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Post subject: EVH 5150III 100W Head No Sound/Output
Posted: Sat Mar 07, 2015 11:29 am
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Hey guys, the other day I went to go play ny amp after not using it for about a week. I turned it on to let it warm up the flipped the standby switch and when I went to play you could hear my guitar coming through the amp but it was crackling and buzzing and then after about 15 seconds there was a pop and then nothing. The tubes seem to be fine as all are glowing and I've tried other speakers to make sure it wasn't that. Any suggestions?


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Post subject: Re: EVH 5150III 100W Head No Sound/Output
Posted: Sat Mar 07, 2015 12:57 pm
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Did you check fuses inside ?

There are few fuses , need a meter to check them . Eyes is not enough.
Why fuse blow ?
Could blow for nothing , it is happen some times.
Power tubes fail
Power supply fail


Glowing tube mean only there a heater voltage in the amp , the heater circuit work .

50 watts shematic here , no 100 watts

https://www.evhgear.com/support/


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Post subject: Re: EVH 5150III 100W Head No Sound/Output
Posted: Sat Mar 07, 2015 1:46 pm
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Yeah I need to check the fuses... are they inline? Could it be the output transformer? Any other commons problems with these?


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Post subject: Re: EVH 5150III 100W Head No Sound/Output
Posted: Sat Mar 07, 2015 2:24 pm
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jeff-tranchina wrote:
Yeah I need to check the fuses... are they inline?
In line ? What do you mean ? They are inside the amp

Could it be the output transformer? Any other commons problems with these?


Could many many thing . I write most popular.
I guess it power tube(s) short

1-Open the amp , check fuses with a meter , if you know how to use .
2-If you find a blow fuse , buy some , not only one . Same power , not more , not less
3-Put new fuse in the amp
4- Remove all you Power output tubes
5- Power amp on , with speaker plug. Yes NO power tubes in
6- Wait 10 -15 minutes

Power amp Off
7-check if fuses are always good
8 - If yes one or more power tube look short

You can do a double check to be sure ;

Put all power tubes in amp .
Power amp ON , fuse must blow if power tube(s) are short . You may need to wait . Play guitar in amp and see.


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Post subject: Re: EVH 5150III 100W Head No Sound/Output
Posted: Sat Mar 07, 2015 2:53 pm
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I just checked the fuses... I counted 4 (I don't know if I am missing anymore) but they all had continuity.


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Post subject: Re: EVH 5150III 100W Head No Sound/Output
Posted: Sat Mar 07, 2015 4:39 pm
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jeff-tranchina wrote:
I just checked the fuses... I counted 4 (I don't know if I am missing anymore) but they all had continuity.



One or more Power tube could be blow or resistor in power supply or ..... Did you see something burn ? Any picture inside amp ?

You may see some qualified tech


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Post subject: Re: EVH 5150III 100W Head No Sound/Output
Posted: Sat Mar 07, 2015 4:45 pm
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Nevermind, went back to double check and found a bad fuse... replaced it, turned on amp with no output tubes and it was fine... put tubes back in, powered it up and got sound out of the cab but I can hear a noise coming from one of the output tubes, sounds like something is rattling in the tube... I'm assuming this is a bad tube? How do I figure out which one(s) is the bad one


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Post subject: Re: EVH 5150III 100W Head No Sound/Output
Posted: Sat Mar 07, 2015 5:36 pm
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You use 4 output tubes IMO

Best is to put a new one at different place and listen .

Low cost job ; replace only the bad one and hope , with bias check and adjust if needed ) , this tube is match with 3 other .

Good job for reliable amp ; replace all four tubes with quad match and check bias and adjust if need. That is what I'll do .


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Post subject: Re: EVH 5150III 100W Head No Sound/Output
Posted: Sun Mar 08, 2015 6:13 am
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stratele52 wrote:
You use 4 output tubes IMO

Best is to put a new one at different place and listen .

Low cost job ; replace only the bad one and hope , with bias check and adjust if needed ) , this tube is match with 3 other .

Good job for reliable amp ; replace all four tubes with quad match and check bias and adjust if need. That is what I'll do .


Alright ill look into it, thanks for your help!!


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