Reworking 5E3 Questions

[Ed_Chambley]

I bought a 5e3 in need of attention.  It was a home built job and has 2, 22uf and one 16uf for filter caps.  Also the turret board is almost touching the input jacks as it has a ground bus off the side of the board.  The board is on 1/2 inch standoffs and I either need to lower it or simply move it down.

How close to the chassis can you put a board?  Also, will the added capacitance on the filters cause any problem?  Also, the amp hums some and someone has put shielded wire from both volume knobs.  I guess trying to reduce any hum, but I have never used shielded wire here and never had any problem with hum.  I would assume the hum is coming from how close the inputs are to the board.

[guitardude57]

Got pix?  Is the circuit pretty traditional?  Wiring a mess?
Would help to see.

[phsyconoodler]

The extra filtering is not really an issue.I've built 5E3's with stock 16uf and with 22uf and the difference is negligible.
 The inputs do not even need shileded cable and closeness to the board has nothing to do with hum.
It's all about the lead dress,the heater wiring and grounds in a 5E3.
  I just finished a 5E3 and it's dead quiet at idle.You follow Fender's original grounding scheme and they are quiet.Heater wires need to be away from other wires and indexed to the tubes.
i.e. on the power tubes theyneed to be pin 2 to pin 2 and pin 7 to pin 7,smae for the preamp tubes.Pins 4&5 to pins 4&5 and pin 9 to pin 9.
  The layout for the rest of the wires need to be oriented like the layout.
The board in an original 5E3 is on a backing board and screwed directly onto the chassis.If you have standoff's they are elevated off the board so they don't ground out against the chassis.I would just make a backing board and bolt it down to the chassis with two small 6/32 bolts.It doesn't have to be tight,it 'aint going anywhere.

[stratele52]

1- Shield to volume pot is good if it a job well done.

2- For your hum,do you have a heater center tap ? It is a must. Original circuit don't have.

3- Jack close to the circuit is not a problem by itself ; short wire = less hum.

4- Improper matched 6V6 pair = could hum.

5- Non shorting input jacks = hum.

6- Improber lead to each tube's grid = hum.

7- Noisy 12xx7 tubes

8- Defective filter cap = hum

If you check and fixe all of that , I'm sure you won't have hum

[Ed_Chambley]

1- Shield to volume pot is good if it a job well done.

2- For your hum,do you have a heater center tap ? It is a must. Original circuit don't have.


If you check and fixe all of that , I'm sure you won't have hum

Shield not done well, but no center tap, need to add the resistors.  Lead dress to tubes are not very good either.  The jacks are so close that when you put a 1/4 jack in, you could not get a piece of thread between it and the turret below.

Thanks for the info, I think I will just back the board and bolt it down.  Then I will have enough room to do a proper lead dress.  Did not seem like much of a problem as I have built a few and never had any noise.  That is why I bought it for cheap.

Thanks for the input.

[stratele52]

No heater center tap , that's a source of hum.

You are welcome Ed

[stratele52]

Your heater should have 2 wires from Power Transformer.  5E3 heaters use chassis ground on one side, you have to modify it before putting two 100 ohms resistors for artificial ground.

[phsyconoodler]

Here are some pics of my 5E3.Quiet.

 not a shielded wire in there.

[Platefire]

I just started back working on an old 5E3 head project tonight I've had on hold for a long time. I guess this will be my forth. Platefire

[stratele52]

Phsyconoodler;

Well build amp with 2 heater wires = quiet.

[HotBluePlates]

The board is on 1/2 inch standoffs and I either need to lower it or simply move it down.

That was silly for the guy to use standoffs with an eyelet board instead of the blank fiberboard below it as an insulator (a la original Fender).

How close to the chassis can you put a board?

If it gets really close, you'd want an insulator between the board & chassis.

You could use 1/4" standoffs, and that's what I typically use with Hoffman-style turret boards.

Given you have an eyelet board, I'd use the blank fiberboard insulator and self-tapping screws like the original amp. Every little bit of extra space is precious in those tight tweed chasses.

