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Thread: AmpClones.com Mesa Boogie Mark IIC+ Help total newb

  1. #36
    Old Timer defaced's Avatar
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    Voltage rating on caps is a "do not exceed" value. It has no real bearing on the actual voltage in the circuit, the transformer drives that value.

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    -Mike

  2. #37
    Old Timer tedmich's Avatar
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    Hey Wes keep it going! and keep reading!! The voltages on caps is their maximum voltage, and their lifespan is greatly reduced if you exceed their rated voltage, a 350v cap may last ~80% of its rated 3000h lifespan at 400v, or burn out in a couple hours at 500v. In general you can't go wrong with higher voltage ratings, as long as they fit, and caps of the same rating generally get smaller and smaller as the technology improves. Because of this my old PV amp now has caps of identical size to when it was made but 2-3 times higher value in micro farads (uF). More filtering makes the amp quieter and "stiffer" sounding and generally has no down side unless you have a tube rectifier (which few modern amps have)

    The separate power supply board is where the 220uF 350v snap in caps go, but notice the caps are connected in series: the C45 negative terminal (dark box) is connected to the C46 positive terminal (open box)
    +(C45)- +(C46)- Ground

    parallel caps have a total capacitance equal to 1/220 +1/220 = 1/x so the total capacitance C45 +C46= x = 220uf but the trick is that the voltages are now additive, so you've turned 2 x 220uF/350v caps into one 220uF/700v cap!

    this is essential cause you can't buy a single cap which will work, the R71 and R72 resistors are sometimes called "equalizing resistors" and serve to make sure each series cap sees the same voltage, otherwise one could end up with 90% of the voltage and burn out way fast, they also allow the charged cap to discharge safely when you unplug the amp; a capacitor without a resistor across it can store a charge for a long time and discharge instantly when touched and kill you. Bigger value power supply caps are the dangerous ones; a 0.022uf cap holds very little charge!

    The way a tube amp power supply is (almost always) designed is to take a VERY high B+ voltage and feed it to the power amp tubes plate, a bit lower voltage to the power amp tube screens and then much lower voltages to the preamp tubes. All on a single rail from the power transformer (PT) through a series of series resistors which drop the voltages. B+ plates/screens/preamp tubes. The very low heater /bias and accessory voltages usually come off different PT taps and separate rails.

    You should feel comfortable with series and parallel resistors and caps. Voltage ratings on caps are minimum values, and cap values are MUCH more important in the signal path away from the power supply.

    Power supply cap 220uf vs 330uf little if any difference
    Signal path coupling capacitor 0.022uF vs 0.047uF big difference!

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    Last edited by tedmich; 01-24-2012 at 05:16 AM.

  3. #38
    Don't forget the joker g1's Avatar
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    Quote Originally Posted by tedmich View Post
    parallel caps have a total capacitance equal to 1/220 +1/220 = 1/x so the total capacitance C45 +C46= x = 220uf but the trick is that the voltages are now additive, so you've turned 2 x 220uF/350v caps into one 220uF/700v cap!
    Ted, you lost me a bit here. 2 identical caps in parallel will give double the capacitance but not affect the voltage rating. 2 identical caps in series will give you half the capacitance but double the voltage rating.
    From the schematic it looks like 4 caps in series-parallel so we end up with the equivalent of a 220uF 700 volt cap.

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  4. #39
    Old Timer tedmich's Avatar
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    Quote Originally Posted by g-one View Post
    Ted, you lost me a bit here. 2 identical caps in parallel will give double the capacitance but not affect the voltage rating. 2 identical caps in series will give you half the capacitance but double the voltage rating.
    From the schematic it looks like 4 caps in series-parallel so we end up with the equivalent of a 220uF 700 volt cap.

    may have lost you but we both got to the same place, each set of (2) series caps comes in at 220uF/~700v, so we have 220 x 2 = 110uf/700v total. There are equations which let you calculate the "R balance" values using DIFFERENT caps to balance the voltages, and rail gun and laser guys regularly use N>4 series caps, like this big unit from apexjr.

