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Blown fuse? (Read 912 times)
Melvin
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Blown fuse?
11/19/21 at 10:46:29
 
Good morning. Turned on the amp this morning and experienced a brief flash of white light and ... nada. No power. I'm assuming this is a blown fuse, however, I have no experience in this regard. I've had a tube fail in the past but no arcing, red-plating, etc. So, before I do a thing, thoughts? Much appreciated gentlemen.
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Bilyeaux
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Re: Blown fuse?
Reply #1 - 11/19/21 at 11:37:35
 
My amp shipped yesterday my first tube item. Sounds like it, should be a spare I would swap and see or PM Lon or one of the Veterans. Good luck and update us
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Lon
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Re: Blown fuse?
Reply #2 - 11/19/21 at 11:56:12
 
Melvin, from my experience this is likely a rectifier failure. . . . If so. you'll need another rectifier, good idea to have one on hand. Your main fuse may have blown and that will be easy, there should be a spare in the holder, a short slow blow 3 Amp fuse.

If that fuse is replaced and you still have no "action" . . .one of the rectifier safety board fuses inside the amp may have blown. These are two small slow blow 200 milli-Amp fuses and a single 6.5 Amp small slow blow fuse. Take the screws off holding the top plate to the base and flip the amp over and you'll immediately see these fuses.

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Melvin
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Re: Blown fuse?
Reply #3 - 11/19/21 at 11:58:52
 
Thanks @Bilyeaux. That's a good suggestion and I will do exactly that if need be. Congrats on your purchase. Great little amps .. love mine.
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Melvin
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Re: Blown fuse?
Reply #4 - 11/19/21 at 12:03:34
 
Lon, thank you. I'm using a near-new rectifier and have a spare. Should I check that first? And will a blown fuse be obvious? I know, newbie question.
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Lon
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Re: Blown fuse?
Reply #5 - 11/19/21 at 12:09:39
 
I would certainly try the spare rectifier first. If a fuse is blown it will not activate, and there will be no harm done to the spare rectifier. If it TOO blows, there's another problem in the amp that Steve should investigate. If it doesn't power up there is likely a blown fuse. I would look at the power inlet fuse first perhaps to see if it appears blown then try the rectifier.

The clear glass fuses usually seem blackened or the filament running across it within appears to be burned into two pieces. Not always though, I've had a few bad fuses over the decades look as if they might be good but aren't. The 6.5 amp within will likely have a "porcelain" or opaque sandy look and it may not immediately look as if it has gone bad.
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Melvin
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Re: Blown fuse?
Reply #6 - 11/19/21 at 12:18:25
 
OK, great. Much appreciated Lon. I've run out of time this morning so it will have to wait a bit.
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Melvin
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Re: Blown fuse?
Reply #7 - 11/20/21 at 16:04:19
 
I would look at the power inlet fuse first perhaps to see if it appears blown then try the rectifier.


Had time this morning. I checked the power inlet fuse first and it looked shot so I put in the spare, leaving the rectifier in place. Powered up the amp and the rectifier briefly sparked like fireworks and the spare fuse blew immediately. So, bad rectifier I assume (glad I have a spare). Now I need a fuse and some spares. I would like to purchase fuses similar to the stock fuse and hope I can get them at a local hardware store. Anyone have an idea of what the stock fuse is? Using a magnifying glass I made out "T3.15AL 250V" on the cap and I know it's 5mm x 20mm. This is basically all Greek to me and could sure use a link or whatever info you'd care to share. Thanks guys.

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CAJames
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Re: Blown fuse?
Reply #8 - 11/20/21 at 16:41:19
 
3.15 amp 250 volt 5x20 mm is all you need to know, they are very standard and common. If you’re interested you can try a ceramic fuse in addition (or instead of) a glass one, they are relatively inexpensive and a lot of people think they are an upgrade. But be careful, it can lead you down the path of audiophile fuse rolling.
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Melvin
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Re: Blown fuse?
Reply #9 - 11/20/21 at 17:21:33
 
Thanks CAJames.

