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Post subject: Hot Rod Deluxe caught fire....What can I do?
Posted: Mon Dec 05, 2011 9:34 am
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My kids Hot Rod Deluxe caught fire over the weekend, he brought it home to me to see if I can fix it. After draining the caps, I took the tube PCP loose and noticed a black scorch and 3 melted resistors next to the right side power tube and two melted resistors below the far right pre-amp tube.

The pre-amp tube ones are label R80 and R81 on the PCB and the other not legible due to the burn but according to the schematic are R62, CR5, and R65 left to right.

Would anyone know if this is a common occurrence. My son is in college but this amp looks un-molested as if nothing was spilled in it, and/or modded in any way. Disturbing that this could have possible started a fire.

Gonna try to attach photos of the damage. EZ fix? I'm pretty handy with a soldering iron and if I can ID the parts, might go at it myself unless I can talk Bakos into fixing for me under warranty.

Seems dangerous to me, might not let him have it back once it gets fixed.

[img]photo-11.jpg[img][/img]photo-12.jpg[/img]


Last edited by oldmactech on Mon Dec 05, 2011 6:18 pm, edited 1 time in total.

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Mon Dec 05, 2011 10:03 am
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Ouch!
I've seen some damage done to the circuits by output tubes blowing,
but this sounds more extensive and serious.

Best a trip to visit a Fender amp tech to find out what happened and repair it.
(if amp is under 5 years old this should be a warranty repair)

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Mon Dec 05, 2011 10:10 am
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Your photos aren't showing up. My HRDlx let out some magic smoke but never went up in flames. Sorry to hear that. Mine was always giving me problems so I sold it.
You would think a fuse would kick before the flames started. There are a few serious tech experts here like Arjay, BMW, stratele, shim and many others. I'm the expert at complaining about the HRD series and pushing Egnater, Victoria and the DRRI and stating why I hate Groove Tubes. :lol:

Seriously though, there is a serious and possibly deadly reason for this. Could be something in the power supply circuit.

I agree, let a tech handle it. If the amp still makes you feel uncomfortable, I'd sell it.

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Mon Dec 05, 2011 12:55 pm
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63supro wrote:
Could be something in the power supply circuit.


+1!

It sounds like a catastrophic failure somewhere in the B+ supply.

63supro wrote:
I agree, let a tech handle it. If the amp still makes you feel uncomfortable, I'd sell it.


+1000!

Even repaired, if I couldn't sell it I'd drop it into the donation bin at St. Vincent dePaul's......no way would that sonofabitch ever come back into my home!

JMOOC

Arjay

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Mon Dec 05, 2011 2:50 pm
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Hi oldmactech,

No, it is not common, and is quite unusual for this much damage to occur without blowing a fuse.

Sounds to me as if an output tube shorted, dumping the high DC voltage on the filament circuit. And possibly the wrong power supply fuse allowed the damage. The fuse should be a 3 amp fast-blow fuse.

R80 and R81 are the pull down resistors on the filament supply.

CR5 is the flyback diode for the V4 output tube.

Not sure what "RG2" or "RG5" are supposed to be, not numbers used on the schematic. If it is R62 and R65, those resistors are also connected to the screen grid and control grid of output tube V4, respectively. I wouldn't trust any of the tubes after this, replace all, but seems as if V4 output tube is the source of the problem.

Quite possibly, replacing the burnt components and a complete set of tubes may take care of the problem.

With this much damage, I would bet that the fuse has blown before and was replaced by the wrong value fuse, allowing the damage to occur when the wonky tube finally completely let go. The last amp that I looked at with damage like this, had the 3 amp fuse replaced with a 20 amp! :shock: The wrong fuse didn't get there by itself. :wink:

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Mon Dec 05, 2011 4:18 pm
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Retroverbial wrote:
63supro wrote:
Could be something in the power supply circuit.


+1!

It sounds like a catastrophic failure somewhere in the B+ supply.

63supro wrote:
I agree, let a tech handle it. If the amp still makes you feel uncomfortable, I'd sell it.


+1000!

Even repaired, if I couldn't sell it I'd drop it into the donation bin at St. Vincent dePaul's......no way would that sonofabitch ever come back into my home!

