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465M goes dead and then magically comes back to life.

 

My 465M went dead. It started with the power LED flashing. Then it went dead. I went to a fuse inside in the power supply that was 1/4 amp. It had 56 volts on one side and zero on the other. I pulled this fuse out and ohmed it. It measured good. I ohmed the fused circuit to ground. It measured 2.5K ohms. I reinserted it in the circuit. The scope started working again. I did change the fuse anyway and now I cannot get it to fail. Can a fuse be intermittent? My experience is that a blown fuse is just that, blown forever. I am suspicious there is some other problem lurking in that scope. I have a digital Hantek scope, but I just love using this 465M for troubleshooting anyway. It is an old friend. I don't know if they still sell analogue scopes anywhere. I am guessing not. I love the real time high resolution display.
Michael
 

I had something similar on a piece of audio equipment --- the
intermittent nature had me baffled for ages.
I should add that each time it failed I checked the fuse and put it back.
Then one day it failed and one of my kids just bashed it and it came on
again!
Turned out that one end of the fuse wire wasn't connected properly to
the end cap!
Caused a lot of bad language at the time but funny now.

I've also had fuse holders go "iffy" - in one case it was corrosion.

Regards, Dave

On 03/10/2018 20:45, ironcoder@... wrote:
My 465M went dead. It started with the power LED flashing. Then it went dead. I went to a fuse inside in the power supply that was 1/4 amp. It had 56 volts on one side and zero on the other. I pulled this fuse out and ohmed it. It measured good. I ohmed the fused circuit to ground. It measured 2.5K ohms. I reinserted it in the circuit. The scope started working again. I did change the fuse anyway and now I cannot get it to fail. Can a fuse be intermittent? My experience is that a blown fuse is just that, blown forever. I am suspicious there is some other problem lurking in that scope. I have a digital Hantek scope, but I just love using this 465M for troubleshooting anyway. It is an old friend. I don't know if they still sell analogue scopes anywhere. I am guessing not. I love the real time high resolution display.
Michael



.
 

Yes Dave, I have had fuse holders go iffy on me before. Sometimes replacing a fuse holder turns into a big project. This fuse holder on the 465M interface board feels very tight when I snap in a new fuse. I will just have to wait and see how things go with this.

Michael
 

Ditto on the fuse holder possibly being the problem. Have previously had an issue with fuses making good contact with a holder, or the cap with the socket was never sure which, but wiggling the cap would demonstrate the problem. Ended up just replacing after trying contact cleaner.
 

Have you checked the fuse holder solder joints?

On Wed, Oct 3, 2018 at 04:28 PM, <ironcoder@...> wrote:


Yes Dave, I have had fuse holders go iffy on me before. Sometimes replacing a
fuse holder turns into a big project. This fuse holder on the 465M interface
board feels very tight when I snap in a new fuse. I will just have to wait and
see how things go with this.

Michael

Dave
 

No I have not. I will do so forthwith.
Michael
 

The solder joints are good.
 

That¡¯s a weird stale connection.

On Sat, Oct 6, 2018 at 11:36 PM <ironcoder@...> wrote:

The solder joints are good.

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