[dangerbird]

I left it on,, as I have done many times,,overnight,, this am,, no power---blown fuse,,, checked connectionsmm no shorte---repasced fuse--power up---blown fuse---replace fuse,, disconnect pre,,,power up---blown fuse---power supply? Any ideas would be appreciated.

[Steve]

Hi Dangerbird,

Not necessarily in order, you might check:

1) Rectifier in the power supply shorted (one or more legs)

2) An output device that is shorted or missed biased

3) Power transformer, shorted winding

4) Another part in the power supply that is shorting out the rail

5) Wiring that is shorted to the chassis. Look for sharp edges that might cut through insulated wire

Late, maybe someone else might come up with another idea

Hope this helps.
Steve

[dangerbird]

Thanks Steve,, I'll get started--george

[lazydays]

I left it on,, as I have done many times,,overnight,, this am,, no power---blown fuse,,, checked connectionsmm no shorte---repasced fuse--power up---blown fuse---replace fuse,, disconnect pre,,,power up---blown fuse---power supply? Any ideas would be appreciated.

I hope your using slow blow fuses! Regular ones wont last fifteen seconds.
gary

[Wayner]

Short in speaker wire?

[lazydays]

I still have an Amp one here at the house, and it to blew the fuses once, so I went over to Radio Shack and bought some fuses. It just kept eating them. Spoke with an electrician at work that I knew was very familure with tubed equipment, and the first thing he said was to get slow blow fuses. Changed them out and never had another problem.
gary

[cityjim]

 Are you inserting the proper fuse for the application ? There are many many types of fuses out there . Ceramic , slow , fast and delay to name a few .

cityjim

[dangerbird]

Thanks to all for the help/input,,, I replaced the fuse with a slo-blo 3.5/250v variety,,and noticed that one of the EL-34's was waaaaaaaaaay out of bias,, rebiased,,checked bias after 20 minutes,,AND placed it in a better ventilated spot,,and for the last hour,,,it's all been good. Happy again. Now to upgrade the 4 caps on the board and I'm done,,at least for the moment.

[lazydays]

Thanks to all for the help/input,,, I replaced the fuse with a slo-blo 3.5/250v variety,,and noticed that one of the EL-34's was waaaaaaaaaay out of bias,, rebiased,,checked bias after 20 minutes,,AND placed it in a better ventilated spot,,and for the last hour,,,it's all been good. Happy again. Now to upgrade the 4 caps on the board and I'm done,,at least for the moment.

sounds like you have a biasing resistor going bad. It's right next to the tube, and should be changed out when retubing. If you do change the resistors I'd suggest you replace them with higrade metal oxide resistors (5% or lower)
gary

[DaveC113]

Thanks to all for the help/input,,, I replaced the fuse with a slo-blo 3.5/250v variety,,and noticed that one of the EL-34's was waaaaaaaaaay out of bias,, rebiased,,checked bias after 20 minutes,,AND placed it in a better ventilated spot,,and for the last hour,,,it's all been good. Happy again. Now to upgrade the 4 caps on the board and I'm done,,at least for the moment.

sounds like you have a biasing resistor going bad. It's right next to the tube, and should be changed out when retubing. If you do change the resistors I'd suggest you replace them with higrade metal oxide resistors (5% or lower)
gary

I actually just had a resistor go out on my Anthem Pre1... same vintage as the Amp1. It was in the ps right next to the 5ar4. I heard some crackling in the speakers, and a nice light show as the resistor burnt kind of like a sparkler. I unplugged it in time, the tube wasn't damaged and everything works fine. Luckily, I happened to have a suitable resistor in with some other parts I salvaged...

Are there any other resistors or components that should be replaced as routine maintnence on tube gear thats now over 10 years old?

 

[Steve]

That brings up a good point. When purchasing a component, check for reliability. Look for any parts that might be near heat producers such as heatsinks and tubes. One needs to check for themselves.

Electrolytic and even film caps next to such heat (say an inch or so) is a no no for sure. Resistors are not quite so bad.

For example, electrolytic caps are only rated 85 and 105 degrees C. That translates to about 175 and 220 degrees F. Life is greatly reduced for each 20 degree F rise. Complete failure can occur without warning.

Some heat sinks and most importantly tubes will get much hotter than that, say 175 to 450 degrees, depending on load. Reliability, or lack thereof, is definitely related to heat.

I would check any component over in person, or at least inspect photos before purchasing. Otherwise, get ready for some repair bills and possible damage to componets down the chain. One can almost always tell a professional layout from an amateur one by parts placement.

Glad things worked out George. Bad tube will certainly cause the problem described.

Cheers.
Steve