Tube Doctor 5E3 Build

[mayburyds]

Hi,

New to the forum and new to building amps!

I have modded an amp before and built several effects pedals so thought I'd have ago at building an amp kit.

I'm taking the build very slowly, rereading and research everything.

Bit of advice on something that looks obvious but as I said I'm double checking everything with anybody that will listen.

Part of the Tube Doctor 5E3 build is to drill a couple of holes in the chassis so that a terminal strip can be attached. Looking at the circuit diagram the only things that get attached to the strip are the 240v feed from the power transformer and two resistors from the pilot light. Nothing else.

To save drilling holes I could secure the 240v feed cable with a cable tie and tape the end up as it's not needed and solder the resistors to a ground point on the chassis.

Do people think that will be OK?

Part of the circuit diagram I'm talking about is attached.

many thanks for any help.

[sluckey]

To save drilling holes I could secure the 240v feed cable with a cable tie and tape the end up as it's not needed and solder the resistors to a ground point on the chassis.

That's what I would do. I'd use heat shrink rather than tape only because heat shrink looks better. I would also take the resistors off the pilot lamp assembly and mount them directly on one of the 6V6 sockets. Since the layout shows pin 1 of the 6V6s connected to chassis ground I'd mount one resistor between pin 1 and pin 2. The other resistor would mount between pin 1 and pin 7.

There's an alternate connection for the resistors on the socket. Connect one resistor between pin 2 and pin 8. Connect the other between pin 7 and pin 8. This gives the benefit of elevating the heater string to the dc cathode voltage which may help reduce filament hum a bit.

[mayburyds]

Cheers, many thanks for the confirmation and the alternatives for the resistor hook up.

[mayburyds]

Build is progressing well but I'm a bit confused about the input sockets.

If I check the continuity on the tip of any of the sockets to ground I get a signal? In fact, any of the connections on the sockets gives me a signal to ground. Is this correct?

I've attached part of the circuit and a picture of the socket wiring I'm using.

Cheers.

[sluckey]

If I check the continuity on the tip of any of the sockets to ground I get a signal? In fact, any of the connections on the sockets gives me a signal to ground. Is this correct?

I assume when you say "I get a signal" that means you get a beep? If so, that's correct. Every lug on properly wired input jacks for a 5E3 will read zero ohms unless you have a 1/4" phone plug inserted into the jack.

[mayburyds]

Yep, sorry meant a beep.

Thanks for your help again.

[mayburyds]

I've got another question!

In with the kit are 11 nuts and bolts for securing 3 of the tube sockets (6 bolts) and the fibre board (2 bolts). This leaves 3 nuts and bolts for what is listed as Radial Caps.

I can't see anywhere where radial caps could or need to be bolted down!

Am I missing something here?

Cheers.

[sluckey]

Look on page 4 of the pdf documentation and you'll see where those three screws were intended to be used.

[mayburyds]

Of course, forgot about the not using the terminal strip. In my defence it was the reference to Radial Caps that throw me!

Cheers.

[sluckey]

I never saw anything about radial caps either.

[mayburyds]

Sluckey,

Many thanks for your help it's really appreciated.

I'm at the final stages of the build now - wiring up the mains transformer and running the power to the tubes.

So I have started to think about what testing needs to be done.

I have translated (thanks to Google) the testing paragraph in the Tube Doctor documentation -

Without Variac: All controls on Full: Switch on the device: Red indicator light goes
immediately, high voltage (measured at the first Elko is 0V) This increases within
of about 20 sec to about 490V then slowly decrease to about 400V. the
Voltage at the cathode of the output tubes (pin 8) slowly rises to about
22V. Now the amp has noise, if not immediately off again and
back to point 27)

I'm assuming that the first Elko is a cap but I'm not sure which one.

And I'm not sure if the voltage testing on the power tubes is with the tubes installed or not.

I have read the testing process in the Tube depot documentation which is more extensive but their board design is totally different.

From reading the Mojo and the Tube Doctor documentation the testing process seems to be -

No tubes installed, switch on and look for smoke, crackles etc.

