[Kw6]

I had a scare today. Turn on amp and heard small buzz and amp died. Sure enough fuse blew. It was fairly new JJ GZ34s. I will call in for an exchange. Not sure which one either took both out. So if tube goes bad what causes it to blow main fuse? In future is it necessary to have tube amps with tube rectification? Does it really sound better than solid state rectification? Thanks!

[jjss49]

modern day gz34 5ar4's are made so poorly, cheapened construction and impure metals... so failures such as this one are far too frequent

this why most knowledgeable owners of good 5ar4 rectified gear find old stock british or american ones immediately - not worth the risk running the jj shuguang or sovtek garbage

[FullRangeMan]

So if tube goes bad what causes it to blow main fuse?
Short circuit, electrons run fast, seems your amp dont have soft start also.
In future is it necessary to have tube amps with tube rectification?
It depend on the personal taste, but SS diodes have a long life if properly cooled by the huge aluminum heat sink.
Does it really sound better than solid state rectification?
SS diodes have better bass and are cheap, tube rect have better mid range but need replacement and be a have a cathode to be heated by the power transformer.

This romance book may help or no:
http://www.glowinthedarkaudio.com/rectifiertubes.html

[Kw6]

I really appreciate all your replies!🙂

[JakeJ]

Agree with FRM, most likely an internal short in the tube.  Why don't the tube mfr make the highest quality they can and once proven they could charge a resonable pricew for reliability and quality.  I looked at the Tube Depot and they range from $15 to $41.  If they made very good ones they could charge up to $100?  NOS are just ridiculous on pricing but if reliability puts the equipment at risk then we need better rectifiers.

[DaveC113]

modern day gz34 5ar4's are made so poorly, cheapened construction and impure metals... so failures such as this one are far too frequent

this why most knowledgeable owners of good 5ar4 rectified gear find old stock british or american ones immediately - not worth the risk running the jj shuguang or sovtek garbage

+1... After having a few new 5AR4s go one me, one taking out the Power Trafo on a SF preamp rather than blowing the fuse, I only use NOS for the last 10 years and no issues.

Kw6, what happened was an "arc-over"

https://www.google.com/search?q=recitifer+tube+arc-over&rlz=1C1SQJL_enUS879US879&oq=recitifer+tube+arc-over&aqs=chrome..69i57.4504j0j7&sourceid=chrome&ie=UTF-8

It can be caused by bad caps, or bad chokes, or a design that uses too large of a cap right after the rectifier, but in your case it's probably just a poorly made tube. For most new tubes the input cap must be smaller than the spec for that tube because the quality is lower. I think it's 47 uF for a 5AR4, but that will take out many new 5AR4s.

Please inspect your components on the input after the rectifier. It sounds like your fuse blew pretty quickly, but if you see any black marks that's an indication the resistor is bad. Coils you may need to check DCR. Make sure caps are not buldged or swollen.

IMO, tube rectification is a little better, yes. Use NOS and you may not have an issue again. I'd recommend the Japanese-made tubes with the seam-top as being the best value and they are made extremely well with a very hard vacuum, most of the getters on these tubes are black, which indicates a hard vacuum, and they rarely leak or go bad. Mullard is the standard for NOS but cost 2-3x or more vs the seam-top tubes, which were made with the Mullard equipment AFAIK. Also Sylvania big-bottle are good but a bit more, about $100 or so, seam-top are maybe $50...

Good luck!

[jjss49]

i agree w dave on his comments

good point that the japan made seam-topped 5ar4's are still (relatively) inexpensive, and work as well as the much-in-demand old brit made mullards and dutch amperexes, for much less $

usa sylvanias and ge's are excellent durable rectifiers too, although the glass bottles are bigger, so depending on gear, they may present clearance issues

btw, i have collected a good number of these over the years, am happy to pass along a few to a fellow member if the need arises ... i think i have many more than i could ever use!

cheers and good luck

[vonnie123]

So if tube goes bad what causes it to blow main fuse?
Short circuit, electrons run fast, seems your amp dont have soft start also.
In future is it necessary to have tube amps with tube rectification?
It depend on the personal taste, but SS diodes have a long life if properly cooled by the huge aluminum heat sink.
Does it really sound better than solid state rectification?
SS diodes have better bass and are cheap, tube rect have better mid range but need replacement and be a have a cathode to be heated by the power transformer.

This romance book may help or no:
http://www.glowinthedarkaudio.com/rectifiertubes.html

This is a similar question that I had.  In modern production, is the rectifier tube the preferred design or would solid state be just as good. 

[FullRangeMan]

This is a similar question that I had.  In modern production, is the rectifier tube the preferred design or would solid state be just as good.

On vintage and current amps usually for SE amps tube rect are used in small amps under 10W using tubes as 45,2A3,EL34,300B due the due to the fact that the manufacturers already know that this audience is very conservative and already know that tube rect offers better quality if sound in the middle and treble, since these amps have little power, the powerful bass that SS diodes offer is not expected, but I already have seen small amps with SS rectification.
http://mcnally.cc/amps.htm
Darling - 1626 Single Ended Triode
3/4 watt per channel
12SL7 Driver - 1626 Outputs - SS Rectifier
Built 12/30/2017(sold)

[avahifi]

In general,a tube rectifier has a slow turn on ramp up to full voltage.  This protects the downstream supply capacitors and power tubes from a sudden voltage spike when a diode bridge turns on instantly. This is true for Dyna ST-70 amps and its variations.  You can get a 50V overshoot at turn on over the maximum rating of the supply capacitors.  Very hard on the equipment.

[FullRangeMan]

Allow me suggest the inexpensive Russian 6D22 a indirect heating diode with 30 seconds slow warm-up, unfortunately its a simple diode requiring two tubes for a full-wave rectification, direct heating tubes have a faster warm-up.
https://shop.ehx.com/catalog/addimages/6d22-svetlana.pdf

http://www.gstube.com/catalog/?key=6d22&submit=Find

[vonnie123]

On vintage and current amps usually for SE amps tube rect are used in small amps under 10W using tubes as 45,2A3,EL34,300B due the due to the fact that the manufacturers already know that this audience is very conservative and already know that tube rect offers better quality if sound in the middle and treble, since these amps have little power, the powerful bass that SS diodes offer is not expected, but I already have seen small amps with SS rectification.
http://mcnally.cc/amps.htm
Darling - 1626 Single Ended Triode
3/4 watt per channel
12SL7 Driver - 1626 Outputs - SS Rectifier
Built 12/30/2017(sold)

I actually own two of those Darling design amps. A&S Kenzie, and Kenzie Encore.

[sfox7076]

You could always make/buy a solidstate rectifier replacement.  Cools down the 5v power winding in the transfer.

Shawn