High voltage from Sovtek 5Y3GT

harpo · Post by **harpo** » Fri 03/09/07 9:37 pm

I just finished rebuilding my old 5E3 (first amp I ever built). Used one of David Allen's Deluxe Upgrade PTs. Great PT, puts out 331VAC on each side of the secondary from 121VAC line. Put a brand new out of the box Sovtek 5Y3GT that I had picked up in for the first fire up (didn't want to risk a NOS tube). The power section was putting out 407V B+ loaded!!! This was enough that one of the old Jan Philips 6V6s I had in started to red plate. I shut down and swapped the recto for a old GE 5Y3GT. B+ came in at 367V with a real 5Y3. DONT USE THE S*** Sovtek 5Y3 tubes!!!
Anyone else ever had an experience like this with a rectifier before? I've had them go POP but never way high voltage before.

Alexo · Post by **Alexo** » Fri 03/09/07 9:40 pm

Yup, that's a Sovtek 5Y3 for ya

, welcome to the club!

Trout · Post by **Trout** » Fri 03/09/07 9:43 pm

harpo wrote:I just finished rebuilding my old 5E3 (first amp I ever built). Used one of David Allen's Deluxe Upgrade PTs. Great PT, puts out 331VAC on each side of the secondary from 121VAC line. Put a brand new out of the box Sovtek 5Y3GT that I had picked up in for the first fire up (didn't want to risk a NOS tube). The power section was putting out 407V B+ loaded!!! This was enough that one of the old Jan Philips 6V6s I had in started to red plate. I shut down and swapped the recto for a old GE 5Y3GT. B+ came in at 367V with a real 5Y3. DONT USE THE S*** Sovtek 5Y3 tubes!!!
Anyone else ever had an experience like this with a rectifier before? I've had them go POP but never way high voltage before.

Yep,, Those 5Y3's totally S*** unless your needing extra voltage and even then they still S***. I have had a lot of them fail sometimes right out of the box. I wish I had MM's home address, I would mail him the 9 bad ones I still have here along with a nice pleasent note.

Trout

bigsbybender · Post by **bigsbybender** » Fri 03/09/07 10:20 pm

The Sovtek 5Y3 is more closely related to GZ34 than 5Y3.....it has an indirectly heated cathode that allows for very small voltage drop, it is technically an improvement but "improvement" isn't what we are looking for.
The real 5Y3 is built like a small 5U4....Sovtek's is a small GZ34 for all practical purposes. We want big voltage drop and sag from the filament/cathode being far from the plate.

I use the Sovtek 5Y3 sometimes, but never as a direct replacement for a "real" 5Y3. Fortunately real 5Y3 is still easy to come by....I wonder if anyone will start making a new "real" one?

j.

nomad100 · Post by **nomad100** » Fri 03/09/07 11:01 pm

That seems like product mis labeling, they really should have came up with a different name. They should be held accountable for any damaged gear.

Eric · Post by **Eric** » Fri 03/09/07 11:08 pm

Is there any data on the Sovtek 5V4 ? More or less voltage drop? Compared with the Sovtek 5y3 ?
Thanks

teletroy · Post by **teletroy** » Sat 03/10/07 2:03 am

I learned a long time ago, for 5y3gts - buy NOS not Sovtek your 6v6s will love you for it

beamer · Post by **beamer** » Sat 03/10/07 3:53 am

I needed lower voltage for my P-P 6L6 build, so I bought Sovtek 5Y3. Mr. smart guy din't bother to read the specs., seems like any 5Y3 only good for 125mA

Maybe I'm not the only one.
Then I wondered why my voltage didn't match PSU designer.
Then I ordered Sovtek 5AR4, see what happens.
scott

bigsbybender · Post by **bigsbybender** » Sat 03/10/07 12:51 pm

Eric wrote:Is there any data on the Sovtek 5V4 ? More or less voltage drop? Compared with the Sovtek 5y3 ?
Thanks

"Real" 5Y3 should drop about 50v under usual load

5V4 Drops about 25v @175ma which would be a relatively high load for a small amp

I can't find a real Data Sheet for Sovtek 5Y3GT but in the case of my 18 watt the Sovtek 5Y3 dropped ~20v It may go more in an amp that will load it down more and it'll drop very little in a champ. I really didn't notice much operating difference between it and the 5V4

j.

Eric · Post by **Eric** » Sat 03/10/07 4:30 pm

what does the EZ81 drop about?

bigsbybender · Post by **bigsbybender** » Sat 03/10/07 10:39 pm

Eric wrote:what does the EZ81 drop about?

Around 25-30v depending on the load.

harpo · Post by **harpo** » Mon 03/12/07 7:44 am

Thanks for all the feedback. I guess I will pay better attention to the manufacturers specs from now on. I though a 5Y3GT was a 5Y3GT but I guess it's different in Russian

Someone mentioned voltage drop in low load circuit ala Champ. My experience was with a 5E3 circuit measuring 92mA across the cathode resistor. I agree with BigsbyBender that this tube is more like a small 5AR4 or a 5U4 that doesn't draw as much filament current.
Spent Saturday driving around town to several small guitar shops trying to find a suitable 5Y3. Everyone had the Sovtek. One guy pulled out a new looking Fender box with a "5Y3GT". I opened it up and it had a tube with Fender silkscreened on one side and Sovtek on the other. It was the Sovtek 6-sided plate tube. I said "No Thanks" and ordered several NOS tubes online that night.

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High voltage from Sovtek 5Y3GT

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