Measure voltage at first Elko (any idea which component this is?) starts at 0v goes up to 490v then back down to 400v. This test is not mentioned in the Mojo documentation.

Measure the voltage on pin 8 on the power tubes - 22v.

Turn off - put the tubes in - turn on - check for smoking, crackles etc.

Hopefully good to go!

Does that sound about right, should I check anything else?

Cheers.

[sluckey]

I've added comments in red...

Without Variac: All controls on Full zero: Switch on the device: Red indicator light goes
immediately, high voltage (measured at the first Elko is 0V) This increases within
of about 20 sec to about 490V then slowly decrease to about 400V. the
Voltage at the cathode of the output tubes (pin 8) slowly rises to about
22V. Now the amp has noise, if not immediately off again and
back to point 27)

I'm assuming that the first Elko is a cap but I'm not sure which one. It's the first 16µF cap on the left on the board.

And I'm not sure if the voltage testing on the power tubes is with the tubes installed or not. Tubes must be in the sockets.

I have read the testing process in the Tube depot documentation which is more extensive but their board design is totally different.

From reading the Mojo and the Tube Doctor documentation the testing process seems to be -

1. No tubes installed, switch on and look for smoke, crackles etc. Indicator light should be on also.

2. Install all tubes EXCEPT the 5Y3. Turn on and verify that all tube filaments are glowing.

3. Now Install 5Y3 also. Turn on and check for smoking, crackles, arcing, etc.

4. Measure voltage at first Elko (any idea which component this is?) starts at 0v goes up to 490v then back down to 400v. This test is not mentioned in the Mojo documentation.

5. Measure the voltage on pin 8 on the power tubes - 22v.

6. Connect your guitar and test for normal sound.

Turn off - put the tubes in - turn on - check for smoking, crackles etc.

[Willabe]

Sluckey's web sit is back up, if you don't have a light bulb limiter yet build 1 for testing and 1st turn on.

http://home.comcast.net/~seluckey/amps/misc/Amp_Scrapbook.pdf


               Brad     

[mayburyds]

Too late, already tested :+) Thanks for the link though, very useful stuff.

Well all was going well till I put the last tube in then all hell broke loose!

There was a humming / vibrating type of noise slowly building so turned off.

Started checking the wiring and found that I had the speaker connection wired back to front :+( Rewired.

Still getting the humming type sound so turned off.

Started checking again and found I had missed a ground wire off :+(

Result! No humming, no buzzing, no crackles, no smoke, in fact very quite.

This amp is amazing! Only played for 5 minutes but you could just tell how good it is.

So even though I triple checked everything as I was building the amp, things were still missed. Still, not bad for my first amp build.

The only oddity is the voltage on pin 8 on the power tubes read 24v not 22v.

Many thanks to Sluckey for his help.

Cheers.

[eleventeen]

"The only oddity is the voltage on pin 8 on the power tubes read 24v not 22v."

In tubeland, those voltage readings are identical! Virtually *anything* in tubeland can vary by 10% with no ill effect.

[mayburyds]

Me again!

Something has been bothering me about the wiring on my amp.

It seems to work fine, no excessive hums and sounds sweet but.............

The 2 green wires coming off the pilot light down to the tubes - do you have to have 1 green wire connected to pins 2 on the 6V6's and pins 4/5 on the 12 AX7's and the other green wire to pins 7 on the 6V6's and pins 9 on the 12AX7's?

As the wire supplied is the same colour and when I checked for continuity across the two connections on the pilot light and got a beep I assumed it didn't matter if wires crossed over running from one valve to another as long as the valves got power!

Cheers.

[mayburyds]

Couldn't stand it so checked the wiring and found one pair of wires crossed over. Swapped them around but I can honestly say it didn't seem to make any difference to the sound or the level of hum.

Cheers.

[sluckey]

Couldn't stand it so checked the wiring and found one pair of wires crossed over. Swapped them around but I can honestly say it didn't seem to make any difference to the sound or the level of hum.

Cheers.

Oh no! The secret is out!

[mayburyds]

Ops!