[Ed_Chambley]

Thanks for all the input guys.  I ended up just putting an insulator under the board and rewired the amp.  Changed a few cap values while there.  Removed all the shielded wire.  Quiet as a mouse.  For about $150 total in it and it had a hammond PT and a classictone multi-tap OT. Weber 12 ceramic 30 watt vintage.  Voltage  are little low, but it sounds good so I guess that is what matters.  There was way too much wire length everywhere and most everywhere would change the the hum.

I was wondering since I am not a huge fan of a deluxe.  I did the mod to separate the volume controls using a dual tone pot and increased headroom some.  Changed the bypass to 4.7 and 820 ohm and removed the flab.  .22uf and .47uf.  The cathode resister was a 125 ohm so I had to change it to a 250.
They sound good and break-up nice, but lack any clean.  I guess it is the nature of the circuit.  Now I have 2, but this one has better parts and a nice wood cabinet.  I guess I will sell the old one I have.

I actually referenced Sluckey's 2006 build layout and added a couple of more turrets and got rid of ALL the underboard wiring.

Here is the tone stack mod if anyone is interested.  I did not   I like much better than the stock deluxe I already have.

Is there any problem with using a 5v4 rectifier tube as long as the voltages stay within the schematic figures?  I don't know if it will help to clean it up any.

[Ed_Chambley]

If it gets really close, you'd want an insulator between the board & chassis.

You could use 1/4" standoffs, and that's what I typically use with Hoffman-style turret boards.

Given you have an eyelet board, I'd use the blank fiberboard insulator and self-tapping screws like the original amp. Every little bit of extra space is precious in those tight tweed chasses.
[/quote]
It is actually a turret board, that is why it landed so close to to the input jacks.  I used some rubber isolator from work that is designed to keep high voltage cabinets from touching the frame on the large printing presses.  It worked great and it is .125 thick and I bolted everything down.

[HotBluePlates]

It is actually a turret board ...

Do you mean it is a glass/epoxy board? I ask cause those are eyelets in the picture. I did assume the board holding the eyelets was the typical fiberboard.

You could use a 2nd glass/epoxy board (or a fiber board or other insulator) under the existing board. It's just easier with the fiberboard to get the holes to line up properly.

They sound good and break-up nice, but lack any clean.  I guess it is the nature of the circuit. ...
Is there any problem with using a 5v4 rectifier tube as long as the voltages stay within the schematic figures?  I don't know if it will help to clean it up any.

You can use a 5V4, I'm not sure it will give you much if any extra clean.

This is a circuit with plenty of gain and a low-loss tone circuit, with output tubes that don't need a tone of drive signal. So clean is what happens when you turn down your guitar volume knob.

That said, you can regain the impression of headroom by swapping pot types. Are those Weber or Alpha pots? A lot of typical guitar amp pots have a 20-30% "audio" taper. A true log pot would be 10% resistance at half rotation, so they seem to increase in volume slower and have a broader range of volume on the dial before distortion kicks in.

To be clear, what I'm saying is the amp distorts when signal voltages through the preamp to the output tubes reach a certain limit. 20-30% taper audio pots turn up higher-faster, meaning that signal limit happens at a lower number on the volume control. A real 10% taper audio pot will seem to have distortion occur at a higher number on the pot, only because it is ramping up slower (and in a more-correct log fashion).

Why do 20-30% tapers exist? They can be a guitar shop gimmick: "Look how loud this amp is on 2!!" Assuming they're not used for gimmick effect, they can make distortion happen at an earlier point on the control, giving a wider range over which to dial in your exact fave distortion setting.

But in a 5E3, which some people malign for having no headroom, 20-30% taper pots might be a detriment. Of course, that depends on how loud/clean you need the amp to be (I get great cleans with my 5E3, but I also don't expect it to be very loud; at least, not like my 5F4 Super).

[stratele52]

They sound good and break-up nice, but lack any clean.  I guess it is the nature of the circuit.
 
