Sovtek 5Y3GT went poof!

[mresistor]

Well, fired up my Champ build today and it had been sitting for a while. I put an old RCA 6V6GTA in it to see how it would sound. The only thing I did to it before firing it up was I drilled a 3/8 inch hole in the back for the 1/4" phone jack so the speaker plug could plug straight in the back instead of coming up from underneath the chassis. No rca jack on this one. This amp also has a feedback in/out switch wired in and selectabel 4 or 8 ohm output switch.
Well I fired it up and there was no sound and I heard the flashover. Check the fuse and it was blown. So I checked the rectifier on the tube checker and it was also history. I rechecked the RCA 6V6 and it is very good. Pulled out the chassis and pulled the 6V6 and did some looking around. Nothing wrong that I can see. Tried and old marginal GE 5Y3 I had and it redplated with no 6V6 installed.
I'll need to order another 5Y3GT to test it further. I'm thinking maybe there is a problem with the feedback switch I used, its an old one I had in the box of goodies. I'll have to bypass it and run the feedback loop normally  prior to testing again. The switch tested good with the ohm meter but that doesnt mean its good in circuit.
Anyone have any problems with Sovtek 5Y3GTs? Could it just be a rectifier gone south?

[dwp]

check continuity between power rail and ground. The only rectifier issue I've had was a dead short, tube socket lead hitting the chassis. caused the rectifier tube to red plate. other than that they've all died peacefully.....

[mresistor]

I found it. A while back I had pulled the octal socket mounting screws to install tube retainers and evidently when I reinstalled the screws I somehow managed to get one rectifier filament lead slightly pinched under the edge. I could kick myself.  
That was an expensive little lesson/reminder to always physically inspect the area where you just worked to make sure everything is OK, prior to firing it up.
The old GE recto still lives, amazingly.

[HotBluePlates]

Tried and old marginal GE 5Y3 I had and it redplated with no 6V6 installed. I'll need to order another 5Y3GT to test it further.

I'm guessing you say "marginal" based on tube tester results.

I have some rectifiers that test quite weak on a tube tester, but appear to give fine performance in an amp. I can only imagine that the limitation would be that full peak current output is probably not available, and maybe the output voltage would be low. All are fine with me.

When I get a chance, I'll take a picture of a 6V6 that I have. It's a nice Westinghouse blackplate, and tests wonderful on the tube tester and sounds great in an amp. It has a hole melted through the plate where it obviously really redplated at some point before I got it.

Don't be cavalier about redplating, but redplating doesn't instantly kill a tube. It could cause it to become gassy and provoke future problems and more redplating, but then again... it doesn't always.

[Rev D]

 Easy to pinch those wires ain't it? I pinched an underboard wire on a stand off and kept blowing fuses until I got a dental mirror and noticed it. I've redplated some EL84's before on the blues jr. I sold and after fixing the problem tried them again and they worked fine for hours and hours after I made the repair and were still working when I sold it, as long as its not doing it for a long time it'll probably be ok, but as was mentioned above real long term I donno.

D.

[eleventeen]

Well, you:

1: learned a lesson you will probably NEVER foirget (to look for)

and

2: destroyed the cheapest tube in the amp.

I can think of several worse outcomes!

[mresistor]

Well, come to find out, the Sovtek 5Y3GT is just fine to. ??  They must be pretty durable buggers. .....
What I was really worried about was if there was any harm done to the filament winding of the PT, but after playing it for an hour or so in total it's fine, as far as I can tell.

Yes, the old GE is marginal on the tube tester but works well. The Sovtek reads like new on the tester.

I love fuses.... 

[jeff]

I personally don't trust sovtek 5Y3's. I've had two and I don't think they are real 5Y3's. They are rectifier tubes but they don't seem to have the same sag as a real 5Y3 and have an extra pin. I used one in the champ copy I made and the B+ voltage was way higher than it should have been for a 5Y3. Champs already run high, 420V but with the Sovtek I was getting 460V! Something to check. Maybe I just got two bad ones but I've heard that sovtek uses tubes similar to 5Y3 in the fact that it's a rect tube but they aren't 5Y3's and just rename them 5Y3's.

[Rev D]

 They don't have the voltage drop of a real 5y3 (I can't recall which rectifier they are internally someone will remember) and I've had bad luck with Sovteks too. I'm at 50% with them, 2 for 4 burned out, they were pretty doing it though! I've heard others with no problem, so I donno, its just below average or no quality control.

RD

[mresistor]

that interesting to note..... thanks 

[Danskman]

it seems that Sovtex 5Y3 are more 5AR4 rectifiers. I never used them as 5Y3. You can find nice NOS 5Y3GT on flybay or other sources.
Regards,
Danskman