I've read a bit on various fora and most fuse threads seem pretty contentious. And yes, fuse rolling is something I'd like to avoid (for now anyway)! Of course, if the ceramic type are reasonably priced I'll likely purchase a couple out of curiosity.
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CAJames
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Re: Blown fuse?
Reply #10 - 11/20/21 at 17:34:43
 
Yes, as are discussions about e.g. cables and rectifiers. “Audiophile” fuses was a cliff I was sure I would never look over, but since Decware I’ve decided pretty much everything matters and now I have hundred dollar fuses in my system FWIW. You’ve been warned.
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Melvin
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Re: Blown fuse?
Reply #11 - 11/20/21 at 18:04:11
 
LOL .. thanks for the warning. I've already been down a few rabbit holes myself. And you're right, of course, about cables and rectifiers. I suppose just about everything "audiophile" is pretty contentious these days.
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Lon
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Re: Blown fuse?
Reply #12 - 11/20/21 at 18:22:08
 
CA is right about the fuse, it can be a plain 3A fuse as well, that's what the manual calls for. Get a slow blow.
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CAJames
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Re: Blown fuse?
Reply #13 - 11/20/21 at 19:03:21
 
Good point re: slow blow Lon.
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Melvin
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Re: Blown fuse?
Reply #14 - 11/22/21 at 11:03:58
 
I couldn't find slow blow fuses locally yesterday so I grabbed the fast blow ones I could find. They looked to be the same as the 2 fuses that came with the amp, btw. The first blew immediately and I didn't try the 2nd. So, I placed an order for some slow blow fuses which should arrive tomorrow. Now I'm 2nd guessing myself and wondering if my spare rectifier is a problem. It's the original tube that shipped with the amp and there's nothing I can see "wrong" with it, but I'm such a neophyte.

In the meantime I started my search for rectifiers figuring it was a good time to try one of the NOS variety and I need a spare anyway. I've read about them here and elsewhere and am more confused than I'd care to admit. There are so many variants with numbering/lettering schemes clouding my feeble brain. Anyone care to help me? I'd like a drop-in replacement (I don't want to even think about adapters at this point). I'm going to purchase 2. I'd like to stay under $150 for 1. I'd like to spend less for the spare. Thank you kindly gentlemen.
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Lon
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Re: Blown fuse?
Reply #15 - 11/22/21 at 12:37:55
 
Gosh, not sure why this is happening. I didn't think a "fast blow" would blow so quickly but perhaps so, that's why I have always used the "slow blow."

I honestly would suggest a call in to Sarah to schedule a talk with Steve about this. It may be the rectifiers. . .it may not be. And you don't want to risk more rectifiers. His advice might be the most important right now.

As for NOS and other rectifiers. . .there are so many that can work and I would experiment with some lower priced options before going deeply into the more expensive items. I would look on eBay for NOS American 5U4 and/or 5V4 types as a start, either straight shouldered or bottle type as a start. These can be found at reasonable prices and should sound a step above those sent by Decware.
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Melvin
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Re: Blown fuse?
Reply #16 - 11/22/21 at 14:28:03
 
Thanks Lon. I was a bit surprised as well. I just pulled the rectifier again and this time with flashlight in hand I see damage (burn). This was the original that came with the amp and had plenty of time on it when I replaced it. I will do as you suggest and order a lower-priced one first. The new fuses will have arrived by the time I get a new rectifier. If I have a problem thereafter I will call Sarah.

So, to be clear, a 5U4GB (these letters!) is a drop-in replacement? In addition, some seem to have 4 pins and others 5. Are both ok?
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Lon
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Re: Blown fuse?
Reply #17 - 11/22/21 at 14:55:07
 
Go for a 5 pin. All the 5U4 and 5V4 types are fully compatible with the amp.
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Melvin
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Re: Blown fuse?
Reply #18 - 11/22/21 at 14:59:07
 
OK, great. Thanks again for the info Lon. I'm learning, albeit slowly, but learning nonetheless.
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JBzen
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Re: Blown fuse?
Reply #19 - 11/22/21 at 15:02:53
 
Melvin,
It seems odd that both rectifiers went bad in short order.
What part of the original looks burnt? Could be a short developed in the power transformer causing errant amperage draw/voltages. I suggest give Steve a call before you put another rectifier in.
John
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Melvin
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Re: Blown fuse?
Reply #20 - 11/22/21 at 15:49:18
 
John .. I think you and Lon both have given me good advice in giving Steve a call and I will do so to be prudent.

