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Post subject: My new 76 Vibro Champ, couple of questions
Posted: Tue Mar 21, 2017 9:04 pm
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Been reading up trying to learn how to work on my amp myself. I was wondering if anyone would know if the circuit looks original and if there's anything I should replace, I also noticed that someone added an extra cap (47uf 500v) to the cap can, should this be of any concern? Also the pins in the power/rectifier tube sockets have quite a bit of up and down play in them the tubes clip fine but hang low and the actual tabs in the sockets move. Can this be fixed or will they need to be replaced? Thanks for any help offered.
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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Wed Mar 29, 2017 11:07 pm
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I'm wondering if one section of the cap can blew out and someone rigged up a workaround rather than just replace the entire can......?

Arjay

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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 1:10 am
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That's what happened. May have been done more than ten years ago. When good quality CE cap cans were not available. I'd replace the whole can with a 20/20/20 at 525 VDC can. These last forever. I've replaced four or five Champs or VC with it. No problems. Well, except soldering the cap's tabs to the chassis. You need a 100 watt soldering iron to do a good job. :D

https://www.tubesandmore.com/products/c ... v-202020-f


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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 1:58 am
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+1

Thankfully we now have Mallory clones that do an excellent job and eliminate the need for such creative "engineering".

:mrgreen:

Arjay

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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 2:16 pm
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The can on there now is 40/20/20. Should I stick with these values or go 20/20/20, will it make a difference?


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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 3:39 pm
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The 40 mfd reservoir portion of the cap can will tighten up the bass response at higher volumes, especially useful if the OEM Oxford is still installed. With a better speaker the 20/20/20 can will be adequate for the task.

Arjay

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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 4:03 pm
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It currently has a usa jensen in it. I was also going to replace the rest of the caps and wondering if there's a certain brand I should go with? ImageImage


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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 5:31 pm
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cali234 wrote:
...I was also going to replace the rest of the caps and wondering if there's a certain brand I should go with?...


I wouldn't replace any of the coupling/tone caps unless they are defective (capacitance tester). Most of the time, the electrolytics are the only ones that need replaced.

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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 6:41 pm
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shimmilou wrote:
I wouldn't replace any of the coupling/tone caps unless they are defective (capacitance tester). Most of the time, the electrolytics are the only ones that need replaced.


+1!

Fix only that which is broke and nothing else.

Arjay

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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 7:39 pm
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Will do. Thanks for the advice.


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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Thu Mar 30, 2017 10:12 pm
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New CE can soldered into VC. :mrgreen:

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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Fri Mar 31, 2017 1:07 am
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Nice job BMW, looks good. 8)

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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Fri Mar 31, 2017 7:06 am
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Shimmilou,

Thanks! :D


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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Fri Mar 31, 2017 7:28 pm
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A common modification to Champs and other Class A amps is to increase the filtering to reduce AC hum.
The class A configuration doesn't have the hum cancelling ability of a class AB push pull amp.
If it aint broke, don't fix it


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Post subject: Re: My new 76 Vibro Champ, couple of questions
Posted: Fri Mar 31, 2017 7:34 pm
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Though Tim, I don't think I'd run much more than 20mfd, in the first filter stage after the 5Y3GT rectifier. If you really want to go "whole-hog" --- I'd put a nice low DCR choke in the first (or between first and second stage) of the PSU.


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