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Soldano Avenger plate voltage and tube questions.

SlaveUnit

Member
Messages
68
Posted this over at the Soldano forum but I thought Id throw it up here too.

I bought a used avenger 100. It arrived with a dead tube. Not knowing, I ran it for about 30 mins this way and it sounded good. Once I noticed it was dead by measuring I removed them all. They were Sovtek 5881wxt. I ordered another set. While I waited I put in some JJ 6l6gc ones. At that time the plate voltage was at 507. I set them to about 32ma. Used it for a while one day. Went to turn it on the next and 2 of the tubes blew...insanely loud pop and bright light in the tube. Next I took it to an amp tech to make sure no screen resistors or anything was damaged. Everything checked out fine. The plate voltage was at 507 at the tech's house as well. We figured it was a bad tube and maybe once that went it took out the one next to it.

Now the other day my Sovtek replacements arrive. Being really nervous about the last one dying a loud horrible death, I decide to first make sure each one is good with a tube tester, then put a probe on each one in the amp. When I do this the plate voltage is at about 525 now. Also one tube is much higher than the rest (14.7ma higher). I did move to tubes around and remeasured just to be sure its not a socket. My outlet voltage is at 118 but of course moves a tad all the time. The tubes are biased at about 10 ecept for the one which is at about 25. I havent even played the amp since the new tubes have been in. Ive only tested.

My concerns:
1) Should I be concerned with the plate voltage being about 20 volts higher now? Is this high for this amp?
2) I will be sending the tubes back. But they do have a bit of a staticy sound. Like when someone rubs a mic on their shirt or something. Could this be caused because of the tubes being so mismatched?

Thanks everyone for taking the time to read this.
 

James BCM

Member
Messages
727
Hey,

I just saw your PM to me. Sorry, I fly 777's for a living and have been covered up with real work.

WXT's are the wrong tubes. Needs to be 5881/6L6WGC's.

Call Mike in Seattle on Monday. You need to talk to "the man" about his amp where no one else here, me included, can do a better job. I'd leave it off until you and Mikey figure it out.

Keep in touch.

LB
BCM
 

SlaveUnit

Member
Messages
68
Thanks for the reply Lynn. I thought the 5881WXT tubes were the same as the 5881 ones and just had the bigger base? The replacement tubes I did order today were the wafer/smaller bottom 5881 ones though.

I did try to give Mike a call but there was no answer. I will give him another ring on Monday. I know he and Bill arent that tough to get ahold of.
 

wyatt

Member
Messages
4,169
You are correct.

They are the exact same tubes (both 6Π3C-E) with different bases. The large base was added to the WXT to make them compatible with tube retainers. Manufacturers use the wafer base version OEM because they are cheaper in price (which adds up as you go through thousands).

Plate voltage seems a bit excessive for these tubes. Officially they are a 375VDC Max Plate Voltage, but most people have no problem to until around 500VDC.
 

SlaveUnit

Member
Messages
68
Let me ask this dumb question. If you give a tube more current (mA) via the bias trimpot, does the reading on the plate voltage drop at all?
 

riffmeister

Silver Supporting Member
Messages
16,673
Shouldn't. Plate voltage should stay constant unless there is some fluctuation at your wall AC outlet.
 

SlaveUnit

Member
Messages
68
I didn't think so. My wall fluxuates a little between 114 to 119 or so. Could that chage the amps pV by 20 though?
 

riffmeister

Silver Supporting Member
Messages
16,673
I think voltage and mA bias current are directly proportional........114 to 119 volts is about a 5% change.
 

SlaveUnit

Member
Messages
68
Just spoke to Mike...
He said the 525 plate voltage at idle is no big deal. Now just have to wait for the new tubes to get here.
 

JB6464

Silver Supporting Member
Messages
4,420
My HR100+ plate voltages are 495-505 at 120V AC .
You should be fine with those tubes since they are a beefed up 5881 .
 

Structo

Member
Messages
9,555
It depends on the power transformer and circuit whether or not the plate voltage fluctuates.
A softer transformer will drop voltage under a full load.
Not unusual for the voltage to drop a few when you bias it hotter.

I have heard that Soldano's have high plate voltage so you want some pretty robust tubes in there.
Generally, vintage tubes are better at handling higher voltage and current.
You should try to buy matched power tubes that have been burned in before they are matched.
Have a few ma's difference between is no big deal but I don't like to see any more than 8-10ma, after that they get pulled.
 

SlaveUnit

Member
Messages
68
I agree. The set I bought had 3 that were really close and 1 that was way off. I sent them back for a refund and purchased from a dealer who personally tests them.
 

alerich

Member
Messages
39
Let me ask this dumb question. If you give a tube more current (mA) via the bias trimpot, does the reading on the plate voltage drop at all?
Yes. As you increase current through the tube you increase the load on the B+ supply which will cause the plate voltage to drop a bit. That is why you check the plate voltage and current then re-check the plate voltage whenever you make any adjustments to the current. If you lower the current then B+ will rise a little. If you increase current then B+ will drop a little. This is why B+ is significantly higher if you measure it at the socket with no power tubes installed. No load = max B+.
 






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