-Ed Chamberly
__________________________
Too munch gain ?

Voltages too low on 12AX7 ?

Put a limiting resistor ( 100K ) between the pot wiper and 12AX7 grid .

[Ed_Chambley]

The amp has 2 CTS pots (Volume) and one Alpha dual (tone).  All are B1M.  I have another problem ant that is a PT getting hot.  It has a hammond 272dx, marked 2008.  It is 300-0-300.  Attached is the spec sheet, but it is a little different.  This PT only has 2 blacks, 2 Green, 2 Yellow and 2 red with a center tap.

Yes it is a fiberglass board, Those photos are Psyconoodles amp.

It took a while for it to get hot (couple of hours). Just wondering if it is too small.  I have a deluxe PT I can use, but I did not check this one initially.  I went on the assumption since it was on there it was fine.  It may just be the tubes I have, I don't have very good supply of 6v6 and the first 5y3 I put in was shorted.

Anyway, the specs seem fine, but I am not sure now.  Let me know if I need to put another one on it.

[stratele52]

A 104 ma PT for 5E1 is powerfull enough.

How many volts you read at each tube's plates .

[Ed_Chambley]

I will get all voltages and post them soon.  Initially I checked them unloaded and everything seemed ok.  Loaded I was only getting about 300 on the power tubes, but as I mentioned, I am not sure which 6v6's I have are good and if any are matched.  I will need to test them as I have never built many 6v6 amps.  I have ordered some matched new Tung-Sol 6v6gt and will have them in a few days.

I am not sure, but I think it was from the tubes.  I thought the PT specs was fine.  It was the one that was on it.  Stock voltages should be around 355 I think and I have seen where many people like 330 in these amps.  That is why I asked about the 5v4 as I could get the voltages up a little more.  I am fairly certain it is tubes.

[Ed_Chambley]

This is a circuit with plenty of gain and a low-loss tone circuit, with output tubes that don't need a tone of drive signal. So clean is what happens when you turn down your guitar volume knob.


But in a 5E3, which some people malign for having no headroom, 20-30% taper pots might be a detriment. Of course, that depends on how loud/clean you need the amp to be (I get great cleans with my 5E3, but I also don't expect it to be very loud; at least, not like my 5F4 Super).
[/quote]
It doesn't really clean-up when you turn down the guitar.  I do not expect it to be like my 5f4 either.  I love this amp.  Other than my Super Reverbs, the 5f4 is my favorite.  I have 2 of them.  One is bone stock with 2, 10's and tweed/oxblood.  The other one is built in a bluesbreaker combo cab and is heavily modded with a master, reverb and tremolo, 1, 12's alnicos and a VVR.  Great amp, but heavy.

[stratele52]

An unbalanced Phase Inverter circuit = less clean

Check for proper resistors values. 

Bias toooooo hot ?

[Ed_Chambley]

An unbalanced Phase Inverter circuit = less clean

Check for proper resistors values. 

Bias toooooo hot ?

I am going to wait for some new tubes and I did order a few balanced 12AX7.  The only resistor that was not correct was the first one on the B+.  It was a 3.3k and I changed to a 3 watt 4k7.  I have seen people put a choke here but I do not know if it should have one.  Differing opinions on this.  Some say it helps to clean the amp up and others way you lose touch sensitivity.  I might try one, but I don't think the choke has enough resistance by itself.

The tubes are biased way too hot, you can tell just by how hot the glass is (no red plating) but for now it is all I have that are even closed to matched.  I do have a few old singles I can test and probably find some better matched.

Let me know your thoughts on the choke.

Thanks,

[stratele52]

The tubes are biased way too hot, you can tell just by how hot the glass is (no red plating)

Are you serious ???? Checking bias like that ??

[Ed_Chambley]

The tubes are biased way too hot, you can tell just by how hot the glass is (no red plating)

Are you serious ???? Checking bias like that ??

No, it is not the way I check.  I just know I don't have the proper matched tubes.  When I get what I need I will do a proper bias and check all the voltages.  There is really no need to check what you already know is bad.

