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Thread: pignose 30/60

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    pignose 30/60

    hi.
    Does anyone have a schematic of a pignose 7-3060 amp.
    i have one to repair but not sure if it has correct components looks like been repaired a few times before and some strange transistors, the output stage has 2n6031 and 2n3055 but they are not really a complimentary pair, should be either mj2955 with the 2n3055 or a 2n5631 with the 2n6031,
    thanks
    Dennis

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    Supporting Member The Dude's Avatar
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    You might try them directly.

    Contact Us ? Pignose Amps

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    Old Timer J M Fahey's Avatar
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    Used to have it many hard disk crashes ago; if I find it, i'll post.

    That said, 2 details:
    1) I seem to remember that output rail (transistor collector/case) is grounded, so "speaker out" is`the midpoint between filter caps.
    Not 100% certain, please check.
    2) even if not strictly complementary, both pairs you mentioned still meet and exceed what's needed there so a mix is`still functional.
    No need to address that unless one is blown.
    3) what is the actual problem you are trying to solve?

    Edit:
    this is its larger brother , the`150R, should be very similarv , kindly posted by Teemuk at DIY Audio:


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    Last edited by J M Fahey; 03-23-2016 at 12:45 AM.
    Juan Manuel Fahey

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    filter caps

    Quote Originally Posted by J M Fahey View Post
    Used to have it many hard disk crashes ago; if I find it, i'll post.

    That said, 2 details:
    1) I seem to remember that output rail (transistor collector/case) is grounded, so "speaker out" is`the midpoint between filter caps.
    Not 100% certain, please check.
    2) even if not strictly complementary, both pairs you mentioned still meet and exceed what's needed there so a mix is`still functional.
    No need to address that unless one is blown.
    3) what is the actual problem you are trying to solve?

    Edit:
    this is its larger brother , the`150R, should be very similarv , kindly posted by Teemuk at DIY Audio:

    Thanks for the information the amp is working but does sound distorted and my main aim is to return it to original spec, the power supply is more basic than the 150R i don't know if the the 2200uf is the correct value for the filter cap as they were an old aluminum can electrolytic and a modern day capacitor.
    so if i can get the original schematic it would be very good
    thanks
    dennis

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    Old Timer J M Fahey's Avatar
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    Feed it 100mV 440Hz, set all tone controls to 5, rise volume until the output until it just starts clipping and *a little* beyond, and show us waveform and voltages (+/- rails and RMS across load) .

    That will clearly show us whether you have a real problem or not.

    http://www.mediacollege.com/audio/to...6bit_30sec.mp3

    Play it through MP3 player, phone or computer , and set player to "loop/repeat" so after it ends (30 seconds) it starts again indefinitely.

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    Juan Manuel Fahey

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    Quote Originally Posted by J M Fahey View Post
    Feed it 100mV 440Hz, set all tone controls to 5, rise volume until the output until it just starts clipping and *a little* beyond, and show us waveform and voltages (+/- rails and RMS across load) .

    That will clearly show us whether you have a real problem or not.

    http://www.mediacollege.com/audio/to...6bit_30sec.mp3

    Play it through MP3 player, phone or computer , and set player to "loop/repeat" so after it ends (30 seconds) it starts again indefinitely.
    OK i will set that up i have a signal gen so the input is not a problem i will have to put in another 2200uf cap as one is no good after testing so it may be better with just that replaced, still want to bring it back to original i have emailed pignose but not had a reply as yet.
    i will be working on it over the weekend
    thanks
    dennis

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    3060 crossover bias

    hi
    i got the schematic for the pignose 3060 and have replaced the parts that were not as original, it is working but the idle current is too high about 450ma so it gets very hot. on the schematic it says at note 3) crossover bias should be set for just visible at 95-100 vac (use variac) but i have no idea how or what to adjust. help is required.Click image for larger version. 

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by mellowamoya View Post
    hi
    i got the schematic for the pignose 3060 and have replaced the parts that were not as original, it is working but the idle current is too high about 450ma so it gets very hot. on the schematic it says at note 3) crossover bias should be set for just visible at 95-100 vac (use variac) but i have no idea how or what to adjust. help is required.Click image for larger version. 

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    Double check the component values. These are usually set to a very low bias current and don't need adjusting. They rely on feedback to fix any crossover issues. It seems odd to me the the current is so high. Could one of the D4/D5 1N4148 diodes be open? How about the 33 ohm resistors R21/22? If they are low it will increase the idle current.

    Failing that you could try increasing R23 and R24 - keep them the same value - I wouldn't go any higher than about 10K as you might starve the output stage of needed drive current.

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    thanks nickb
    on the schematic and on the board r21 is 33 ohm and r22 is 47 ohm? i see on similar circuits they have a pot between the bases of q1 and q2 to set bias.
    i know this is a variation of an old amp circuit i have found quite a few similar designs. i will try and change the value of r22 to 33 ohms and see what happens the diodes are fine.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Yes, one is 33 and the other is 47. I didn't spot that. I expect that they experimented with the values and that is where they ended up. I agree that you can change them to alter the bias and it is probably a better way to do it but be aware that it's much more sensitive to the values. Bigger resistance will lower the bias.

