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Post subject: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 5:09 pm
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Ok, Here are the questions.. I am working on a friends 2008 Hot Rod Deluxe that has a few major problems.
Here are the symptoms:
1. The reverb is not working.
2. With reverb tank out of the amp it still makes springy crashy noise.
3. Power Capacitors read 360v-390v. (please correct me if im wrong about this but, arent they supposed to be closer to the 470v-500v range?)
4. The rectangular shaped Capacitors had scortch marks on the motherboard.
5. The Preamp tube furthest to the right was found to be Milky White, So its a given that that tube needs to be replaced.

What I have done and come to find: I did replacce the tube that was white with one that I have in my extras box. I have isolated the reverb problem into two locations one is that the HR's reverb tank is somehow inoperable. I say "somehow" due to when i pulled it out and ran my finger down the springs it made the usual springy crashy noise. But when hooked up to a guitar and reverb set at 12 it has no reverb effect. Also, the problem lies somewhere on the motherboard I but do not know where exactly to diagnose the issue. I have swapped out the tank in the HR with my 69 Deluxe Reverb tank and with the reverb turned to 12 it sounds as if it is a 2. (My 69 sounds amazing and if you know anything about the reverb channel on a 69 i need to say no more) The question is, what else can i do to diagnose the problem on this reverb issue?

As for the capacitors I have found that there are scortch marks on the motherboard just, as all forums that i have read, under the white ceramic cap's. The "quick fix" to this is to re-heat the solder and ensure that the bond has not come undone. What I have read is that these ceramic capacitors should be replaced if scortch marks are found. Since I do not have any replacement Cap's I performed the "Quick Fix" for now. No real change in the behavior of the amp was noticable.

Are there any techinical manuals that I may purchase so I can learn more about working on these types of issues??

Thanks!!


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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 5:41 pm
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Hi michaelbpuccio,

You should probably start by reviewing the schematics (link below), as it lists the expected voltages. And, the "rectangular capacitors" that you mentioned, with the scorch marks under the board are actually 5 watt resistors. You probably have a problem with solder joints around those 5 watt resistors, which may be why the reverb doesn't work, as those two resistors are in the supply to the reverb op amps. The scorched board itself is not a problem, but may indicate solder joint problems on the other side of the circuit board, or even a cracked circuit trace.

http://support.fender.com/schematics/guitar_amplifiers/Hot_Rod_Deluxe_schematic.pdf

Also check this site out for tons of great info on the HRDlx.
http://www.justinholton.com/hotrod/

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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 5:48 pm
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Thank you very much for your input!! Though i do have to say that i have done what is on the Hot Rod website you have forewarded to me and re-soldered the contacts. The reverb effect had no change and still was not working with its own reverb tank at all and with the reverb level at 12 and a known working tank it sounded like it was at 3.


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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 5:56 pm
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Sounds like the driver/recovery op-amp is toast.

Very common with this series of amp -- it happened to mine as well.

Arjay

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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 6:07 pm
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Remember that not all reverb tanks are the same impedance, or even the same on the hook up, make sure that the one that you tried matches the original closely, and check that the original is plugged in properly. If the reverb tank is plugged in backwards, it may not work either, the output cable shield is grounded on the circuit board, and connected to the tank itself, the input shield is not grounded, and the tank negative input is not connected to the tank. And check to see if one or both of the 5 watt resistors might be open.

But check for the voltages on the schematic and that may help you narrow down the problems. For example, it seems that your DC supply voltages (B+, etc) are too low, indicating a power supply problem among other issues that you mentioned. I would start with the power supply first, one thing at a time, then move to the next problem. If your power supply voltage is low, the power to the 5 watt resistors could also be low. :idea:

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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 6:09 pm
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Ok Driver/Recovery op-amp, where is that on the schematic? I am looking and dont see it.

Also is there any way to get the link to the schematic and service diagram for the Hot Rod 410 Deville?

Thanks!!


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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 6:14 pm
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Thanks for the pointer!! I will study the schematic and trace the power issue you have mentioned. As for the reverb tank I have checked and the little transformer looking parts I will check as well..


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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 6:16 pm
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Far upper right on the schematic. Reverb circuit.

HRDvl schematic:
http://support.fender.com/schematics/guitar_amplifiers/Hot_Rod_DeVille_schematic.pdf

Check here for many Fender schematics:
http://www.fender.com/support/articles.php?section=downloads&category=amplifier-schematics

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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 6:44 pm
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Is there any manual or service reference that i can buy to learn more on how to diagnose and become more familiar with Fender tube amps??


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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 8:42 pm
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No, one single manual like that would be at least 6 feet tall and weigh hundreds of pounds. :lol:

Seriously, if you divide any amp into sections (power supply, signal control, output section), and study each, you can learn about Fender or any brand of amps. Each section can be further divided into subsections for simplification. All electronics will work the same in any equipment, there is nothing special about the electronics in an amp, but diagnosing a problem is basically a process of elimination, an understanding of electronics, and a developed procedure.

Tubes would be a great place to start learning for example, if you already have a good understanding of electronics. The "RCA Receiving Tube Manual" is a great resource for tube info. Don't worry about getting a "vintage" copy, the newest one (late 70s?) will have the latest (at the time) tube data and the data from the older manuals. All of that info is just as valid and applicable today, as it was then.

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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 8:51 pm
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Yes I can understand how that type of book would be huge!! Ill look into the reccome ded book.. And in looking at the schematics earlier and going back to the amp and probing the test points I find that the values in the reverb section are way off in comparison to the schematic. Makes me think that I need to start somewhere else as the reverb portion of the amp is not the first in line when power is being distributed.


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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 18, 2011 9:09 pm
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Sounds like you are starting to develop a good procedure already, power > control > output. :) With experience you will get a feel for how far you can skip ahead in your procedure. And eventually you will develop a sixth sense and be able to diagnose the problem by simply reading someones post........OK, the last part was a slight exaggeration, but close. 8)

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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 25, 2011 12:45 pm
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Good news!! I took the reverb tank out and looked at it closely. The Problem was found!! It turns out that the resistance was 60 on one side and 0 on the other. So I took the tank into good lighting and saw that fine copper wire was not attached to where the connector plugs into. I unwound it once giving me enough slack to re solder it. Checked out good at 230ohms, plugged it back in, played like i was at PIPELINE!!

Thanks for all of your guys help and support!!

Mike


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Post subject: Re: Hot Rod Deluxe - Couple questions.... Please Help!!
Posted: Mon Jul 25, 2011 1:13 pm
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Congrats, Mike.

Rawk on!

8)

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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