What do you think of a choke on a 5e3?

[stratele52]

Choke or not on 5e3 ? I don't know . I don't have any opinion.

[HotBluePlates]

It doesn't really clean-up when you turn down the guitar. 

Dunno what to say... My 5E3 cleans up when I turn down the guitar volume or the amp volume knob. Same with the '55 Tremolux I used to have. I don't mean they clean up easily when the amp is at max volume, but some reasonable distorted volume level.

Regarding the pots, you'd just need to measure the resistance from wiper to ground at half-rotation. I'm not certain at the moment if the pots you mentioned are 10% or some other audio taper. The data sheets I saw didn't specify

Let me know your thoughts on the choke.

I haven't tried it on a 5E3-type amp. The loss of touch-sensitivity would be due to a more-constant supply rail at the screen node. I don't think it would alleviate the 5E3 being quick to distortion, as I just think that's the balance of the amp's design. If nothing is obviously wrong with the amp or its components, I'm thinking that's just the way it is.

[Stankfut]

My 5E3 has a choke....it does not clean up when I turn down my guitar volume, instead it just gets muddy and  less loud. I need to put a small cap in the guitar to cut back on the mud, but I don't think it would clean up the distortion. I may try a resistor there at some point.....

[stratele52]

For clean sound , choke have nothing to do with that , same for the pots. With B pot ( linear),  full volume come early than A pot ( log ) , but clean sound is the same.

[Danskman]

Hello!
Don't forget a 5E3 is a 5E3 is a 5E3... Past 4, it doesn't sound that louder; instead, you get a higher distortion (but what a distortion, baby!!). IMHO, you should build it following factory standards (power rail resistors, log pots, 12AY7 in V1 socket, etc.). Try another speaker if you find it "muddy". Mine is not muddy at all, with a Weber vintage ceramic, trust me 
Just one thing you don't speak about: what mikes in your guitar? 'Buckers? Single coils?
BR,
Danskman

[Ed_Chambley]

Hello!
Don't forget a 5E3 is a 5E3 is a 5E3... Past 4, it doesn't sound that louder; instead, you get a higher distortion (but what a distortion, baby!!). IMHO, you should build it following factory standards (power rail resistors, log pots, 12AY7 in V1 socket, etc.). Try another speaker if you find it "muddy". Mine is not muddy at all, with a Weber vintage ceramic, trust me 
Just one thing you don't speak about: what mikes in your guitar? 'Buckers? Single coils?
BR,
Danskman

I have a Lollar pickup Tele and Strat.  The Strat is a little hotter, the Tele is low output and twangs real good.  I have Les Paul with PAF and a 335 with classic 59's.  Tried all of them and the Tele is the cleanest and has the best touch response.  The Les Paul has the most powerful sound.

I agree, the distortion is really nice.  I do have a stock one and had a weber ceramic in it.  I tried a Jensen and a a couple of other alnicos.  Ended up with a Celestion Gold 12 in this one.  They all sounded good, but the celestion seems to compress the best and the upper mids are smooth.

The reason for the cap value changes is I was using the tube data sheet for a 12AY7 and 12Ax7 some math I learned with help from HBP to amplify specific Hz and draw a loadline as I wanted to begin to apply this new, to me, knowledge.  You know, move from theory to actual use.  I like the results, but our tonequest changes as fast as my hair falls out.

I will find some more closely matched tubes and get some loaded voltages, if I can find 2.  Got some on order, but with the holiday, the wont ship till tomorrow.  I hate pulling tubes from a working amp as I could just plug in the ones from other amp.  I think I can come up with 2 6v6's that are close enough to work ok.  I have just been lazy.

BTW, I provided the wrong info on on the pots.  The 2 volume are audio taper, the dual tone is linear.

[Ed_Chambley]

It doesn't really clean-up when you turn down the guitar. 