    550uf at ~1800v (2100v surge!) $35

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    Last edited by tedmich; 01-25-2012 at 05:44 PM.

  5. #40
    Don't forget the joker g1's Avatar
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    Quote Originally Posted by tedmich View Post
    may have lost you but we both got to the same place, each set of (2) series caps comes in at 220uF/~700v, so we have 220 x 2 = 440uf/700v total.
    Sorry to bicker and I don't want to derail the thread but we are not getting to the same place. We have four 220uf 350V caps. Each set of (2) series caps comes in at 110uf/700V, not 220uf. The final result of the 4 caps (110 in parallel with 110) is 220uf@700V, not 440uf.
    Quote Originally Posted by tedmich View Post
    parallel caps have a total capacitance equal to 1/220 +1/220 = 1/x so the total capacitance C45 +C46= x = 220uf but the trick is that the voltages are now additive, so you've turned 2 x 220uF/350v caps into one 220uF/700v cap!
    This is the formula for series, you said parallel, I think that is a typo. However the equation works out to 110uf, not 220. You can not turn 2 x 220uf/350V caps into one 220uf cap. In parallel they add, in series they divide (opposite of speaker impedance formulas).
    You want the OP to "feel comfortable with series and parallel resistors and caps" so I will hold you to that .

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  6. #41
    ToneOholic! big_teee's Avatar
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    Quote Originally Posted by g-one View Post
    Sorry to bicker and I don't want to derail the thread but we are not getting to the same place. We have four 220uf 350V caps. Each set of (2) series caps comes in at 110uf/700V, not 220uf. The final result of the 4 caps (110 in parallel with 110) is 220uf@700V, not 440uf.
    This is the formula for series, you said parallel, I think that is a typo. However the equation works out to 110uf, not 220. You can not turn 2 x 220uf/350V caps into one 220uf cap. In parallel they add, in series they divide (opposite of speaker impedance formulas).
    You want the OP to "feel comfortable with series and parallel resistors and caps" so I will hold you to that .
    According to the valve wizard you are correct.
    Their example is 2- 100uf at 400 Volts in series= 50uf at 800Volts.
    The Valve Wizard
    at the bottom of the page.
    Keep Rockin!
    B_T

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  7. #42
    Old Timer tedmich's Avatar
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    Quote Originally Posted by g-one View Post
    Sorry to bicker and I don't want to derail the thread but we are not getting to the same place. We have four 220uf 350V caps. Each set of (2) series caps comes in at 110uf/700V, not 220uf. The final result of the 4 caps (110 in parallel with 110) is 220uf@700V, not 440uf.
    This is the formula for series, you said parallel, I think that is a typo. However the equation works out to 110uf, not 220. You can not turn 2 x 220uf/350V caps into one 220uf cap. In parallel they add, in series they divide (opposite of speaker impedance formulas).
    You want the OP to "feel comfortable with series and parallel resistors and caps" so I will hold you to that .

    silly me, you are right

    gotta brush up the math skills!

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  8. #43
    Don't forget the joker g1's Avatar
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    Was never much for math myself, then the calculator changed everything .

    I noticed the bias diode is missing from the schematic. But it is there on the circuit board so no problems. Also the caps polarity is shown wrong on the schematic, but the board is correct. Here is a revised schematic of the bias circuit:
    Click image for larger version. 

Name:	markIIC+bias.jpg 
Views:	148 
Size:	43.6 KB 
ID:	17019

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    Last edited by g1; 01-26-2012 at 07:02 AM.
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  9. #44
    Old Timer soundguruman's Avatar
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    Quote Originally Posted by tedmich View Post
    silly me, you are right

    gotta brush up the math skills!
    C1 times C2, divided by C1 plus C2, equals two caps in series.

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  10. #45
    Old Timer tedmich's Avatar
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    Quote Originally Posted by g-one View Post
    Was never much for math myself, then the calculator changed everything .

