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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Tue Jul 26, 2011 8:05 am
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GOOD NEWS and obviously BAD NEWS as well.. Here is a link to what i am looking at.

http://a2.sphotos.ak.fbcdn.net/hphotos-ak-snc6/262815_247375245287386_100000447361897_920797_3911196_n.jpg

In the picture you can see that the trace is broken and is not making connection to R78. The card is dropped down and still in the amp. Finding this broken trace was the easy part as you have pointed me in the direction for sucess. The hard part, or maybe not so hard, is how in the world do i repair the trace? Also I am certian that the pad is probably going to come up from the board if i work on it, so how do i go about repeiring the pad as well?

Thanks


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Tue Jul 26, 2011 8:51 am
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Here are instructions for fixing broken circuit traces, very similar to what you have. Note the pictures where the protective coating is scraped off of a good part of the trace on either side of the break so as to be able to solder to the trace, and a piece of wire (component lead) used to bridge the gap. You can also use solder wick (chem-wick) instead of wire, as long as you have a solid connection, being careful not to make any unwanted connections to other parts of the circuit. Inspect the entire area closely, to make sure to get any other bad connections that you may have, while the board is out, you don't want to remove it twice if you don't have to.

http://billmaudio.com/wp/?page_id=204

Let us know how you make out. :)

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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 9:27 am
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Complete success!! Thank you for your help and support!! Though I do have a question. 330ohm vs 470ohm.. My buddy's Deville is running 330ohm. And thinking about what was posted, would it be bad to install 470ohm? Is this the same as volts where you can have more but not less? My friend saw how I installed the 470's on the HR Deluxe, by using hi-temp sillicone rubber (RTV), between it and the circuitboard to keep the heat off of the board itself. In the schematic it shows 330ohm being used on the Deville and though we all know and abide by the same "if it's not broke, don't fix it" rule as there are no signs of overheating on the board, I'm just asking a general/tech question.. (lol!! Is there such type question?)

Thanks


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 9:52 am
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The Deville is a hotter platform than the Deluxe (60W vs 40W) though I doubt it's the rationale behind the differing resistors. Frankly any "MWO" like that would likely need to be thoroughly researched prior to actually swapping them out.

JMO

Arjay

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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 10:19 am
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Completely understandable.. Thanks again!! Ill post up a new thread with pictures when I get home from work, along with a description of what we did to the HRDLx..

Thanks again!!


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 12:37 pm
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I'll just add that the Dvl power supply starts with a lower AC voltage than the Dlx, from the transformer before it gets to the rectifiers and those two 5-watt resistors to begin with (check schematic). Why the higher voltage in the Dlx? Beats me. If the voltage from the transformer in the Dlx for this supply were lowered to the same level as it is in the Dvl, THEN 330 ohm resistors would be appropriate. But with the higher voltage in the Dlx supply, the bigger resistors are necessary. As Retroverbial pointed out, there is more to it than simply swapping resistor values. That's why I don't agree with the use of the 330 ohm resistors in the Dlx. Maybe someone noticed that the DVl doesn't have the same problem with the supply that the Dlx has, and thought that the resistors were the only difference (of course they're not), starting a trend of false assumptions. :)

Oh, congrats on your repair. That must be a huge relief. Good job. :)

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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 12:51 pm
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Very true. Guess lower voltage means lower resistance and higher output wattage.. This is where it all gets confusing to me.. But in the end, I have read on the "unofficial Hot Rod" website that there was a change in how Fender changed from 470's to 330's in their hor rod amps.. Though i love the website and it is a very good as a how to guide, it still is pretty vague on the facts on this particular issue.. I wonder how we could find out what MWO's (modification workorder), Fender has implemented into their amps because it certainly isn't posted anywhere..


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 12:58 pm
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That may just be an unsubstantiated rumor, and I thought that it was referred to as such on the JH website. Maybe send an email to Fender with this question, anything is possible. But, for me, I wouldn't do it even if there is a bulletin from Fender about it. As I've stated, changing these resistor values to 330 ohms in a simulator yielded absolutely no positive results. Remember, you don't get something for nothing. Change the resistance in a circuit and Ohm's law says that either the current and/or voltage must change also (I=E/R). Less resistance = more current. :idea:

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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 1:04 pm
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Sensor an email to Fender wouldn't be a bad idea.. And you have mentioned "the simulator" before.. Care to explain what it is your working with? It may be a neat tool to have in my box of goodies.


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 1:15 pm
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I use software for circuit simulation (no smoke :lol: ). Multisim, Electronics Workbench, and LT Spice IV are just some of the programs that I use. I believe that LT Spice and others are available for free download, but some are more limited as far as components that are included with the programs.

Check here for some good simulator programs (at least a good start).
http://www.duncanamps.com/spicesim.html

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 1:50 pm
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Thanks!! I'll check it out


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Thu Jul 28, 2011 3:08 pm
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Where's them pics, troop?

It's nearly time for retreat!

:mrgreen:

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 - Channel switch inoperable
Posted: Thu Jul 28, 2011 3:30 pm
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Standby, I stopped the canteen for a few then I'll be to home to upload..

SFC P


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Sun Nov 13, 2011 4:54 pm
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I'm having problems with my Fender Hotrod Delux (recent edition) similar to what's been discussed in this thread.
The facts are these: I recently acquired this amp with the reverb inoperable. Upon inspection, there was severe heat damage to the two 5W resistors. Upon the advice of a friend, I replaced the resistors with 2 500 OHM, 5Watt. All channel switching is now inoperable, although the amp occasionally operates on clean channel for a few minutes after being turned on, before switching permanently to overdrive.

After reading this thread, I'm fairly certain this is being caused by using 500 OHM resistors instead of the original value (470 OHM), but I'd appreciate some input before I go and order/replace them.

Readings:
31.7 V over both resistors (R78,R79)
16.7 V over both zener diodes (CR13, CR14)

-Sergris-


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Post subject: Re: Hot Rod Deluxe - Channel switch inoperable
Posted: Sun Nov 13, 2011 10:24 pm
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Hi sergris,

500 is close enough to 470, so that's no problem. But, it very well could be the same problem with your amp as the OP's; a poor connection such as a bad solder joint or broken trace. These resistors must be supported to keep stress from the connections on the back of the circuit board.

Your original resistors were probably good, and it was likely only a poor connection that was missed when changing the resistors. Trying to solder in new resistors without pulling the circuit board is asking for trouble IMO. Check the original resistors with an ohm meter, they should be close to 470 ohms within tolerance. All solder joints and traces near those 5-watt resistors must be closely inspected, use a magnifier, and checked for breaks. The heat from these resistors can cause the dark coloring on the circuit board, and weaken the connections. To do it properly, pull the circuit board to have access to the back where the connections are.

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