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    Last edited by nickb; 04-02-2016 at 11:14 PM.
    Experience is something you get, just after you really needed it.

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    Pignose Industries was basically born from a bright idea to fit circuit board of a cheap transistor amplifier kit inside a wooden cologne box. But to produce a "real" amp like the 30/60...

    ...well they had to outsource that and the job went to this fairly unknown little boutique called the "Quilter Sound". Many of us know that Quilter Sound eventually became QSC, and that in his late career Patrick Quilter returned back to designing musical instrument amps and started the Quilter Labs.

    This explains the utilisation of grounded collector topology (popularised by QSC amps) but perhaps more interesting is that "zero crossing processor", "soft clipping cell" and "current feedback" elements described in pending patent(s) of Quilter Labs LLC (e.g. http://oi57.tinypic.com/zjjus7.jpg) are already featured in this nearly 40-year old design.

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    Quote Originally Posted by mellowamoya View Post
    hi
    i got the schematic for the pignose 3060 and have replaced the parts that were not as original, it is working but the idle current is too high about 450ma so it gets very hot. on the schematic it says at note 3) crossover bias should be set for just visible at 95-100 vac (use variac) but i have no idea how or what to adjust. help is required.Click image for larger version. 

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    Repost link to the schematic: http://music-electronics-forum.com/a...ose-7-3060.pdf

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    Got one of these that had the output transistors Q3,Q4 and driver Q2 blown.

    Replaced those and Q1 and this amp is running quite hot also.

    I'll double check what Nick mentioned but this one is getting some nasty oscillations once you get over 8w out.

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    Lifetime Member Enzo's Avatar
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    Check the drop across the diodes at the op amp output.

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    Across D4 & 5?
    .7v across each.

    When I bias it harder lowering the value of R23 & 24 it gets rid of the nasty oscillations on both halves of the sine wave.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by drewl View Post
    Across D4 & 5?
    .7v across each.

    When I bias it harder lowering the value of R23 & 24 it gets rid of the nasty oscillations on both halves of the sine wave.
    I would leave the bias so that it runs cool and increase the 470pF C7. But I really should ask, about what frequency are these oscillations?

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    Hard to tell, looks to be about 800khz Burst's in the middle of each peak, then fuzzing out the whole wave as the master is dimed.

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    I think you are on to something there with the 470pf C7.

    While probing it the oscillation is all but gone.
    Seems to be an intermittent connection as there were others I fixed.
    I'll re-flow the IC socket and clean the connections also.

    Output devices still running hot, increase the 4.7K's R23 & 24 as you suggested?

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    Lifetime Member Enzo's Avatar
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    In my mind I would have paralleled those diodes with resistors, like 100 ohms or less.

    Increasing current might stop oscillation, but won't cool the amp.

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    It seems the amp is very particular about what opamp you use.
    With a 4558 it had 120hz buzz with the master over 3/4 up.
    That seems to be the point where it oscillates even with a good 353/TLO72.
    I'll try lowering the bias and see if that cools it down and gets rid of the oscillation.

    Thanks.

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    Quote Originally Posted by Enzo View Post
    In my mind I would have paralleled those diodes with resistors, like 100 ohms or less.

    Increasing current might stop oscillation, but won't cool the amp.
    Resistors across D4 & 5?
    I'll try it.

    Bumping up the 4.7K resistors has the amp cool at idle.

    Still getting that burst oscillation around 8vac out.


    I've been testing it with a 3055/2955 pair. now that it's idling cool I'll see how it responds with 15022/15023.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by drewl View Post
    I think you are on to something there with the 470pf C7.

    While probing it the oscillation is all but gone.
    Seems to be an intermittent connection as there were others I fixed.
    I'll re-flow the IC socket and clean the connections also.

    Output devices still running hot, increase the 4.7K's R23 & 24 as you suggested?
    Not intermittent. Your probe adds capacitance and that is what fixes the problem. Increase C7 gradually and see where it gets you.

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    Well I put 100 resistors across D4 &5 and upped the cap to .001uf
    Amp is much more stable up to 20v out where it has some oscillation
    It's basically a screaming square wave at that point.

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    So with 100 ohm resistors across D4 & 5, amp had nasty crossover distortion. 220 Ohm seems like the sweet spot.

    After installing MJ15022/23's was still getting oscillation on top of sinewave even with C7 up to .01uf.

    Putting an 82pf from master volume wiper to ground killed the oscillation, signal looks good up to full volume and bandwidth.

    Will try it with guitar and speaker when I get home.

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    Lifetime Member Enzo's Avatar
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    Did adding those resistors make the amp run cooler?

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    Yes, it ran much cooler and put the feed resistors back to 4.7K.
    Thanks.

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