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FYI Chinook Owners -- Diode Failures and Repair Upgrade

Hey There Manley Chinook Owners!

My Chinook stopped producing sound a few weeks ago.  All tubes checked out fine as well as connections.  I checked on things and everything looked great.  I was stumped. 

I placed a customer service ticket with Manley.  Well, the lovely EveAnna Manley contacted me herself!  Wonderful person and a great business owner in this hobby--in my humble opinion. 

At any rate, Ms. Manley informed me that several diodes (On the power supply board, D9, D10, D11, D12) need to be replaced with some Micro Commercial Components (MCC) Schottky 5A Barrier Diodes Part# SR5200-TP.  I think the previous values were lower amperage and now Manley specifies 5A.  

My unit is out of warranty so I told EveAnna that I'm decent with a soldering iron so I'd give it a go myself.  She said if it doesn't work her guys could fix it.  EveAnna was super gracious and offered to send a tech bulletin and the schematic to make my surgery easier.  

By the way, (and I'm paraphrasing here), I think EveAnna mentioned that not everyone will have this issue.  It does, however, occur over time.  I thought it might be helpful for other owners to know this as--if you're like me--it's easy to get frustrated when such a great piece of gear quits and I cannot easily diagnose the issue. 


128x128jbhiller
9 responses Add your response
noromance's avatar
noromance
9,404 posts
 
Hi JB. Good to hear. Hopefully, that will fix it. 
millercarbon's avatar
millercarbon
12,531 posts
 
Rectifier diodes have a HUGE impact on sound quality. High speed smooth diodes will give a deeper more liquid sound. Far be it from me to butt in, but a quick search turns up the part you listed is dirt cheap. In other words, however good that thing sounded before, if you can be persuaded to crack open your wallet for some $5 hexfreds (or whatever, anything will be better than SR5200-TP) you will be floored at the improvement.  

I've done diode swaps like this before. One of the more astounding improvements you can make. Why everyone gushes and obsesses over caps while never mentioning diodes, is beyond me. Just do it. You can come and gush and thank me later.


audio2design
1,351 posts
 
I don't think Miller would know a Schottky diode if it bit him on the behind.

Stick to the Schottky diode. Schottky diodes are fast, and are every bit as soft as the HexFred (better really).  The value in HexFreds comes in at higher voltages where you can't get Schottky diodes, but if you don't mind the cost, even that is not true any more as you can get SiC high voltage Schottky diodes.
vinylvalet
836 posts
 
I've also found Manley customer service to be outstanding.
Post removed 
audio2design
1,351 posts
 
By the way, (and I'm paraphrasing here), I think EveAnna mentioned that not everyone will have this issue.  It does, however, occur over time.  I thought it might be helpful for other owners to know this as--if you're like me--it's easy to get frustrated when such a great piece of gear quits and I cannot easily diagnose the issue.


One issue with Schottky diodes is they don't do well with over-voltage, and have limited "avalanche" capability, basically how much energy they can withstand if they break down due to over voltage.

millercarbon's avatar
millercarbon
12,531 posts
 
Notice, not one word about how anything sounds.

Tin ear, can't hear.
audio2design
1,351 posts
 
Notice not one idea of how things work and hence why they sound the way they do.  When you refuse to learn, you are destined to keep recreating the wheel while the rest of us long ago moved onto cars.

What makes Hexfred diodes potentially sound better than regular rectifier diodes is they have a fast and soft recovery. The soft recovery is how fast they snap off and the reverse current.   A good amp will have snubbers around diodes to negate this even with regular diodes.  Schottky diodes are even better than Hexfreds if you are looking for soft switching / low noise.
jbhiller's avatar
jbhiller OP
1,361 posts
 
Thanks audio2design.  I had to do a little research on the subject as I'm only a hobbyist.  You summed up the points that took me much reading to get to.  

It also seems a Hexfred could sound better but not likely where switching needs are soft--here, it's a phono pre and I would think noise would be better with the Schottky.  


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