Can Someone Proof My Schematic? BF PR

[PeaveyBandit]

I may have found a few more mistakes if you want to check and see if I'm right or wrong. Amazing job on that schematic. I cannot thank you enough. Although I just spent a good while working this out on my own now I have a much cleaner version to work from on my Princeton project coming up when all the parts arrive . My eyes are not too good and reading the old fuzzy schematic makes my head hurt.

Is there any possible way you can print that file to gif or jpeg? The PDFs always seem to print out too lightly on my system for some reason.


1. One of the V1A's and one of the V3A's may need to be changed to V1B and V3B? This is such a great idea to label these like that!!!!! Thank you!

2. Not sure if R37 is supposed to be 22K or 27K

3. I also have no problem putting in the 100ohm centertap for the filament. But I play festivals and gigs with bad grounds or no grounds and I love being able to flip that ground switch one way or the other and eliminate the shocking when my lip touches a mic stand and my amp and the PA are out of phase. If I'm not mistaken this is still correct. Was the death cap ALWAYS considered a bad idea? I actually like the darn thing.

4. I'm not sure th cap you have listed as an .003 on the output of reverb (C19) is right. Should that be an 002? I guess it's an .003 in the deluxe... maybe your right

5. Are you going to draw the reverb foot pedal in?

Again, fantastic job. Are you thinking of doing a layout drawing also? I have an old one here that I've tried to edit and correct the values so you can read them all. I used an old Princeton to help me verify everything and I'll post those photos and diagram in efforts to help you any way I can.

Thanks for indicating the 18K for the voltage divider resistors because Mojo and others often ship or list a 15K in that location as a means of filling the logistics easier and I dont like to vary from the original specs unless I understand why.

SEE ATTACHED and thanks x10

[PeaveyBandit]

P.S. I also started drawing a new tube chart today after being inspired by your work. That's when I noticed something else that's not making sense to me. If you look at the back of the amp and then the old tube chart below I would call the tubes V1,2,3,4 in order starting from right to left looking at the rear of the amp or tube chart. In that chart V2 is a 12AT7 and in your schematic V4 is a 12AT7. So my question is if you want the V7-V6-V5-V4-V3-V2-V1 numbering to be that way on the back and match the schematic. I could then label that on the new tube chart I'm making and have not only a tube chart but even more info you can use on the gig troubleshooting. I always like to label which tube does the reverb, vibrato etc. so I can quickly and brainlessly swap a tube and fix a problem literally in seconds during a performance. Rarely do I need it but I've always stuck my own little tube chart in the back of my Fender amps for reference on the road. If I'm making a dumb mistake with this assumption please accept my apologies and explain to me where I'm mixed up please.

Thanks again!

SEE SUGGESTED NUMBERING BELOW....

[Bruce / Mission Amps]

Does that mean that if I'm willing to give up the output power I can mod it for a 5y3 at a later date without harming the amp? I'd be interested in hearing the difference.

Yes.

I also want to try it with cathode bias. Perhaps try a 12AU7 in the first stage.

Boring

I use electric guitars mainly in an acoustic guitar setting. I don't really care about output volume. I want a lower powered amp with reverb and tremolo.

A great amp for lower to medium levels and can really rock out at a nice semi-loudish level with a good sensitive speaker.

[dwhutchens]

The concern is the saftey

of a properly grounded 3 wire power cord and having the fuse in the hot line before the switch. That way if a hot wire or component should come loose and come in contact with the chassis it will blow the fuse rather than put 120vac on the guitar strings and electrocute the musician.
David H

[Milnoque]

PeaveyBandit,

I didn't have a tube chart when I did the drawing. I'll re-number the tubes when I get a chance.

I'll look over my schematic and verify the values where you have referenced them. I was just copying a schematic. I don't yet know enough to do any second guessing.

I'm sure I can find a way to convert everything to a jpeg. It may be a couple of days before I get time.

Bruce,

I'm sure you're right about buggering up the circuit. I guess I'll have to learn that the hard way. I won't say I wasn't warned.

[Milnoque]

PeaveyBandit,

The tubes on my drawing are now numbered as you suggested. I had given them numbers in the order I drew them and had no higher purpose than that. I have a lot to learn.

How do people do the quote boxes in the replies?

[PeaveyBandit]

PeaveyBandit,

The tubes on my drawing are now numbered as you suggested. I had given them numbers in the order I drew them and had no higher purpose than that. I have a lot to learn.

How do people do the quote boxes in the replies?

Thanks, I can't tell you how much I appreciate you working out that schematic. I've been combing through this one for weeks.

Besides clicking the QUOTE button when replying to a topic the only way I know to do it is cut and paste the text you want to quote into your post then edit it to have the QUOTE and /QUOTE tags surrounding it in the same format as you see when you automatically quote one person.

