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Post subject: Déja vu: HRD sizzling
Posted: Mon Dec 23, 2013 7:19 pm
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Aspiring Musician
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My HRD is sizzling but not in a good way. :(

It sounds like a cross between static, noise, and frying bacon. It's happening on both the Clean and Drive channels and to top things off it's intermittent.


If this sounds familiar that's because the same sizzle happened just over a year ago. The culprit was a faulty pre amp tube. I have yet to exhaust all diagnostic measures - i.e. cable, power supply, input 1, input 2 - but given my track record I'll put money on the tubes. Six months out of the box the first pre amp tube goes. Two months later another pre amp tube dies. Fast forward five more months and yet another tube zaps the dust. Then there was that yet unresolved drive channel dropping out issue but leaving this aside and assuming the current problem is indeed a faulty tube, could four tube changes in less than two years be considered "normal"? The amp is used daily for several hours at a time but when I'm not playing it's on standby. Could I be doing anything to shorten the life of the tubes?

Thanks and Cheers!
BM

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Post subject: Re: Déja vu: HRD sizzling
Posted: Mon Dec 23, 2013 9:56 pm
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What brand tubes are you using?

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Post subject: Re: Déja vu: HRD sizzling
Posted: Mon Dec 23, 2013 10:00 pm
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Your amp's pre-amp stage is prolly setup on the hot side. That is, some of the 12AX7 are set in hot bias. Short of re-doing the parameters (a PITA) --- you prolly need mil spec NOS 12AX7A/7025 for long life. Or keep replacing tube with standard modern 12AX7.

Or one or more of the coupling caps maybe leaking too much DC. How is the bass response of the amp? Is "farting" (from the amp :lol: ) an issue?


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Post subject: Re: Déja vu: HRD sizzling
Posted: Tue Dec 24, 2013 12:49 am
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Aspiring Musician
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I just had same problem w/my DRRI. Intermittent. Luckily it was just the seating of the tubes. I don't know what tubes you use but I've been using standard JJs with pretty good results.


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Post subject: Re: Déja vu: HRD sizzling
Posted: Tue Dec 24, 2013 4:57 am
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Aspiring Musician
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Hi guys and thanks for the replies.

bluesky636 wrote:
What brand tubes are you using?
    At present the power tubes are original and I have the following pre amp tubes:
    • V1 > JAN Philips 5751
    • V2 > Groove Tube GT12AX7
    • V3 > 12AT7/ECC81 Mullard

BMW2002Ti wrote:
... you prolly need mil spec NOS 12AX7A/7025 for long life. Or keep replacing tube with standard modern 12AX7.
Or one or more of the coupling caps maybe leaking too much DC. How is the bass response of the amp? Is "farting" (from the amp :lol: ) an issue?
    If I'm not mistaken I believe the 5751s I've used as well as the Mullard 12AT7 are mil spec. As for the bass response, I'm glad to report there is no "farting". At least not from the amp. :lol:


Cheers!
BM

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Post subject: Re: Déja vu: HRD sizzling
Posted: Tue Dec 24, 2013 8:16 am
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Good tubes.

I seriously doubt there is a problem with too hot a bias on the tubes. Unless there is a faulty component, these amps are pretty standardized in their design and construction.

I suggest you retension the preamp tube sockets, clean them, and make sure there are no cracked solder joints around the socket pins. Poorly fitting tubes can cause all sorts of problems which can easily be fixed.

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Post subject: Re: Déja vu: HRD sizzling
Posted: Tue Dec 24, 2013 4:16 pm
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Aspiring Musician
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bluesky636 wrote:
Good tubes.

I seriously doubt there is a problem with too hot a bias on the tubes. Unless there is a faulty component, these amps are pretty standardized in their design and construction.

I suggest you retension the preamp tube sockets, clean them, and make sure there are no cracked solder joints around the socket pins. Poorly fitting tubes can cause all sorts of problems which can easily be fixed.

    Aftrer the holiday hustle has subsided I'll do as you suggest and hope this resolves the sizzling. I have never performed this operation but I have read about it on the "Internets" so if there is any advice - especially with regard to safety :shock: - I'm all ears.

    Thanks, Bill
    and Merry Christmas!
    BM

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Post subject: Re: Déja vu: HRD sizzling
Posted: Tue Dec 24, 2013 5:47 pm
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Bluer Monkey wrote:
bluesky636 wrote:
Good tubes.

I seriously doubt there is a problem with too hot a bias on the tubes. Unless there is a faulty component, these amps are pretty standardized in their design and construction.

I suggest you retension the preamp tube sockets, clean them, and make sure there are no cracked solder joints around the socket pins. Poorly fitting tubes can cause all sorts of problems which can easily be fixed.

    Aftrer the holiday hustle has subsided I'll do as you suggest and hope this resolves the sizzling. I have never performed this operation but I have read about it on the "Internets" so if there is any advice - especially with regard to safety :shock: - I'm all ears.

    Thanks, Bill
    and Merry Christmas!
    BM


Just make sure the power supply caps are discharged before sticking your hands inside the amp.

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Post subject: Re: Déja vu: HRD sizzling
Posted: Wed Dec 25, 2013 3:22 am
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bluesky636 wrote:
Just make sure the power supply caps are discharged before sticking your hands inside the amp.


Or else an ER trauma surgeon might be sticking his hands inside you!

:shock:

Use utmost caution and follow bluesky's safety protocols explicitly.

Arjay

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Post subject: Re: Déja vu: HRD sizzling
Posted: Wed Dec 25, 2013 12:34 pm
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Aspiring Musician
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Retroverbial wrote:
... Use utmost caution and follow bluesky's safety protocols explicitly. ... Or else an ER trauma surgeon might be sticking his hands inside you! :shock: Arjay
    :shock: :shock: :shock: You know ... ah, on second thought ... maybe I should leave the socket pins alone ... I'll try changing the cable ... :lol:

    Cheers!
    BM

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