Silent Champ 5F1

Discussion in 'Amp Central Station' started by JoshW77, Feb 19, 2019.

  1. Intubator

    Intubator Tele-Meister

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    I just finished a Boot Hill 5f1 myself and am very happy with it. I noticed that my initial voltages were very high, I attributed this to the AC output of my home outlet which is 121V. The amp is designed for 110V which is I guess is what was standard in the 50's and doesn't' seem like much of difference but really is. I am running vintage NOS RCA's from 1960 so I really wanted to get the voltage right so as not to prematurely burn out the tubes. My solution was to run a chain of 3 12V 5W Zener Diodes from the PT center tap to ground. Took my B+1 voltage from just over 400V to 343V. The tubes are running much cooler now and have a very nice dim glow. The amp is sounding great too. Pic shows the diode chain on the left on a ground strip bolted to the chassis side wall.

    20190228_091142_resized.jpg
     
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  2. jimgchord

    jimgchord Tele-Afflicted

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    Glad you got it going
     
    Last edited: Mar 1, 2019
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  3. Intubator

    Intubator Tele-Meister

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    Thanks jimgchord. I'm still playing with some bypass cap values but its more or less my OCD kicking in.. LOL.
     
  4. jimgchord

    jimgchord Tele-Afflicted

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    Oh you'll have that, tweak away!
     
  5. Intubator

    Intubator Tele-Meister

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    BTW, that's both a beautiful chocolate lab and tomato in your avatar!
     
  6. jimgchord

    jimgchord Tele-Afflicted

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    Thanks! Love my pup.
     
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  7. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    I'm backtracking a bit intentionally jut to emphasize a few things -

    Everyone reading this who is contemplating any amp building project should understand this. Voltage charting is part of the *building* process - if not as each stage is wired, first with only the rectifier installed - then stopped if something is WAY off and the problem fixed - THEN with tubes installed.

    But "my amp doesn't work" with q bunch of pictures is really not enough information. As shown in this thread voltages expose major issues right away. You don't turn a completed amp on and hope it works - you TEST an an amp before final completion note the results, THEN finish it - and note the results AGAIN, working or not. ALAYS keep a record of test results - because when something DOES go awry (and on a first amp something often does) you'll have something "real" to compare with .

    This should have ben understood before the project was started. Vintage schematic and layout voltages are always lower than test voltages due to modern wall power having higher voltage. And modern layout/schematic voltage are still often different - rectifiers do not all supply the same voltage and other parts vary in tolerance. *Exact voltage matches to schematics and layouts are irrelevant*.

    As loud as you *think* it should be. If you don't know how loud it's supposed to be - and ceramic or Alnico or Neo magnet types make no significant difference - the speaker model's DB specs - the sensitivity - determines the relative loudness of the specific speaker - but only once it's broken in. The *speaker's* volume won't usually be at optimum for 20 or so hours - this, again, should have been understood before building an amp. It's not basic amp building, it's basic speaker comparing.

    As far as the amp loudness - if you never played a similar one before building yours it's a question that flat can't be answered.

    I'll add one - there are extra loops of wire (at least one very long red one) near the power supply that should be cut short. Extra wire means more noise.

    If you look up "lead dress" there are specific conventions to follow when wiring an amp - things like not running signal and high voltage wires next to each other; crossing wires at close to 90degree angles; keeping grid (signal) wires as short as practical and so on.

    These are more details that should be understood before starting, not after an amp is built. Wiring diagrams/layouts often show just connection points - NOT "lead dress". Many layouts, if followed precisely, result in noisy amps and/or ones with oscillation issues.

    I mentioned this above, but it's worth repeating.

    This needs to be understood BEFORE starting an amp build - otherwise you will have no idea what voltages are right, wrong, or close. This is one reason I personally feel a *basic* understanding of electronics is important - vital, actually - if you are going to build an amplifier. They are not plastic model kits and can't be "built" well just looking at a chart and inserting part "87" into eyelets "9A and 10A" or whatever.

    First and foremost is understanding amp safety and following consistent safety rules.

