpose seems to be to prevent priming current leakage from the trigger of a cold cathode valve (fed via a 200 Meg resistor), in to a voltage divider network on the other side, while still allowing the voltage divider to influence the trigger voltage. The current is in the microamp region, any back leakage would totally negate the purpose of the rectifier / diode.

Slightly aside I've measured the capacitors in the unit as being leaky too, showing 15Meg for the worst ones. 0.1uF 350V.

On the verge of putting it away for another day.
__________________
Adapt, Improvise, Oh Bother.....
Tyso_Bl is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 8:12 am.


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 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.