Manley Varimu motorboarding!

[mikeyB]

Hello folks!
Just got hold of a Manley Varimu to retube and maybe repair!
It has just started "motorboarding" (low freq oscillation at extreme settings) with no signal passing through.
I'm told the tubes are "well tired" and it's well overdue a retube. (Just seen the Manley retube kit - YIKES!! - over $250 to get to UK!)

Is this motorboarding likely to be due to the tubes or is there something else i should be checking - like psu filtering etc?

Any UK/Europe tube gurus know of  12AL5 (for the sidechain) equivalent. I think i can source all the signal valves quite easily, but pointers to good sources most welcome!

As always - Thanks in advance!

 

[pucho812]

does the motorboating happen on both channels or just one channel? If it's on both channels then it's more likely further up in the chain like a PSU for example. The chances are 2 tubes in one unit having the exact same identical wear is very slim.  So if it's one one channel then more it will more then likely not be the psu. if it's on both then yeah good chance it is the PSU.

Now if it is on one channel only swap the tubes with the good channel and see if it follows.

Motorboating in general is usually related to a cap going bad or a dead cap.

 

[ruairioflaherty]

(Just seen the Manley retube kit - YIKES!! - over $250 to get to UK!)

Remember that the Manley tubes are selected from thousands.  EveAnna is a good friend and we've had many conversations about this.  The crapshoot of finding your own tubes that work is only worth it if you have a whole lot of free time.

 

[Kingston]

(Just seen the Manley retube kit - YIKES!! - over $250 to get to UK!)

Remember that the Manley tubes are selected from thousands.  EveAnna is a good friend and we've had many conversations about this.  The crapshoot of finding your own tubes that work is only worth it if you have a whole lot of free time.

Testify! From my own perspective $250 is chump change.

I mean compared to making a reliable measurement/matching rig (can be non-trivial) and sorting out 40+ tubes on excel sheets. And you pay for those 40+ tubes too. That's a couple of days right there and how much was your time worth again. You do this for learning purposes only.

 

[mikeyB]

Much appreciated guys!
Pucho - yes left channel only - i'll swap out and see.
Kingston/Ruairi - Yep - chump change indeed - he needs it back quick - so i'll try cure the oscillation, give it back and let him buy the tubes in.
Kingston - done anymore on M670?

 

[hop.sing]

Did you try to rebalance the tubes? I think you can do that with a manley... If one tube is getting tired, than you should still be able to reach a nonmotorboating state that way. (Without compression though, compression would thump than, probably.)