    I noticed the bias diode is missing from the schematic. But it is there on the circuit board so no problems. Also the caps polarity is shown wrong on the schematic, but the board is correct. Here is a revised schematic of the bias circuit:
    Click image for larger version. 

Name:	markIIC+bias.jpg 
Views:	148 
Size:	43.6 KB 
ID:	17019
    what value of R83 R84 are used? Is there a variable bias mod? Figure a series 15k and 20k pot in place of R83 R84 would give you a decent voltage range (40-60v)

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  11. #46
    Member WesPalladini's Avatar
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    Wow guys looks like your building this thing with out me!!!

    Sorry I got busy with the holidays went back home. When I came back to my place I found a TERRIBLE smell. Took me about two weeks to figure out and remove. I was on another forum posting all about it looking for help. You can read about it here if your interested: Another Bad Smell In Vents. Kitty Litter Odor But No Cats!? - General Discussion - DIY Chatroom - DIY Home Improvement Forum

    So the chassis arrived at my parents house my friends going to bring it to me in 2 weeks. Wahoooo bot not like I can do much with it yet -_-

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  12. #47
    Member WesPalladini's Avatar
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    Quote Originally Posted by tedmich View Post
    Hey Wes keep it going! and keep reading!! The voltages on caps is their maximum voltage, and their lifespan is greatly reduced if you exceed their rated voltage, a 350v cap may last ~80% of its rated 3000h lifespan at 400v, or burn out in a couple hours at 500v. In general you can't go wrong with higher voltage ratings, as long as they fit, and caps of the same rating generally get smaller and smaller as the technology improves. Because of this my old PV amp now has caps of identical size to when it was made but 2-3 times higher value in micro farads (uF). More filtering makes the amp quieter and "stiffer" sounding and generally has no down side unless you have a tube rectifier (which few modern amps have)
    hmmm I get the first part, higher voltage is no problem, safer for the cap.

    But then you say you installed higher micro farad values in your PV when we were talking about higher voltages. I feel like you meant to say voltage... if not then basically what your saying is you can have higher voltage and capacitance ratings and it should still be fine, in fact quieter (I assume you mean in terms of humm)

    -Wes

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  13. #48
    Member WesPalladini's Avatar
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    The 4 caps have a lead spacing of 10mm and diameter of 30mm. So I began looking at caps on mouser and I have some questions:

    Can I use either solder or snap in caps? What do you guys use, recommend? Any difference in quality?
    Anything I need to know about the brand? I want to put good stuff in my amp.

    I was thinking of one of these 2 but don't really understand why one is double the $ of the other. What is ripple current?
    UVZ2V221MRD Nichicon Aluminum Electrolytic Capacitors - Leaded

    UVY2V221MRD Nichicon Aluminum Electrolytic Capacitors - Leaded

    Question for anyone in Canada who has ordered an amp worth of parts, say $400 (I have no idea how much my BO for the circuit boards will be, just a guess) worth from mouser. What was you customs fee like? I am really tired of getting raped by them for stuff. I live in Windsor, Ontario so I might be able to work out some sort of mailbox pickup scheme in Detroit.

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  14. #49
    Supporting Member loudthud's Avatar
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    After digging thru the data sheets it looks like the VZ series has slightly higher ripple current rating, but that is the cheaper part. Sometimes the prices don't make sense, you just have to dig out the data when selecting parts. There might be some small differences in the materials used. Mouser and most online vendors are good about having links to data sheets on their sites.

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    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
    REMEMBER: Everybody knows that smokin' ain't allowed in school !

