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About KUstom L1 [message #28799] Tue, 18 October 2022 03:26 Go to next message
Cherry Blossom is currently offline  Cherry Blossom
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Registered: October 2022
Junior Member
Hi!! folks I recently got my hands on an early 70s kustom L1 in pretty good shape.
the amp was in a pawn shop near the stripclub where i work.
I think it sounds great, but it has a hum in the background, it's not like the 60 cycle hum. and I was wondering if it's normal?
Re: About KUstom L1 [message #28800 is a reply to message #28799] Tue, 18 October 2022 11:42 Go to previous messageGo to next message
stevem is currently offline  stevem
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Registered: June 2004
Location: NY
Senior Member
Ah! The good old days, stumbling on a nice amp on the trek to a strip club, Lol!

The problem with amps many times that are in good cosmetic condition is that there in that condition because they got a used very little.

Parts in then amp called electrolytic power supply filter suffer from not enough usage.

This condition will make for 120 hz hum being heard.

You will likely needed to replace the two main positive and negative power supply rail filters for starters, and maybe some of the other ones that are in the gain stages of the amp.

[Updated on: Tue, 18 October 2022 11:43]

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Re: About KUstom L1 [message #28801 is a reply to message #28800] Sun, 23 October 2022 22:58 Go to previous messageGo to next message
Cherry Blossom is currently offline  Cherry Blossom
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Registered: October 2022
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Hi! Stevem ty for repplying <3 <3 <3

Did it really used to be like that in the old days? in that case they used to be better times from what i see

I think that's the problem, because that "hum" has diminished a little with the use that I have given it recently.

but I suppose that I will have to replace those electrolytic capacitors eventually

Also the reverb is a quite noisy, but when I checked inside and put the rever out of the chassi (the small reverb unit is inside the chassi) the hum completely disappeared.

Now I am wondering if there is something to change or would it be better to make the tank go outside the chassis.
Re: About KUstom L1 [message #28802 is a reply to message #28799] Mon, 24 October 2022 06:59 Go to previous messageGo to next message
stevem is currently offline  stevem
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Registered: June 2004
Location: NY
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Your reverb noise issue it would seem is due to the end of the pan marked as input sitting near the amps power transformer.

It's very important to having low noise / hum levels for the output end of the pan to be the closest to the transformer.
Re: About KUstom L1 [message #28839 is a reply to message #28799] Mon, 07 November 2022 20:02 Go to previous messageGo to next message
Cherry Blossom is currently offline  Cherry Blossom
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Registered: October 2022
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Hi again!!!, you were right, the tank was facing the wrong way.
the reveb noise decreased considerably.

Thank you so much.

but now I am having problems finding the replacement of the filter capacitors, (1900uf 40v) is there any other value that I can use?


Again Thx.
Re: About KUstom L1 [message #28840 is a reply to message #28799] Tue, 08 November 2022 11:43 Go to previous messageGo to next message
stevem is currently offline  stevem
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Registered: June 2004
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Are these caps can type with screw terminals on top, or axial type with leads on each end?
Re: About KUstom L1 [message #28843 is a reply to message #28799] Wed, 09 November 2022 20:22 Go to previous messageGo to next message
Cherry Blossom is currently offline  Cherry Blossom
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Registered: October 2022
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axial type, with leads on each end. two old looking, but pretty mallory caps.
Re: About KUstom L1 [message #28844 is a reply to message #28799] Thu, 10 November 2022 10:04 Go to previous messageGo to next message
stevem is currently offline  stevem
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Registered: June 2004
Location: NY
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Order from Newark electronics part number 30K6693, these will be a good replacement.
Re: About KUstom L1 [message #28845 is a reply to message #28799] Fri, 11 November 2022 00:32 Go to previous messageGo to next message
Cherry Blossom is currently offline  Cherry Blossom
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Registered: October 2022
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looking in newark i found 2000uf 50v capacitors, ( sprague Atom brand ) I remember seeing those in fenders, are those better quality?

also there is a similar ones to the ilinois you recommended, but 40v, so now i'm curious,

is it better scale up to 2200uf 50v? will the amp have "better filtering" and therefore be quieter ?

is it an improvement to the original value of 1900uf40v? or i should do my best to get the exact replacement? (found this website called "tedss" where it seems to be available)

Finally, In this situation, it is better to increase the voltage and capacitance value or decrease it? for example use 35v or 50v. 1900uf or a bit less vs 2000/2200uf

as I understand Increasing the capacitance = steady supply of current than reduces the gain compression, yielding a truer, less "spongy" response.
But a lower supply voltage makes signals clip at a lower volume right?. and ofc caps aren't precise +/- 20%

the thing is... i want to keep the amp with that nice "cristal clear" but also "kind of warm clean sound" or improve it (if its possible) you know the typical concerns in guitar players...

If I sound silly, (I'm sorry) don't be so harsh with me, I'm not a college girl, just a pole dancer with an enthusiasm for electronics.


Much love and thx<3
Re: About KUstom L1 [message #28846 is a reply to message #28799] Fri, 11 November 2022 06:24 Go to previous message
stevem is currently offline  stevem
Messages: 4610
Registered: June 2004
Location: NY
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Hi again!
With today's on average higher wall outlet volages then when these amps where first made I would go with the 50 volt rated filters.

With the cheap price of these parts get two different Uf value of filters and audition them in the amp and let YOUR ears be the guide.

What will help out the most for added warmth will be to replace the power supply diodes with fast recovery types and a speaker with a frequency peak at more like 1K and not 2K.

It's also cheap with a solid state amp to play around with bypassing these two power supply filters with a a pair each consisting of a .022uf and .22uf cap.
The common Orange drop types are fine for this and you only need a rating of 100 or 250 volts whichever you find works best for your wallet.
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