Help please! (If this should go in another thread, please advise!)
I switched on my Cure today to play a bit, and as the amp warmed up, there was a hum and other noises I've never heard before from this amp. So I powered off, checked the back to ensure the speaker was connected in the correct spot (I leave power disconnected as my 2yr old daughter likes to play with patch chords - and swap plugs - so Im used to checking the back before powering on). Everything was where it should be. So I 0'd all the knobs incase it was related and powered back on, the hum and noises were still there and as I was about to power back off, there was a "pop" - not from the speaker - from inside the chassis, which was followed by smoke! My heart increased, and my anxiety spiked...
So I took the chassis out and low and behold one of the components had burst. Pics attached. Any body able to make sense of this? What are my next steps? There is a Z retailer not too far from me, but they are a "big-box" retailer and Im not sure I would trust their techs to diagnose/fix this...
I do know a decent custom builder who is about 2 hr's from me - should I go to him? Will he know what to replace/repair just by looking? Is anyone able to diagnose via these pics? Is this just an issue with this component or is there other issues lurking?
I'd send an e-mail to Email: firstname.lastname@example.org Looks like more than one component popped. Just knowing they popped doesn't tell you why. They will take care of you. It is the weekend. It may be till monday till you hear from them but they do great work.
Last Edit: Aug 17, 2019 7:25:51 GMT -7 by roscoenyc
Even if it was a tube issue, it's failing took out several components. (and I'm not saying it was a tube) But something taking out multiple components would be for me: A trip back to the Z-amp factory.
Excellent reputation for customer service and making your amp as good as new. Use the email Roscoe gave you.
Did you buy it new from an authorized dealer?
Was your amp on the water? ('smoke on the water'....see what I did there?)
Ok you did have the Bias resistor by pass cap burst Sprauge Atom 25uF @ 50 V. It burst because an output tube failed , that was the weird noise you heard the tube running away pulling excessive currant. I bet it has a crack, it loss vacuum and failed. Also the 1.5 K Grid resistor on the socket looks burnt from over draw. You need a new set of Output tubes, a Sprauge Atom, and a 1.5 K Carbon Comp. 1 W resistor I would change both V4 and V5 they cost a dime. Also check the 10 watt Bias resistor it surely got stressed. Oh yeah a fresh fuse. It's Don's birthday Monday so he's off. Let me know if you want to send it in or have it repaired locally. It can be good as new with a few new parts.
Thank you all for the speedy replies! I'm a relatively new Z owner (a couple months!) and I'm confident that awesome customer support and great community (here on ztalk) are part of what I bought into. Thanks for all the info.
FYI, I am a 2nd hand owner, and outside the US! Ill get in touch with drzepairs, and go from there.
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Follow up question! Amp tech has fixed the issue but is recommending the following:
" It is biased VERY hot. There is no bias adjustment. Bias is set by the 200 ohm cathode resistor they are using in this circuit. If it was my amp, I'd put a 250 ohm in this spot. That's what Fender used on their 50's tweed amps, and it would cool the bias down a bit into a safer range. I don't think you'd notice any difference in tone at all, but would probably get much more life out your power tubes."
Post by daddyelmis on Aug 23, 2019 12:17:06 GMT -7
If you watch Docs videos on bias, he’s real clear that the numbers are a starting point and really have to make final determinations by ear. If that 200ohm resistor is stock (i.e., prior owner didn’t mess around with it) then I’d leave it where Doc set it.
My guess is that 10 amp techs would have 10 opinions about where the bias should be set. Doc designed it and built it, so I’d stay with his spec.
Post by premiumplus (Dave) on Aug 23, 2019 17:29:55 GMT -7
I was told by a tube 'guru' that my Maz 8 was biased way too hot, and I should change it. I talked to Doc about it and was reassured that the tubes would last just fine. And he was right, I've got hundreds of hours on the original output tube and it's still sounding great. Doc knows what he's doing. My Cure is still on it's original output tubes too and I'm doing just fine.
"Tone, tone, tone, tone. Is there a substitute?" -Dr.Z
I'll add to several of the guys' comments.....I'd keep it stock. My Cure is my main gigging amp and has a lot of hours on it. Also, if it's not prohibitively expensive, I highly recommend returning it to the factory for a full checkup. I did this with my (purchased used) Remedy and it came back like new.
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The Bad Poodle: cause we all know Too much bass increases "tube rattle"....
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roscoenyc: Oh my goodness!!!
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