  15. #50
    Don't forget the joker g1's Avatar
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    The VY series is smaller. This particular value appears to be the same, but the VY series in general is marketed as a smaller alternative to the VZ, which is probably why it is more expensive.
    Snap in caps will have short kinked tabs so you can snap them into the board and they will hold in place untill they are soldered. Whichever type you use, make sure the lead spacing matches the holes in the board, and make sure the diameter allows for the side by side mounting.
    You asked Ted about the increase in capacitance values as well as voltage, yes you can increase the values for better filtering as mentioned. As he said, no problem unless a tube rectifier is involved.
    As far as customs goes, I try get everything sent via US post. UPS brokerage fees can be very high. I've heard Fedex is ok. All my orders from mouser are small, so $8 shipping, no tax or duty (on less than $25 items) when it shows up at the Canada post office.
    I see a notice on mouser.ca for orders to Canada over $200, free shipping (includes duty and customs fees) via Fedex or UPS, with the exeption of items marked with BIG icon.

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  16. #51
    Old Timer tedmich's Avatar
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    Quote Originally Posted by WesPalladini View Post
    Wow guys looks like your building this thing with out me!!!

    Sorry I got busy with the holidays went back home. When I came back to my place I found a TERRIBLE smell. Took me about two weeks to figure out and remove. I was on another forum posting all about it looking for help. You can read about it here if your interested: Another Bad Smell In Vents. Kitty Litter Odor But No Cats!? - General Discussion - DIY Chatroom - DIY Home Improvement Forum

    So the chassis arrived at my parents house my friends going to bring it to me in 2 weeks. Wahoooo bot not like I can do much with it yet -_-
    usually its just the drain traps drying out and letting sewer gas up, but I have anosmia after too many years as a chemist...

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  17. #52
    Member WesPalladini's Avatar
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    Quote Originally Posted by tedmich View Post
    usually its just the drain traps drying out and letting sewer gas up, but I have anosmia after too many years as a chemist...
    Dang that sux man.

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  18. #53
    Member WesPalladini's Avatar
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    So I tried to look for caps 2 to 3 times the capacitence to get some more filtering but couldn't find anything on mouser with appropriate voltages. They do carry the next higher up model in the VY series that adds about 110uf, (Same dimension sizes) UVY2V331MRD Nichicon Aluminum Electrolytic Capacitors - Leaded. The lead spacing 2.5mm larger than I need but I assume I can angle the leads in, no? The price goes up from $3.70 to $10.8 a cap, you think its worth it?

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  19. #54
    Don't forget the joker g1's Avatar
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    No, I don't think it's worth it. Unless there is data suggesting this model suffers from inadequate filtering. More is not always better (but usually more expensive ).
    Don't overlook the importance of the physical strength of the cap to board mounting. Filter caps like this are usually gooped to the board somehow so they don't break loose or suffer from weakened solder joints. Snap-in types should give you the best mechanical connection to the board.
    Having to bend leads because they don't match the lead spacing will make it difficult to secure the cap to the board.

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    Member WesPalladini's Avatar
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    Quote Originally Posted by g-one View Post
    The VY series is smaller. This particular value appears to be the same, but the VY series in general is marketed as a smaller alternative to the VZ, which is probably why it is more expensive.
    Snap in caps will have short kinked tabs so you can snap them into the board and they will hold in place untill they are soldered. Whichever type you use, make sure the lead spacing matches the holes in the board, and make sure the diameter allows for the side by side mounting.
    You asked Ted about the increase in capacitance values as well as voltage, yes you can increase the values for better filtering as mentioned. As he said, no problem unless a tube rectifier is involved.
    As far as customs goes, I try get everything sent via US post. UPS brokerage fees can be very high. I've heard Fedex is ok. All my orders from mouser are small, so $8 shipping, no tax or duty (on less than $25 items) when it shows up at the Canada post office.
    I see a notice on mouser.ca for orders to Canada over $200, free shipping (includes duty and customs fees) via Fedex or UPS, with the exeption of items marked with BIG icon.
    Snap in leads seem to be pretty good for building, but I feel might be annoying to de-solder and remove if needed. I would have to bend the tabs with some needle nose pliers while the solder is hot but I only have two hands... forget em for now.

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  21. #56
    Member WesPalladini's Avatar
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    WTH happaned to this forum? I swear there at least 3 posts missing from the end....

