Souping up a 5f2a experiment

[newguitarsmell]

Hi guys
I have been toying with the idea of souping up my little 5f2a just to see if it changes the response in tone to instruments with a broader spectrum - like bass, so I bought this transformer. I have the 50ma version.
http://www.lundahl.se/wp-content/uploads/datasheets/1663.pdf

Sorry I can't upload it for some reason.

How do I hook this thing up? I'm assuming the two leads are the hot and ground (I'm using it single ended) but the other five? go to the speaker?
Any help would be appreciated.
I'm using a 5W power transformer - is that big enough? I could also put this thing into a 5e3 I have if you think that might be a better use - but I really just want to make a broader spectrum little no-brains amp.
I am curious if spending this $$ was a total waste or what, but I am curious!

Thanks - Margaret

[shooter]

 
I use oversized Edcor on my SE builds, does help with bass response, worth the $$'s, that's subjective 

wire it just like the DS says for SE
1 to plate 7 to B+
5 to 11
13 to spkr +
17 to spkr -

[newguitarsmell]

Hooray! That's what I thought! Dang. Feeling vindicated. This is a beautiful OT.

[newguitarsmell]

IF I used this transformer in a 5e3 would it work? How would the wiring change with the two tubes instead of one?

[shooter]

look left follow wires 

[newguitarsmell]

Everything was going fine but I had a bit of a buzz - I resoldered some places and now the things makes zero sound. I know there must be a short but I can't find it.

I swapped out tubes - nothing. I even swapped out speakers.
The light goes on - the tubes warm up - and nothing. 
This is such a SIMPLE circuit- I feel like an idiot. <insert select bad words here>
And yes, I traced through the schematic point by point...

UPDAtE: I had a broken resistor between B+ and C.. d'oh. That was hard to see..took me an hour ..I should have known when I got a good B+ voltage then drop to nothing..

I still have quite a loud buzz. The tone knob filters it out, but leaves me with too dark a tone. Ideas?
The new OT sounds pretty great. Too bad about the buzz and my crap wiring chops.
If I can get the buzz reduced, I'll be in bid'ness..

[DummyLoad]

you may have a lead-dress issue, however, you will likely be hearing a significant amount of PS buzz with that OT, larger speaker, and the stock 5F2-A power supply.



--pete

[newguitarsmell]

Hi Pete
Thanks for the help. What is a lead-dress issue and what do I need to do to recover from this issue?

If I use a larger PT, would the buzzing decrease? How about if I swapped it into a 5e3 style amp? would resistor and cap values need to be significantly adjusted?

[shooter]

What is a lead-dress issue

mostly shows itself when you run sensitive signal wires to close, or in parallel with high voltage, big AC signals.  the big n noisy will couple into the small signals.

long wandering leads, poorly grounded stuff.

try pulling V1 and see if buzz drops ALOT, is it affected by tone/gain pots?

 

[newguitarsmell]

Nice. I’m gonna try that Slucky. should I use a different PT?
I need to mull over the “lead-dress” issue... I almost know what you’re talking about.
Are pulling V1 - do you mean removing the power tube or what?

[newguitarsmell]

The buzz is effected by the Volume and tone knobs some but only in that the quality changes and the attenuation changes...

Which are the sensitive wires I shouldn’t run parallel?

[Willabe]

Lead dress is how/where/what you run wires next to/in parallel with and their length. Which also has to do with the amp chassis layout.

Grid wires are the most sensitive. They feed the tubes input grid. Grid wires can act like an antenna. Anything that gets 'picked up' on the grid wire is injected into the tubes grid along with the signal and gets amplified with the signal. After the plate coupling cap that plate wire becomes a grid wire. So try and keep grid wires short (sometimes you have to use shielded wire for grid wire) and plate wires long. The difference is where the coupling cap is located. If building your own eyelet/turret board you can keep this in mind.

You don't need to use a different PT to add that extra B+ filter stage cap/R.   
 
Here are some links that have a ton of great info that you should read if you haven't yet.

Here's a link to the links, to save me from writing them out again. 

http://el34world.com/Forum/index.php?topic=25129.msg271921#msg271921

[Willabe]

Are pulling V1 - do you mean removing the power tube or what?

Tube amps tube line ups are usually numbered from input to output so......

V1 = 1st preamp tube.   

[newguitarsmell]

Slucky did you delete your post? Do you think that solution won't work now?

[sluckey]

Yes, I deleted the post. The solution still works. It's such a simple solution I figured you really don't need a pic.

