HELP on tube amp

[Viva]

Unison Simply 2, 2xEL34, and 2x 12au7. All tubes light up.
One side has no sound. One EL34 tube, blue light inside goes...dim, bright, dim, bright...and gives a buzzing sound in sync with the glow. Swapped the tubes around and problem stayed on the same side.

Changed 2 of the smaller caps near the tube base, still no sound.

Should I change the rest of the small caps, or is it the big power caps?

Appreciate the help.

 

[kmac]

Try swapping interconnect from the source around as well.

 

[zanash]

do you have to bias ...?

blue tubes is not great .....could suggest internal problems ...

does the blue tube move ?

firstly use your replacment valve set ...you do have a spare set ... for just such an occasion ?

they don't need to be great ..just working ...

you can then tell if its a vale signal or valve power issue or something else ....

yes check connections from source and speaker cables too !

thats caught me out in the past ...

can't remember what blue tinge is ..someone will know ....

if the burnt and brown ...thats easy !!

 

[SMEagol]

Dry solder joints on my old monoblocks. That did the flashing thing. I let Pete my electrics guru mate sort that out, anyone familiar with my "cocking about with expensive speakers thread" will know that was a good move! If you're anywhere near Macclesfield Pete at Dooleys Hifi might have a look at it for you. They sell Unison gear.

Will ask someone I know and PM you the findings!.

 

[Noel Winters]

HI Eagol
I googled your House ,think i got it right
monkey on the roof Probably listening to Music.
Best Regards Noel W.

 

[Viva]

I had put in new tubes and got the same blue light blink inside.

It had happened as I was listening and suddenly one side lost output. So I suspect it was a cap. Now, another friend thought it might be a resistor.

What do you think?

 

[SMEagol]

monkey on the roof, thats right, frightening that google.

spoke to my friend, suggestion as follows...
the amp is doing something called "motorboating".

He says it very much depends on the circuit but try the easiest thing first. Replace input valves

 

[Viva]

What is motorboating? Safe pleasure ride or the Titanic.

 

[SMEagol]

google it. motorboating and valve, or motor boating and valve, (not valves) theres a lot of stuff thats way too clever for me.

 

[speedy.steve]

The change in light on off or colour variation is a new one on me.
Do you have on PSU supplying all tubes? Can you check the PSU output / what's going into the tubes. EL34's run at lower V than my KT88's from memory about 230 or 300 or something like that.
If you have one PSU then it would suggest a component specific to that side. It could be a resistor or cap breaking down (you suspected the caps) but not I guess a signal cap as that would probably make noises.
I would change all the passives on that tube.


Nothing wrong with a nice blue tinge in the right light. Here's my KT88'er SoH at work:MILD:

 

[zanash]

http://www.netads.com/~meo/Guitar/Tubes/blue_glow.html

found this ....

looks like you need to take a peek inside [with everything unpluged] check out for burnt or failed components ...with valves due to the high voltage failures are usually catostophc and therfore easy to find ...not nessesarily easy to fix as you need to work out what caused the issue

 

[Viva]

See the before and after...Big Black Gates.
Gong to change all the other little ones to Black Gates and Hovland the yellow ones.

 

[Viva]

Before

http://farm4.static.flickr.com/3340/3661658807_afdf4bbeb7_o.jpg

 

[Viva]

After

http://farm3.static.flickr.com/2606/3662458496_e6ca4882bf_o.jpg

 

[Viva]

Before...

 

[Viva]

after...

 

[Viva]

http://farm3.static.flickr.com/2665/3688695654_f4834a5eff_o.jpg


Changed all caps ...and no more motor boating...good to be back on dry land.

Thanks for all the help