Tube Amp Gurus... need help!

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SFW

SFW

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So last week I plugged in my Splawn for the first time in a few weeks and was greeted by silence. While attempting to troubleshoot the issue, I noticed that I'm getting a weird high pitch whistle when signal goes to the amp. And its coming from the actual tubes! Which are only a month old. Video below shows the issue. DO you think its just bad tubes?

 
Arcing. Turn it off and replace the tubes as they are gassy and arcing internally.

I’m honestly really surprised that isn’t completely obliterating your ears out of standby.

I will say it seems only that one tube is doing it - it would be safe to replace that only one and then rebias based on whatever is the hottest tube still.
 
Its actually all four tubes doing it. These are the TAD Red Plate EL34s that Pete Thorn did a video on recently. I can say that they aren't looking very durable to me at this time. They have been in the amp about a month and have only been turned on twice in that time.
 
You should pull all the new tubes out and replace the old ones you pulled out just to verify it is the new tubes. I remember you recently turned this amp on without a load connected and it seemed you escaped any OPT damage but you never know.

If the amp is fine with the old tubes that were working fine when you pulled them out then it would be time to return those new ones if you can. It's so hit and miss these days with tubes. Sorry about your misfortune SFW....

To me they appear to be redplating and arcing at the same time........NO BUENO..........:eek:
 
harddriver said:
You should pull all the new tubes out and replace the old ones you pulled out just to verify it is the new tubes. I remember you recently turned this amp on without a load connected and it seemed you escaped any OPT damage but you never know.

If the amp is fine with the old tubes that were working fine when you pulled them out then it would be time to return those new ones if you can. It's so hit and miss these days with tubes. Sorry about your misfortune SFW....

To me they appear to be redplating and arcing at the same time........NO BUENO..........:eek:
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What would cause red plating? They are biased at 30mA.
 
It appears the tube are just shorting out internally could be the anode plate to cathode plates hard to tell could be anything shorting internally. Redplating is usually caused by excessive current draw across the plates and then that condition usually leads to shorting out and complete tube failure. When tubes go they go could be an early death or a long life, never can tell sometimes.

Usually the 24 hour burn in process weeds out the weak ones that die early and some squeak by and fail rather quickly as you are experiencing. I wouldn't keep running them to troubleshoot any further because if one completely shorts it could take out a grid resistor and possibly damage your output transformer. None of the tubes look healthy to me. What tubes did you pull out of it? Stick them back in and see how things go.

If the amp is fine with the old quad then it's the new ones with severe issues.
 
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We assume shorting from plate to cathode but honestly it could be plate to heater or plate to grid (not screen grid).

Honestly that kind of arcing can stress the primary winding of your OT and is hard on your B+ and screen grid caps as it pulls the maximum current possible from the PT. Even the rectifier diodes can overheat and be damaged due to arcing like that. It’s normally never something you want to turn on and video as it can cause further damage up stream from the defective tubes.

Pop in the old tubes and bias them up. I believe you got a quad of bad tubes. Throw every one of those in the trash. The second they have internally shorted they can no longer be trusted as you don’t know what it shorted to internally.
 
I had a brand new quad of JJ 6CA7 that were bad from the first start up. It had been so long since I had bought them I couldn't ask for a replacement set. Sometimes it's just luck of the draw.......:bash:
 
SFW said:
Ordered a new quad of tubes. They smoked as soon as I turned the amp on. So I guess it's either get a hold of a local amp tech, or see if Dave Friedman will work on a Splawn. If Dave will take it on, I plan to have the amp modded as well.
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Sorry for your troubles op. Seems like there was a run of Splawns with cold solder joints? Splawn had some help in shop soldering and they didn’t do a very good job. Wonder if you have one from that time? I don’t know exactly the time frame this was. Probably over 10 years ago.
Good luck!
 
Racerxrated said:
Sorry for your troubles op. Seems like there was a run of Splawns with cold solder joints? Splawn had some help in shop soldering and they didn’t do a very good job. Wonder if you have one from that time? I don’t know exactly the time frame this was. Probably over 10 years ago.
Good luck!
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My amp is from 2005, when Scott was a one man shop.
 