[HotBluePlates]

... do you have to have 1 green wire connected to pins 2 on the 6V6's and pins 4/5 on the 12 AX7's and the other green wire to pins 7 on the 6V6's and pins 9 on the 12AX7's? ...

... Swapped them around but I can honestly say it didn't seem to make any difference to the sound or the level of hum. ...

I don't know what gave Gerald Weber the idea that "heater phasing" mattered. But your results are same as mine: no difference either way (just in case you didn't catch Sluckey's joke).

[mayburyds]

I got Slukey's joke, thanks.

The heater power is confusing as a beginner.

Some information talks about phase being 180 degrees out if the wires are crossed and some builds have two different colour wires for the heaters.

But as you and I have found it makes no difference either way!

Cheers.

[mayburyds]

Hi, back again!

Heard a demo of a Trinity 5E3 on Youtube and has more grind and is much more compressed then the Tube Doctor version.

Trinity Deluxe 5E3 Demo Fender Tweed Deluxe Clone

So I've compared the various voltages between the two.

Main voltage differences between the two -

V1 pin 1 - Trinity 131.2v TAD 116.5v
V1 pin 6 - Trinity 135.7v TAD 121v
V5 pins 4 and 6 - Trinity 366v TAD 326v

Would the voltage differences account for greater compression and grind?

Cheers.

[Slimtim]

yep,running the higher voltages will alter the sound.but i'm sure there are more differences between that setup and yours besides the voltages.

[mayburyds]

For sure, but the power differences seemed to stand out.

The valves are the same but different vendors.

Orange drop caps look the same.

But I guess all the small differences add up to something different.

Cheers.

[HotBluePlates]

Heard a demo of a Trinity 5E3 on Youtube and has more grind and is much more compressed then the Tube Doctor version. ...

Are you playing the same guitar & the same setting as that guy for all comparisons? If not, you're comparing apples to T-bones.

That said, there is some recording trickery to his demo. I've got a 5E3 copy I built, and I used to own a '55 Tremolux (basically a 5E3 with tremolo).

The recorded demo sounds more compressed than my amps, and I'm betting the guy used compression to get an even, high volume level for his video. The tip-off is that the clean sounds are basically as-loud as the distorted sounds. In person, the distorted sounds may not hit a higher peak voltage on the speaker, but will give the impression of being louder.

He says "no compression" but his recording has a slight bit of reverb to it (you can hear that in the "Long Cool Woman" quote if you use headphones). I bet he at least normalized the volume levels of the different sections, which will give an impression of compression.

Also, if you're not playing as brightly as he is, or if you used a different speaker with smoother highs, your amp will sound "less crunchy". If you want more rasp, turn up the treble. He may not have EQ'd the track, but he uses a Shure SM57 (which has an EQ curve with a presence rise) and an AKC condenser mic (which will also likely bump up highs a bit); these will probably make the recording "brighter than live".

Not a knock against that guy or his claims, just that microphones impart their own sonic signature.

Main voltage differences between the two -

V1 pin 1 - Trinity 131.2v TAD 116.5v
V1 pin 6 - Trinity 135.7v TAD 121v
V5 pins 4 and 6 - Trinity 366v TAD 326v

This is almost "no voltage difference". V1 Pin 1 is 11.2% lower, V1 Pin 6 is 10.8% lower and V5 is 10.9% lower.

What could account for this? The voltage at the rectifier of your amp is lower than the Trinity amp by essentially the same fixed percentage as every other part of the amp. So that's why the difference: either your output tubes are pulling a little more current and dropping the B+ a bit (which seems likely as you noted you had a couple more volts at the 6V6 cathodes), or your power transformer is outputting a tad less voltage.

Overall, that's probably a good thing, as you're likely to run into a situation where wall voltage is higher than you have at the moment, and B+ will be pushed upward. And most people run into the problem of having too much B+ voltage because their new production 5Y3 has less internal resistance than original 5Y3's.

I think you'll run into distortion a hair quicker with the lower B+ you have now.

[mayburyds]

Thanks for the really comprehensive reply, wasn't expecting that take at all!

