Reviving a Dead KB2

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9lives304
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Reviving a Dead KB2

Post by 9lives304 » Wed Aug 24, 2022 6:27 am

Hello all,
So, when retrieving my tools from the trunk of my Uber driver I see this Amp and inquire about it. A former passenger forgot about it in the trunk or whatever days ago and it's been in there ever since with no word from the owner. He let's me have it. I take it inside, plug it in, and there is no power. Now I understand why the "owner" just left it.

Being that I disassemble and Repair electronics all the time finding that normally when there's just a lack of power it's normally an "internal power circuit board" with a transformer, capacitors, etc. and something on that board has gone bad after failed.

First thing's 1st, I check it, and the fuse isn't blown (if only it were ever that easy). I then remove and inspect the transformer and lemme tell ya....unless that's just the way it looks when assembled ...this thing looks rough!!
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If anyone knows where I can get this part I believe I'll start here
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Nothing looks burnt up or problematic on the circuit boards so if anyone has some experience with this or a similar project and could throw me a bone that'd be great.
Before I replace this transformer I'll probably find a detailed walkthrough on how to perform functionary tests on it with my multimeter to find out if it is indeed the culprit

Justin

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JamesPaul
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Re: Reviving a Dead KB2

Post by JamesPaul » Thu Aug 25, 2022 11:44 pm

You can call Peavey and get the schematic. It was taking multiple calls during the pandemic, but they should be catching up by now.

I have had to check a couple output transformers in the past 40 years, but do not remember having a power transformer issue. I would Google it, and you will likely get some generic checks you can complete with your multimeter.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

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dak
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Re: Reviving a Dead KB2

Post by dak » Thu Sep 01, 2022 6:07 pm

JamesPaul wrote:
Thu Aug 25, 2022 11:44 pm
You can call Peavey and get the schematic. It was taking multiple calls during the pandemic, but they should be catching up by now.
Well, I found the KB2 schematic "somewhere on the Internet"™. I've had mixed success with asking Peavey customer service (the mail address) for schematics: sometimes I get an answer with the schematics (if I do, it tended to be about a week after asking), sometimes the mail appears to drop through the floor. I haven't figured out what would make the difference. The KB2 schematics are somewhat related to the KB/A50 schematics I currently need (similar preamps and similar power biamp), but part identifiers are all different and so is the layout.

It's astonishing what a difference in maintainability access to the schematics makes, so Peavey is to be lauded for being comparatively generous handing them to people who need them, even if the process ends up being a bit hit and miss sometimes.

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Re: Reviving a Dead KB2

Post by JamesPaul » Sun Sep 04, 2022 12:48 am

dak wrote:
Thu Sep 01, 2022 6:07 pm
JamesPaul wrote:
Thu Aug 25, 2022 11:44 pm
You can call Peavey and get the schematic. It was taking multiple calls during the pandemic, but they should be catching up by now.
Well, I found the KB2 schematic "somewhere on the Internet"™. I've had mixed success with asking Peavey customer service (the mail address) for schematics: sometimes I get an answer with the schematics (if I do, it tended to be about a week after asking), sometimes the mail appears to drop through the floor. I haven't figured out what would make the difference. The KB2 schematics are somewhat related to the KB/A50 schematics I currently need (similar preamps and similar power biamp), but part identifiers are all different and so is the layout.

It's astonishing what a difference in maintainability access to the schematics makes, so Peavey is to be lauded for being comparatively generous handing them to people who need them, even if the process ends up being a bit hit and miss sometimes.
I give them a call and they usually email me with a .pdf while I am on the phone.

They will send you any schematic, except the truly recent stuff. I think they are still trying to patent some of those circuits, and will hold on to them until the patents are granted.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

9lives304
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Re: Reviving a Dead KB2

Post by 9lives304 » Sun Sep 04, 2022 3:09 am

Thank you I'll do that.

