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Circuit Issue with a Fender Hot Deluxe III

Gally1985

Member
Messages
109
TGP Crew, I've got a sick Fender Hot Rod Deluxe IIi. It's been making a rattling type sound when I play certain chords or notes (most lower types type, Em etc). I had just replaced all the tubes. So I opened it up and looked it the circuit while playing. I found that the R79 component (next to the bias wheel) is rattling when playing. I used a wooden tooth pick to hold it in place while playing and the rattle stopped. Needless to say this component needs to be replaced but it doesn't look a regular resistor or capacitor. It kind of looks like a white foam piece covering it. Can any one help me identify the part I need to order and maybe where I can order it from? Thank you!!




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Trout

Member
Messages
7,557
Looks like a 470 ohm 5W ceramic wire-wound power resistor. Common as dirt and under a buck.

I stopped using those long ago for various reasons.
A good upgrade is the Vishay/Dale Brand from Mouser
Mouser Part #: 71-CW5-470

Better leads, better design.
 

Gally1985

Member
Messages
109
Looks like a 470 ohm 5W ceramic wire-wound power resistor. Common as dirt and under a buck. I stopped using those long ago for various reasons. A good upgrade is the Vishay/Dale Brand from Mouser Mouser Part #: 71-CW5-470 Better leads, better design.
Thank you my friend! What is with the large white piece over the resistor? It looks almost like I could just remove the white piece. Is it just an insulator?

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Fuchsaudio

Member
Messages
7,742
Best bet is to remove and/or replace these resistors with new ones. They should also be mounted with an eighth of an inch under the part and a healthy blob of silicone should be under them and between them to prevent future rattles. Hard to believe Fender still hasn't fixed so many of the known issues with these amps...and they are making them how many years ?
 

phsyconoodler

Member
Messages
4,315
Fender doesn't care.Simple.

To the OP: you've got pretty sensitive ears my friend!! Hearing resistors rattle? Wow!
Silicone will work just fine.
 

Gally1985

Member
Messages
109
Fender doesn't care.Simple. To the OP: you've got pretty sensitive ears my friend!! Hearing resistors rattle? Wow! Silicone will work just fine.
It's pretty noticeable as the chord slows down. Not to mention when playing and looking at the PCB it's was clear as day. The strange thing is that the Army ruined my hearing haha!

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tresspassor

Member
Messages
1,107
My older model HRDX has silicon under those resistors. Someone needs to contact Fender's Quality Control Dept. about this. I'm sure they will get right on it.
 

Trout

Member
Messages
7,557
It could be that the ceramic has loosened/fractured around the lead causing an electronically audible rattle sound that is actually coming out the speaker.
I have had on more than one occasion seen leads actually come out of that style resistor when suspended without silicon.
If I remember right it was an Xicon brand.

I do not see any ceramic dust on the board though, mine had a good dusting around one end.

Edit,, unless it is the white dust by the screw in the lower picture, sure looks like it.
 

Gally1985

Member
Messages
109
Thank for all the info everyone! I may take a closer look this weekend and see if I dare try to replace them myself (I'm good with a soldering iron but never worked on an amp before). I did get a quote from a local tech who said he could replace then both for $50. Decent deal?

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bob-i

Member
Messages
8,776
Take it to the tech. You're opening a real can of worms there. Those resistors are part of the power supply for the reverb and channel switching and run extremely hot. As a result the PCB is easily damaged. The pads lift very easily (don't ask how I know) and then you're into a very difficult repair.
 

bob-i

Member
Messages
8,776
My older model HRDX has silicon under those resistors. Someone needs to contact Fender's Quality Control Dept. about this. I'm sure they will get right on it.
LOL. This has been a problem since day 1 on the HRD. Since it doesn't show until after the warranty expires fender doesn't care.
 

Gally1985

Member
Messages
109
Any ideas on who the best tech in Massachusetts is? I'd prefer someone in the Worcester County area but if I have to go towards Boston then I will.

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wagdog

Member
Messages
125
Please don't stick your hands anywhere near your opened up amp that is on with a guitar in your hands. Seriously, don't do this.

The best solution I have found for those 470r resistors is to obtain chassis mounted ones with heat sinks on them and run leads.

Your inclination to find a tech is a good one.
 

Gally1985

Member
Messages
109
Please don't stick your hands anywhere near your opened up amp that is on with a guitar in your hands. Seriously, don't do this. The best solution I have found for those 470r resistors is to obtain chassis mounted ones with heat sinks on them and run leads. Your inclination to find a tech is a good one.
Don't worry my friend. The guitar was on a stand. I strummed the chord and then used a wooden skewer to touch the resistor. I've done enough research to know not to touch anything in there bare hand or with a guitar strapped to me. Great advice on the parts though. Thank you.

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