    I have been working on the other small board too.

    I can't seem to find slide potentiometers with the right dimensions. I will keep looking through data sheets but was thinking of e mailing mouser or bourns to find it for me, you think they would do it?

    They don't have 2 of the inductors I need in stock nor do they carry a 1H inductor that would work for my board.

    The caps on this board have no voltage rating. When I searched the capacitance on mouser most common results returned either 50v and/or 100v versions. The limiting cap is the 3.3uF which I only found 50v versions. Do you think I am good if I just go with 50v versions for all of them on this part of the board? Does anyone know by looking at the schematic how much voltage would be going across this part of the board?

    Click image for larger version. 

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    There are several view modes. I usually go into my profile and set it to linear so I don't miss anything if I read top to bottom.

    Maybe you could ask some other builders at the amp garage or other forums (SLO clone?) where to find these very specific parts. As for the caps just stick with the original values- no need to mess with what worked.

    jamie

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  23. #58
    Member WesPalladini's Avatar
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    Quote Originally Posted by imaradiostar View Post
    There are several view modes. I usually go into my profile and set it to linear so I don't miss anything if I read top to bottom.

    Maybe you could ask some other builders at the amp garage or other forums (SLO clone?) where to find these very specific parts. As for the caps just stick with the original values- no need to mess with what worked.

    jamie
    Good idea about checking other forums!

    The caps don't have a voltage rating on the schematic or the PCB board so I don't know "what worked" to begin with.

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  24. #59
    Member WesPalladini's Avatar
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    Quote Originally Posted by imaradiostar View Post
    There are several view modes. I usually go into my profile and set it to linear so I don't miss anything if I read top to bottom.

    Maybe you could ask some other builders at the amp garage or other forums (SLO clone?) where to find these very specific parts. As for the caps just stick with the original values- no need to mess with what worked.

    jamie
    Dude thanks!!!!!!! So many people over at SLO clones building this thing. They have lots of pictures and already have a lot of answers to the questions I have.

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    Glad it helped! There are still lots of nice people out there that are willing to help.

    jamie

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    Help with Mark II-C+ Channel switching.

    Hello my name is Edward and I own a 1984 Mark II-C+ 100 watt unit with EQ and Reverb. My amp has worked wonderfully for the past six months flawlessly and I am quite happy with it. Last night though I came to find out that I am unable to switch between either of the channels. In other words the lead channel no longer works properly. I have tried the obvious tube scenerio, foot switch, and also the pull lead parameter and nothing works. Im thinking that it is internal then. The schematics on the web are all hand drawn as well all know which creates a major issue for those of us who live on very tight budgets. If anyone has an idea or a resource that would or could be helpful I would greatly appreciate it. Thank you for your time.
    Edward
    Quote Originally Posted by WesPalladini View Post
    Hello.

    My dream amp (right now) is a mesa boogie mark IIC+. I was tired of constantly getting out bid on e bay for one, then waiting months for another to appear. If I won and wanted to send it to Mike B at mesa for a mod/upgrade it is even harder because he said if it comes from the states they can only ship it out once they upgrade it to someone in the states, (I live in Canada). So that means I would have to get it shipped to me then ship it to Mike then him ship it back, such a mess. So I decided to give a shot at making one.

    I ordered the chasis and the PCB from MARK 2C+ Chassis + Complete PCB set - $155.00 : AMPCLONES.COM, Tube guitar amplifier PCB boards, chassis, transformers and DIY kits
    It came with 3 boards, and 6 pages of schematics. FML this is not as easy as lego, nor as safe.

