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 18th Jul 2020, 9:11 pm   #1
eddie_ce
Hexode
 
eddie_ce's Avatar
 
Join Date: Aug 2010
Location: nr. Hannover, Germany
Posts: 372
Default UY85 Heater voltage

Good evening all,
according to the data sheet the UY85 has a heater voltage of 38V @100mA. For a home brew project I have a transformer that supplies 35,6V off load and 34,5V when connected to the valve.

Is it bad practice to under-run the rectifier like this?
__________________
Eddie
BVWS Member.
Friend of the BVWTM
eddie_ce is offline  
Old 18th Jul 2020, 9:33 pm   #2
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
Default Re: UY85 Heater voltage

Heater voltages are generally best kept within 5% of nominal. This is low by slightly more. But unless you are pulling near the maximum current, I'd say don't worry.

For maximum life, slightly under is better than slightly over.
kalee20 is offline  
Old 18th Jul 2020, 10:12 pm   #3
broadgage
Nonode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
Default Re: UY85 Heater voltage

What was the mains voltage at the time of the test ?
If on the low side, then that should be fine since any subsequent variation should be upwards and therefore towards running the heater at nominal voltage, or closer thereto.
If however the mains voltage was on the high side, then that is of greater concern since future fluctuations are likely to be downwards, and thus running the heater further below the design voltage.
broadgage is offline  
Old 19th Jul 2020, 9:31 am   #4
eddie_ce
Hexode
 
eddie_ce's Avatar
 
Join Date: Aug 2010
Location: nr. Hannover, Germany
Posts: 372
Default Re: UY85 Heater voltage

Guys, thanks for your replies. I fed the Transformer from a variac at the nominal 230V. There will not be a great deal of demand on the rectifier, so I think I'll go ahead with the idea. The mains voltage around here is quite stable and normally hovers around 234-236V which I suppose is good.
__________________
Eddie
BVWS Member.
Friend of the BVWTM

Last edited by eddie_ce; 19th Jul 2020 at 9:33 am. Reason: additional information
eddie_ce is offline  
Old 19th Jul 2020, 10:05 am   #5
snowman_al
Octode
 
snowman_al's Avatar
 
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
Default Re: UY85 Heater voltage

It will be fine. These are designed for series operation normally, so in real use would see different voltages for the spec depending on the mains voltage, other valves in the chain and so on. Slightly lower is better as kalee says...
__________________
Never Leave Well Enough Alone...
snowman_al is offline  
Old 24th Jul 2020, 1:39 am   #6
Maarten
Dekatron
 
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,185
Default Re: UY85 Heater voltage

Quote:
Originally Posted by eddie_ce View Post
Good evening all,
according to the data sheet the UY85 has a heater voltage of 38V @100mA. For a home brew project I have a transformer that supplies 35,6V off load and 34,5V when connected to the valve.

Is it bad practice to under-run the rectifier like this?
Since the heater voltage is not the tightly controlled parameter in 100mA valves, you should check the current in the actual circuit. If it's within 5% the valve will be perfectly fine. Even if the voltage is 10% out from nominal, the current might still be within tolerance depending on production tolerances of the valve.
Maarten is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 11:19 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 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.