For clarity, I had a power tube fail about 3 years ago (about 10 months after the SE84UFO arrived). I spoke with Steve about it at the time and ordered a replacement set (I needed spares anyway). When the replacements arrived, without thinking, I replaced all of them. A while later I realized I should have approached that differently. Live and learn. I kept the original rectifier and input tubes and tossed the power tubes. Again, live and learn. So the original rectifier had nearly a year on it and the replacement had approximately 2 years on it when this little hiccup happened. Neither rectifier was new. Should I still be concerned something else is going on?

Oh .. the burnt part is near the bottom where there were some sparks.

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Lin
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Re: Blown fuse?
Reply #21 - 11/22/21 at 15:57:09
 
If you want inexpensive, but good and pretty.

https://nesstone.com/product/sed-5u4g-winged-c-premium-rectifier-tube/
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Melvin
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Re: Blown fuse?
Reply #22 - 11/22/21 at 16:19:13
 
Thanks Lin  :)
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Dana
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Re: Blown fuse?
Reply #23 - 11/22/21 at 17:14:20
 
You can use the four pin rectifiers but you'll need an adapter.
I purchased the cheaper one but it was difficult (for me) to determine which were the big pins and which were the smaller.  I was really conserned when I first plugged it in but i believe even on the cheap adapters they only go in one way.  https://www.ebay.com/itm/283166297929?hash=item41ee06cf49:g:4NgAAOSwehZfSfIQ

This one seemed better to me but i haven't tried it yet.
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JBzen
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Re: Blown fuse?
Reply #24 - 11/23/21 at 10:22:26
 
Melvin,
While it is entirely possible that both rectifiers could have been faulty from rough handling, IMO, the area that the sparks are happening is where the connections are made inside the tube. A connection is usally the weakest link in a circuit and any anomaly in a circuit would have a good chance of showing up at the connection. In short, and hope it is wrong, I think you have something else going on besides a group of bad rectifier tubes.
I would take the amp out of the base and look closely at all the components/connections for heat damage or refer it to Steve if the new rectifier/slow blow fuse does not solve the problem.
Good luck.
John
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CAJames
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Re: Blown fuse?
Reply #25 - 11/23/21 at 15:58:18
 
Just my two cents: I'm not surprised at all that a fast blow fuse blew when you turned on the amp. There is a (very) brief high current inrush when you turn on the amp and the power supply caps charge up. That is pretty much why slow blow fuses exist.

It is never a bad idea to talk to Steve, but if it were me I would try again with the new rectifier and slow blow fuse before I got him involved. And re: rectifiers if someone were to ask me for a recommendation that you can buy once and most likely forget about for a decade or two I would suggest go here:

https://www.surplussales.com/Tubes-Sock-Acc/0-5/TubesListed-5.html

And get a 5U4WG/5931 milspec rectifier for $35. It isn't the best sounding rectifier in my tube caddy, but it sounds fine and is built like a tank.

One other note about "5 pins" vs "4 pins." The 5 pin tubes are really 8 pin (aka octal) tubes that don't have 3 unneeded pins to save money. They all have the center guide pin. The 4 pin tubes like the 5Z3 and 80 are a different base (UX4) and do need an adapter. IMO the adapters are pretty foolproof, and there is only one way the tube will seat properly but I don't blame anyone who doesn't want to mess with them. There are lots of them on ebay but I always buy adapters from:

xulingmrs

I've always had good luck with them, and I can't say that about other vendors.

Good luck.
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Melvin
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Re: Blown fuse?
Reply #26 - 11/24/21 at 00:56:28
 
Thanks again gentlemen. I appreciate your thoughts and advice. The slow blow fuses arrived today and hopefully the new rectifiers will arrive soon as well. I'll follow up when appropriate. Happy Thanksgiving to those of you who are in the USA and celebrate. Peace.
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JBzen
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Re: Blown fuse?
Reply #27 - 11/25/21 at 12:08:30
 
From the SE84UFO25 owners manual:

As a mater of practice, any time a fuse blows it is wise to remove the rectifier tube,
replace the fuse, and start up the amplifier again WITHOUT the rectifier tube plugged
in. If the remaining tubes in the amplifier light up, then the amplifier is fine. Turn it off
and install a new rectifier tube and enjoy some music.

John
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Lon
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Re: Blown fuse?
Reply #28 - 11/25/21 at 12:11:31
 


Thanks for adding that John.
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Melvin
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Re: Blown fuse?
Reply #29 - 11/25/21 at 16:54:15
 
Yes, thanks John. I assume it's the same for the non-25th Anniversary amps? Just making sure because I didn't see that in the manual.
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Re: Blown fuse?
Reply #30 - 11/25/21 at 17:03:43
 
Quote:
Posted by: Melvin      Posted on: Today at 16:54:15
Yes, thanks John. I assume it's the same for the non-25th Anniversary amps? Just making sure because I didn't see that in the manual.


