Babelfish XJ , or JX …….. or whatever (Aleph X servo for Greedy Boyz)

[pinnocchio]

Hi Zen Mod,

Today I finished assembling the Mosfets on the OPS PCBs and I decided to go in the garage to see how I would fit them in the chassis, only to realize that the chassis might be way too small for the thermal of this amplifier...

Here's a few pictures, please tell me your honest thoughts... Dimensions are as follow :

Internal measurements :
188mm Height
413mm Dept
255mm Width







If you tell me there's no chance I can make this work, could you send me a link to a proper chassis?

Thanks
Do

 

[pinnocchio]

If the chassis configuration does not work as is, I have an idea that might just work... Take the heatsinks and put them in the middle to make like a wind tunnel and finish the sides with expensive looking wood. This way I could 3x Noctua fans under the chassis pushing or pulling air through the heatsink tunnel. This should give it way enough cooling.

My only problem would be the PSU sharing... Putting the PSU on one side would require extreme long cables for the other side and it would not be good... So, I'm thinking of having a dedicated PSU per side but connected to a single AC rectifying scheme feeding the two PCBs. Would this work? Or what about using two SLB PSU (from XRK971) per mono-block? I'm just worried that sharing a single pair of primaries on two bridge rectifiers would cause issues (humming noise, seen this before..).

Thoughts?

Thanks
Do

 

[Zen Mod]

either make it properly , or don't make it at all ..... too much compromises always ends in pain - in most cases price is decreased level of reliability .....

you got PM

 

[Zen Mod]

another thing - it's always good first to clamp/bolt mosfets to heatsink , then solder to pcb - simply because rotation of part is inevitable while tightening , even if you have it fixed with adjustable spanner , as you can see on pictures in my blog

however , as you already soldered them to pcb , you must re-flow all pins after heatsinking ..... to relieve mechanical stress from pins

 

[gaborbela]

Interesting project (maybe good replacement for my AX) all do my Xformer is only 2x18V 1.5KVA.
The heatsink only gets with the AX 40-45C after many hours of listening.
I used the Kristijan K type of PC boards and schematic biased to 7A / channel

 

[pinnocchio]

So just to be on the safe side and double check everything...

OPS :
U-1, U-2, U-3, U-4 : PSU Negative supply (all tied together)
U+1, U+2, U+3, U+4 : PSU Positive supply (all tied together)
W1, 'W1, W2, 'W2 : PSU 0V (all tied together)
SA, 'SA, SB, 'SB : Speaker output (all tied together)

Thanks
Do

 

[Zen Mod]

in a middle of re-OS-ing and re-all main programs-ing my main PC , so I can tell you that tomorrow , when I can open pcb files

 

[res07njc]

another thing - it's always good first to clamp/bolt mosfets to heatsink , then solder to pcb - simply because rotation of part is inevitable while tightening , even if you have it fixed with adjustable spanner , as you can see on pictures in my blog

however , as you already soldered them to pcb , you must re-flow all pins after heatsinking ..... to relieve mechanical stress from pins

Aint that the truth, but he has so many parts to navigate, and they're already mounted. What's wrong with tapping well-selected holes for M4 between every other fet to fasten a beefy piece of aluminum bar or small u-channel stock to press clamp all those parts against the sinks? They'll slide under, then tighten.. Allows a little slop factor, and maybe even structural too. It's an idea!

 

[Zen Mod]

all roads leads to Rome

 

[pinnocchio]

Hi Zen Mod,

If you did not yet ship the parts (jfets and other parts we talked about), could you please sell and ship me two more matched quads of BD139 (Q2, Q3, Q11 and Q12), please?

Please let me know how much and I'll send you the moooney by Paypal.

Grazie mille!
Do

 

[Zen Mod]

beeezeee , and headless (mindless?) even more than usual

eeemail me your snailmail addy , to save me searching for , put full list what you need and I'll send with some packages I'm preparing to send pre-BAF

no money

 

[pinnocchio]

ok, email sent, thanks so much!!!!

 

[pinnocchio]

Hi ZM,

I see the BZX90 is a 6.5V zener but a temperature compensated zener. You told me I could forget about those in the OPS, not populate or 9.1V zeners would be ok since there are already some in the IPS, correct? If I put in the 9.1V zeners on the OPS, do they have to be temperature compensated type?

The 7.5V zeners on the IPS, do they have to be temperature compensated type (OTC)?

I'm asking because this type of zener goes for about 10$ a piece!

But if it is what I need then it is what it is! hehe

Thanks
Do

 

[Zen Mod]

you certainly read from Eagle generated BOM ( if I remember OK that I sent you that) that these are temp. compensated ones ........ in any case - use plain simple zenners , do not worry .... and now you know why I'm always saying that BOMs are baaaad for brain

my general rule is to avoid parts made of preputium wherever and whenever I can ....... we decided to use JFets here and there , SIT here and there , special voltage references here and there , but you'll never catch ZM - using fancyschmancy part , if there is proper industrial quality cheap one

in any case - good that you asked

I received your e-mail , btw.

 

[pinnocchio]

ok ,cool! Thanks for the info!

So, 9.1V zeners on the OPS it is! 500mA

Thanks ZM!!!

 

[pinnocchio]

Hi ZM,

What brand/model were those bridges in the picture of your Babelfish build?

Thanks
Do

 

[Zen Mod]

Powersem , 72A , 5mm (M5) bolts as contacts

 

[pinnocchio]

We don't have those here but I did find this one, which seems to be hyperfast and soft recovery 60A... Not bad at all...

VS-UFH60BA65 Vishay Semiconductor Diodes Division | Discrete Semiconductor Products | DigiKey

 

[Zen Mod]

shoot!

 

[pinnocchio]

Hi ZM,

When you get a chance to review post #206 please.

Thanks
Do