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Thread: Blues junior III tube socket

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    Blues junior III tube socket

    Any suggestions on this repair?? Is point to point my best option?? I haven't been able to find a replacement board
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    Fender-Blues-Junior-III-Schematic-Rev-D.pdf

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    Senior Member nevetslab's Avatar
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    Quote Originally Posted by shortcircuit View Post
    Any suggestions on this repair?? Is point to point my best option?? I haven't been able to find a replacement board
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    Fender-Blues-Junior-III-Schematic-Rev-D.pdf
    First, I would carefully de-solder the remaining solder terminals, then re-solder, using leaded solder, NOT lead-free. Pins 1, 6 & 8 are NOT used on the EL-84 tube. Granted, you've lost the mechanical integrity of Pin 1. If you're careful with the de-solder & re-solder operation, you should still have solid mechanical integrity on the remaining pins. This PCB is one of the many Fender has produced, with extremely poor foil adhesion. Those pads and traces lift with the greatest of ease. You don't need a replacement PCB.

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    Supporting Member Randall's Avatar
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    That would not warrant a board replacement, it's a common failure corrected by soldering in bits of solid wire or snipped component leads to replace what has burned. What concerns me most here is why did pin 1 of a EL84 burn when it should have no connection?

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    It's weird, because it WAS working fine.....

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    Quote Originally Posted by Randall View Post
    That would not warrant a board replacement, it's a common failure corrected by soldering in bits of solid wire or snipped component leads to replace what has burned. What concerns me most here is why did pin 1 of a EL84 burn when it should have no connection?
    The owner had a heavy hand when they tried replacing tubes , popped the connections,including some pads on both v4 and v5 . On a 1st attempt to re seat them that pin 1 pad lifted out with the iron tip . Now I will follow nevetslab and Randall advice and remove and replace lead free, add trace jumpers where needed , thanks MEF is the best !!!

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Should you change your mind there are PCBs available e.g. https://reverb.com/item/10803881-fen...-points-by-mox

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    Last edited by nickb; 07-15-2019 at 08:54 PM.
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    Don't forget the joker g1's Avatar
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    Quote Originally Posted by nickb View Post
    Should you change your mind there are PCB available e.g. https://reverb.com/item/10803881-fen...-points-by-mox
    Nice work nickb, and very reasonably priced.

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    Seen 2 others on Reverb that didn't look right, didn't see this one, looks like it would work, thanks nickb. Have repair done but it's not re assembled yet. I noticed in the pic a resistor connected to R51 ??? why ??
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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by g1 View Post
    Nice work nickb, and very reasonably priced.
    Aw shucks. Thx

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by shortcircuit View Post
    Seen 2 others on Reverb that didn't look right, didn't see this one, looks like it would work, thanks nickb. Have repair done but it's not re assembled yet. I noticed in the pic a resistor connected to R51 ??? why ??
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    It's a common tweak to lower the bias current. Nothing to do with the tube PCB.

    I have two other other versions on Reverb. One is for the early V1 "Green Board" FBJs. The other "premium version" is also for the "Cream" board FBJ's but comes with gold sockets and an adjustable bias mod kit.

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    Last edited by nickb; 07-15-2019 at 09:07 PM.
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    Senior Member SoulFetish's Avatar
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    Quote Originally Posted by nickb View Post
    Should you change your mind there are PCBs available e.g. https://reverb.com/item/10803881-fen...-points-by-mox
    Excellent! I was wondering if you were going to make these available. I thought I remembered reading that they were only available to UK buyers on bmamps once upon a time.
    I just saved your reverb shop in hope that one day, you'll be offering the highly anticipated PIC/triac power supply controller as well.

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    nickb, BRILLIANT!!!

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    It's weird, because it WAS working fine.....

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    Senior Member Pedro Vecino's Avatar
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    I think the really bad thing in that pic has not been the mechanical problem with the original welds but with the new ones.
    I d´ont want to imagine (it may not be the case) the installation of a new board using that same technique.
    In any case the board maintains its integrity and I would recompose it instead of replacing it. Something of this style:

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    Quote Originally Posted by Pedro Vecino View Post
    I think the really bad thing in that pic has not been the mechanical problem with the original welds but with the new ones.
    I d´ont want to imagine (it may not be the case) the installation of a new board using that same technique.
    In any case the board maintains its integrity and I would recompose it instead of replacing it. Something of this style:

    Click image for larger version. 

