No light no sound.. but I can see tube glowing..

[khjng]

Yesterday, I found out that my amplifier Kustom Contender doesn't work...

When I turn on I hear something hit sound as usual when it is turned on. But I also checked the light was soon turned off.. making low hum sound. Also I noticed that it doesn't make any sound from my instrument. I checked the tube was glowing..
I visited like 4~5 places in Brooklyn earlier because I need to use it for a gig coming this week.. But most of them, they told me that they don't repair amplifier or some of them didn't open the shops even. One place located in Manhattan looks like really professional they told me that they charge 75$ per hour. But since I got this like 125$, maybe if I can do this myself I thought maybe doing myself can be a good lesson for me also good to save money..

if someone can give some advice, share some please.
Thank you

[nevetslab]

The You Tube presentation didn't help, as most of what is seen is very dark images . I didn't look long on the internet for a schematic for this combo amp, but perhaps one of us on the forum has one in their database.

I'd suggest you remove the amp chassis from teh combo case, and take some still photos of that that show a lot of detail. It will be easier to help direct you to the initial steps.

What are your electrical skills? If this is your first time on the insides of a piece of gear, there are safety issues you need to know and understand. What do you have in way of service equipment (DMM, probes, scope, generator, etc?

[Axtman]

If the amp is humming as loud as the video then you definitely have sound from the speaker. My guess is broken input jack or bad filter capacitor or output transistor.

Just curious, have you swapped out the tube?

[khjng]

The You Tube presentation didn't help, as most of what is seen is very dark images . I didn't look long on the internet for a schematic for this combo amp, but perhaps one of us on the forum has one in their database.

I'd suggest you remove the amp chassis from teh combo case, and take some still photos of that that show a lot of detail. It will be easier to help direct you to the initial steps.

What are your electrical skills? If this is your first time on the insides of a piece of gear, there are safety issues you need to know and understand. What do you have in way of service equipment (DMM, probes, scope, generator, etc?

-------------------------------------------------------------------------
I hope it helps.. Actually what I remember is pure basic stuff when I was in middle school in Korea. It was really basic electric circuit skill like turning on the lightbulb.. But I've been learning how to level fingerboard or some guitar maintenance stuffs to save some money after I moved to NYC. So, I'm really pure beginner of this area.. I don't have any equipment right now. So If I need it, I wanna get some sure. I started watching a basic safety video about amplifier trouble shooting.

[khjng]

If the amp is humming as loud as the video then you definitely have sound from the speaker. My guess is broken input jack or bad filter capacitor or output transistor.

Just curious, have you swapped out the tube?

Not yet, because I thought maybe I need to know how to find where the problem is.

[J M Fahey]

With due respect, a few reality points.

1)

maybe I need to know how to find where the problem is.

That is the main one.

You first need to learn basic Electronics how how stuff works, then focus on Guitar amplifier circuits, learn how to use measuring instruments, and only knowing what circuits "should" be doing, then you notice what is NOT working properly or shows wonky results when you measure and make you think what might be causing that.

This whole package is called "troubleshooting" and is the core knowledge of makes you a Tech.
Besides Electronics Theory you also need some experience.

This can take anything between 1 or 2 years to start finding your way inside an amp IF you are very focused, to 4 or 5 years if not.

At this point if we tell you "check supply voltages, that all Op Amps receive proper voltage, that outputs are at 0 volts, get chipamp datasheet and check voltages, also check voltage on all tube pins (mind you, there should be *deadly* 250/300V on some of them), inject signal and follow it" etc., none of this will make any sense for you, yet I described the basic troubleshooting procedure.

2) we donīt even have the schematic; that alone can/will stop even en experienced Tech, go figure.

3) now the disgusting side of this particular amp: when I first saw the deeply corroded rusty flaky surface power transformer I thought: this amp has at least spent 5 years in a *very* damp basement or a couple years as the house amp in a beach restaurant , under constant seawave salty drizzle, there is NO way an amp gets so corroded.

But then I saw the rest of the PCB and all of it is sprayed with "something" corrosive.
Immediate thought is rat pee because a cat or dog canīt get access to amp innards. YUCK!!!!

I have had my fair share of such amps, or filled with cockroach nests complete with empty cockroach eggshells and/or ones that when open showed a swarm of the little critters escaping into my shop. (restaurant amps usually) so now many Techs (included me) run outside with such amps, put them inside a bag and spray RAID or similar all around them and inside.

