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Post subject: Hot Rod Deluxe Popping and Buzzing
Posted: Sat Oct 05, 2013 8:06 pm
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Hello,

I have a Hot Rod Deluxe that I bought used from a Guitar Center in Orlando. I had it shipped to Omaha where I live. The power tubes were removed and packed separately when I opened the box. It worked great at first when I powered it on and played it for a few hours. I noticed that the reverb wasn't working very well which wasn't a big deal since I wouldn't be using it that much. The problem is that about one out of every three times I go to play it, it makes this very loud buzzing sound when I turn the standby off. Unplugging my cable or swapping it out for another doesn't change it. The volume nor any of the controls affect the buzzing. I have to shut the amp off and let it sit for a few minutes and hope that the next time I turn it on the buzzing isn't there. I let the amp warm up for a few minutes and it doesn't matter if a guitar is plugged into it or not.

I returned it to GC for work and they fixed the reverb but couldn't find out what the other problem was. I adjusted the bias and its sitting at 71. I reseated the tubes and opened the back to check for cold solders or anything that would look fishy but found nothing. It also does this slight popping sound when warming up but quits after a few minutes of playing. Any ideas?

This video shows the sounds it makes. This particular time I was recording it stopped the buzz on its own but then started back up again. This is the first time that has happened.

http://youtu.be/uMbcSOgHHWU


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Post subject: Re: Hot Rod Deluxe Popping and Buzzing
Posted: Sat Oct 05, 2013 8:15 pm
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bluesmetal, welcome to the Forum! :D

http://www.youtube.com/watch?v=uMbcSOgH ... e=youtu.be


You mean to tell me that the Fender folks couldn't find the problem? That is crazy. This is a classic 120Hz issue. I'd venture a guess that 1.) The caps in the power supply are bad. 2.) There is a bad grounding point within the PT, rectifier, cap circuit. 3.) There is a bad grounding/solder point on one of the gain stage tubes.

Best to return amp for a good one, while under warranty.


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Post subject: Re: Hot Rod Deluxe Popping and Buzzing
Posted: Sat Oct 05, 2013 9:25 pm
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FMIC does not train any service tech personnel, nor does GC. They merely hire warm bodies based on who's done the best job at padding a résumé.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Hot Rod Deluxe Popping and Buzzing
Posted: Sat Oct 05, 2013 10:14 pm
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Location: Natural Bridge, Virginia
bluesmetal wrote:
I returned it to GC for work and they fixed the reverb but couldn't find out what the other problem was. I adjusted the bias and its sitting at 71. I reseated the tubes and opened the back to check for cold solders or anything that would look fishy but found nothing. It also does this slight popping sound when warming up but quits after a few minutes of playing. Any ideas?


Setting bias to 71 mV at the Fender test point means nothing. You also have to measure plate voltage of the power tubes and calculate the plate dissipation at idle.

With regard to checking for bad solder joints, with the exception of the tube socket solder points and the tube mounting PCB, you must remove the main PCB from the chassis in order to inspect the back side of the PCB. If you have a series III HRD this is not necessary, but your post seems to indicate it is an older amp.

The ribbon cables are known problem areas as they are fragile and can easily break. If your amp is like my BDRI, there is one ground point that runs from the main PCB to a screw near the power transformer. You can easily check to be sure that the screw is tight and there is a good solder connection to the main PCB.

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Post subject: Re: Hot Rod Deluxe Popping and Buzzing
Posted: Sun Oct 06, 2013 1:14 am
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Location: Province de Québec, Canada
BMW2002Ti and Bluesky gives you the best advice you can find on the forum.

A qualified tech not easy to find.

Good luck


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Post subject: Re: Hot Rod Deluxe Popping and Buzzing
Posted: Sun Oct 06, 2013 7:18 am
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Thank you very much for the replies. Unfortunately I cannot return it as its past the 30 day mark. GC took it to a local amp repair shop that deals with tube amps but I doubt much effort was put into the repair other than replacing a pot or whatever the tech did to fix the reverb.

BMW2002Ti and Bluesky, my knowledge of amps is pretty limited but Im eager to learn as I go. It is an older model, B-872426 with the chrome pot backing as you may have seen in the video. I will take a look at your recommendations and see if anything works. Thanks!


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Post subject: Re: Hot Rod Deluxe Popping and Buzzing
Posted: Sun Oct 06, 2013 10:03 am
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Location: Natural Bridge, Virginia
Here's the schematic. Good luck.

http://support.fender.com/schematics/gu ... ematic.pdf

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Post subject: Re: Hot Rod Deluxe Popping and Buzzing
Posted: Sun Oct 06, 2013 11:51 am
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Check ALL grounding points to the chassis. Tighten or resolder any that look suspicious.

Use a good contact cleaner on ALL buss-strip connections, tubes/sockets, switches, jacks, plugs, speaker connections, fuse holder, lamp holder --- everything that has a connection which can be disconnected. I like Caig GN5.

Good luck! Tell us your results.


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Post subject: Re: Hot Rod Deluxe Popping and Buzzing
Posted: Mon Oct 07, 2013 7:08 am
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Excellent, thank you all again for the help! I will go through it with some contact cleaner like you recommended BMW2002Ti and review the schematics. If anything changes I will let you know.


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