Home » VintageKustom.com » Repairing Kustom Amps » Kustom IV Bass Power Supply Caps (seeking info on what the original uf value of the caps)
Kustom IV Bass Power Supply Caps [message #28729] Wed, 03 August 2022 20:11 Go to next message
corona blue is currently offline  corona blue
Messages: 25
Registered: January 2015
Junior Member
Hi everyone-
Been a long time since I have logged in here.
Great to see so many Kustom enthusiasts in the forum.

I am helping a friend repair his Kustom IV Bass head.
His technician is telling him that the two power supply caps have failed.
The caps in there are two 9800uf 100V G.E. caps.

I have looked at various schematic data I have on hand and it seems to me that there were different versions of the Kustom IV Bass head. The only schematic I have that shows power supply detail is for a version that had two separate power amp output channels. The value of those caps is shown at 9000uf 50V dc.

I am wondering if anyone here might have schematics for this Kustom IV Bass that has only a single power amp output channel so that I can confirm what the original spec was for these caps?

Also any suggestions on modern replacement caps would be welcome.

Thanks in advance,
corona blue





Re: Kustom IV Bass Power Supply Caps [message #28730 is a reply to message #28729] Thu, 04 August 2022 07:22 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4733
Registered: June 2004
Location: NY
Senior Member
Hi.
I few months ago I picked up one of these monsters that needed repair, so I have learned a lot about them.

First off these amps as far as I know have two 5065 output boards and 8 output Transistors, this is what makes for the need of 9000 uf power supply rail filters.

The Kustom III models only had one output section for a rating of 135 watts.

Bending that this is a Kustom IV model then tag on the rear of the amp should say 270 watts RMS into a 4 ohm load because each outout section puts out 135 watts .

Note that this amp has only one speaker jack per output section, so to get the full 270 watts both need to be used.

In terms of replacement filter cans, newark electronics has them.
They are part number 69K1780.
They are 10,000 uf at 50 volts.
They are only 2 inches in diameter so you will need to rap cardboard and tape around them so to build them up and fit in the factory mounting clamps.

I would also clear silicone glue them down to the chassis.

These cost 42.25 each, but these size filters are what should be used.

Make sure that the fan in your amp still works, it should come on as soon as you turn the amp on as it's not controlled by a temperature sensor.

Keep us posted on there repair work.

[Updated on: Thu, 04 August 2022 08:46]

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Re: Kustom IV Bass Power Supply Caps [message #28731 is a reply to message #28729] Thu, 04 August 2022 12:32 Go to previous messageGo to next message
chicagobill
Messages: 2005
Registered: April 2003
Senior Member
I would suggest testing the old caps before replacing them. I don't see them die too often.
Re: Kustom IV Bass Power Supply Caps [message #28732 is a reply to message #28730] Thu, 04 August 2022 15:54 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1452
Registered: June 2004
Location: Belding, Mi
Senior Member
I think corona blue is speaking of the Big K series amp which would be a mono 300 watt bass amp. I just can't locate my photos of the amp right now. Head would be the same tolex of the Big K series amps. Kustom also did a huge 4x15 cab to go with the head.
pleat
Re: Kustom IV Bass Power Supply Caps [message #28733 is a reply to message #28729] Thu, 04 August 2022 17:05 Go to previous message
stevem is currently offline  stevem
Messages: 4733
Registered: June 2004
Location: NY
Senior Member
Well if he can give us some of the PC board numbers we would have a better shot at figuring things out to help him.

One thing is for sure, GE brand caps are likely not original so the amp may now be getting its second set of power supply rail filters .

I agree Bill, I too have seen very few of these computer grade filters that Kustom used just outright fail, in fact many times I can reform them over the course of a weekend.

If this amp has only one output section then it's original filters would have been 4500uf and the larger GE made ones where installed as a upgrade.
Unfortunately that 100 volt rating is likely to be what lead to there demise.
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