[newguitarsmell]

You'd be surprised. I think it said a 33uf between the plate and the OT?
Pictures are great for me.

[shooter]

I think it said a 33uf

since you have a tube Rectifier, look up the datasheet for "that" tube;
I'll even give you this free, case you don't have it 
https://frank.pocnet.net/

the tube specs determine cap size
If you're soupin up consider going SolidState (SS) rect.
you'll get a bump up in B+, maybe too much, but if not you should get a small bump in "tighter" tone, might get a smallish bump up in cleanness with the bump in B+
DO your homework, get an idea how much B+, how "stiff" a PS you want, read schematics with your Latte' 

[newguitarsmell]

Ah shooter...
Thanks
But I still don’t know how to add the thing into the mix. Yeah - I will do my homework.. I need a tutor though from time to time.

[newguitarsmell]

Slucky ... re shoot me the pic please! Or a schematic.
I don’t like SS rectifiers but I could try that ..
Please?

[DummyLoad]

your 5f2-a has 2 x 16uF in parallel - replace those caps with a pair of 33uF 500V parts. see attached plan; pg. 2 - remove the jumper from C1 and C2 and install a 100R 5W resistor. NOS 5Y3GTA will work with a 33uF as the first filter.

IF you decide to use solid state rectification with the existing PT, the B+ will jump significantly - you DON"T want this as you will need to basically redesign the output stage or replace the PT that has a lower B+ winding that will yield the same B+ as the tube rectifier does.

i have used up to 47uF SAFELY with the 5Y3GTA NOS rectifiers coupled to a marginally rated PT (higher source impedance winding), however, i have no experience with the current production asian or russian tube rectifiers, so your on your own there.

as stated already, there are PT available with lower volt/multi tap high voltage secondaries that will let you run solid state rectifiers in champ/priceton SE amp. classictone comes to mind, as do allen amps parts - see attached, if you want to leap down that rabbit hole.

BTW, page 3 is way i would have wired things... 

regards, and good luck!

--pete

 

[Willabe]

Yeah - I will do my homework.. I need a tutor though.

This whole forum is a tutor/tutorial.   

Do the homework 1st, then if you still have questions, post them. The more you know before posting, the easier it will be for someone to posibly help you.

Do a search here and on the web, several will come up. If you would have done a search, you would have found it on your own how to add the extra B+ filter stage.   

There -surely are many threads- with a 5F2a or Champ or other single ended amps that discuss/show the extra B+ filter stage. This extra B+ filter stage fix for single ended amps (SE) comes up often on the forum.

There's a difference between wanting a privet tutor to guide someone through every step of a build/repair and asking for help with a build/repair where someone gets stuck. 

I built a 5F2a/Princeton that I had a full build thread on.

Also try looking Archives of favorite topics;

http://el34world.com/Forum/index.php?board=11.0

Edit;

I just did a search for;     Killing hum in single ended/SE amps.

A ton of stuff came up, threads in forums, youtube, web pages.   

[sluckey]

Here it is. I had assumed you used the Hoffman layout but the idea works with any layout. If this is useful to you I suggest you save it to your computer. Nothing on the internet lasts forever.   

[shooter]

fwiw
I built a straight clone 5E1-ish turned out well, someone wanted a souped up version, came up with this.  It's my early days so pencil/paper, LOTS of undocumented tweaks.  This was my dive into xSE amps, got better 

[newguitarsmell]

Thanks for all the help. I will try each of these solutions.

I don't want a private tutor for my builds, I want practical advice from people who understand this stuff. I did many google searches and I read everything I could. It's like playing the guitar, or fully understanding music theory - sometimes it just takes an idea from someone who has been there.
Sometimes I don't even know the questions to ask. I truly appreciate all of your help and do not take any of you for granted. I am learning, I am studying and I am experimenting all the time.
Thanks guys! I will report back once I have tried some of these things.