    But basic electronics knowledge is invaluable - knowing what resistors and capacitors DO; how tubes operate and what their parts are; how each transformer does its job; wiring rules; grounding rules (like why ALL grounds can't be connected to the same point); speakers, impedance, and sensitivity; voltage, resistance and current - a few hours reading AND a simple reference book next to you while you're working will do wonders.
     
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  8. JoshW77

    JoshW77 TDPRI Member

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    Current state of project:
    1. Wire nut removed and replaced with soldered connection and heatshrink.
    2. All nuts have had Loctite applied.
    3. Solder joints re-flowed in many places.
    4. Excess wire trimmed.
    5. Missing ground on speaker jack corrected.
    + side of capacitor to ground starting with cap closes to power transformer:
    1. 375v, roughly within 10% of Dave's specified 340v
    2. 345v, more than 20% higher than specified 275.
    3. 318v more than 20% higher than specified 250v
    4. 20v, about 10% greater than specified 18v.
    5. 300v, 100% greater than specified 150v
    6. 200, more than 20% greater than specified 150v.
    7. 1.6v, almost exactly specified 1.5v.

    So, 4 out of 7 are much higher than specified.
    8. Made copy of layout, traced all wires.
    9. Rerouted input resistor well clear of anything.
    10. Noticed that when you just turn amp on and the volume set to 1 or 2, there is significant hum which tends to drop in the middle volume range and then increase to when the volume is set at full. This happens whether there is a guitar plugged in or not. Also, the amp seems to break up sooner than I would expect and when the amp is set to "12" or loudest, the distortion is excessive (not pleasant) and the volume still seems low. And I do not mind distortion, my Catalinbread Dirty Little Secret is more on than off when I play rock or blues.


    I will get pin voltage and resistance readings next. I thought the missing ground from the speaker jack would be much more significant than it turned out to be. This is using a set of used but tested good tubes. Could one of them gone south?
     
  9. JoshW77

    JoshW77 TDPRI Member

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  10. JoshW77

    JoshW77 TDPRI Member

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    OK, I will bite: why CAN'T all grounds be run to the same point? It would seem that once you connect to the chassis, it is all the same. As for voltages, I am comparing to the instructions which I assume use modern voltages because they come from Boot Hill directly. As for volume, I have played 5 watt amps before and unless watts are not watts I would expect a similar output, an output watt should be roughly equivalent to any and all other output watts. And as for the TONE of statements like this:
    "But "my amp doesn't work" with q bunch of pictures is really not enough information. As shown in this thread voltages expose major issues right away. You don't turn a completed amp on and hope it works - you TEST an an amp before final completion note the results, THEN finish it - and note the results AGAIN, working or not. ALAYS keep a record of test results - because when something DOES go awry (and on a first amp something often does) you'll have something "real" to compare with ." it's kind of harsh, don't you think? So, in conclusion, if you don't want to help, that is just fine. I know you know more than I do. Otherwise I wouldn't waste my time posting here. And if this is some kind of "tough love" deal, I get my fair share of it in AA and I don't need any more of it here. I see you have a very large number of posts. Good for you! Thank you for your help, but please do not feel compelled to give any more of it.
    1. Resistors reduce current flow, probably as common a component as any.
    2. Capacitors are passive components like resistors, and store (electrical) energy. In old cars, they could be known as condensors. Where you stored up energy until it got released to throw a spark across the two conductors in a spark plug.
    3. Tubes (or valves) are where a relatively small voltage is used to control a current. Passing from anode to cathode, the current goes through a grid which is where the voltage controls the current. The same thing a transistor does, basically, but the effect of tube current control is often thought more pleasing in audio amplifiers, certainly guitar amps.
    And finally: "They are not plastic model kits and can't be "built" well just looking at a chart and inserting part "87" into eyelets "9A and 10A" or whatever." That sure seems true. I guess that's why I joined TDPRI and posted this initially. The "chart" is the only instruction that comes with the "kit" and so I m doing my best with what I got.
    And once more, this bears repeating: Thank you for your help, but please do not feel compelled to give any more of it.
     
