alligator Messages: 4 Registered: January 2014 Location: julian, nc
Junior Member
I had the amp restored by a guy that does vintage amp restoration, he replaced all the caps but failed to notice the input chip problem even when pointed out. A second repair guy found the problem, I already had the schematic from the first guy, second guy said he could'nt find the part anywhere. The board is listed as pc5131. Musicparts.com,who provided notes on the schematic have a part number IC1 = SE540L. I'm assuming the amp was roughly early 70's being solid state, I'd be interested if you know more. This was my first amp in high school and I recently restored the Egmond bass I bought with it,that only took about 35 years, my wife threatened to throw it away if I did'nt finish it!The amp works but there is a slight muff fuzz-esque finish to notes allowed to sustain, curious if you've run into that?
Thanks much for any help you can offer
alligator Messages: 4 Registered: January 2014 Location: julian, nc
Junior Member
The repair guy who saw it last referred to it as such, so thats the chip I need, any idea where to get one? The Kustom schematics have have the a/b chip you referred to as Kustom part # 007-7023-00. The input chip on the same diagram set has Kustom # 007- 7120-00( SE540L musicparts.com),there was no other number associated with the a/b output chip.
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
I have to dig out my old radio shack master catalog, but I recall a xx390 chip (I forget the first two letters of the part number) that is a small a/b power amp of its own, with probably enough wattage I would guess to do the job as the driver.
As I recall it runs on plus and minus power rails like the 540, but I am not sure what it's can handle for peak power supply voltage.
This is a much newer type chip and can likely still be had, I will check my catalog tonite and reply tomorrow.
If the amp uses a SE540 chip, it must be similar to a Kustom Challenger circuit. The chip is a power amp driver and is no longer made.
In the past I have used the NE540 chip as a direct replacement in the Challenger amps, even though they are rated for a lower voltage. I have always used a fairly large heatsink to help keep the chip cool.
If you want to try the NE540, they are available on eBay all the time as NOS parts. They are pretty pricey, but if you need one, then you have no other choice.
pleat Messages: 1452 Registered: June 2004 Location: Belding, Mi
Senior Member
From the description of the sound the amp is making, it is just like a Challenger I had at one time. It was the 540 IC. Kustom really did a good job on naming the amp Challenger. It was a challenge to keep it going.
pleat
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
I have some letters of correspondence sent to me by one of you folks on this site,forgive me for forgetting who, but these letters where from the former Kustom engineer Bob Brinkman .
In one of the his response letters to the sender they discuss the repair of a challenger with a bad 540 and part of the fix for that blown chip is a diode that Bob says to add in the circuit to protect that chip, but he does not spell out where it goes.
I can only assume it's added to block voltage transient spikes?