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Post subject: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 2:42 am
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Hey all!

Ill start at the beginning! I recently bought my prized Vibroverb blackface, have had it for about 3months now. Strangely on occasion i will turn the amp on and everything seems fine i can hear the speaker humming, tube's light up but no signal! from any of the input jacks!

At first i thought it would be a simple wiring issue but when i brought the amp to a specialist with over 30yrs experience with amps he couldnt figure it out either. When i brought the amp to him it mysteriously started working again, everything was working perfect. He kept it for a little while and tried to get it to stuff up like it had before but nothing! It was working great... So i took it back home and after 1day it stuffed up again, same problem. :shock:

I have changed leads, guitars etc. Just wondering if anyone has had this kind of issue before? Would like to get some insight before i take it back.

Thanks in advance for your thoughts. Jeremy :D


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Post subject: Re: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 3:29 am
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Have you tried all the input jacks with same result? Sounds like it maybe poor contact or signal short-to-ground. I presume the tech checked all the tubes... & their contact with the sockets?


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Post subject: Re: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 4:02 am
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BMW2002Ti wrote:
Have you tried all the input jacks with same result? Sounds like it maybe poor contact or signal short-to-ground. I presume the tech checked all the tubes... & their contact with the sockets?


Yup i used all input jacks and same problem. And yes, the tech checked everything, thats whats so strange when he had it, it was working perfectly for 2weeks, all wiring is sweet. When i have it it takes one day til it stops working again. This would be the fourth time its done this... only at my house too. Perhaps the electrical at my house is poor? ive heard of amps not working in old houses. My house is about 30yrs old. Electrical work done by my gramp who built the house, a qualified carpenter but not electrician lol. Could be the problem?
I will test my amp at a friends house over the weekend see if it is the problem


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Post subject: Re: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 7:42 am
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It sounds like this could be a problem with the printed circuit board (not familiar with your amp--- not sure if the Custom VV has point-to-point wiring or printed boards). Anyhow, there is an issue with the continuity. It maybe the house wiring, but you'd prolly see this problem in all of your plugged-in appliances as well.

First thing to check is there a FUSE on the output stage of this amp? Often it resides the printed circuit board. Check the fuse for continuity, if you find it. I also noticed (at least on the schematic I could find) that the power section has some diodes off the power tubes. Often, these will act like fuses--- if you get too much current flow in use or back-flow after turning the amp off. If all these parts in the power section seems ok...

You are going to need to go from one end to the other to find the problem. I like going from power section (power tubes) back to the input, section by section. You can use a DVM and selectively pull tubes to test each section. A signal on the input (signal generator) with an oscilloscope on the output greatly helps narrow down which section is bad. Not common items in most households.

For example, pull all the tubes and check the B+ for proper voltage off the power tranny (prolly ok since your tubes light up). Turn amp off, insert rectifier (if it has a tube rectifer), check B+. Turn of amp plug in power tubes, check voltages on the anode. Then, plug in phase inverter tube, check voltages. Then each subsequent gain stage?EFX/input stage tube. Usually, Fender amps are setup in that order, if you look at the chassis. From Rectifer -> Power tubes -> Phase Inverter -> EFX/GAin Stage(s) -> Input stage. Leo designed it this way to make it easier for techs to diagnose.

One caveat! You'll be dealing with the chassis out of the cab and turned on... in other words lethal volatges. I strongly suggest that if you've never done this before, you are better off taking the amp to your tech. Sometimes these things are simple. Sometimes they take while to find and fix.



http://www.prowessamplifiers.com/schema ... _mods.html


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Post subject: Re: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 8:46 am
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Try replacing the speaker wiring harness. A fellow I know had a problem with his TRRI Custom 15 displaying identical symptoms to yours. Turned out to be an intermittent open somewhere in the speaker wire or with the plug itself.

HTH

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: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 3:22 pm
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Very helpful guys! thanks alot.

Yes it has point-to-point wiring. :D

I could check a couple things you mentioned, but im just too scared to fiddle around with it. Might just leave it to the tech haha.

Thanks again for your help, very useful! Jeremy


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Post subject: Re: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 8:33 pm
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jeremydawg wrote:
I could check a couple things you mentioned, but im just too scared to fiddle around with it. Might just leave it to the tech haha.


If you're loath to perform even the most basic and non-invasive of maintenance and troubleshooting procedures, why waste your time on this forum? Did you think someone here could "miracle" a diagnosis and repair for your amp via telekinesis?

:roll:

Arjay

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Post subject: Re: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 9:38 pm
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Ok, just to clear this up for ya Arjay. Below i quote. I mentioned If anyone else has had this problem before maybe they could give some valuable insight.

jeremydawg wrote:
Just wondering if anyone has had this kind of issue before? Would like to get some insight before i take it back.


Like you mentioned, could be speaker wiring harness because a friend had the same problem, that i can do! And some other basic things mentioned. Secondly the tech had my amp for two weeks, he checked alot of things so i doubt it would be something basic and "non invasive". Like what BMW2002ti said: "Sometimes these things are simple. Sometimes they take while to find and fix".

My wording was not that great from my last post, my apologies. What i meant was I could do the basic stuff mentioned (and i will), but i am too scared to work on a chassis out of the cab and powered up. Ill leave the more complicated stuff for the pro's.
I wasnt asking for a repair diagnosis. Just some thoughts, as i have never encountered such a problem before... perhaps it is common. Was just curious. :D

Anyway sorry if i did waste anyones time. I will though write up what the problem was when i find out! 8)

thanks again, Jeremy


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Post subject: Re: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Sun Sep 11, 2011 9:59 pm
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That's certainly understandable, Jeremy -- there are lethal voltages within a chassis (both when powered up AND when totally unplugged) and electricity brooks no forgiveness for the unwary. That said, pick up an inexpensive DVM (if you don't already own one) so you can perform some basic "non-dynamic" tests. Intermittent problems like yours are not typical and can sometimes take time to sort out. I know you love your Vibroverb as I do mine so I'm hopeful that your tech can diagnose and repair whatever issue is at play.

Best of luck

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: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Mon Sep 12, 2011 4:22 am
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will do. Thanks alot for your help! Hopefully she'll be pumping soon. :D


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Post subject: Re: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Mon Sep 12, 2011 9:41 am
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jeremydawg wrote:
will do. Thanks alot for your help! Hopefully she'll be pumping soon. :D


Right on!

I often thought Fender should re-issue the Vibroverb within their standard blackface re-issue line, using less-expensive PCB construction to make it more affordable to the masses. I even discussed this possibility at length with FMIC's Shane Nichols last March. No idea whether or not this proposal will ever become reality (I think it'd be a real moneymaker though).

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: Fender 64 RI Custom Vibroverb. Mysterious issue!
Posted: Mon Sep 12, 2011 3:27 pm
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Now thats an idea!
It took me a long while to save for my VV!
Especially here in Aus where everything is more expensive!!


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