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    Thanks for the reply Pedro,the pic in post #1 is pre repair , an attempt to see if re-flow was an option. I'm green but I would never leave anything looking like that. I have since de-soldered and re-flowed the socket per nevetslab's suggstion,but would trust your pics re-trace even further. With pins 1,6,8 all comprimised nickb's replacement board is tempting.

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    Went back and added re-trace jumpers to suspect looking pins, not much I could do with 1,6, 8 , so I wrapped with a doughnut piece of wire and soldered those, put some corona on them as some sort of adhesive (good/bad/dumba**??) After thought, are these going to break away and float around as shorting doughnuts??(easily removed) . Put in new JJ's , biased at 2.75ma , should be a happy Junior III .
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    Last edited by shortcircuit; 07-24-2019 at 05:26 AM.

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    Supporting Member The Dude's Avatar
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    IMO, your "glued doughnut" isn't any more likely to cause problems than the original configuration.

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    Sorry for jumping in so late to your thread. Can you tell me what the original complaint/symptom was from the customer on this Blues Junior?

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    Quote Originally Posted by mikeskory View Post
    Sorry for jumping in so late to your thread. Can you tell me what the original complaint/symptom was from the customer on this Blues Junior?
    They were playing a club , amp was good for sets 1&2 , set 3 no sound , power light on, no fuse blow , just no sound . Amp was repaired before when the owner installed new PT's and broke every solder connection on V4 & V5 , improper re flow(guilty) lasted 10 months. Amp just went out Friday, they had a wedding gig Saturday . Phone hasn't rang , so hopefully all is good.

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    Last edited by shortcircuit; 08-06-2019 at 09:16 PM.

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    The reason I ask is I have one on my bench now. It makes a loud crackling-gurgly noise...sometimes. I worked on it last year, another guy worked on it 6 months ago and now I've got it again. So far: New tube sockets, replaced 3 of the ribbon cable with wire, new r3000 diodes, new output trans and more. Noise still there and it looks terrible. Embarrassing. So after reading this post I ordered the new board and new ribbon cables.

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    Just have to ask , have you replaced the jacks ?? Double check all your pot connections as well if you can, all vulnerable culprits. Did you order one of nickb's boards ??

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by mikeskory View Post
    The reason I ask is I have one on my bench now. It makes a loud crackling-gurgly noise...sometimes. I worked on it last year, another guy worked on it 6 months ago and now I've got it again. So far: New tube sockets, replaced 3 of the ribbon cable with wire, new r3000 diodes, new output trans and more. Noise still there and it looks terrible. Embarrassing. So after reading this post I ordered the new board and new ribbon cables.

    Does removing the PI tube make any difference? If no, have you tried removing the EL84's one at a time and then both? If it still happens with both, disconnect the output transformer one terminal at a time, first the plates then the center tap. Remember safe practice, the discharge the B+ and pull the power plug from the wall

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    Sorry. Gigs this week have me buried. @shortcircuit: In answer to your question, yes I ordered Nicks board. It was like $38 w shipping plus ribbon cables fro Darren's website. It makes sense but also I started thinking about you guys looking at my work. LOL! @NickB With both EL34s out there is no noise as I can tell with the scope. When both tubes are in I can see the noise on the speaker leads and a smaller version going in. Note: I put in a new OT, noise the same. The noise is loud and at full volume...controls don't change it. But I'll try one at a time and see if I can isolate the cause. 2 more gigs. I'll be back to work Monday and will fill you in. Thank you.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by mikeskory View Post
    Sorry. Gigs this week have me buried. @shortcircuit: In answer to your question, yes I ordered Nicks board. It was like $38 w shipping plus ribbon cables fro Darren's website. It makes sense but also I started thinking about you guys looking at my work. LOL! @NickB With both EL34s out there is no noise as I can tell with the scope. When both tubes are in I can see the noise on the speaker leads and a smaller version going in. Note: I put in a new OT, noise the same. The noise is loud and at full volume...controls don't change it. But I'll try one at a time and see if I can isolate the cause. 2 more gigs. I'll be back to work Monday and will fill you in. Thank you.
    When you get back put the EL84's back in and pull the 12AX7 next to the EL84s and report on the noise status.