Appreciate it's like comparing one apple to another, there are the same but not quite.

Don't get me wrong the Tube Doctor 5E3 is a great sounding amp. My interest was in finding out what made the Trinity variant sound different. To a noob like myself those voltages seemed too different, but from what you said a 10% variance doesn't mean much.

Thanks again for the responses.

Cheers.

[sluckey]

Different speakers can make a huge difference in the sound.

[HotBluePlates]

Different original Fender tweed Deluxes sound different from each other, too.

... My interest was in finding out what made the Trinity variant sound different. ...

When he plays clean (say through channel 1), he has the channel 1 volume at 1/2 and the channel 2 volume (which is not being played through) at full-up. You will find that cuts midrange in the channel whose volume is only half-up.

When he plays (say channel 1) full-up, he puts the other channel's volume at half. With that setting, the channel that's full-up gets maximum midrange and seems to distort more.

Are you doing this same setup, taking advantage of the interactive volume controls? If no (you keep the volume of the unplayed channel at 0), that might account for the tonal difference and apparent lower distortion.

[mayburyds]

Must admit I haven't tried going through channel 1, I'll try that today.

I do get distortion when I adjust the volume controls but there is a lack of compression or sag.

I measured the 16uf caps again and they have changed - cap 1 was 400v now 408v, cap 2 was 360v now 366v, cap 3 was 249v now 254v.

Pin 8 voltage went up from 388v to 408v.

The amp had a more crisp tone to it if that makes sense.

The Tube Doctor documentation states the cap voltage should be 400v but the circuit diagram shows a voltage of 387v. The diagram shows cap 2 voltage as 346v and cap 3 voltage as 283v.

Cheers.

[mayburyds]

Sorry, confusing myself with channels numbers and bright and normal channels.

I have been using channel 1.

Tried all channels now and various volume combinations and the main difference in sound does seem to centre around lack of compression / sag rather than the distortion aspect.

Cheers.

[sluckey]

Get a real NOS 5Y3. B+ voltages will be lower and you will have more sag.

[mayburyds]

This is the one I got with the kit -

http://www.tubeampdoctor.com/en/shop_TAD_Premium_Tubes_TAD_Rectifier_Tubes_SELECTED/5Y3GT_TAD_PREMIUM_SELECTED_Rectifier_Tube_827

Cheers.

[sluckey]

Search ebay for NOS 5Y3. Plenty of international shippers.

[HotBluePlates]

Quoting FYL in an old thread:

"The Sovtek 5Y3GT is a rebadged 5Ц4М (5Z4M), a Russian indirectly heated recto quite close to a 5Z4GT or 6106.

http://www.tubes.ru/techinfo/HiFiAudio/5z4c.html (C = large bulb, M = compact version)"

What all that means is it is a Russian tube type different from a true 5Y3, but close enough to be used in the same circuits. The Russian type drops less voltage and creates less sag.

[mayburyds]

Just to clarify, I'm looking for a NOS 5Y3 and not a NOS 5Y3GT or can it be either?

Why can't you get this stuff in the UK! It's the same as trying to get hold of a DIY pedal!

Cheers.

[sluckey]

Just to clarify, I'm looking for a NOS 5Y3 and not a NOS 5Y3GT or can it be either?

either. I like these...

http://www.ebay.com/itm/NICE-PAIR-OF-GENERAL-ELECTRIC-5Y3GT-VACUUM-TUBES-NOS-IN-BOX-/380764768409?pt=Vintage_Electronics_R2&hash=item58a7594899

or

http://www.ebay.com/itm/NEW-Sylvania-Electron-Tube-JAN-5Y3WGTA-Black-Plate-NOS-/171024264494?pt=Vintage_Electronics_R2&hash=item27d1d72d2e

[mayburyds]

Many thanks for the info, much appreciated.

Once I get a replacement I'll report back.

Cheers.

[HotBluePlates]

Just to clarify, I'm looking for a NOS 5Y3 and not a NOS 5Y3GT or can it be either?

5Y3G



5Y3GT


The difference is the shape of the bulb.

