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Post subject: Hot Rod Deville 410 "CRACKLE FROM HELL!!" FIXED!!!!!!!
Posted: Wed Aug 17, 2011 11:37 am
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Joined: Mon Nov 01, 2010 10:31 pm
Posts: 154
Problem: Loud intermittent crackle at no volume.
Fixes: Tubes, Plate Load Resistors 82K and 100K, Dirty Pots, Cracks in solder joints, Dirt, and many more......

I am adding one fix to the list of things that can go wrong and explaining it.

Ok, Some of you may know, and helped me in the numerous ways to fix the unwanted "Crackle From Hell" that I WAS having on a Hot Rod Deville 410. I just wanted to let you all know that I found what was making the amp crackle. I took the amp to a friends house where he has an osicilloscope. We were able to see the sound was coming from a plate load voltage that was bleeding through the tone circuit. C5 (bass), C6 (middle), and C7 (treble), all are located between the plate voltage of V1B and the grid of V2A. If ANY of these caps are intermittent they WILL conduct voltage on the plate of V1B to the grid of the next stage. V2A pin 1 R16 goes to the power supply of 388 volts the same as V1B pin 6 does, both through 100K resistors. This is what convinced me that it is that plate voltage on V1B that is getting through one of the caps. Either way I replaced all three parts and this CURED THE CRACKLE FROM HELL.. So in a nutshell C5, C6, and C7 were replaced and this CURED the issue I was having. 8)


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Post subject: Re: Hot Rod Deville 410 "CRACKLE FROM HELL!!" FIXED!!!!!!!
Posted: Wed Aug 17, 2011 12:58 pm
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Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
Very diligent troubleshooting protocols, sir -- congrats are definitely in order.

We'll put you in for another ARCOM.

:mrgreen:

RAWK ON!

8)

Arjay

_________________
"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 Deville 410 "CRACKLE FROM HELL!!" FIXED!!!!!!!
Posted: Thu Sep 08, 2011 5:48 pm
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Joined: Thu Sep 08, 2011 5:24 pm
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Seeing as you guys know what you're talking about I figure this is the right place to post a hot rod deville 4x10 related question. While I don't get a "crackle from hell" at no volume, what i do get is what I would consider a very bad break-up on the clean channel even at very low volume. I'm playing a blacktop strat and get a really crummy "crackle" or "break-up" or something that sounds ugly even when using the single coil (just not as bad as when using the humbuckers).

I bought the amp used so there is no telling how old the tubes are or if they need replacement. I know nothing of electronics but it would be nice to be able to tell a repair guy something other than, "it sounds bad." The power cable on this thing is also missing the ground input on the plug. Not sure if that has anything to do with my issue. Any insight would be greatly appreciated.


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Post subject: Re: Hot Rod Deville 410 "CRACKLE FROM HELL!!" FIXED!!!!!!!
Posted: Thu Sep 08, 2011 5:55 pm
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Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
Hi yuno_hu,

Definitely fix the ground before doing anything else, it is very dangerous. The missing ground can not only add unpleasant noise to the amp, but it can lead to a nasty shock for you or someone jamming with you. This could be the source of your problem. Those who break off the ground plug from electrical devices should be summarily beaten to a pulp, no joking. :idea:

Have the tech go through the amp while the plug is being replaced to see if there are other issues.

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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 Deville 410 "CRACKLE FROM HELL!!" FIXED!!!!!!!
Posted: Wed Sep 21, 2011 4:27 pm
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Joined: Fri Jan 02, 2009 7:36 am
Posts: 93
Location: Dallas, TX
I read with great interest your oscilloscope diagnosis and wished I had this level of knowledge. Can you recommend some books to help those of us interested, how to learn to do this level of diagnosis? Also, any tool/scope recommendations?
Thanks!
John


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