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Kustom IIIB Bass Head [message #16326]

Thu, 27 October 2011 04:09

blindmouse
Messages: 25
Registered: February 2011
Location: The Netherlands

Junior Member

Evertime I have a gig I take with me a 1976 Kustom IIIB head as a back up. I never needed it, but you never can tell. At home, so now and then, I check it to be sure it is still working. It still does. Now I went into the chassis and noticed everything was in good shape, even the two HUGE GE 4500uf/50V fltercaps. From the outside these giants look brandnew. Now my first question: after 35 years and not much use, is it for reliabilities sake wise to change them? Second: todays same value caps are much smaller, will these caps do the job properly soundwise?

(Mouser has them big screw terminal caps, but they are pretty expensive)

Thanks.

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Re: Kustom IIIB Bass Head [message #16327 is a reply to message #16326]

Thu, 27 October 2011 07:42

stevem
Messages: 4772
Registered: June 2004
Location: NY

Senior Member

Even though the new smaller caps are much better at having a low ESR value, the stock large computor grade caps to me pack more punch/reserve when called for voltage wise.
The best way to keep those electroyltic type caps good is to at power the amp up once a week, and you do not even need to have a speaker hooked up, just ley it sit and idle for a hour.

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Re: Kustom IIIB Bass Head [message #16329 is a reply to message #16327]

Fri, 28 October 2011 03:54

blindmouse
Messages: 25
Registered: February 2011
Location: The Netherlands

Junior Member

Does this mean you'll need a smaller size cap with a higher voltage handling, let's say 100V, or you'll have to find a cap that's about the size of the original ones?

I'll have the IIIB run with no load for a while.

Thanks

[Updated on: Fri, 28 October 2011 03:55]

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Re: Kustom IIIB Bass Head [message #16331 is a reply to message #16326]

Fri, 28 October 2011 11:20

stevem
Messages: 4772
Registered: June 2004
Location: NY

Senior Member

No, the original size filters can be had by mouser electronics in the Mallory brand.
You can go up to double the MFD value for more clean head room before the amp clips and going up to a voltage rating of 75 to 100 volts will extend the life range of the filters, its just that higher voltage filters in the original size computor grade cans go up in price real fast as you go up in voltage!

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Re: Kustom IIIB Bass Head [message #16333 is a reply to message #16327]

Fri, 28 October 2011 12:05

pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi

Senior Member

Good idea to let the amp run for an hour or so a week, but I think having a speaker hooked up might be a good idea, it may provide some information if the amp has any other issues (motorboating, excessive hiss, or static that comes and goes)If you take the amp out as a spare and had to use it, only to find out that the caps are good, but something else has developed.
pleat

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Re: Kustom IIIB Bass Head [message #16340 is a reply to message #16333]

Sat, 29 October 2011 07:09

blindmouse
Messages: 25
Registered: February 2011
Location: The Netherlands

Junior Member

Thanks for all the input. This Kustom forum is a great platform to gain some knowlegde on these great USA amplifiers.

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