Krell KSA 50 pcb - Page 849 - diyAudio
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Old 28th April 2013, 03:11 PM   #8481
Marra is offline Marra  United Kingdom
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That is nice work henryve it must be a two man lift.
Two power switches?Is each channel with its own mains switch?
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Old 28th April 2013, 04:47 PM   #8482
henryve is offline henryve  South Africa
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Quote:
Originally Posted by Marra View Post
That is nice work henryve it must be a two man lift.
Two power switches?Is each channel with its own mains switch?
Yes, it's actually one switch assembly containing 2 switches. Each switch goes to a separate transformer. Yes, it is damn heavy. I guess about 40kg.

Casework all done by hand. Hard work, no wonder the guys just buy from Modushop. Unfortunately the shipping to SA will be astronomical, so I have to DIY. I made a few mistakes and learned a few tricks along the way. I might redo the top plate. The countersinking is a buggerup. Countersinking in Aluminium is a nightmare with fluted bits. Don't use them. Ever. Rather use the hole-type countersinks. I am still trying to find where to get them.

Ali, try passive. It is worth it. The amp is dead quiet.

Last edited by henryve; 28th April 2013 at 04:54 PM.
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Old 28th April 2013, 05:18 PM   #8483
alibear is offline alibear  United Kingdom
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Thanks Henryve, I will try again as I Would really like it passively cooled.
Now I will ask a question that has been asked before but I have not seen a definitive answer . Is the circuit that is used for both Jans and pink mouse boards the ksa50 mk1 or the mk2 version? There are boards for sale on eBay from JIMS Audio that are listed as ksa50mk2 and the circuit for these is quite different to those on this thread.
Any information please.
Thanks for your help
Alan
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Old 28th April 2013, 08:31 PM   #8484
AVWERK is offline AVWERK  United States
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Henry
Zephyr aircraft tools makes some nice adjustable stop countersinks for aluminum
Also, most of the flush screw head angles for a first class fit and finish match the angle of the countersink along with the right drill bit that matches the countersink pilot size. Most aircraft sizes are number drills #10,13,21,30 etc.
This prevents wobbling when countersinking of course.

The early Krell enclosures had this same fit and finish only done this way for consistancy.
Most store bought flush countersunk machine screws have steeper angles that don,t quite match some countersinks

Regards
David

Last edited by AVWERK; 28th April 2013 at 08:49 PM.
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Old 28th April 2013, 09:21 PM   #8485
henryve is offline henryve  South Africa
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Thanks AVWERK for that insight. I guess that is why most builders don't bother with that hassle and just use capscrews.
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Old 29th April 2013, 05:44 AM   #8486
neychi is offline neychi  Croatia
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Quote:
Originally Posted by alibear View Post
Thanks Henryve, I will try again as I Would really like it passively cooled.
Now I will ask a question that has been asked before but I have not seen a definitive answer . Is the circuit that is used for both Jans and pink mouse boards the ksa50 mk1 or the mk2 version? There are boards for sale on eBay from JIMS Audio that are listed as ksa50mk2 and the circuit for these is quite different to those on this thread.
Any information please.
Thanks for your help
Alan
Actually, both. The mk1 after '83 and the first version of mk2 had the same circuit. The only difference is in the cooling fan placement (mk1 on the top, mk2 on the bottom). The mk2 version had relay speaker protection, mk1 had fuses. The final mk2 version had the mosfets, same as ksa100mk2 (Jims audio).
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Old 29th April 2013, 04:16 PM   #8487
JKoch is offline JKoch  Poland
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Hi henryve

I made KSA-50 Mk2 based on my own project of pcb. This is a copy of original Krell's pcb.

Janusz
Attached Images
File Type: jpg KSA50mk2 Pcb.jpg (151.7 KB, 542 views)
File Type: jpg PCB Pack.JPG (150.1 KB, 516 views)
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Old 29th April 2013, 07:35 PM   #8488
henryve is offline henryve  South Africa
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Very well done PCBs.
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Old 29th April 2013, 08:49 PM   #8489
Jozua is offline Jozua  South Africa
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Janusz

Any boards for sale ?

Jozua
Cape Town
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Old 4th May 2013, 09:20 PM   #8490
JKoch is offline JKoch  Poland
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Quote:
Originally Posted by Jozua View Post
Janusz

Any boards for sale ?

Jozua
Cape Town
Hi Jozua

Two years ago I designed the pcb and organized group buy. Finally I ordered ca 50 pcs for members of polish DIY Audiostereo forum. But notice that the pcb has the same pattern of traces and dimensions like original KSA-50 Mk2 amp and designed for original transistors only: first stage build on 2SC1845/2SA992 NEC and second stage on 2SC2238-Y/2SA968B-Y Toshiba. Buy this type of both Toshiba transistors is nearly impossible at this time. Probably all devices offered in nets are fakes. I bought bunch of both types of Toshiba' transistors in China and resold them to pcb' buyers. Both Toshiba transistors were used parts and disassembled from old electronic devices. They are 100% genuine Toshiba. Drivers are MJE15030/MJE15031 ON Semi. Power stage is build on MJ15003/MJ15004 or MJ21193/MJ21194 ON Semi and are out this pcb (on heatsinks). Resistors were the same type as in original Krell: Vishay-Dale CMF type.

Regards

Janusz
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