OH, before I forget. You could make one silly correction that might not be important but will match your schematic to the real amp even closer. Reverse the numbering on the rectifier tube for pins 2 and 8. That's because in the real amp pin 8 is the one that shoots up into the amp and not pin 2. I think the amp would work either way though.

Again, if you did this schematic from limited resources you sure did a good job in my opinion. I'd thought about drawing a replica of the layout also. Are you planning on doing one of those? Would you like a copy if I make one? I can also provide you a tube chart like the one I posted above and edit it any way you like it. Just to pitch in any way I can.

Sorry to dominate this thread so much, I'm done now but thanks so much. I'll back off and just read now.

BYW, I meant to say that R37 22K resistor should be 2200 ohms, I made a typo and said 2700. My bad.

[Milnoque]

2. Not sure if R37 is supposed to be 22K or 27K

I haven't found a schematic clear enough to know for sure.

3. I also have no problem putting in the 100ohm centertap for the filament. But I play festivals and gigs with bad grounds or no grounds and I love being able to flip that ground switch one way or the other and eliminate the shocking when my lip touches a mic stand and my amp and the PA are out of phase. If I'm not mistaken this is still correct. Was the death cap ALWAYS considered a bad idea? I actually like the darn thing.

It seems like you could work out a suicide switch that puts the amp in ungrounded circiut mode if you wanted to.

4. I'm not sure th cap you have listed as an .003 on the output of reverb (C19) is right. Should that be an 002? I guess it's an .003 in the deluxe... maybe your right

As above, I haven't found a schematic clear enough to be sure.

5. Are you going to draw the reverb foot pedal in?

Can you make me a sketch?


I looked at the layout drawing. I can't read the values at all. It will take me some time to cross reference everything, so don't expect it anytime soon. It seems like it would be a very useful thing to have. I'll work on it as time permits.

[PeaveyBandit]

It's looks like to me you can be sure the C39 is a 003. And the R37 is indeed a 2200. You can see it in the photos I posted. I also posted a schematic with the foot pedal drawn in. It's not perfect but I have corrected all the values so you can actually read them and you can use that as a good reference. Then the tube numberings and switching pin 2 and 8 on the rectifier tube and you're really getting somewhere. Thanks again.

[Milnoque]

I changed the connection at the rectifier rather than the pinout. R37 is now 2.2K. Would it be better if I expressed that value as 2K2 instead?

I drew this to print in dark brown rather than black. It's easier on my eyes. If this jpeg prints out too light I can make you a black one.

[PeaveyBandit]

I think 2.2K is fine but Fender would always call it simple "2200" on the schematic. Now if it was 22,000 ohms I know they would call that 22K on the schematics but for anything below 9999 ohms I guess they just wrote it out.

[Milnoque]

Reverb Pedal Added

[PeaveyBandit]

Killer! I just verified about 3 different ways too that you'll have to change R37 to 22K.

You might also want to add the part number 1N-4007 to that diode since Fender fails to identify that anywhere in their drawings.

I'm not sure I understood your comment on the rectifier pins 2/8 but if you simply reverse the number 2 and 8 on the drawing it will match the stock layout from Fender.

One thing to consider might be added two words on the power circuit by adding the color "white" to the lower wire which should be the neutral and then the black wire is the hot. Green is ground. That's at least the USA standard and might eliminate some newbee like me from wiring my amp up in a less than safest way.

Thanks again!
PB

[Milnoque]

Killer! I just verified about 3 different ways too that you'll have to change [B]R37 to 22K.

This has been done. Please confirm the value. We have discussed this with 2.2K earlier in this process.

You might also want to add the part number 1N-4007 to that diode since Fender fails to identify that anywhere in their drawings.

This has been done

I'm not sure I understood your comment on the rectifier pins 2/8 but if you simply reverse the number 2 and 8 on the drawing it will match the stock layout from Fender.

The three schematics I looked at all had the tube pin numbering running clockwise from low to high. That placed the 2 and the 8 as drawn on the rectifier. My schematics all reflect the B+ connected to the #2 pin by the way. Since you were using a real amp as a reference, I chose to move the wire connection to reflect your real world example rather than change the way the pin layout is drawn. Doesn't that work as well?

One thing to consider might be added two words on the power circuit by adding the color "white" to the lower wire which should be the neutral and then the black wire is the hot. Green is ground. That's at least the USA standard and might eliminate some newbee like me from wiring my amp up in a less than safest way.

I'm not sure what I should do here. I just copied the schematic as originally drawn. I went back and moved the fuse as recommended (rightly) in another post. I guess I'll go back and redraw the whole AC supply for a modern grounded supply, and remove the courtesy outlet and Phase switch. That's how I was going to build my amp. It can't hurt to add the color codes. I'll try to make time to do this today.

I really appreciate all the help you've been on this. It has been a great learning experience.

[Milnoque]

Updated Schematic

I also included a tag board layout I did. I think it will be useful as long as I cross check as I go.