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  11. t-luxe

    t-luxe Tele-Afflicted

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    What Rectifier are you using? Sovtek "5y3"s seem to really be re-labled 5AR4s that didn't make the grade and can run the voltage 20-30 volts higher than a "Real 5Y3".
     
  12. JoshW77

    JoshW77 TDPRI Member

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    Old used RCA Electron 5Y3GT. I got a full set of old but tested tubes from Dave at Boot Hill. I should say, at no time in my testing have any of the tubes gotten what I consider "hot".
     
  13. pirana

    pirana Tele-Meister

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    I don't understand any of the technical jargon in this thread but it does remind me of an amp I once had. David Allen of Allen Amps built me what he called a 5F1+ chassis which I made my own "head" cabinet for. You could use 3 or 4 different types of output tubes for it & it sounded great. I was an idiot for letting it go & it sold right away. For whatever reason he doesn't make them anymore. I played it through a 1 x 12 cab & it was perfect for the house.
     
  14. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    First - sorry is any of my comments offended you. The Caps were not ...and never are..."harsh". They just emphasize points that are important that often (some of them "usually", in my experience) get skipped over in the haste to get a first build completed.

    Doing it in phases and testing/noting results multiple times was the established way of performing electronics construction projects since the 60's - and kits in those days included electronics instruction. Only recently have amp kits been introduced that expect you to bring the electronics knowledge with you and/or provide full "assembly" instructions. This is the source of the plastic model kit reference .

    The difficulty with "full assembly - and them power up" is that is makes troubleshooting extremely difficult - the problem has to be isolated, and "assemblers" with little or no electronics knowledge don't know where to start.

    Phased construction and testing usually eliminated "final power up" troubleshooting needs. It makes the project easier and less troublesome.

    As far as the grounds - noise. A single star ground nearly always results in excessive hum. If you look on some of the purely amplifier-related sites like David Allen's, the "design convention", which was also used by nearly every builder of better point-to-point (or eyelet/turret hand-wired...and there's a difference) tube amps:

    1. The Mains AC ground is connected to the chassis at its own point, most often a solder point attached to a transformer bolt. NO audio section grounds are even connected to the AC mains ground.

    2. Power section grounds from the power filter caps, power section/driver filters, transformer center taps, cathode bypass cap (if cathode biased) and so on. They are NOT connected to the preamp grounds directly.

    3. Preamp grounds. These are often connected to a brass plate behind the controls (and some builders lift the pot and jack grounds from this and connect them using separate wiring) - Preamp filter caps, cathode bypass caps etc.

    This is all part of the amplifier "lead dress", along with the wiring conventions (separating high voltage and signal wires, wire crossing rules, twisting of filament leads/keeping them far away from other wiring and so on)

    Watts have little to do with output, actually. And watts have to be measured using consistent "total harmonic distortion" standards - which they aren't. i.e. 5 watts at 1%thd could mean lower volume than 2 watts at 10%thd. This was exactly how cheap imported things like "200 watt" amplifiers in the 60's and 70's were sold to unsuspecting players who expected a Marshall Major and ended up with the volume of a Princeton.

    Also, speaker efficiency (or sensitivity) in "db", cabinet construction/wood/design and amp topography and output stage design are normally as - sometimes more - important that simply "watts" in determining "output in db" (I hesitate to use the word "volume" for the audible "sound pressure level" level because some confuse the "volume control" setting with the actual sound pressure level.

    The volume control is arbitrary, and depending on the pot type and circuit may have little relationship to the comparative rise in sound pressure level - or "output". And has almost nothing to do with "watts" as comparative tool. A hundred watt amp turned up to "5" on a 1-10 knob may be pumping out 10 watts, or 20 - but almost never 50, or even close to it.

    And two identical amps - one with a speaker rated at 96db and one with a speaker rated at 100db - will sound completely different, output-wise.

    Again, none was meant to be harsh. I apologize wif it came across that way. Some have complained when bold, or italics, or underlines are used the same way - so sometimes you just can't win when providing information.

    You made your point several times. I hope I clarified mine. As well as answered your questions and explained why "watts" are not a simple comparative piece of information.
     
