B&K EX-442 Recap Project

[code46]

A couple of years ago my B&K EX-442 started having some channel cutting issues and I stored it away. Now I'm hoping to recap it, set the bias and put it back into rotation.

 

[code46]

Schematics

 

[code46]

Innards

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[code46]

Additional schematics of older versions.

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[painttoad]

be careful. b&k folds the leads over tight and those pads are fragile and easy to blow out.

 

[code46]

The 5 yellow axial caps need replacing. Schematic says C2,C3,C4,C9, and C10, are 0.1uF. Fellow AK member vsat88 replaced these with Wima MKP 10's for their rehab project.

Yellow axial caps Marked:

100V
1.50MKT
.1/5
90/21​

Wondering if I should also change out the mica caps C7 and C11. Schematic says C7 is 200pF and C11 is 30pF.

C7 marked:

CMO5FD
221 J03
SAHA​

C11 marked:

30+-5%
500V K​

Bridge Rectifier:

Electronic Devices EDI
9037 FPI4020W
40A 200V​

 

[code46]

be careful. b&k folds the leads over tight and those pads are fragile and easy to blow out.

Thank you, this is good to know. I have a Hakko desoldering gun but still need to be careful not to lift a pad.

I plan to pull all the Toshiba 2SJ115/2SK405 and test them out of circuit.

 

[rompstar]

man that PCB Board leads look crispy / on my non-Sonata, its a bit easier I think, anyways, I am learning KiCAD (free open source) electrical engineering type of software and will re-create the PCB board for the left-right channel board that go on top of the capacitors, you should consider doing the same on that PCM Board, learning curve is slow, but you can do it.

mine are no where near crispy like yours from those pics, but the edges are slowly curling up, anyways, soon new board will be made... drop me a line if you interested, and I can print anyone else extras, I will post later pics in a new post to let others know.

 

[TimPD]

Useful thread, thanks.

I took delivery of a Ref 2220 today. Good cosmetic condition. DC offset on one channel is close to zero, whereas it is about 3.5 mV on the other channel. Planning to open it up and have a look around later, or tomorrow.

Tim