Dunno what to say... My 5E3 cleans up when I turn down the guitar volume or the amp volume knob. Same with the '55 Tremolux I used to have. I don't mean they clean up easily when the amp is at max volume, but some reasonable distorted volume level.

Regarding the pots, you'd just need to measure the resistance from wiper to ground at half-rotation. I'm not certain at the moment if the pots you mentioned are 10% or some other audio taper. The data sheets I saw didn't specify

Let me know your thoughts on the choke.

I haven't tried it on a 5E3-type amp. The loss of touch-sensitivity would be due to a more-constant supply rail at the screen node. I don't think it would alleviate the 5E3 being quick to distortion, as I just think that's the balance of the amp's design. If nothing is obviously wrong with the amp or its components, I'm thinking that's just the way it is.

The volume pots read just under 700 ohms at 1/2 turn.  I don't think anything is wrong, I just do not trust my rectifier or power tubes.  That is one of the reasons I asked about the 5v4.  I have lots of NOS tubes in 5v4.  I guess all I can do is try it and see where the voltages land.

[HotBluePlates]

The volume pots read just under 700 ohms at 1/2 turn.

Hmmm... Did you mean 70kΩ (showing on your meter as 70.0 and a small k off to the side)?

I probably should have said keep the volume control not being measured turned up to max to minimize effect of parallel loading.

But let's say you have a 10% taper. That would be 100k from wiper to ground at half-rotation. Let's say you also turned the other pot to half when measuring the first. That's also 100k to ground. From the wiper of the first pot, the meter lead will see a 220k resistor in series with another 220k, then the 2nd pot's 100k to ground.

So the meter sees 100k to ground in parallel with 540k to ground, for a total of 84kΩ measured. Tolerances in pots and resistors, little slop in finding exactly 1/2 rotation... I'd call your pots 10% taper.

[Ed_Chambley]

I have found a problem.  I have no voltage on pin 8 of the power tubes.  I changed the layout to the attached.  It is one I got from Sluckey.

I took s.ome photos.  I have missed something.  Maybe you can see it and give me a direction

[Ed_Chambley]

More

[Ed_Chambley]

All the other voltages check out very good, I do not have any bias.

[phsyconoodler]

Pin 8 to bias resistor and cap on board,other end or resistor to ground.Pins 5 connested to the top of the 220k resistors and caps on the board.You HAVE to have some voltage at pin 8 if these are connected.
  You likely have no ground.

[Ed_Chambley]

Pin 8 to bias resistor and cap on board,other end or resistor to ground.Pins 5 connested to the top of the 220k resistors and caps on the board.You HAVE to have some voltage at pin 8 if these are connected.
  You likely have no ground.

I have a stranded ground wire from the negative end of the 250ohm-25uf/50v attached to the PT bolt.  From the positive side I have a wire connecting to pin 8 of both power tubes.  thought the same thing so I ran a new wire in case of a bad joint.  Still no voltage.

Since I rarely do cathode bias, should there be voltage on pin 8 when no tubes are in or does the tube provide the voltage.  From the schematic I have I should see around 18 volts at pin 8.

[sluckey]

should there be voltage on pin 8 when no tubes are in

no

[Willabe]

Since I rarely do cathode bias, should there be voltage on pin 8 when no tubes are in or does the tube provide the voltage.  From the schematic I have I should see around 18 volts at pin 8.

Cathode bias (self bias) on power tubes is just like with preamp tubes.

The tube is standing on a resistor and as the tube draws current it develops a dcv on the top of the cathode R. The more current the tube draws the bigger the cathode dcv.  This makes the cathode more positive then the grid. (Self bias part.) Grid bias the cathode is at ground and the grid has a negative dcv applied to it. Again the cathode is more positive then the grid.


                   Brad      

[Ed_Chambley]

Thanks guys, I found it.  I did not crimp the turrets in, just added a couple.  The positive was grounded.  Pulled the turret and wired direct to the resistor/cap.  Bias 21.  All is good and it will play clean as well.  Now when I get my hands on a matched pair of 6v6, I will be in business.

