HH Scott 222c Power Tube Issue.....

Sorry for the delayed response but thanks so much for all the input so far.


Is it possible that this whole redplating incident was just a hiccup and the amp needed some cool down time for the bias to be stable again?
No, not really. Cooling down will not make your problem go away. If it were not an issue with something in the bias circuit or a bad tube.
 
No, not really. Cooling down will not make your problem go away. If it were not an issue with something in the bias circuit or a bad tube.

Thanks primosounds.

I couldn't resist. Based on last weeks playing the amp for a whole day straight and the bias not seeming to be affected, I just fired it up an hour ago. Checked the bias after about 20 minutes of the initial start up and it's right there. No erratic fluctuation and the amp is still cool....slightly warm to the touch and sounds fantastic.

I feel like I'm really doing something wrong but I've talked to a couple audio buddies that have had tubes redplate on them and they said they cleaned the tube pins and socket and didn't have any more issues after that.

Another thing is that I found a post by Nosvalves that I think kinda specializes in these Scott integrated amps..... and he said that these amps when new from the factory did not come with the ability for the consumer to check the bias. Which is why I'm guessing they ate up power tubes as mentioned by a previous poster in this thread.

Anyway, I'll keep a close eye on it and report back.
 
As I remember from when I bought my 222C new it was a real tube eater. more so than my 299D. I finally got fed up with them both and bought a MA 230. At least I didn't have change tubes every 6 months any more. I used Telefunken at the time or GE. But it seemed like every time I took the 222C for a check-up it needed a new tube here or there. Boy was I glad when SS Mac amps came along. I still have my original 2505, and except for cleaning pots and switches and polishing connectors I have never had an issue in 48 years. You can keep your tubes..

Here's the quote I mentioned .

Screenshot_20181021-124945_Messages.jpg
 
Thanks primosounds.

I couldn't resist. Based on last weeks playing the amp for a whole day straight and the bias not seeming to be affected, I just fired it up an hour ago. Checked the bias after about 20 minutes of the initial start up and it's right there. No erratic fluctuation and the amp is still cool....slightly warm to the touch and sounds fantastic.

I feel like I'm really doing something wrong but I've talked to a couple audio buddies that have had tubes redplate on them and they said they cleaned the tube pins and socket and didn't have any more issues after that..
Your initial problem may have been like JK mentioned where a bad connection in the tube pins was cleared up when tubes were removed and then re inserted. But if one socket was acting up then others may well need to be cleaned as well. I don't recommend anything but a dental flossing brush and some contact cleaner. Others recommend Caig, but those kinds of metal treatments may break down into something bad under high temperatures. You might also notice that the amp sounds better after cleaning the socket pins.
 
So I played the amp for 6 hours straight today. Checked the bias a couple times and it was good. Checked the amp periodically by hand to make sure it wasn't getting too hot and it was normal every time.

After a few hours I took the 7189 Preferred Tubes out and rolled in a brand new quad of EL84M's I got from Tube Depot quite a few years ago. Set the bias after about 20-30 minutes and it set fine/normal. Nothing erratic.....checked the bias a couple hours later and it was real close. These tubes sound great.....which reminded me of why about 8 years ago I bought a couple of extra quads because I really liked them in this amp.

At this point everything seems totally normal since now running the amp a total of 18 hours since the tube redplated. I won't take it for granted though.....I still plan on having it checked out and won't leave it unattended while it's on.
 
I still plan on having it checked out
I'd save your cash. The tech won't "find" anything wrong if it's working fine. The problem was intermittent and most likely a tube-pin-contact issue. However, if it's due for a checkup, there's nothing wrong with a little preventive maintenance.
 
I'd save your cash. The tech won't "find" anything wrong if it's working fine. The problem was intermittent and most likely a tube-pin-contact issue. However, if it's due for a checkup, there's nothing wrong with a little preventive maintenance.

Thanks jkaley that's good to know.
 
It didn't cost me anything so I had my tech check it out anyway a couple days ago. Everything is totally cool......except for the fact that I've been biasing it WRONG this whole time and I wasn't even checking the balance!

He got me all straightened out (it's very simple actually) and everything is cool. The amp sounds like a million bucks and I'm rollin tubes like there's no tomorrow......
 
It didn't cost me anything so I had my tech check it out anyway a couple days ago. Everything is totally cool......except for the fact that I've been biasing it WRONG this whole time and I wasn't even checking the balance!

He got me all straightened out (it's very simple actually) and everything is cool. The amp sounds like a million bucks and I'm rollin tubes like there's no tomorrow......

Eeek! Glad you've got this all sorted out :)
 
So I learned my lesson by putting regular EL84 tubes in my 222c. I got lucky and the only damage was to the tube and not the amp. Confirmed by my tech.

I have several quads of EL84M tubes and I like them but not as much as the newly aquired NOS RCA 7189's I just got about a week ago.

I've been reading recently about an E84L power tube made by Siemens. It's supposed to be a long lasting tube and can handle plate voltage up 420 which sounds like it would work well with my 222c.

I want to pick up another nice set of 7189's or these E84L's. Anybody have any experience with these E84L's? What's your opinion/ take on these?

Thanks for any input!

-Scott
 
I picked up a Scott LK48B years ago from CL...it was built by the seller's uncle, had all the original tubes, wood case, owners manual. The original 7189 are Telefunken, and have an extra quad of Lowery organ labeled Amperex 7189. Couldn't go wrong with those...

One of the original Telefunken 6GH8 had issues, and I didn't have big money for Telefunken, so I picked up RCA 6GH8. All the 12AX7 are Telefunken smooth plates, and Mullard GZ34 rectifier...
 
I've been running Mullard EL84s in my 222C without any problems, precisely because these amps are conservatively biased.
 
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After some research I found that the E84L (not EL84) are not recommended to put in a 222c.

I'm gonna play it safe and stick with the 7189's the amp was designed to use. This amp is damn near 60 years old and I don't want to take any chances.
 
After some research I found that the E84L (not EL84) are not recommended to put in a 222c.

I'm gonna play it safe and stick with the 7189's the amp was designed to use. This amp is damn near 60 years old and I don't want to take any chances.
This was mentioned in the much earlier post when the Siemens el84 were used instead of the 7189 type. As good as those german tubes were, they are not designed for the higher voltages required in this Scott amp.
 
This was mentioned in the much earlier post when the Siemens el84 were used instead of the 7189 type. As good as those german tubes were, they are not designed for the higher voltages required in this Scott amp.

Right but the reason I was interested in the E84L (not EL84) was because of it's ability to handle higher plate voltage like a 7189. I'll have to dig up the info I found on this because they're were other factors that disqualified the E84L from being suitable in a 222c.
 
What do you have the bias set at on your 222c? I have mine set at 200mv.
Sorry, I'll have to dig out my unit to check. It's not in rotation right now. Scott says the 222C runs the tubes at 75% of the tubes rated average dissipation.
 
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