LSS 5w and 15w rectifier question

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claumi
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LSS 5w and 15w rectifier question

Post by claumi » Mon Aug 20, 2012 2:13 pm

Hey guys and gals I'm new here. I have recently acquiered a LSS and just love it. Yesterday I was playing and switched the power output on the clean channel to 15w. No sound at all!! Switched to 5w. No sound again. Switched it back to 30w : all is fine. So I thought to myself : rectifer gone bad. Pulled out the rectifier, looked it over and there where no apparent sign of damage. So I ordered a new 5y3 (Mesa) and I'm waiting for it to come. Today, just for the heck of it , I put the tube back in the amp and the 15w and 5w settings work just great on either channels. Play the amp a bit at the 30w setting and everything is fine. Switch it back to 15w and again no sound....
I'm comfused.......

Blue Fin
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Re: LSS 5w and 15w rectifier question

Post by Blue Fin » Mon Sep 10, 2012 4:51 pm

It's probably still the tube and likely to act up again.
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rfrakes
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Re: LSS 5w and 15w rectifier question

Post by rfrakes » Thu Sep 20, 2012 3:16 pm

I haad a bd rec and EL-84 when mine did this. Put 2 new EL-84s in and a

new rec and it has worked fine till last week when I was testing the dual ODs.. I use 5 watt mode most of the time.

The 5 watt mode uses only 1 of the power tubes which is the outer of the pair and the tube rec.
Last edited by rfrakes on Thu Jan 02, 2014 1:13 pm, edited 1 time in total.

rfrakes
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Re: LSS 5w and 15w rectifier question

Post by rfrakes » Wed Jan 01, 2014 1:16 pm

The 5w and 15w run the 5Y3 rectifier, 30 w uses 4 solid state diodes.


VR,

Ron
Last edited by rfrakes on Sun Apr 13, 2014 2:06 pm, edited 2 times in total.

lespauljoe1
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Re: LSS 5w and 15w rectifier question

Post by lespauljoe1 » Thu Jan 02, 2014 8:35 am

rfrakes wrote:The 5w and 15w run the 5Y3 rectifier, 30 w uses 4 solid state diodes. There is a know problem with this amp below a serial number of 06418. Mesa boogie has a mod to reduce current through the Rec tube so this won't happen. If you take it to a Mesa Boogie authorized service center, they will repair it. I have blown 3 5Y3s 2 EL-84s.


I also did the Reeder volume pot mod. There is another mod where you can combine ch1 and ch2 with a pot to dial in the amount. I did not do that mod. I am going to have the current reduction mod put in thought.

VR,

Ron
I just bought a returned LSS from Sweetwater. I had it about 2 weeks and lost the 5Y3 tube. I contacted Sweetwater, stating in my message that I suspect that is why it was returned. I received phone call promptly from the service tech. He confirmed that was the reason for return, but he made the resistor update when it was returned. He told me that Mesa has suggested another change to lower the voltage.

He also said the he and Mesa were working on a permanent fix for this situation. One thing he came up with is to use a 5R4G rectifier tube. They are designed to handle higher voltage without overloading the power tubes. Mesa agreed with his choice and has okay'ed the use of this type of tube. I placed an order for a 5R4G tube and it should be here any day. I will report back in a few weeks. Hopefully this will hold up. I love the amp and don't want to unload it.

I had on hand a NOS 5U4G & NOS 5AR4, but didn't want to try either until I spoke with someone. The Sweetwater tech told me that using either would have increased the plate voltage to the power tubes too much and would have lead to premature tube failure, so I'm happy I didn't do that.
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rfrakes
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Re: LSS 5w and 15w rectifier question

Post by rfrakes » Thu Jan 02, 2014 1:10 pm

I did the current redux mod last night and it works great. Pushed it through louder high gain. I still need to push TS9 and Sparkle drive on it and see if it holds up.

I used a 5U4GB. I had to cut the mids in half. It made the amp louder and took away some sweetness.

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