Kustom Quad65 DFX resistor has blown

[skibber]

Hi all I have a little problem with an old amplifier with a resistor has
blown and I do not have a diagram of the amp as it is an old guy.
It is a Kustom MODEL quard 65 DFX Serial 0423 to 002,348 from Koustom Mucical
Amplification INC
Cinninnati Ohio USA
Designed in the USA but Made in China.
Resistance is on the PC card (power out to the speaker) a small board and the
opposition have part number R24
In addition, there is a slight pipe tone when it is switched on, believe that
it has been set to the wrong external speaker
it comes from a school.
So if there would be anyone have a repair manual about how I would be happy
to get a copy so I can see the value of the resistance, it is only an attempt
when the power out perhaps is burned, it is defective also goes it for scrap.

/ fb

[Flasherly]

On Wed, 11 Sep 2013 23:24:44 +0200, "skibber"
<fredibau@(remove)gmail.com> wrote:

>Resistance is on the PC card (power out to the speaker) a small board and the
>opposition have part number R24

Maybe something else is causing it to blow. . .clean it with alcohol
and if necessary put it under a x25 magnifier for color resistance
codes or a positive to a better designate stamped on it to identify
its value. Of course a shop-type person through experience should be
able to examine the circuitry for determining a suitable replacement,
provided that's all that went wrong.

[David L. Martel]

Skibber,

Had a Kustom amp many years ago. Kustom was quite happy to send me a
schematic. Have you e-mailed them?
http://www.kustom.com/contact_us.aspx

Dave M.

[skibber]

Hi Dave no i have not e-mailed to them
but i will do'it now.

Tangs

[skibber]

Thanks for your reply, but R14 is totally wasted nothing to look at it and if
I can not breathe life into it with a new opponent, it must go to the trash.
I have just written to Kustom to hear whether they have a little schematic of
the amplifier. I will not send it to any workshop, it is too old

[jtees4]

On Wed, 11 Sep 2013 23:24:44 +0200, "skibber"
<fredibau@(remove)gmail.com> wrote:

Good luck with the amp, I'm just wondering how old it can be if it was
made in China. I'm sure they will send you a schematic, so you should
be OK. Good luck.




*************
Some of my music:
http://www.soundclick.com/bands/default.cfm?bandID=789610

[David L. Martel]

jtee,

The Quad 65 is still being produced and sold. I think it came out in
2003.

Dave M.

[Flasherly]

I've heard good things about Kustom from repair shops and getting
support. Might call them if they'll take a call. A resistor is will
be under a buck.

[skibber]

Hi all thanks for the reply and I have also received schematic of the
amplifier from Kustom so thanks to Dave for the address.
I can say that the resistance should be 10 ohms 1/2 watt in series with a .42
uf, very little resistance I felt ok but I try.
Thanks for replying to all.
/ fb

[David L. Martel]

Skibber,

Mouser stocks both the resistor and capacitor.That's less than a dollar
in parts but around $5 s&h. Radio Shack also often stocks these parts so
check the local shops. I'm guessing that the resistor is a carbon film and
the cap is a ceramic. The Shack should sell these for about $1 each.

Dave M

[jtees4]

Thanks! The OP said "old"....I guess the meaning has changed, or I'm
just REALLY old ;-)

[Lord Valve]

My prediction:

You will replace those parts and they will burn up
again almost immediately. I can't be sure without
seeing the schematic - if it's in digital form, you
can e-mail it to me at t u b e s @ p r o d i g y dot net -
but those two parts may form what's known as a high-
frequency load, a circuit commonly placed from output
to ground in solid-state MI (guitar) amps. If that circuit
fried, it has almost certainly done so due to ultrasonic
oscillation, which will have occurred elsewhere in the
amplifier. The parts you found fried were a symptom,
not a cause. E me the schemo and I'll take a look.

Lord Valve
Expert (like it or not)

[skibber]

skematic.pdf is e-mail to
hope you get it.

/fb

[skibber]

Ok but i live in Denmark (DK) i can get here.

/fb

[Lord Valve]

Yep, got it.

As I suspected, that circuit is a high-frequency load on the amp's output.
These loads often burn up if there is ultrasonic oscillation present to
any significant degree. Your amp uses a power IC as the output stage;
this is common with many of the cheaper Chinese amps on the market,
regardless of what brand they are. There may be a fault in this IC which
is causing oscillation, or the fault may be elsewhere in the circuitry.
An oscilloscope and a test load will be required to chase this problem
down. Unless you have plenty of experience working on this type of
gear, you need to stop messing with it right now and take it to a tech.
Bear in mind that if the problem is hard to find, a pro tech may well
charge you more for the repair than the amp is worth. Get an estimate.

Lord Valve
Expert

[Flasherly]

On Fri, 13 Sep 2013 14:35:06 -0600, Lord Valve
<detr...@ix.netcom.com> wrote:

> Get an estimate.

In the case of that amp, another working model for $150 used, and a
$50min+ estimate fee to troubleshoot to the parts replacement costs -
math just won't add up.

[Kaie Fabiaen]

On Fri, 13 Sep 2013 14:35:06 -0600, Lord Valve
<detr...@ix.netcom.com> wrote:

>As I suspected, that circuit is a high-frequency load on the amp's output.
>These loads often burn up if there is ultrasonic oscillation present to
>any significant degree. Your amp uses a power IC as the output stage;
>this is common with many of the cheaper Chinese amps on the market,
>regardless of what brand they are. There may be a fault in this IC which
>is causing oscillation, or the fault may be elsewhere in the circuitry.
>An oscilloscope and a test load will be required to chase this problem
>down. Unless you have plenty of experience working on this type of
>gear, you need to stop messing with it right now and take it to a tech.
>Bear in mind that if the problem is hard to find, a pro tech may well
>charge you more for the repair than the amp is worth. Get an estimate.
>
>Lord Valve
>Expert

This was the same type of thing that happened when all them neat
& swifty 'Dean Markly' era amps 'designed' with power IC output stages
came out. Cheap, plug in, sound like puke. Kaman found out the hard
way when they bought DM, it took the right folks to fix them. Same as
those Sunn Beta stuff. The tech either knew what CMOS IC had to be
boinked, or the whole thing fried. VERY bad designs. Things have
gotten better now, but it's the same old story with the same ol' song.

..and I've been here so many times before...

..with the same old ??? and the same ol' doors...

(yes, lyrics are c/righted)

..anyway...Kustom at least is real good about making problems
go away, they support the product, and they care. Should go..

JJTj

< home with broken left foot, but at least playing a REAl Z guitar >






"...I'm the Hare, and I'm NOT the Turtle..."