Fuse popped on Fender DR. not your typical question... please chime in

[bluesboy]

HI, so last nightout of the blue i was playing along at low volume, and the fuse popped out of nowhere. there was no degradation in tone, and i didnt see a flash (i wasnt facing the back of the amp).

 

I understand that a fuse popping typically could be bad power tubes, or something else.

 

Could it be the cold weather? I did transport the amp in frigid weather to where our band practices, and i thought maybe the tubes heating up and going out in the cold could do it?

 

Also, on to my main question. On the back where the fuse plugs in, it says 2 AMP / 125 V. On the fuse that I took out, it says 2&1/2 A, 250V. It seems like the previous owner had the wrong fuse in there? Im not sure... this amp has been heavily modified from the reissue version to "original blackface specs" - PTP wiring and some other mods by Torres Engnerring. Would an orignal circuit blackface DR need a different fuse?

 

What kind of fuse should I put in now?

 

im confused...

[JonathanD]

It could be the cold weather. Did you turn it on standby for a while? Especially in colder weather, I like to let the tubes get warm and cozy before I play.

 

And if the amp calls for a 2A/125V fuse, that's what I'd use. The 2 1/2A fuse just needs a higher threshold before it blows, so it's less likely to go. Which I think is dumb, because the fuses are meant to be a safety net for more serious damage.

[Weathered]

Unless the PT was changed, I don't see the amp needing a higher amperage fuse. Go get a 125V or 250V 2A fuse.

 

But keep in mind that fuses don't blow for no reason - it's entirely possible that you have a bad power tube.

[knucklefux]

fuses CAN blow for no reason, i've had it happen to me numerous times...although, mainly on power up situations, not while playing. i'd pop another fuse in there and see what happens. if it blows, take it to a tech. if it doesn't, then it was just time for that fuse to go.

[bluesboy]

hi guys, here is info from the ebay auction i bought it from:

 

Torres Marketing Propaganda

http://www.torresengineering.com/reisfenamppo.html

 

This is the sharpest thing in the music world right now. We are doing lots of amps with this complete rebuild - it makes the amps sound absolutely incredible - up to the quality of a Pre CBS amp.

 

All are built to Pre CBS specs.

 

The entire Printed circuit board is removed from your amp and an all new Torres point to point Eyelet board installed and wired.

 

New pots and controls, new switchcraft jacks, all carbon composition resistors, Torres super quality 418P Orange drop caps and all hand wired point to point.

 

A new Point to Point correct value power supply with the highest quality filter caps is also installed!! (Fender really missed it on the power supply for these amps)

 

Adjustable bias set up correctly and all 100% tested

 

Standard price uses your reverb, tubes (new tubes available of course), the original transformers, on-off, standby switches, fuse holder and tube sockets.

 

We have been doing this for a long time - we introduced it to the world many years ago when these amps first came out.

 

Finally we are caught up enough to offer it on our web page"

 

does this help? weathered, does this mean the PT has been altered? should I get a slow blow or regular fuse? ok, so it should be 2A, but what difference would the difference in Voltage (125-250) make?

 

thanks guys, i love the way this amp sounds, and i dont want to ruin it

[bluesboy]

 

It could be the cold weather. Did you turn it on standby for a while? Especially in colder weather, I like to let the tubes get warm and cozy before I play. And if the amp calls for a 2A/125V fuse, that's what I'd use. The 2 1/2A fuse just needs a higher threshold before it blows, so it's less likely to go. Which I think is dumb, because the fuses are meant to be a safety net for more serious damage.

 

 

well, i keep my amp on standby for a few mintues... lets say no more than 5, but could be as little as two or three.

 

Also, it was the first time I had used the amps vibrato... i used it for a few minutes, then turned it off (the vibrato i mean). then i played regular for maybe ten mintues when the fuse popped. Also, I had hooked up an attenuator to try it, and there was a lot of noise, so i removd it. it was only connected for a few minutes. could any of this cause a bad tube, or make a slightly bad tube worse?

[bluesboy]

 

FWIW: When I bought my DRRI, it was a floor model at Guitar Center. I took it home to clean it up, tighten all the screws, switch out the tubes, etc. and noticed that the fuse installed was like a 7 or 8 amp fuse. I installed a 3 amp fuse, as I had some spares (all my other amps used 3A fuses), and I haven't had a problem with the amp. It may not be the exact recommended value, but I'll take my chances.

 

 

that's interesting that it came with high of a fuse... it seems like the people at GC probably just slapped one in there after it had previously blown. Is your 3A fuse 250 or 125V?

 

Also, just curious if you ever biased the amp. If so, what kind of numbers were you dealing with (what was the plate voltage, what mA did you bias your tubes to, etc.)

[bluesboy]

thanks man.. i biased a DR a few years ago, but i only did it once and i dont remember the details

[bluesboy]

i just bought a new rectifier tube, as well as a matched set of power tubes (all JJ). I also bought myself a weber bias rite.

 

i previously owned a bias probe, which was basically a socket with banana plugs that goes into a DMM. it wasnot very convenient to use... with the weber i can check th eplate voltage and bias on both tubes at once.

[bluesboy]

im going to pick up a few fuses today at radio smack... any last minute opinions?

[NickCaveFan]

HI, so last nightout of the blue i was playing along at low volume, and the fuse popped out of nowhere. there was no degradation in tone, and i didnt see a flash (i wasnt facing the back of the amp). I understand that a fuse popping typically could be bad power tubes, or something else.

 

Okay, first, I'm not the sharpest knife in this drawer, but here are a few comments from my peanut gallery.

 

Fuses don't just blow, some condition leads to them blowing. Environment, tubes beginning to fail or something starts the process.

 

Have you considered talking to the folks that rebuilt this amp about the fuse size and why it might have blown? Seems to me they are pretty smart folks to have done all the work they put into it and will have an opinion and some suggestions.

 

Last, there are other forums on the web. I've been trying to learn about amplifiers and other things and have found some other folks can be great resources. I'm not trying to cast aspersions at folks here, but there seem to be a lot of folks doing amp troubleshooting and repair for a living here. Now maybe I've just not read enough here, so take the link with a grain of salt. The thread I've provided a link to is for a fuse blowing problem with another brand and style of amp, but if you put "blowing fuse" and stuff in their search engine you'll find more than a few threads to give you ideas.

 

If I've crossed some unwritten line of honor sending you to another forum, I apologize in advance. I just think there are lots of bright and helpful folks in many places and knowing where as many as possible are can help get to the root of your problem faster.