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    Quote Originally Posted by mikeskory View Post
    I started thinking about you guys looking at my work.
    can we get before and after pics

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    I got the new output board. It fit perfect. looks great and also replaced input jack and the ribbon cables for V1, V2,V3. Still noisy. A whooooshing sound. I gotta forget everything I've done and start troubleshooting all over...like its a fresh job. I also pulled the EL84s individually. Same whooshing sound either way. BUT...IT LOOKS GOOD! Talk tomorrow.

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    @Shortcircuit No! Lol!

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    Quote Originally Posted by mikeskory View Post
    It makes a loud crackling-gurgly noise...sometimes.
    Still noisy. A whooooshing sound
    Is the noise consistent or intermittent ??? Did you also pull the phase inverter tube as nickb suggested ??
    When you get back put the EL84's back in and pull the 12AX7 next to the EL84s and report on the noise status.

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    Yes I pulled phase inverter. It got quiet for about 5 seconds then started the ...shshSHSHSHshsh...again. I've had it on now for about 30 mins. After about 10 mins the noises get louder and more of a sharp crackling. NOW If I pull the phase inverter, the sounds are not as loud but the same intensity. I also put in a fresh set of tubes just to eliminate that. ALSO, this may be completely unrelated but I've just noticed the reverb does not work. I asked the customer (he works here at the store) if that had been an issue. He said a few years ago he replaced the reverb tank with a used one). The signal lead was unsoldered so I'm replacing the aftermarket RCA on the "out" cable plus cutting it back an inch. I'll let you know....

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    Last edited by mikeskory; 08-13-2019 at 04:57 PM.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    We now know
    1) It's before the EL84's
    2) It's after the LTPI
    3) It's common to both EL84's
    The common things in that area are the bias supply and the HT supply to the LTPI. Of course there is an outside chance that you have two faults but will cross that bridge if we come to it.

    So let's look a the HT supply first. There are a few ways you can do this. Super easy is just to cut one leg of the 10K filter resistor R48. This will kill the HT supply to everything after and including the LTPI. Remember to discharge the power supply. If that fixes the noise then the 22uf cap C27 is the prime suspect. Just solder another one in parallel and carefully solder the resistor wire you cut to bridge the cut and reinstate the connection.

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    Just a note , I replaced C34 on the BJ3 I had

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    Last edited by shortcircuit; 08-14-2019 at 01:54 AM.

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    Bringing you up to date. The reverb had a 3rd problem. The OUT jack was intermittent so I re-soldered the thin wires inside the tank. Once the reverb was working, the noise settled down. For 2 days I had no noise. This morning it had a quiet shshsh-ing sound. I replaced C32/C33 but still had the quieter shhhh sound. Replaced C31/C34 and still had the same quieter shhhing sound. However, NOW when I pull out the phase shift V3 all the stray noises are gone. Clipped in the 22mf over all 3 caps...same. Now the noise is so quiet I could barely hear it. Something else I notice...the Treble and master pots were very noisy. After spraying them a second time their noise quieted down. Now the amp is quiet as a church mouse. Can pots be so bad they cause a noise? We'll let if cool down and rest till Friday.

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    Last edited by mikeskory; 08-14-2019 at 10:56 PM.

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    The noise came back. Curiously not as loud as it was prior to all the current work. It's more predictable now. Pulling V3 PI stops the noise. Pulling V1/V2 will not stop it. I cut the R48 like nick suggested. It's like clock work. When I unhook R48, it the noise fades out in a few seconds. When hook R48 back up the noise starts right in. Clipping in a 22mf over clipping in a fresh 22mf onto C26,C27 or C28 make no change.

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    Last edited by mikeskory; 08-15-2019 at 09:51 PM.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by mikeskory View Post
    The noise came back. Curiously not as loud as it was prior to all the current work. It's more predictable now. Pulling V3 PI stops the noise. Pulling V1/V2 will not stop it. I cut the R48 like nick suggested. It's like clock work. When I unhook R48, it the noise fades out in a few seconds. When hook R48 back up the noise starts right in. Clipping in a 22mf over clipping in a fresh 22mf onto C26,C27 or C28 make no change.
    I think the B+ supply test rules out the bias supply as the issue. Next most likely suspects are the coupling caps into the EL84 grids i.e. C15 and C16. Also the plate resistors R28, R30 and R29 are candidates. Not my first choice but as you found you had to remove both EL84 to make the noise stop it means more than one component has died. Sadly you'll have to get to the back of the main PCB to do this and lift one end of each cap to test.

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