New production "5Y3's" are really a Russian tube with an American label, though the Russian tube is not identical in performance to the American original. Just like Different companies have a "KT66" but they're no Genalex (original Genalex, not the new Russian/Chinese stuff with the old logo).

[eleventeen]

I acquired a bunch of those VT-197 5Y3s NOS in a pile of stuff I bought. Maybe it's that they are 60-70 years old; they test rather poorly. Completely unused, many of them test barely acceptable, as used-used. Though they are possibly useful as tubes to put into amps under repair, so that a fault does not blow up a more valuable tube. Fortunately I also got a load of NOS GE 5Y3WGT's from 1958 with brown bases which look (internally) like the orange-boxed ones Sluckey pic'ed (the characteristic rectangular plates that GE used) and they are honeys.

[mayburyds]

Managed to buy a NOS GE 5Y3WGTB and put that in today.

This dropped the voltages as follows - cap 1 to 374v (diag 387v), cap 2 to 338v (diag 346v) and cap 3 to 233v (diag 238v) which are a lot closer to the voltages on the circuit diagram.

The only voltages that are down compared the circuit diargram are - V1 pin 1 is 110v (diag 131v), V2 pin 1 is 148.4v (diag 167v) and V2 pin 6 184.5v (diag 193v). Just noticed that the circuit diagram voltage for V1 pin 1 131v is for the normal channel, the bright channel is 126v.

How do you go about measuring the difference in voltage on V1 pin 1 between the normal and bright channels? I measured the voltage with nothing plugged in all the controls turned down and red probe on pin 1.

One other voltage I checked is the AC coming into the amp which measured 244v, the PT is wired for 230v. Don't know if that makes a difference.

Sound wise I would have to say it hasn't changed the sound much, if anything it is slightly quiter.

Cheers.

[sluckey]

One other voltage I checked is the AC coming into the amp which measured 244v, the PT is wired for 230v. Don't know if that makes a difference.

Since the actual line voltage is higher than what the PT expects, the secondary voltages will be higher accordingly. If you have a 240v tap available on the PT, connect the line to that tap and the secondary voltages will drop. But if you are happy with the voltages don't bother.

[mayburyds]

What I don't understand is the voltage going into V1 pin 1 before the 100k resistor is 233v the other side of the resistor it's 110v but the circuit diagram shows it should be 131v!

Do the voltages vary that much?

Cheers.

[HotBluePlates]

What I don't understand is the voltage going into V1 pin 1 before the 100k resistor is 233v the other side of the resistor it's 110v but the circuit diagram shows it should be 131v!

Do the voltages vary that much?

You're familiar with Ohm's Law?

Voltage = Current * Resistance  ---> Current = Voltage / Resistance

Your Amp
233v - 110v = 123v (this is the voltage dropped across the 100kΩ plate load resistor)
123v / 100kΩ = 1.23mA of tube current

Amp Diagram
238v - 131v = 107v (Diagram B+ node minus Diagram plate voltage; voltage dropped across diagram plate load)
107v / 100kΩ = 1.07mA of tube current

The math above assumes your plate load resistor is exactly 100kΩ (it almost certainly is not). It shows your tube current is ~15% higher than the diagram current. But you have a plate load resistor (100kΩ) which is probably rated +/-10%, a cathode resistor that's probably rated +/-10% and a tube that can have variations in characteristics of more than 20%.

I'd say your voltages are "exactly" where they should be. If it were my amp I wouldn't give them a second thought.

[sluckey]

On my homebrew 5E3 I have 224v before the 100K plate resistor and 111v on pin 1. Do you have a 12AY7 plugged into V1 socket? Different tube types will cause different plate voltages.

Don't be concerned about the slight differences in voltages. Unless you have some problem with the amp, I'd say you're done. And don't be concerned that your amp doesn't sound just like some YouTube video. Just start twisting the knobs and see if you can nail Honkytonk Woman.  

[mayburyds]

Agreed, I'm getting too wound up by the numbers now instead of enjoying the amp.

Thanks for all your help guys.

Cheers.