Yes, it never hurts to start an amp without the rectifier.
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Melvin
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Re: Blown fuse?
Reply #31 - 11/25/21 at 17:18:13
 
Thank you.
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Melvin
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Re: Blown fuse?
Reply #32 - 11/25/21 at 17:27:49
 
Just tried it sans rectifier and the good news is the tubes lit up! I'm relieved to say the leaset. Now I just have to wait a few days for the new rectifiers to arrive. One is supposed to arrive on Saturday and the others on Monday or Tuesday. I can't thank you guys enough.
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Lon
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Re: Blown fuse?
Reply #33 - 11/25/21 at 17:40:08
 
YAY!
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HR-1,ZTPRE,ZBIT,ZROCK2,SE84UFO3-25th x2, CSP3-25th.Taboo Mk IV; Rega RP3 w all GrooveTracer mods PS Audio: PST+DSD,P15,NPC,PowerBases,AC-12 pwr cbls, Reference spkr cbls;Mapleshade:Samson V3;;VooDoo:Cremona+Amati intrcncts, Iso-Pods;headphones:PM1,HD800S,ZMF Ori
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JBzen
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Re: Blown fuse?
Reply #34 - 11/25/21 at 18:57:46
 
Good news for sure!
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AMC CD8b>XO3>Cambridge CXN2>Stokes DAC>low dilectric 5-9s silver>CSP2+>ZKIT1 Milflex copper 25th>cotton clad #8 silver plate>lii Crystal 10 in Huijgen cabinets. Ortofon 2M Bronze>JVC QL-F4>ZP3>Sims isolation. ASKA>Wicket One. Isolation-AC filtering-Room treatments
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JBzen
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Posts: 372
Re: Blown fuse?
Reply #35 - 11/25/21 at 19:04:33
 
I was reading up on the SE84UFO25th for an anticipated purchase and found Steve's reference of running the amp without the rectifier for troubleshooting. I did not want to recommend running an amp without tubes installed but it seems that running one without the rectifier causes no harm.

John
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AMC CD8b>XO3>Cambridge CXN2>Stokes DAC>low dilectric 5-9s silver>CSP2+>ZKIT1 Milflex copper 25th>cotton clad #8 silver plate>lii Crystal 10 in Huijgen cabinets. Ortofon 2M Bronze>JVC QL-F4>ZP3>Sims isolation. ASKA>Wicket One. Isolation-AC filtering-Room treatments
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CAJames
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Re: Blown fuse?
Reply #36 - 11/26/21 at 04:24:08
 
Quote:
Posted by: JBzen      Posted on: Yesterday at 19:04:33
I was reading up on the SE84UFO25th for an anticipated purchase and found Steve's reference of running the amp without the rectifier for troubleshooting. I did not want to recommend running an amp without tubes installed but it seems that running one without the rectifier causes no harm.


Running the amp without the rectifier effectively turns off the high voltage aka B+ to the plates of the tube. There is a separate, independent low voltage circuit to the cathodes of the tubes that makes them light up. Removing the rectifier has no impact on that circuit so if if the amp working properly the tubes ought to light up. Or conversely if they don't light up there is some kind of problem.

I don't understand how Steve can say "if the tubes light up the amp is fine" because most of the complexity of the amp is in the B+ circuit, and taking out the rectifier effectively turns that off. I don't see how the tubes lighting up confirms there is no problem with the B+. But far be it from me to argue with Steve about how his amp works.
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Lin
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Re: Blown fuse?
Reply #37 - 11/26/21 at 15:37:10
 
"The  only thing that blows a fuse is the rectifier tube or a power surge. Any time a rectifier tube arcs on start-up you will likely blow a fuse. Eventually the rectifier itself will fail if it is continually arcing on startup and should be replaced.

As a mater of practice, any time a fuse blows it is wise to remove the rectifier....."

