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Post by rustycaster on Feb 10, 2017 12:57:49 GMT -7
I recently bought this amp and it was shipped to me from Nashville in a Brady Road case.. the only changes from Factory a ..weber Silverbell matched up to a vintage 30 both 16 ohm wired parallel to a 8 ohm. The problem with it is when it is taken off standby there is a very audible AC hum.. adjusting the knobs on the chassis make no difference in volume or tone. I have also tried replacing all the tubes with another matched set still no change. I have a Monza 112 as well as the Ghia Head with matching 210 cab neither one hum when plugged into that rooms Outlets.. keep in mind at this time there is no cord or instrument plugged into the front of the amp. I have currently been using a radial headload prodigy with the 50% power cut this reduces the hum by about 90 percent but also reduces the overall volume I did pull the head out and look four signs of burned components but to my eye everything looks good ..any thoughts anyone?
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Post by Jaguarguy (Mike) on Feb 10, 2017 13:32:29 GMT -7
Welcome to the Forum - a lot of good people and info here! You've got a great amp there (I have several of them in various formats). A couple of things: 1) make sure all chassis bolts are tight - that can sometimes cause a problem. 2) spray a little deoxit on a cable and work into the inputs to make sure they are clean 3) make sure there isn't a cell phone nearby - that can cause a hum. 4) reseat all the tubes 5) follow Doc's trouble shooting guide drzamps.com/info/faq-troubleshoot/If all the above fail send a note to Don at repairs@drzamps.com Good luck!
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Post by KeithA on Feb 10, 2017 15:30:25 GMT -7
At 17 years old it could be aging caps in the power supply, maybe?
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Post by zpilot on Feb 11, 2017 9:12:03 GMT -7
I would hope that the seller would have been forthright enough to have told you if it had that problem up front. As for filter caps, I've heard the old rule-of-thumb that they only lasted about 15 years. My actual experience is that they last much longer than that in vintage amps. Caps manufactured in the last 20 years last even longer. My money is on it being something else.
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Post by KeithA on Feb 11, 2017 9:50:27 GMT -7
I would hope that the seller would have been forthright enough to have told you if it had that problem up front. As for filter caps, I've heard the old rule-of-thumb that they only lasted about 15 years. My actual experience is that they last much longer than that in vintage amps. Caps manufactured in the last 20 years last even longer. My money is on it being something else. True, but I'm even thinking that maybe a lead cracked on one of the caps during shipping or similar. However, you are right it may very well be something else completely.
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Post by zpilot on Feb 11, 2017 10:25:03 GMT -7
I've seen a lot of broken solder joints on filter cap leads that occurred during shipping. However they were ALL in amps built on PCB's. Turret boards are much more robust.
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Post by rustycaster on Feb 13, 2017 14:29:34 GMT -7
Good info folks and I really do appreciate the help.. the seller is a reputable source and said it was dead quiet before shipping. Idk. Everything looks visually good. I did find over the weekend bthe power tube furthest left looking from the back felt a little looser in the socket than the other three . I took it out and reinserted it a few times....No change
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Post by zpilot on Feb 13, 2017 20:39:55 GMT -7
OK, here is the old troubleshooting routine. One by one pull the tubes until you find the tube or area of the circuit that is causing the hum. Start with V1. If you don't have a tube chart it is probably the one closest to the input jack. Put the amp on standby, pull the tube, take the amp off standby and listen. If it still hums then continue on to V2. My bet is that the EF-86 is bad.
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Post by rustycaster on Feb 14, 2017 12:17:23 GMT -7
I stopped by church this morning and loaded it up. Will dig into it again tonight or tomorrow. Driving me crazy. Will update then. Thank you fellas for all your insight. Keep referring back to tubes. I guess I could have gotten a bad new one.
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Post by rustycaster on Feb 14, 2017 18:06:19 GMT -7
I did the preamp tube test again..No change...For giggles I put the old tubes back in. No change....I started fiddling with the EQ knobs again and noticed on the treble if I set it about 10:00 the hum is 95 percent gone. I left it there for a couple minutes and heard a pop and the hum came back louder than before...
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Post by mudman on Feb 14, 2017 20:00:36 GMT -7
I stopped by church this morning and loaded it up. Will dig into it again tonight or tomorrow. Driving me crazy. Will update then. Thank you fellas for all your insight. Keep referring back to tubes. I guess I could have gotten a bad new one. I recently got a Maz Jr. from 2011. It hums like crazy with certain tubes in v1. Definitely worth trying another tube there.
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Post by rustycaster on Feb 16, 2017 13:46:02 GMT -7
Tubes didn't help 😔 left today to see the doctor hopefully Don won't be too hard on me.
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Post by rustycaster on Mar 17, 2017 7:06:50 GMT -7
Got the chassis back yesterday and put everything back together last night and you should bare the smile on my face ! Mike the Dr personally replaced btge filter caps and tweaked it himself ! Bad caps and back in business !!! Thank you everyone who gave input 😁
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Post by Jaguarguy (Mike) on Mar 17, 2017 8:32:37 GMT -7
It is amazing how reasonable Doc is with repair work - and of course they come back as good as new!!
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