[newguitarsmell]

In case anyone is interested in the continuing drama... first, the 5f2a schematic that is posted by Doug doesn't use two 16uf filter caps, rather a single 33uf.
https://el34world.com/Hoffman/files/Hoffman_5F2A.pdf
I rewired the amp following pete's suggestions.. I didn't get a voltage drop... I took it apart again and rewired it like Steve suggested but still didn't quite get it right.
In the end I rewired v1 and shortened the leads...trying to be sure everything was neat and properly dressed. I exchanged the 33uf filter cap with a 47uf. No real change. I upped it to around 60uf and it started to clean up buzz-wise but my voltage is much lower. The amp sounds clean, and there is still a buzz but not as bad. I feel like I need another resistor in the mix, or a choke, to really clean it up.
The confusing part for me was the original schematic combining the first two filter caps, and how to retrofit that into two filter caps.
I appreciate all the help. I feel like I learned a lot yesterday swapping things around. If I can figure out where a choke would go on doug's layout, I will try that today.
Or maybe just do something I am good at..like make a pie. - Margaret

[sluckey]

I rewired the amp following pete's suggestions.. I didn't get a voltage drop...

Ain't looking for any voltage drop. Listening for hum reduction.

Or maybe just do something I am good at..like make a pie. - Margaret

I'm fond of apple cinnamon. 

[newguitarsmell]

Apple pie it is!
Hum drop it is too. Haven't tried the filter on the rectifier yet, just a resistor.
Wish I could send a pie to all of you guys.
If you ever need to know the secret of the crust, just post.

[dude]

Forget all the cap changes you did, I assume you used a 5Y3 rectifier tube, wire exactly as Doug's layout, same cap values, just add Sluckey's extra cap and that resistor, it's this easy. Lift the wire from the OT on pin 8 on the rectifier tube, attach it to the board or a stand-off, put a 10 watt, 250 ohm cement resistor on the wire you just attached from the OT on the bd. or stand-off, take the other end of the 250 ohm resistor and attach it to a 33uf filter cap's positive thermal, also attach a wire from that + side of the filter to pin 8 of the rectifier tube, run the neg side of the filter to your star ground. That's it. Follow the diagram, hopefully you hum is gone. 60uf is too high for a 5y3, use that extra 33uf and either 22ufs or 16ufs as Doug's layout probably shows. Secure the added cap so the + side doesn't touch the chassis or other wires (can't move)  if this doesn't help, then fool with lead dress as mentioned and other things mentioned.


Then bake us a pie, you can eat it but be sure to tell us how good it was so we can drool. 

[PRR]

> doesn't use two 16uf filter caps, rather a single 33uf.

In 1956, Leo could find two 16u caps cheaper than one 32u cap. The 16s were going out of style for most designs, and Fender was still a small shop willing/eager to use-up odd-lot parts.

[newguitarsmell]

Over achiever I am, I added the resistor+ filter cap to the OT. I took out the big cap and put in a 47uf I had. I tried doing an a/b trial with the Lundhal OT vs a Classic Tone OT. Could only tell a difference on one speaker - other was pretty so so. Got the hum reduced a lot and the buzz fixed. The amp sounded glorious with a 5u4 but I worried I wold fry something so I replaced it with a 5y3.
Something is hinky in the volume-tone area so I am reworking that.
I am getting closer. The fact that both OTs had the same hum...significant? Don't know but I might be getting closer.
More pie to come..and cinnamon rolls...Margaret

[sluckey]

Can't make a silk purse out of a sow's ear.

[shooter]

I was this close to buying a '50s era NICE black silk sports coat, Pam didn't think it would make it a day before it was snagged, painted, n a burn hole.  just got the tie

[newguitarsmell]

Yes. I agree. I figure if it was possible, somebody would have done it by now.
Oh well. Only shocked myself once.
Shooter - white shirts and chili are my specialty

[newguitarsmell]

Hi guys - I rebuilt about every part of this SIMPLE amp - and along the way found a few broken things - got the thing up and running and now all I hear is the sound of the speaker. No hum..no signal. HOW on earth can this be so hard? I have made this amp before  - I check everything for continuity and yet I KEEP making mistakes.

Anybody else ever feel like such an idiot or have I cornered the market?!

[sluckey]

It's time to show us what your handywork looks like. May be some clues in the pics.

[bmccowan]

I am also interested in seeing pics. Am also interested in this quote

along the way found a few broken things - got the thing up and running and now all I hear is the sound of the speaker. No hum..no signal.

I can't figure what you mean by the sound of the speaker? Without hum or signal - huh? Redoing connections is tough. Pretty common in my experience to end up with a bad solder joint, or unintentionally grounding something.
No worries on the idiot thing - we all have scars.
BTW - the pie crust secret. Something besides not over-working the dough? You need to leave bits of butter/shortening to create the flaky consistency. My mother (RIP) was known as Mrs. Goodpie. Make mine Rhubarb; and no damn strawberries in there.