No serious Tech will work on that amp, which requires gloves at least for handling.
If anything, most/all connectors, pots, jacks, switches, any metal to metal contact will probably be corroded which is a nightmare.

Personally Iīd say junk it and buy a new one, at a shop, so itīs guaranteed new, clean, and carries a warranty, should give you years trouble free performance.
This one canīt be trusted even IF repaired.

Best case, ditch the chassis but keep the cabinet+speaker (if it works and is not corroded like the amplifier) and either use it as an extension speaker for another amp or you may build an amp (nice way to start into Electronics) and mount it there.

IF cabinet is humid/moldy and speaker frame is corroded, maybe thatīs not feasible.

IF NOT, then that confirms my rat pee theory.

In any case, donīt eat or smoke while handling it, and wash your hands afterwards. No kidding.

[khjng]

Thank you so much! Actually I got this from eBay.. when I opened it yesterday I was so shocked... I think I should throw it away..

With due respect, a few reality points.

1)
That is the main one.

You first need to learn basic Electronics how how stuff works, then focus on Guitar amplifier circuits, learn how to use measuring instruments, and only knowing what circuits "should" be doing, then you notice what is NOT working properly or shows wonky results when you measure and make you think what might be causing that.

This whole package is called "troubleshooting" and is the core knowledge of makes you a Tech.
Besides Electronics Theory you also need some experience.

This can take anything between 1 or 2 years to start finding your way inside an amp IF you are very focused, to 4 or 5 years if not.

At this point if we tell you "check supply voltages, that all Op Amps receive proper voltage, that outputs are at 0 volts, get chipamp datasheet and check voltages, also check voltage on all tube pins (mind you, there should be *deadly* 250/300V on some of them), inject signal and follow it" etc., none of this will make any sense for you, yet I described the basic troubleshooting procedure.

2) we donīt even have the schematic; that alone can/will stop even en experienced Tech, go figure.

3) now the disgusting side of this particular amp: when I first saw the deeply corroded rusty flaky surface power transformer I thought: this amp has at least spent 5 years in a *very* damp basement or a couple years as the house amp in a beach restaurant , under constant seawave salty drizzle, there is NO way an amp gets so corroded.

But then I saw the rest of the PCB and all of it is sprayed with "something" corrosive.
Immediate thought is rat pee because a cat or dog canīt get access to amp innards. YUCK!!!!

I have had my fair share of such amps, or filled with cockroach nests complete with empty cockroach eggshells and/or ones that when open showed a swarm of the little critters escaping into my shop. (restaurant amps usually) so now many Techs (included me) run outside with such amps, put them inside a bag and spray RAID or similar all around them and inside.

No serious Tech will work on that amp, which requires gloves at least for handling.
If anything, most/all connectors, pots, jacks, switches, any metal to metal contact will probably be corroded which is a nightmare.

Personally Iīd say junk it and buy a new one, at a shop, so itīs guaranteed new, clean, and carries a warranty, should give you years trouble free performance.
This one canīt be trusted even IF repaired.

Best case, ditch the chassis but keep the cabinet+speaker (if it works and is not corroded like the amplifier) and either use it as an extension speaker for another amp or you may build an amp (nice way to start into Electronics) and mount it there.

IF cabinet is humid/moldy and speaker frame is corroded, maybe thatīs not feasible.

IF NOT, then that confirms my rat pee theory.

In any case, donīt eat or smoke while handling it, and wash your hands afterwards. No kidding.

[Axtman]

Yeah that looks like a LOT of corrosion for such a "young" amp. My guess is that corrosion is the problem. If it were my amp, I would deoxit all the molex connectors and input jack. I bet there are cracked solder joints, especially at the input jack.

I have had good luck cleaning a chassis by removing it from the speaker/cabinet, taking it outside, spraying it with Simple Green, spraying it with the garden hose and leaving it in the hot sun to dry.

[The Dude]

That looks like cockroach remnants to me. Agree with the above- if you're going to work on it, give it a good clean first. Next step would be to get a hold of a schematic. Maybe contact Kustom themselves. It looks like a relatively simple amp, and an experienced tech could probably fix it without a schematic, but if you want us to help you, we'll need a diagram to help guide you through the process.

[glebert]

Couple thoughts: 1.) I have had Kustom supply me schematics and support pretty well last year. 2.) Mr. Fahey does not give up on amps lightly, so if he says to junk it that is a pretty serious indictment 3.) Did you just get it on ebay? Was it sold as defective? File a complaint unless it was sold as a fixer.