EchoWars' KA-7300 cap mod and my KA-4006

roger2

roger2

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Here's the link to the modification I am referring to:
http://www.audiokarma.org/forums/showpost.php?p=597666&postcount=3

EW quote from that post:
"You can see the new large 1.5µf Matsushita metal polypropylene input cap at the amp input stage, replacing the stock .47µf job."



Capacitors Ce3 and Ce4 on my KA-4006 are, I believe, serving the role of "input cap at the amp input stage" just like the ones replaced in the KA-7300 mod.

Would someone please verify this by looking at the schematic?

This link will lead you to a .pdf of board # X07-1350-10.
http://www.eserviceinfo.com/download.php?fileid=55043


Pic below is of one of the caps in question in my KA-4006. It is called C3 on the board and Ce3 on the schematic.
 

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Ce3 and Ce4, indeed.

Looks like a pair of alternate solder pads for you there. How convenient.
 
EchoWars said:
Ce3 and Ce4, indeed.

Looks like a pair of alternate solder pads for you there. How convenient.
Click to expand...


Did Kenwood do that for mods or did this board have a bigger cap in a different amp?

I noticed that your KA-7300 had the same set-up.
 
Your Ce3 is a tantalum cap, good reason to replace it. I Think you may have similar caps in the tone and phono preamp boards also.
 
roger2 said:
Did Kenwood do that for mods or did this board have a bigger cap in a different amp?

I noticed that your KA-7300 had the same set-up.
Click to expand...
Boards are often built to accept several possible parts when the final decision for the part has not been made yet. I'm sure the engineers wanted a film cap, but somewhere along the way a tantalum was chosen, likely to save a dime or two.
 
ecluser said:
Your Ce3 is a tantalum cap, good reason to replace it. I Think you may have similar caps in the tone and phono preamp boards also.
Click to expand...


Yes, the phono pre-amp board does. I know that because of your advice in another KA-4006 thread to replace those tantalums :thmbsp:

The tone board has all electrolytics as far as I can see.
 
Regarding my Ce3 and Ce4:

Is it OK to increase the uF of these a little? As in the KA-7300 where they went from .47 to 1.5

The originals in the Ka-4006 are 1uF.


Also I could not find (D-Key, Mouser, Madisound) any of the same very pretty looking polypropylene caps that EchoWars used. May I ask where did you find those?


At Digikey I found:
metalized polypropylene:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=BC2076-ND

and metalized polyester:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=EF1155-ND


Either of these would fit nicely in the space I have. But the first sample does not look like any cap I have seen used in an amp. Maybe my search went astray?

What should I use?
 
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The caps I use are Panasonic Metallized Polypropylene, the ECWF(B) Series. Increasing the value is fine. Go with a 1.2 or 1.5µf 250V cap (PF2125-ND or PF2155-ND).
 
Thanks again...

Yes those are at Digikey. When I searched earlier I specified a lead spacing that excluded those Panasonics. My holes are @ .68" apart and that cap's leads are .787"

Should fill up that space on the board nicely. Can't wait to post a pic of that board when it's done.
 
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I used 250v, 1.2 uF Panasonic ECW F(A) polypropylenes

The larger ECW F(B) of same specs would have been crammed in very tight. And the Vishay linked to in post 7 above would have fit but the lead spacing did not match and the leads were too short to stretch.

Finally got these in after only 13 months :D

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roger2 said:
I used 250v, 1.2 uF Panasonic ECW F(A) polypropylenes

The larger ECW F(B) of same specs would have been crammed in very tight. And the Vishay linked to in post 7 above would have fit but the lead spacing did not match and the leads were too short to stretch.

Finally got these in after only 13 months :D

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Click to expand...

Lookin' good. What's the exact hole spacing on the PCB? (in mm)
 
Oil... I learned long ago to never state anything as being exact in an online forum...

My best measurement for the (larger of the two available) lead spacings is 23/32 inch which converts to approximately 18.25 mm


I am happy with the ECW F(A) decision. The pic at Digi-Key was not accurate, it showed the cap as black colored. But it turns out that it looks just like the ECW F(B), just a bit smaller.
 
I just wanted to check (for myself) if the favoured Wima MKP4 or Wima MKS4 would fit, but they don't because Wima seems to have either 15mm or 22.5 lead spacing, but not the ~18mm available pitch.

Your choice seems fine, nothing to say.
 
Lead spacing was not the only consideration. Space is also limited by the presence of other components. The numbers I came up with for max overall physical space available were 9.5 mm x 22.25 mm. These numbers include an arbitrary and unmeasured (guestimate) for free space between the new cap and nearby existing components.

I did not do an exhaustive search, but I did thoroughly utilize both the Digi-Key and Mouser parts search tools seeking a polypropylene (not polyester) cap in the 1.0 - 1.5 uF range and also with a workable physical size. As alluded to before, the ECW F(B) may have fit but it would have been crammed in very tight in relation to other components.

As for the Orange Drop, well I don't know if there is more than one version of that cap. It did not appear in any of my searches. But I did follow a link in one of avionic's posts and the Orange Drop cap from that link, in 1uF, had measurements of 18.29mm x 31.75 mm. Definitely would not fit in the space.
 
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I see your point, space can be very limited in kennie amps. I just did today an autopsy to recover the PCB from a KA-2002 amp (the remains of that unit are up on sale in barter town), which I will completely rebuild and then use it as a replacement PCB for an idling KA-2002A amp. Amazing how many components they did fit on one board, it will be the same search as you have for components that actually fit, and less a matter of what I would like to have on it...
 
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