GZ34 (5AR4) rectifier tube

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  • george daniel
    george daniel Posts: 12,096
    edited April 2011
    you too eh?
    JC approves....he told me so. (F-1 nut)
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  • Fongolio
    Fongolio Posts: 3,516
    edited April 2011
    heiney9 wrote: »
    Hope there's no Mercury in these old tubes :wink:

    It's ok, I didn't inhale. :eek:
    SDA-1C (full mods)
    Carver TFM-55
    NAD 1130 Pre-amp
    Rega Planar 3 TT/Shelter 501 MkII
    The Clamp
    Revox A77 Mk IV Dolby reel to reel
    Thorens TD160/Mission 774 arm/Stanton 881S Shibata
    Nakamichi CR7 Cassette Deck
    Rotel RCD-855 with modified tube output stage
    Cambridge Audio DACmagic Plus
    ADC Soundshaper 3 EQ
    Ben's IC's
    Nitty Gritty 1.5FI RCM
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  • mhardy6647
    mhardy6647 Posts: 33,804
    edited April 2011
    Well, suck it and see is a popular expression in merrie olde England...
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  • Fongolio
    Fongolio Posts: 3,516
    edited April 2011
    I've checked all the power supply caps by removing one leg or in the case of the can caps removing the ground. All check out ok. All resistors in the power supply area check out good. Solder joints are good. The amp and the schematics jive. I then tested voltages with the rectifier tube in and out. Here's what I have:

    5AR4 removed:
    pin 2 5.41 AC volts
    pin 4 383 AC volts
    pin 6 384 AC volts
    pin 8 .006 AC volts

    5AR4 in
    pin 2 265 DC volts spec says this should be 455
    pin 4 376 AC volts spec says this should be 370 AC volts
    pin 6 376 AC volts spec says this should be 370 AC volts
    pin 8 268 DC volts spec says this should be 455

    The other pins aren't used. I'm at the point where I want the rectifier to be bad. At least I can replace it. I'm very frustrated at this point. The good part is though, when I'm done testing I can still plug it back in and it sounds wonderful. It will still play loud but I know with these low bias voltages and current, the amp still has a lot more potential.
    SDA-1C (full mods)
    Carver TFM-55
    NAD 1130 Pre-amp
    Rega Planar 3 TT/Shelter 501 MkII
    The Clamp
    Revox A77 Mk IV Dolby reel to reel
    Thorens TD160/Mission 774 arm/Stanton 881S Shibata
    Nakamichi CR7 Cassette Deck
    Rotel RCD-855 with modified tube output stage
    Cambridge Audio DACmagic Plus
    ADC Soundshaper 3 EQ
    Ben's IC's
    Nitty Gritty 1.5FI RCM
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  • Fongolio
    Fongolio Posts: 3,516
    edited April 2011
    Well, I've done a crap load of testing with the help from one of the guys at the Yahoo Eico group and it looks almost certain that the problem is in the rectifier. I've got a Shuguang on the way and will keep saving my beans for a Mullard. I'll let you know what happens when the new tube goes in. Thanks all for the help.
    SDA-1C (full mods)
    Carver TFM-55
    NAD 1130 Pre-amp
    Rega Planar 3 TT/Shelter 501 MkII
    The Clamp
    Revox A77 Mk IV Dolby reel to reel
    Thorens TD160/Mission 774 arm/Stanton 881S Shibata
    Nakamichi CR7 Cassette Deck
    Rotel RCD-855 with modified tube output stage
    Cambridge Audio DACmagic Plus
    ADC Soundshaper 3 EQ
    Ben's IC's
    Nitty Gritty 1.5FI RCM
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  • Fongolio
    Fongolio Posts: 3,516
    edited April 2011
    I think I have solved this problem. I was listening to the rig last night and despite it not biasing correctly the tube amp still sounds delicious, but when I was going to flip the record to the other side I was looking at the GZ34/5AR4 and noticed it only glowing on one side of the tube. This morning I pulled the tube and put it under close magnification and noticed that the filiment on one side of the tube is broken. Shazam!!! Problem solved. So since I've already "smoked" this tube (see above) I may as well "roll" another one.....in. Ok, that was bad. I'm just giddy that this totally frustrating problem is solved.

    Kelvin
    SDA-1C (full mods)
    Carver TFM-55
    NAD 1130 Pre-amp
    Rega Planar 3 TT/Shelter 501 MkII
    The Clamp
    Revox A77 Mk IV Dolby reel to reel
    Thorens TD160/Mission 774 arm/Stanton 881S Shibata
    Nakamichi CR7 Cassette Deck
    Rotel RCD-855 with modified tube output stage
    Cambridge Audio DACmagic Plus
    ADC Soundshaper 3 EQ
    Ben's IC's
    Nitty Gritty 1.5FI RCM
    · Share on FacebookShare on Twitter
  • heiney9
    heiney9 Posts: 25,165
    edited April 2011
    Get yourself a Mullard and be done with it..................for along time :smile:

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • HB27
    HB27 Posts: 1,518
    edited April 2011
    heiney9 wrote: »
    Get yourself a Mullard and be done with it..................for along time :smile:

    H9

    Definitely Mullard or continued problems on a regular basis. Live and learn
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  • Fongolio
    Fongolio Posts: 3,516
    edited April 2011
    I think I have a line on a tests like new Mullard for a good price. I'll keep the Shuguang for testing. As a side note, while doing the upgrade I replaced the 12W7's with 12AX7's and reworked the wiring to work with them. The one's I bought are original Svetlana's (not the newer flying "S" ones) and I have to say they really sound great. I bought 4 and they are in the preamp/eq circuit and the amp/tone circuit and sound just as good as the Mullards they replaced. Extremely detailed and thunderous bass when called for. The only question is how long they'll last.
    SDA-1C (full mods)
    Carver TFM-55
    NAD 1130 Pre-amp
    Rega Planar 3 TT/Shelter 501 MkII
    The Clamp
    Revox A77 Mk IV Dolby reel to reel
    Thorens TD160/Mission 774 arm/Stanton 881S Shibata
    Nakamichi CR7 Cassette Deck
    Rotel RCD-855 with modified tube output stage
    Cambridge Audio DACmagic Plus
    ADC Soundshaper 3 EQ
    Ben's IC's
    Nitty Gritty 1.5FI RCM
    · Share on FacebookShare on Twitter
  • Fongolio
    Fongolio Posts: 3,516
    edited April 2011
    The new 5AR4 arrived today. Dropped it in, powered up, waited 1/2 and biased and balanced perfectly. Sounds fantastic. Fongolio happy. Thanks guys.
    SDA-1C (full mods)
    Carver TFM-55
    NAD 1130 Pre-amp
    Rega Planar 3 TT/Shelter 501 MkII
    The Clamp
    Revox A77 Mk IV Dolby reel to reel
    Thorens TD160/Mission 774 arm/Stanton 881S Shibata
    Nakamichi CR7 Cassette Deck
    Rotel RCD-855 with modified tube output stage
    Cambridge Audio DACmagic Plus
    ADC Soundshaper 3 EQ
    Ben's IC's
    Nitty Gritty 1.5FI RCM
    · Share on FacebookShare on Twitter