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Title: Weird issue with hrm build popping noise Post by: XB9R on January 14, 2013, 09:39:25 AM wondering if anyone has ever come across voltage on the choke frame/casing? Ive got this really weird issue, popping from speaker, and it changes tone. powered up a new hrm build a week or so ago, bulb limiter test was fine, tubes in voltages look ok, slightly hot but well within a 10% range. Continuity is good on all conections, ive been over this amp from both ends and all connections are spot on. Power tubes Biased up fine, PI trimmer bang on with V3A 6VDC higher than V3B. I pulled power tubes and popping stops, swaped them around and rebiased, this is where it got odd. This time i adjusted the bias with the tips of my fingers on the pot wedged between the choke and the power tubes trying very carefully not to get burnt from the heat coming off the 6L6s and touched the casing of the choke, well the popping stopped. Decided to get a reading off the choke casing to ground and the casing has just about 12VDC on it. thats not normal is it? Could that be a grounding issue on the choke casing? Amp seems to play fine apart from the annoying pop. Any ideas? I dont want to just ground this thing if there is an underlying issue.
Title: Re: Weird issue with hrm build popping noise Post by: plasticvonaband on January 15, 2013, 04:11:29 AM sounds like maybe a ground issue, or maybe a short some how?
Title: Re: Weird issue with hrm build popping noise Post by: XB9R on January 15, 2013, 09:27:16 AM Aye, im gonna pull the choke out and check both the resistances from the wires to choke frame and then get the old dremmel out and grind back some more of the powder coating on the chassis at the choke mountings. Have done a dark room test too to make sure there wasnt any visible arcing anywhere indicating a short of some sort, but that was clear. Thought it may have been a bad cap somewhere but none are giving the ol tell tale bulge, Its got to be the choke grounding fingers crossed cause in theory if the choke was ground i would be 12VDC all over the chassis not just on the choke frame. oh the joys of trouble shooting :)
Title: Re: Weird issue with hrm build popping noise Post by: XB9R on January 21, 2013, 09:00:48 AM Resolved. Bung JJ out of the box :( new pair of tubes and my oh my what an amp. Must remember to take the crap tube to my tube guy and get him to throw it in his tester and see what it turns out like.
Title: Re: Weird issue with hrm build popping noise Post by: plasticvonaband on January 23, 2013, 01:10:55 AM Awesome! easy fixes are the best!
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