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Kustom lead II [message #19936]

Mon, 06 January 2014 17:35

argon39948
Messages: 2
Registered: December 2013
Location: United States

Junior Member

Working on Kustom amp with PC5129 ver 7? This version uses a 1458 instead of a 739 op amp. Found schematics and layout for the 739 version but nothing for this one. Wondering if anyone can help.

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Re: Kustom lead II [message #19967 is a reply to message #19936]

Thu, 09 January 2014 08:41

stevem
Messages: 4749
Registered: June 2004
Location: NY

Senior Member

If it uses a 1458 chip in stock form then use that type, they can still be had.
I do not have that schematic for that PC number so I can not comment otherwise.

[Updated on: Thu, 09 January 2014 08:42]

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Re: Kustom lead II [message #19976 is a reply to message #19936]

Thu, 09 January 2014 13:15

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Welcome to the place.

The PC5129 schematic that I have has both a 739 and a 5558 chip. What are you looking for? What is the problem with the circuit?

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Re: Kustom lead II [message #20013 is a reply to message #19976]

Mon, 13 January 2014 14:21

argon39948
Messages: 2
Registered: December 2013
Location: United States

Junior Member

Very noisy with reverb turned up and very low gain. Circuit board had one resistor missing. That resistor is connected to pin 6 of what I think is IC1 (1458). I got some better gain with a 5.6K installed.
Amp also seems to boost low frequencies. Have to turn bass control all the way down.

Thanks

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Re: Kustom lead II [message #20014 is a reply to message #19936]

Mon, 13 January 2014 16:27

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

This board is a single channel preamp with trem and reverb. It uses the later design high impedance input stage with a Mosfet driven tone control stack that is very similar to a Fender tube amp tone control section. I suppose that they went to this circuit because the settings would be familiar to anyone that had used a Fender amp before with its all passive cut controls.

The schematic that I have shows 3 ICs, 2 dual opamps (5558 & 739) and 1 transconductance opamp (3080). The 739 and 3080 are used for the audio stages, and the 5558 is used for the reverb driver and the trem oscillator. The reverb return circuit is a single NPN transistor gain stage.

I don't know what the resistor you added does, so I can't comment there. If the reverb circuit makes noise, check the transistor that connects to the output of the reverb pan.

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Re: Kustom lead II [message #20015 is a reply to message #20014]

Tue, 14 January 2014 08:40

stevem
Messages: 4749
Registered: June 2004
Location: NY

Senior Member

Electrolytic cap C18 may have drifted way high in value making for far too much bass response, in fact the age of all of these caps within the preamp could be the root of some problems.
When you state low gain is this in regards to the reverb level, or the over all gain of the preamp?

[Updated on: Tue, 14 January 2014 08:41]

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Re: Kustom lead II [message #20258 is a reply to message #20015]

Wed, 05 March 2014 21:51

digi2t
Messages: 2
Registered: October 2013

Junior Member

Try this;

http:// www.aronnelson.com/gallery/main.php?g2_view=core.DownloadIte m&g2_itemId=50637&g2_GALLERYSID=0a58d3f397e25d5b2e15 0a343726b6bb

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Re: Kustom lead II [message #20259 is a reply to message #19936]

Thu, 06 March 2014 06:40

stevem
Messages: 4749
Registered: June 2004
Location: NY

Senior Member

Can you take a resistance measurement of the input and output side of the reverb as it may have been replaced and not the right one for the circuit, in which case with the pan unplugged and the cable that plugs into the pans output side shorted is the noise still there?

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