Substituting a 5 amp fuse for a 3.5 amp fuse just for tests?

[SwizzyMan]

Hello all!

I recently blew a power supply fuse in my ctc-7 and was wondering if I could just temporarily use a 5 amp fuse instead of a 3.5 amp (which are difficult to come by) fuse just so I can determine whether my problem is just a fuse or something bigger?

[zeno]

Depending on what it fuses...........
Hook up a 75 watt bulb in series with the 5 A fuse.
If the bulb burns bright you probably got a short.
If dim its probably OK. The lamp will limit current so
you wont do damage. You can also hang a breaker in
that breaks at apx 3.5 amps.

There are a ton of good way depending on what you have etc.

73 Zeno

[SwizzyMan]

Originally Posted by zeno

Depending on what it fuses...........
Hook up a 75 watt bulb in series with the 5 A fuse.
If the bulb burns bright you probably got a short.
If dim its probably OK. The lamp will limit current so
you wont do damage. You can also hang a breaker in
that breaks at apx 3.5 amps.

There are a ton of good way depending on what you have etc.

73 Zeno

It is a power supply fuse controlling I think the flyback

[SwizzyMan]

Originally Posted by zeno

Depending on what it fuses...........
Hook up a 75 watt bulb in series with the 5 A fuse.
If the bulb burns bright you probably got a short.
If dim its probably OK. The lamp will limit current so
you wont do damage. You can also hang a breaker in
that breaks at apx 3.5 amps.

There are a ton of good way depending on what you have etc.

73 Zeno

How exactly would I hook up the bulb with the fuse?

[zeno]

Actually you can skip the fuse. Just put a set of alligator
clips on an old lamp.
BUT there may be as much as 400 V on the fuse so
skip the lamp idea.
If you use the 5A watch the hoz out for red plating & be
ready to pull the plug fast. In any case if it dont come up
do not run it very long !

73 Zeno

[wa2ise]

Originally Posted by SwizzyMan

It is a power supply fuse controlling I think the flyback

The dim bulb test is only valid for the input powerline.

If you use the 5A watch the hoz out for red plating & be
ready to pull the plug fast. In any case if it dont come up
do not run it very long !

Probably a better approach. Of course getting the proper fuse would be better, but the above would work for a brief test.

[centralradio]

More likely the bulb hook to the 400v circuit end up turning the bulb into a camera flash bulb.

Would it.

I'll try it on the line.

[zeno]

Well it is the 4th of July !
If it has a dead short yes. Otherwise it will glow brighter as
the set warms. At that point it depends on how much current
that line draws as to how bright it gets.

I was stuck on solid state on this one. Since they almost all run on
+- 130 V for the hoz stages the bulb will work for both power
supply & hoz problems.

73 Zeno

Originally Posted by centralradio

More likely the bulb hook to the 400v circuit end up turning the bulb into a camera flash bulb.

Would it.

I'll try it on the line.

[dieseljeep]

Originally Posted by zeno

Well it is the 4th of July !
If it has a dead short yes. Otherwise it will glow brighter as
the set warms. At that point it depends on how much current
that line draws as to how bright it gets.

I was stuck on solid state on this one. Since they almost all run on
+- 130 V for the hoz stages the bulb will work for both power
supply & hoz problems.

73 Zeno

For tube sets, I use a circuit breaker with clip leads soldered on. A hold value, close to the fuse rating.
I would never use a circuit breaker on one of the newer solid states. They depend on the fast-acting fuses to protect the semiconductors.