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  15. JoshW77

    JoshW77 TDPRI Member

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    Thank you, I really do appreciate everyone's help here, and that includes you too Silverface. I appreciate all your clarifications and hope we can move forward as friends.
     
  16. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Absolutely. No worries - it was a simple misunderstanding. It can take a while to get used to the quirks of this "shop"! :D

    Part of the problem with tech advice here and on other forums when you're new is "vetting" the help - could be a working amp tech, a knowledgable player/tech, an engineering type who plays little and works from theory, or somebody who just likes to type!

    I think you already found Rob Robinette's site - that's one of the BEST resources on the net, and poking around here a bit you'll find there's a pretty solid group of experienced folks. Most responses - from anyone - aren't as long as my last one, but there were quite a few fairly critical tech issues brought up, and IMO it was important that they be explained as completely as possible (i.e. not answering the ground question with "noise" - which, while correct, wouldn't really be helpful).

    Kit building is tricky because there are only a couple of companies that provide actual electronics instruction in their kits, along with all the testing stuff I mentioned - but they also charge a lot more. So I wasn't kidding when I said most kit suppliers expect you to bring the electronics knowledge with you - they're just selling groups of parts and layouts. for the most part.

    So checking out Allen amps' site and several others...along with reading through Rob's (hehe - which might take a year - I don't know how he does it!) before stating on anything will really be a big help!

    Have fun and good luck!
     
    Last edited: Mar 5, 2019
  17. JoshW77

    JoshW77 TDPRI Member

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    I have achieved success! As noted by Silverface and re-emphasized by D'Tar I had the grounding absolutely incorrect. Of course, D'tar found my two transposed wires on the !2AX7 which got the volume back. But the huge hum was definitely the grounding.
    [​IMG]
    This was a super-helpful graphic. Also, if you look closely at the layout provided by Boot Hill you can see some grounds run to a "box" including the input jacks. Apparently that was a copper plate (?) on early Champs. I had every ground running to one of the mounting screws on the PT. I moved half (aprox) of the grounds off there and to the jacks and the hum diminished to very slight at full volume with nothing plugged into the input. I will put up final pictures and voltages later today or tomorrow.
     
  18. JoshW77

    JoshW77 TDPRI Member

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    Here are some pics of the completed chassis and the final pin voltages:
    12AX7
    1. 186.5 V
    2. 0
    3. 1.57 V
    4-5. 3.44 ACV
    6. 186.2 V
    7. 4 V
    8. 1.42 V
    9. 3.4 ACV

    6V6GT
    1. 0 V
    2. 3.4 ACV
    3. 347.2 V
    4. 339 V
    5. 9.6 mV
    6. 3.7 mV
    7. 3.5 ACV
    8. 19.96 V

    5Y3GT
    1. 0 V
    2. 376 V
    3. 0
    4. 25.2 mV
    5. 0
    6. 25.5 mV
    7. 0
    8. 378.9 V
    IMG_1744.JPG IMG_1743.JPG


    IMG_1742.JPG


    IMG_1741.JPG

    And once again, thanks to everybody who helped make this a success.
     

    Attached Files:

    intensely calm and D'tar like this.
  19. D'tar

    D'tar Friend of Leo's

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    Congrats on getting things straightened out!

    Your voltages are a lot better now. I still don't like the V1 p7 reading tho. Can you check voltage at this location here. You should not have any dc on this. If you are seeing positive dc voltage , you may have a bad coupling cap. To confirm.... lift the cap connection and carefully check for dc on the cap then on the wire. If dc is present on the cap... replace it with new one.

    upload_2019-3-12_10-48-13.png
     
  20. JoshW77

    JoshW77 TDPRI Member

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    I just measured it where indicated and my meter bounces around from - to + a maximum of 3.4 mV, pretty much what it does when I put both probes (not touching) on my sweatpants. Do you think I still need to lift the connection and check? Will I hurt the tubes? There is 186 v on the other side of the capacitor so, percentage wise, it is doing a good job. But I am not the expert here.
     
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