Above is part of the paragraph before quote from UFO25 owner's manual by JBzen.
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Melvin
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Posts: 400
Re: Blown fuse?
Reply #38 - 11/27/21 at 22:46:09
 
Update: 3 of the 4 rectifiers arrived today (thought try out a few at different price points). I inserted the Sovtek 5AR4 and .. success! I'll leave this one in for a while before swapping. I can't tell you how happy I am. This has been a good learning experience for me. Thank you all again.
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SE84UFO (6N1P-EV, TAD EL84 STR, NOS RCA 5U4G)
Omega Super 3i & DeepHemp 8
dB Audio Labs Tranquility
Sonore microRendu
Outlaw Audio ICBM-1
Omega ConnectOne, Better Cables Silver Serpent RCA & Sub, ifi USB
SGC 7V lps, Brick Wall PW8RAUD
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Lon
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Re: Blown fuse?
Reply #39 - 11/27/21 at 22:48:15
 
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HR-1,ZTPRE,ZBIT,ZROCK2,SE84UFO3-25th x2, CSP3-25th.Taboo Mk IV; Rega RP3 w all GrooveTracer mods PS Audio: PST+DSD,P15,NPC,PowerBases,AC-12 pwr cbls, Reference spkr cbls;Mapleshade:Samson V3;;VooDoo:Cremona+Amati intrcncts, Iso-Pods;headphones:PM1,HD800S,ZMF Ori
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Melvin
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Re: Blown fuse?
Reply #40 - 11/28/21 at 17:00:10
 
I've got 10 hours or so on Sovtek 5AR4 so far and I must say it sounds pretty good. I didn't know what to expect for my $21.95. I'll likely try the Winged C 5U4G (thanks Lin) next, followed by the NOS GE 5U4GB and the NOS RCA 5U4G. I think these 4 should at least give me a sense of how swapping the rectifier changes the sound. The RCA intrigues me the most. How much time should I reasonably give to each?
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SE84UFO (6N1P-EV, TAD EL84 STR, NOS RCA 5U4G)
Omega Super 3i & DeepHemp 8
dB Audio Labs Tranquility
Sonore microRendu
Outlaw Audio ICBM-1
Omega ConnectOne, Better Cables Silver Serpent RCA & Sub, ifi USB
SGC 7V lps, Brick Wall PW8RAUD
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Melvin
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Re: Blown fuse?
Reply #41 - 11/29/21 at 16:44:58
 
Couldn't help but try the NOS RCA. Needs some time to burn but at first blush the change is quite obvious. Improvement across the board (tone, density, soundstage). This is the best my system has sounded.
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SE84UFO (6N1P-EV, TAD EL84 STR, NOS RCA 5U4G)
Omega Super 3i & DeepHemp 8
dB Audio Labs Tranquility
Sonore microRendu
Outlaw Audio ICBM-1
Omega ConnectOne, Better Cables Silver Serpent RCA & Sub, ifi USB
SGC 7V lps, Brick Wall PW8RAUD
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CAJames
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Posts: 377
Re: Blown fuse?
Reply #42 - 11/29/21 at 17:11:54
 
My experience is rectifiers don't need a lot of burn in time. Seems like by the time my amps are warmed up they sound pretty much the way they are going to sound. Others may have different experiences though. Very different from input or power tubes that often need several hours to settle down and open up.

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Melvin
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Re: Blown fuse?
Reply #43 - 11/29/21 at 17:30:42
 
I'm glad you shared that CAJames. I'll be paying attention for sure, slowly but surely adding to my experience. I just love the camaraderie here.
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SE84UFO (6N1P-EV, TAD EL84 STR, NOS RCA 5U4G)
Omega Super 3i & DeepHemp 8
dB Audio Labs Tranquility
Sonore microRendu
Outlaw Audio ICBM-1
Omega ConnectOne, Better Cables Silver Serpent RCA & Sub, ifi USB
SGC 7V lps, Brick Wall PW8RAUD
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Lon
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Re: Blown fuse?
Reply #44 - 11/29/21 at 17:33:32
 
NOS RCA are among the easiest rectifiers to build a tube compliment around  . . . glad you are trying one out. The 5V4G is worth checking out in time.
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HR-1,ZTPRE,ZBIT,ZROCK2,SE84UFO3-25th x2, CSP3-25th.Taboo Mk IV; Rega RP3 w all GrooveTracer mods PS Audio: PST+DSD,P15,NPC,PowerBases,AC-12 pwr cbls, Reference spkr cbls;Mapleshade:Samson V3;;VooDoo:Cremona+Amati intrcncts, Iso-Pods;headphones:PM1,HD800S,ZMF Ori
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