[Ed_Chambley]

Since I rarely do cathode bias, should there be voltage on pin 8 when no tubes are in or does the tube provide the voltage.  From the schematic I have I should see around 18 volts at pin 8.

Cathode bias (self bias) on power tubes is just like with preamp tubes.

The tube is standing on a resistor and as the tube draws current it develops a dcv on the top of the cathode R. The more current the tube draws the bigger the cathode dcv.  This makes the cathode more positive then the grid. (Self bias part.) Grid bias the cathode is at ground and the grid has a negative dcv applied to it. Again the cathode is more positive then the grid.


                   Brad      

I thought so, but when you have problems that should be simple you begin to question what you know.

Anyway, everything is good and the 5v4 put the voltages within a few percent what Steve had on his schematic.  Now it will play clean, imagine that.  Anyway, I appreciate you explaining again.

[Ed_Chambley]

The volume pots read just under 700 ohms at 1/2 turn.

Hmmm... Did you mean 70kΩ (showing on your meter as 70.0 and a small k off to the side)?

I probably should have said keep the volume control not being measured turned up to max to minimize effect of parallel loading.

But let's say you have a 10% taper. That would be 100k from wiper to ground at half-rotation. Let's say you also turned the other pot to half when measuring the first. That's also 100k to ground. From the wiper of the first pot, the meter lead will see a 220k resistor in series with another 220k, then the 2nd pot's 100k to ground.

So the meter sees 100k to ground in parallel with 540k to ground, for a total of 84kΩ measured. Tolerances in pots and resistors, little slop in finding exactly 1/2 rotation... I'd call your pots 10% taper.

I disconnect the wires from the pot to check the ohm at a specific rotation.  It is easier than calculating series/parallel resistance, so the 700 ohms is with no wires connected to the pots at about 1/2 turn.

[Willabe]

Glad you got it working Ed.

The 1'st amp I built was a 5E3 and I still have it. It's a good little amp IMO.


              Brad    

[Ed_Chambley]

Thanks again guys.  Everything is working as it should and it is a beautiful old looking wood box with antique radio grill cloth.  No doubt I have another great sounding amp.

[Willabe]

Everything is working as it should and it is a beautiful old looking wood box with antique radio grill cloth.  

Nice.


              Brad     

[HotBluePlates]

I disconnect the wires from the pot to check the ohm at a specific rotation.  It is easier than calculating series/parallel resistance, so the 700 ohms is with no wires connected to the pots at about 1/2 turn.

That's a bit low for a 1MΩ pot (which should be at 100kΩ at half-rotation) isn't it?

That would make me think you have 10k pots, which would enormously load-down the stage ahead of them, almost guaranteeing no clean output.

Are you certain it was 700Ω? 

[Ed_Chambley]

I disconnect the wires from the pot to check the ohm at a specific rotation.  It is easier than calculating series/parallel resistance, so the 700 ohms is with no wires connected to the pots at about 1/2 turn.

That's a bit low for a 1MΩ pot (which should be at 100kΩ at half-rotation) isn't it?

That would make me think you have 10k pots, which would enormously load-down the stage ahead of them, almost guaranteeing no clean output.

Are you certain it was 700Ω? 

Your thinking is correct, mine not so much.  I am certain I have 2, 1meg volumes and a dual 1 meg for tone.  The amp is now much cleaner than my stock 5e3.  I like it.  Next time I open it up I will check, but I would assume you are correct.  It is working, so I will leave it alone until I get some matched tubes.

My thinking got derailed when I found I had no cathode voltage.  I should have looked closer to the turrets while I had the board out especially since it was a rescue.  Anyway, this 5e3 is changing my mind about the amp.  It has cleaned up rather nicely and begins distortion after a healthy volume.  After I got it back together I ran through a couple of Jerry Reed electric tunes and was very pleased with the tone.

Thanks for the help once again.  I have been having a ball with tube datasheets and loadlines.

Being so accustomed to playing supers (5f4 and ab763).  Finger pickers and distortion makes for strange bed fellows.