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Power tube issues with my Traynor YBA-200

Juniorkimbrough

Juniorkimbrough

Mar 22, 2005
3,718
6
Mississippi / Memphis, TN
www.lakland.com
Disclosures
Endorsing Artist: Lakland Basses
#1
At an informal gig/ jam session at my bandmates house this weekend my Traynor quits on me....was pretty sure it had blown a fuse but I didn't have an extra at the time. Pulled the fuse out yesterday and it was definitely blown, so I go get a fuse today and now I'm having some power tube issues. I KNOW I have the right fuse because I checked it already like 5 times.

Back a month or two ago I replaced the stock 6550's with KT-88's, I bought the whole retube kit from Euro tubes. Currently when the KT-88's are in and the amp is on the very last power tube doesn't light up when turned on in standby. I tried switching two tubes places and the same tube didn't light up so that's probably an issue with the tube itself. After taking all the KT-88's out, I put the stock 6550's back in to see I could get it to work. Turned it on in standby and all 4 tubes lit up.....I let it warm up and turned it on and it was still making the same crackling sound it had previously and after being on for a second the next to the last power tube starts to get a whole lot brighter than the rest.

I checked the pre amp tubes as well and they all look fine.

Any suggestions?
 
#2
Since you observed a blown fuse, crackling sounds and one of the tubes getting alot brighter, this is usually an indication that there is a serious problem with the circuitry...and possibly right there in the output stage.

It could be that one or more bias resistors have changed value over time due to heat exposure, and or is actually breaking down and arcing internally. That would certainly explain the crackling sounds you are hearing.

Often a blown fuse is indicative of more serious problems with an amplifier. It usually means that something is drawing excessive current from the power supply. My advice to you is to have it checked out by a knowledgeable and reputable technician. Good Luck!
 
#3
berniebstring said:
Since you observed a blown fuse, crackling sounds and one of the tubes getting alot brighter, this is usually an indication that there is a serious problem with the circuitry...and possibly right there in the output stage.

It could be that one or more bias resistors have changed value over time due to heat exposure, and or is actually breaking down and arcing internally. That would certainly explain the crackling sounds you are hearing.

Often a blown fuse is indicative of more serious problems with an amplifier. It usually means that something is drawing excessive current from the power supply. My advice to you is to have it checked out by a knowledgeable and reputable technician. Good Luck!
Click to expand...

+1 get it checked over by a tube tech!!!!!!! Don't risk doin more damage to it!
 
#8
okay so I dropped my amp off at the tech a week or so ago and I call back today to see if it's ready to pick up and he tells me that the whole power section is fried because of the KT-88's, which I think is total BS. now i'm trying to get in touch with Yorkville and figure out a REAL tech to take it to or it looks like I may have to ship it to them......ugh

The unlimited warranty is great but it is absolute HELL trying to find a dealer that will repair this amp. All 3 or 4 dealers I've spoke with have given me the run around.
 
#9
okay after about 5 or 6 back and forth calls to Yorkville, my local Yorkville dealer, and a local tech I think we have it worked out.

I can get it repaired by an unauthorized tech just as long as it is taken to a Yorkville dealer and the dealer takes it to the tech....hopefully this will work out. I'll keep you guys updated.
 
#10
keep us posted- us tube amp lovers-well me anyway -like to get any info I can re tubes & their actions/re-actions etc.. so I can store it for reference l8r! Also I think U R right re the KT88's frying.... they should be fine IMHO- they're the same -basically- as 6550's aren't they? I thought they were.....but I'm NO tech, pity..... nowhere near.........
 
#11
man you cant just get brand new tubes and stick them in your amp. tubes arent like light bulbs when they burn out they must be rebiased so that they are running and equal current through them. some amps have an auto biasing feature but i do not believe that traynors have this. It should only cost about 20 bucks to have the amp biased by a tech. good luck man
 
#12
BrOwNsOuNd said:
man you cant just get brand new tubes and stick them in your amp. tubes arent like light bulbs when they burn out they must be rebiased so that they are running and equal current through them. some amps have an auto biasing feature but i do not believe that traynors have this. It should only cost about 20 bucks to have the amp biased by a tech. good luck man
Click to expand...

I do my research, the Traynor YBA-200 is auto biasing. Thanks for your input though.
 
#13
FWIW, I called a guy who should know, about the power tube thing, and of course it's kind of like a doctor diagnosing you from a phone call, but what he said sounded like it could be right.

First, he said when the tubes brighten, it often is the filament getting ready to fail. Sometimes it can even sag and short the tube innards (grids, etc) which can cause other damage. The three others turning blue at the same time is unlikely to be a vacuum loss (although as posted above, that does cause a blue tube), but more likely is a situation where the plate voltage is exceeding the tube design max. In that instance, he says, the tube will operate but the life is shortened. If that turns out to be the case, the tech will no doubt find out why the plate voltage is boosted, and fix it. Maybe more important though is that you shouldn't run three power tubes because he says it unbalances the output transformer, so either 2 or 4 are better than 3.
 
#14
I had a Factory drop shipped YBA 200-2 with the factory tubes do basically the same thing worked goof for a few hours then started making crackeling noises. Called Musicians Buyand ups picked it up the next day and I had a brand new amp in a week and it has worked flawlessly. Traynors great warranty works for me.
 
#16
rodl2005 said:
keep us posted- us tube amp lovers-well me anyway -like to get any info I can re tubes & their actions/re-actions etc.. so I can store it for reference l8r! Also I think U R right re the KT88's frying.... they should be fine IMHO- they're the same -basically- as 6550's aren't they? I thought they were.....but I'm NO tech, pity..... nowhere near.........
Click to expand...

They are not the same but will usually work fairly well in the same amp as long as the biasing is addressed. IIRC the 6550 is a beam tetrode while the KT88 is a pentode. Heater current is virtually the same at 1.5A for the '88 and 1.6A for the 6550.

Good luck with the repair.

Paul
 
#17
i realize I never followed up with this thread. It turned out one of the power tubes went bad and ended up frying a few small pieces inside the amp (can't remember exactly what it was, it's been a while). took it to a highly regarded tech in the area and he fixed it up nicely...contacted euro tubes about getting another power tube, told them what happened and they sent me a new tube at no charge. It took a while to get it fixed but once I got it back it was like brand new and I used it for about a year with no problems.
 
#19
This is why I come from the "If It Ain't Broke, Don't Fix It" school of amp repair. I say if it works, leave it. Glad you're getting it worked out, though. Changing out tubes is fun and all that, but it can lead to things like this. That's why I always stick to what they say to use and I only replace tubes when they go bad. Got some 40 year old tubes that are still going strong in some of my amps.

Anyway, you don't need a lecture from Gramps. You learned your lesson ;)
 

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