JMOOC

Arjay


:lol: :lol: Aw man Arjay don't tell him to drop it off at a church, he'll be going to hell on a bobsled for sure for that donation. :lol:

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Mon Dec 05, 2011 6:16 pm
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Maybe I forgot but the fuse was definitely blown. I took it slightly apart so I could get a better look and one of the pre-amp tubes seemed a little cockeyed like maybe someone forced the tube in the wrong way in the socket-not sure of that, just seemed like the pins were slanted funny and didn't come out easy or want to go back in easily. I bought replacement resistors at FRYs' and based on what a local Fender tech suggested, I was able to get the amp to come on and the the pre-amp tubes to light up. Nothing on the Power Tube side though-no reading on the DMM also. I'm thinking the PCB is fried at R62.

I couldn't get the pics up, I don't have permission. If someone wants to post them for me, email me at john@oldmactech.com. Pretty gruesome.

Thanks.

JB


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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Mon Dec 05, 2011 8:01 pm
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shimmilou wrote:
Hi oldmactech,

No, it is not common, and is quite unusual for this much damage to occur without blowing a fuse.

Sounds to me as if an output tube shorted, dumping the high DC voltage on the filament circuit. And possibly the wrong power supply fuse allowed the damage. The fuse should be a 3 amp fast-blow fuse.

R80 and R81 are the pull down resistors on the filament supply.

CR5 is the flyback diode for the V4 output tube.

Not sure what "RG2" or "RG5" are supposed to be, not numbers used on the schematic. If it is R62 and R65, those resistors are also connected to the screen grid and control grid of output tube V4, respectively. I wouldn't trust any of the tubes after this, replace all, but seems as if V4 output tube is the source of the problem.

Quite possibly, replacing the burnt components and a complete set of tubes may take care of the problem.

With this much damage, I would bet that the fuse has blown before and was replaced by the wrong value fuse, allowing the damage to occur when the wonky tube finally completely let go. The last amp that I looked at with damage like this, had the 3 amp fuse replaced with a 20 amp! :shock: The wrong fuse didn't get there by itself. :wink:


I am sometimes amazed by the the technical knowledge of some guys on this forum.. 8)

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Tue Dec 06, 2011 6:13 am
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I put some pics of the damage on Flickr but I don't know if you will be able to see them or not. Try and report back with results please.

www.Flickr.com under oldmactech
Only pics up are under burnedamp1 and burnedamp2

Thanks.

JB


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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Tue Dec 06, 2011 10:29 am
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Nope!

A search for oldmactech, and burnedamp1 came up with no results. Maybe I'm doing it wrong?

Just copy the "IMG" code from your pictures on the Flickr site, and paste the code in your post here.

Or at least link directly to the page that has your pictures.

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Tue Dec 06, 2011 10:51 am
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OK, I searched for "oldmactech" under "people" instead of "images" and found them. Sorry!

In Flicker, right click on the image, select "copy image location", then paste the link in your post here. Then highlight the link pasted here and click the "IMG" button above so that the link looks like that in the code box below. Then your image will show in your post here.

BTW, your amp isn't as bad as you made it sound. Just a few resistors flamed, the amp didn't actually catch fire. I hope that you got flame-proof resistors as spec on schematic. :idea: Make sure to clean off all of that black carbon, it is conductive.

Code:
[img]http://farm8.staticflickr.com/7025/6465628687_fd111d712e_b.jpg[/img]


Image
Image

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Tue Dec 06, 2011 11:59 am
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Thanks for putting the pics up. I ended up taking it to a Fender Authorized Shop, couldn't find the correct Diode and I don't think the repair will be much more expensive (and likely a lot more trustworthy) than if I did it myself.

We'll see...

Thanks.

JB


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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Tue Dec 06, 2011 12:12 pm
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shimmilou wrote:
BTW, your amp isn't as bad as you made it sound. Just a few resistors flamed, the amp didn't actually catch fire.


+1

It could've been a lot worse.

Your son could've been driving a Chevy Volt......

Image

:mrgreen:

Arjay

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Tue Dec 06, 2011 12:15 pm
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Let us know what the tech finds. I am particularly interested to know the cause, my guess is an output tube, V4. :?:

:lol: That is the picture that I had in mind of the inside of the OP's amp, from his description. :shock:

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Post subject: Re: Hot Rod Deluxe caught fire....What can I do?
Posted: Tue Dec 06, 2011 2:48 pm
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Aren't flames usually associated with fire? :shock:

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