I think the bad tubes from prior have caused damage and it’s not the fault of the new tubes.

Let us know what the problem is/was once you’re able to take it in to get repaired
 
SFW said:
Ordered a new quad of tubes. They smoked as soon as I turned the amp on. So I guess it's either get a hold of a local amp tech, or see if Dave Friedman will work on a Splawn. If Dave will take it on, I plan to have the amp modded as well.
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So did you install the old quad back into the amp and those are the ones that burned up when you turned the amp on? Or did you turn the amp on with the tubes in your video that were already arcing?

It is possible that the OPT took a hit when you turned it on without a load that one time and it took a while to surface.
 
Racerxrated said:
Sorry for your troubles op. Seems like there was a run of Splawns with cold solder joints? Splawn had some help in shop soldering and they didn’t do a very good job. Wonder if you have one from that time? I don’t know exactly the time frame this was. Probably over 10 years ago.
Good luck!
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True all of that.
 
harddriver said:
So did you install the old quad back into the amp and those are the ones that burned up when you turned the amp on? Or did you turn the amp on with the tubes in your video that were already arcing?

It is possible that the OPT took a hit when you turned it on without a load that one time and it took a while to surface.
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No, I had new tubes in the amp when I turned it on to bias. And I believe that you are correct. I believe that the OT finally gave out. According to Scott, he can no longer get those transformers. So I guess I'll end up with something different in the amp.
 
If you order a Marshall Plexi clone from Chris Merren, I believe they are less than 200. Vs a Mercury which will probably be 2X that price.
 
SFW said:
No, I had new tubes in the amp when I turned it on to bias. And I believe that you are correct. I believe that the OT finally gave out. According to Scott, he can no longer get those transformers. So I guess I'll end up with something different in the amp.
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Well that sucks.....sorry about the new quad....

To my knowledge Scott was using Heyboer transformers in the early Quickrods and then switched to Classictones, I'm not sure why Heyboer shouldn't be able to make the exact same transformer they have what ever spec Splawn was using. They might be pissed that he took his business to Classictone who knows. Maybe first get it diagnosed then decide what transformer you want to use if it indeed the problem.

I hear Heyboer is backed up with orders and can't keep up. I think the Mojotone transformers might be made by Heyboer maybe check into that and get that clarified. In the pictures of the Mojotones I see HTS model/build numbers on the sitckers and I'm fairly certain Heyboer uses that nomenclature. I think your choices are Hammond, Mercury Magnetics and Heyboer now.

Who build Merren's transformers?

So what is Splawn using now since Classictone has ceased operations?

I have a Mercury Magnetics Axiom MMO-100M in my Splawn modded Marshall and it's a great sounding output transformer, I had Scott install it and a new take out Marshall power transformer when he rebuilt the amp in 2003.
 
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harddriver said:
Well that sucks.....sorry about the new quad....

To my knowledge Scott was using Heyboer transformers in the early Quickrods and then switched to Classictones, I'm not sure why Heyboer shouldn't be able to make the exact same transformer they have what ever spec Splawn was using. They might be pissed that he took his business to Classictone who knows. Maybe first get it diagnosed then decide what transformer you want to use if it indeed the problem.

I hear Heyboer is backed up with orders and can't keep up. I think the Mojotone transformers might be made by Heyboer maybe check into that and get that clarified. In the pictures of the Mojotones I see HTS model/build numbers on the sitckers and I'm fairly certain Heyboer uses that nomenclature. I think your choices are Hammond, Mercury Magnetics and Heyboer now.

Who build Merren's transformers?

So what is Splawn using now since Classictone has ceased operations?

I have a Mercury Magnetics Axiom MMO-100M in my Splawn modded Marshall and it's a great sounding output transformer, I had Scott install it and a new take out Marshall power transformer when he rebuilt the amp in 2003.
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I’ve read on the Marshall forum that Merren winds his own. He’s the first choice for a few guys in England who do spot on restorations( they have inventory of mustards, re formed caps etc etc from the early 60s up till early 70s date codes) next would be Marstran and Metro.
But I’ve also heard good stuff about Heyboer as well.
 
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