    1) So I thought my first step should be to take a picture of each PCB, start writing down every component I need to buy and how many and open the picture up in paint and scratch off that component as I go.
    2) So I am trying to match the boards with the schematics, I believe I have found the board and schematics that are responsible for the Graphics EQ but have some questions:

    I noticed it says 60Hz on the schematic but the equalizer on the boogie is 80Hz (Small issue for the most part, I think)
    RV8 to RV12, does RV mean Variable Resistor (Pot)?, if so why do they call it RV instead of VR?
    are all of those pots supposed to be 50k Ohms?
    How do you call a pot like this that is not round but supposed to be vertical, and where can I buy some?
    Is the pot supposed to fit between position 1 and 2 after the 470 and 1k resistors or in each pair of spots labelled 3?
    How do those 3 holes at the bottom left of the board match up with the schematic?

    Any help would be EXTREMELY appreciated, I think I am in over my head and will need a lot of walking through this, I thought amp clones would have included a lot more detailed instructions.

    THANKS!!!

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  27. #62
    Old Timer tedmich's Avatar
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    Bummer on the switching issue, these amps are a real pain to work on due to the compressed rats nest layout favored by Mesa. Your issue may be due to a problem with the optoisolators shown on page 5 of the pdf schematic I linked to on the first page of this thread. https://drive.google.com/file/d/0Bx4...it?usp=sharing
    They are getting hard to find, too, their data sheet is here http://www.farnell.com/datasheets/87223.pdf

    I wonder if Wes ever got his kit thing working...

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    Thank you very very much. For some reason I was not able to download the pdf files so I could save them. Is there a way you could send them to via email at unfred.edward@aol.com? I will need some time to look them over and then come back to you with questions.
    Edward

    Quote Originally Posted by tedmich View Post
    Bummer on the switching issue, these amps are a real pain to work on due to the compressed rats nest layout favored by Mesa. Your issue may be due to a problem with the optoisolators shown on page 5 of the pdf schematic I linked to on the first page of this thread. https://drive.google.com/file/d/0Bx4...it?usp=sharing
    They are getting hard to find, too, their data sheet is here http://www.farnell.com/datasheets/87223.pdf

    I wonder if Wes ever got his kit thing working...

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  29. #64
    Don't forget the joker g1's Avatar
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    Quote Originally Posted by Edward Unfred View Post
    For some reason I was not able to download the pdf files so I could save them.
    In the upper left corner where it says "mesa.pdf" click on file, then click on download.
    https://drive.google.com/file/d/0Bx4...it?usp=sharing

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    Last edited by g1; 05-16-2014 at 07:40 PM. Reason: ports & starboards
    Just because they don't have tubes doesn't mean they don't have feelings! - glebert

  30. #65
    Supporting Member Corona Blue's Avatar
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    Be sure to replace the 470uf/16 volt cap in the half-wave regulated supply rail. The cap can fail and smoke the resistor or the 1N2006 rectifier diode.



    This little power supply section is tagged onto the back corner of the RP11A preamp board, so you will have to loosen and swing-away the main power supply board which occludes that corner of the preamp board. It is regulated by a 15v zener diode and the rail will make around 13.5 volts without the footswitch box. With the box in line, you should see 12.2v to 12.5v.



    The original schematic seems to call out for a 1W 680 ohm resistor. 1W seems to be a bit close to the edge, but may have been done intentionally to allow the resisitor to be the sacrificial compoonent as there is no fuse in the line. For this reason, I would stick with a carbon composition resistor.

    I replaced the old 470u cap with one of these, because of their long service life and high temp rating...

    MAL211835471E3 Vishay / BC Components | Mouser





    As stated above by Tedmich... this is a tight space to bring a soldering iron into... With the graphic wires traversing the pre-amp board, you really have to be careful... take precautions to protect wiring from accidental contact.

    Also... the RP11A board has the solder pads ON TOP the board for easy access to the components, BUT be careful not to over-extend the electrodes of replaced components through the board as they can touch or even arc to the chassis!! Easy mistake to make, and could have very ugly consequences.

    Hope this helps.

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    Last edited by Corona Blue; 05-16-2014 at 07:14 PM.

  31. #66
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    What happened to the Amp clone site, I cannot get any info on it, wanted to get a IIC+ kit...

    Thanks
    Ed

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