Might have ****ed something up

Discussion in 'Amp Tech Center' started by JeffBro, Aug 29, 2020.

  1. hepular

    hepular Tele-Meister

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    well, OP never said that channel 2 worked without buzzing. that said: "replaced all the caps" doesn't narrow things down much, either. having just briefly perused the schematic (super 6, right? 4 6l6s?) this beast has diode rectification going to a choke, then to a 10k pot before going to resistors, so it's not the fixed bias circuit i've sorta learned to see--which brings us back to, the problem is going to exist in the soldering--or collateral damage that happened during the soldering for "all the caps." if i'm looking at the right schem (6 preamp tubes + 4 power tubes), that's not a fault-hunt i'd be looking forward to. But, going back to bias--if it does seem too hot, that's what the pot's for
     
  2. JeffBro

    JeffBro TDPRI Member

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    I installed new caps and on the bottom and just discharged them by unplugging the amp and turning the power on... They are installed correctly, the same as the originals.
     
  3. JeffBro

    JeffBro TDPRI Member

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    I did think I should just mod it and install a bias adjustment at least I would know if that is causing issues. I probably need someone with greater knowledge than me to do some tests.
     
  4. hepular

    hepular Tele-Meister

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    yep. if it's the correct super6 schematic i looked at, that's a BIG, complicated thing to just dive into.
     
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  5. tubegeek

    tubegeek Friend of Leo's

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    Careful: this is not a method that works on all amps, and especially will not work if there is a failed resistor in the power supply. Not Recommended.
     
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  6. Wally

    Wally Telefied Ad Free Member

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    Imho, it is tech time. I admire a willingness and eagerness to learn, but sometimes the water is deeper than one might think.
    A voltage chart would be the first step after assuring that the power tubes are NOT redplating. No offense intended, but if one does not know what a redplating power tube looks like then one might not be prepared to be working on these things. If one does not understand that when only one channel of such an amp is exhibiting problems then the problem is in that channel, then one is not prepared to be working on the circuit. If one does not understand that a voltage chart is the first thing one wants to accomplish both before and after servicing an amp, one is not prepared to be working on the circuit.
    Jeff, if I were in your position, I would ask that tech what he would charge to get the amp going. Then, ask that tech what extra charge he would apply to the bill to guide you through what he does....and yes, that is worth more than simply letting him work 9n the amp without the extra educational approach.
     
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  7. JeffBro

    JeffBro TDPRI Member

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    heh... I think you just add a pot and change a resistor.
     
  8. Wally

    Wally Telefied Ad Free Member

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    Alright then...the amp is working???
     
  9. JeffBro

    JeffBro TDPRI Member

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    I wish... I have some choices to make in concern of how to fix it

    I honestly don't know how to fix it or where to start and being a man, I was looking for some practical advice, like "get an ohm meter and check this for this and see if this is doing this"

    I was having fun doing repairs on it. Why do you wanna walk me through what I need to do to find the problem?
     
  10. hepular

    hepular Tele-Meister

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    Can you read the schematic? Do you know how to check the voltages? Cuz here's the thing, checking voltages means the amp's gotta be on & you gotta know how to do it without shunting 500v through you.

    Looking at that circuit and at what you did, there's, oh, 20 places to check to make sure that every solder joint's correct & that you didn't torch a wire or resistor close to what you replaced. Now with some troubleshooting and trying to rule out various stages of the circuit, you can start to develop some clarity about where your problem is: yeah, if the problem is bias, the changes are fairly straight-forward. BUT until you measure what the bias voltage is you don't know whether or not that's a problem. (Have you deoxited and adjusted all the socket receptacles?)

    But what folks are trying to tell you (& i'm out after this, cuz just looking at that schematic makes me realize i'm outta my league trying to diagnose a problem with it) is that, sure, that amp's fixable, but given that you changed a whole lot, tracing the fault that actually needs fixing is gonna be maybe more complicated than you can handle. I get it, you don't want to hear that, and you want a troubleshooting list. but it's a big list and you're asking folks who get paid to do this stuff to donate their expertise to a problem that you made for yourself.

    If you wanna measure bias as a starting point, figure out what kinda bias you got, and search for the best way to measure it, and make sure you do it right, correct, and careful. If you're lucky, that'll be related to your buzz, BUT, given my limited understanding of this stuff, I don't see how a problem would develop in a section of the circuit you didn't mess with (since, afaik, you've got filter choke, OT, balance-pot and resistors setting the bias: no filter caps at all that affect the powertubes that i can see.
     
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  11. JeffBro

    JeffBro TDPRI Member

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    hey Hep,

    yeah, I would need some basic walkthrough and you're right it could be dangerous as I don't know the basics of what to watch out for.

    I'm sure there is a master of this tech that could give me some practical advice, like look schematic, set the ohmmeter to this, and read these connections. If it reads this then we are good and move onto the next, but yeah I have such a rudimentary knowledge of electronics that I can't diagnosis anything on my own.
     
