Bringing up old valve radios slowly?
 

gareth wrote:

Thanks to both, but it seems that it might be acadaemic for the moment,
because initial safety checks before applying any power suggest that the
transformer primary is O/C.

This usually happens when people power up stuff with shorted supply caps
or shorted rectifier tubes.

My inclination is to do this:

1. Replace all Black Beauty caps

2. Look for all capacitors which, if they fail, will take out something
impossible to replace (ie. paper interstage coupling caps) and replace
them all pre-emptively.

3. Bring the thing up on a variac with an eye on current. If you don't have
a variac, use a series lamp string.

4. After a few hours of operation, check ESR on all remaining electrolytics
and replace them if they are not good (and in the case of cathode bypass
caps they are seldom any good and should be replaced with a low voltage
mylar so they never fail again).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Bringing up old valve radios slowly?
 

On 30/04/2014 17:06, gareth wrote:
Having now borrowed my friend's Variac, what is seen as
good practice for ramping up old valve radios to reform the
capacitors?

Start off at, say, 50VAC and then increase by 50VAC every
1/2 hour until 240V is reached?


If the caps are dry it's unlikely you'll reach that.


--
J