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dak
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Re: Reviving a Dead KB2

Post by dak » Sun Sep 04, 2022 7:08 am

JamesPaul wrote:
Sun Sep 04, 2022 12:48 am
dak wrote:
Thu Sep 01, 2022 6:07 pm
It's astonishing what a difference in maintainability access to the schematics makes, so Peavey is to be lauded for being comparatively generous handing them to people who need them, even if the process ends up being a bit hit and miss sometimes.
I give them a call and they usually email me with a .pdf while I am on the phone.

They will send you any schematic, except the truly recent stuff. I think they are still trying to patent some of those circuits, and will hold on to them until the patents are granted.
I'll try that, never mind the time zone differences and my accent... I am not actually interested in the truly recent stuff since it is both out of my paygrade and out of my area of expertise (and repairability also goes down with novelty). Right now I am doing a phantom power switch using matched P-channel MOSFETs and basically the only way you get something of that kind is an SMD chip. So I am splitting tracks on a breadboard with a scalpel in order to solder that thing in, and my eyesight is not actually getting any better at my age.

To wit:
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This is garbage, but I'll clean it up and hope none of the gates died of static electricity. And you don't want to know how much time I spent on this garbage...

In 15 years, I'll only be able to fix tube amps, with big parts.
Last edited by dak on Mon Sep 05, 2022 8:16 am, edited 1 time in total.

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JamesPaul
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Re: Reviving a Dead KB2

Post by JamesPaul » Sun Sep 04, 2022 7:16 am

dak wrote:
Sun Sep 04, 2022 7:08 am
JamesPaul wrote:
Sun Sep 04, 2022 12:48 am
dak wrote:
Thu Sep 01, 2022 6:07 pm
It's astonishing what a difference in maintainability access to the schematics makes, so Peavey is to be lauded for being comparatively generous handing them to people who need them, even if the process ends up being a bit hit and miss sometimes.
I give them a call and they usually email me with a .pdf while I am on the phone.

They will send you any schematic, except the truly recent stuff. I think they are still trying to patent some of those circuits, and will hold on to them until the patents are granted.
I'll try that, never mind the time zone differences and my accent... I am not actually interested in the truly recent stuff since it is both out of my paygrade and out of my area of expertise (and repairability also goes down with novelty). Right now I am doing a phantom power switch using matched P-channel MOSFETs and basically the only way you get something of that kind is an SMD chip. So I am splitting tracks on a breadboard with a scalpel in order to solder that thing in, and my eyesight is not actually getting any better at my age.

In 15 years, I'll only be able to fix tube amps, with big parts.
Yes, SMD has ushered in the day of "just replace the board."

Send me a PM if you need a schematic. I can give them a call and get it for you.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

9lives304
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Re: Reviving a Dead KB2

Post by 9lives304 » Sun Sep 04, 2022 7:48 am

I'm from West "By God" Virginia so I didn't even pick up on an accent.
I've come to realize that my problem does not lie in transformer and after removing and extensively checking out the IC boards and attached components, I don't see anything visually wrong with anything.....so now I'm at a stand still with no clue what to do next

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dak
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Re: Reviving a Dead KB2

Post by dak » Sun Sep 04, 2022 8:09 am

Well, MS is running 7 hours behind my timezone which should be working in my favor unless I am running into someone with Monday morning blues. I'll give it a try tomorrow and come back if I fail to get anywhere.

I have "special needs" regarding phantom power (for instrument microphones I don't want to maintain batteries for) and hum resiliency (there's an overland power line starting in a transformer grid about 1/4 mi from here). So I tend to mess with a lot of equipment.

Regarding the original thread: as I said I've managed to find KB2 schematics "somewhere" and could pass them on when asked for by PM. But maybe indeed picking off the phone is the most dependable option here.

I had previously considered asking Enzo by PM since he indicated that he had the combined KB/A30 and KB/A50 circuit diagrams but, well, sadly that is no longer an option. And since he frequently referred people to Peavey customer service, I guessed that he preferred not acting as a clearing house for information that could likely easily be got by official channels.

9lives304
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Re: Reviving a Dead KB2

Post by 9lives304 » Sun Sep 04, 2022 2:39 pm

Fair enough

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