  12. Wally

    Wally Telefied Ad Free Member

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    Jeff, post #16, RichS gives a good observation. If the problem is only evident 8n one channel, the; the problem is in that channel...somewhere from the input jack to to the summing junction where the two channels join prior to the phase inverter. Study the schematic to understand what that entails. If you replaced the cathode bypass caps, then one would want to assure that the work done on that V1/pin 3 cathode circuit is good. ANY point in the non-functioning channel is suspect...especially anywhere to which you touched a soldering iron.
    You say you did some mods. What were these mods?
    I have mentioned a voltage chart. Imho, no one should start any work on an amp circuit unless they understand how to take voltage measurements everywhere in the circuit. Have you taken voltage measurements in this amp? Did you make up a voltage chart?
    Do you know the tube pinouts? If not, you can go to Tube Data sheet locator And look up any tube. Do you understand the elements in the tubes and the basics of what they do? If not, there is a Wikipedia article that is a good primer....”History of vacuum tubes”will get you to it. Knowing the pinouts and what the elements do will aid in reading the schematic. Schematics explain the circuit. The layout merely shows where things are placed. The voltages for that Fender Super Six Reverb give the voltages that one might expect to see in the circuit.
    If you do not understand tube elements and their functions and cannot roughly read the schematic for voltages, Then from my perspective what you have done is what many folks who think this tube amp work is simple have done....you have ‘painted by the numbers’ without understanding much at all about colors or the basics of drawing....except....what you are working on ‘in the blind’ so to speak is a dangerous environment. I never advise someone to get into the middle of these things until they are acquainted to some extent with tubes, schematics, and safety issues connected to working with these amps. So, imho, it is very likely it is time for you to apply yourself to some study. Don’t go to ‘paint by number’ sites. Go read about the basics...tube history and development. Read Aiken Amps Tech info...the White Pages. Tom Mitchell’s “How to Service Your Own Tube Amp” book is a simply written introduction to tube amp work. There are many free sites on the ‘net......but again, don’t go to the paint by numbers sites and think that you are learning much about things. I spent a small fortune in pre-internet days to try to learn what little I understand.
     
    Last edited: Sep 1, 2020
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  13. JeffBro

    JeffBro TDPRI Member

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    Thanks Wally, some good advice there.

    I think I took some advice from a few different places and made some mistakes and probably attempted to do too much at once instead of in stages. End of the day I learned a few things and hopefully I can fix the problem relatively painlessly.

    I'll read these books and see if I can comprehend the stuff contained.
     

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  14. kbold

    kbold Tele-Afflicted Silver Supporter

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    Yep, those tubes are red plating. Check the bias adjustment pot has not gone open cct. This is a more common fault that can cause red plating.
     
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  15. JeffBro

    JeffBro TDPRI Member

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    It's a balance bias, not a bias adjustment pot
     
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  16. Wally

    Wally Telefied Ad Free Member

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    Jeff, are you able to take voltage measurements while adhering to safety rules? If not, ignore this. If you can, then pull the power tubes, fire the amp up, and take bias voltage measurements on pins 5 of the power tube sockets. Did the redplating occur on just one side of the OT primary, or were all four power tubes redplating? If just one side was redplating, you may find a difference between the bias voltage on two tubes compared to the others. The redplating tubes will have a less negative bias voltage. Take note of the bias voltage numbers in each socket...write the two numbers down and get back to us.
    However, this biasing problem is separate from your description of one channel having a problem. One wonders if you checked both channels when that one channel showed a problem or if you did not check the operation in the second channel.???? We have to understand things in this manner....be very systematic in the search and explanation.
    One question....is this a 100 watt Super six, the 100 watt Super .six with a master volume, or the 135 Watt Ultralinear amp? Observation....although there is a schematic for these amps, there is no layout. Do not let that deter you from working with the schematic. You have the layout sitting in front of you. Print out the correct schematic and start understanding what you have been working on.

    https://schematicheaven.net/fender.html

    There are folks here who can help you, but we have to know that you can safely work on a live circuit. Do not go into a live circuit without understanding some basic safety rules. First of all, keep one hand away from that chassis at all times.
     
  17. Wally

    Wally Telefied Ad Free Member

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    And...I still advise you to ask your tech what he would charge to give you hands on experience....or at least ‘eyes on’ experience as he explains safety issues and some basics. Watch some Uncle Doug videos on YouTube.....
     
  18. D'tar

    D'tar Friend of Leo's

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  19. mugen74

    mugen74 Tele-Holic

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    Dude, give up now. Pay someone who knows what they are doing. Why did you even do this in the first place?

    jh
     
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  20. Mud67

    Mud67 TDPRI Member

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    + 1000 on what Wally says.
    I am new here but that is good advice. I spent years trying to figure how to work on my tube amps and with a lot of research I can pretty much handle my simpler amp circuits like my vibro champ or my Princeton reverb. When it come to my super reverb I do go in there with reservation as the circuit is more complex, not to say I don't go in there but I need to scratch my head and ask for help sometimes in there. If you want to work on amps start with wrapping your head around a simpler circuit design first, and when it makes sense move on to a more complex circuit and so on. Here is a good place to start https://robrobinette.com/How_Amps_Work.htm
     
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