5E3 Head Build Power Up

5E3-inspired head chassis with tubes installed.

I fired up my 5E3 head build after my final sanity checks. I connected it to my Suhr Reactive Load into my DAW as my bedtime approached. I was relieved to get a healthy, low noise signal. I used my Monoprice guitar with GFS Mean 90s as my test guitar and the P90 noise was tolerable even with all the EMI and dirty power.

I installed typical modern tubes:

• V1: EH 12AY7
• V2: EH 12AX7
• V3 and V4: JJ 6V6
• V5: JJ 5Y3GT

With a wall voltage of 121VAC, the measured DC voltages off the three 22uF filter caps were 382V, 329V, and 241V. This is perhaps a little bit higher than the desirable range for a 5E3 circuit (350-370V).

I recorded a quick open chord passage using my Monoprice Indio Classic V2 guitar with GFS Mean 90 bridge pickup. The first pass uses a Weber Ceramic Blue Dog SM57 impulse, the second pass a GA10-SC64 SM57 impulse, and the final pass a C10Q M201TG impulse. The tone knob was maxed and the bright volume was set at 12:00. I still have a lot of the nuances of the amp to explore, but the basic sound of the amp is great. I immediately knew that the sound of the 5E3 circuit was more to my liking than the 5F1 circuit.

Outmoded Electronics · 5E3 - Blue Dog - GA10 - SC64 - C10Q

I will mainly be playing this amp loaded down and with IRs applied for now. I like how the amp sounds with the Ownhammer 1012 TWEED and York Audio VLUX 210 P10R libraries. I will have to dig deeper into the older Redwirez and Ownhammer libraries that I have to find IRs that I like. I may look into the CabIR.eu and Tone Junkies Tweed libraries the future.

Edit -12/8/21 - I had read about the interactive controls of the amp, but did not expect some of the more extreme results. I came across the so-called “better than blackface” setting by turning the unused normal channel volume to maximum or almost that value. This dropped the gain of the bright channel significantly: the amp can stay clean up to about 12:00 with bridge PAF-level bridge humbucker guitar on the bright channel when dialing back the tone knob. The amp is otherwise breaking up by about 9:00-10:00 on the volume dial. I would imagine that there would be even more headroom with a single coil guitar, and will try soon.

Edit - 12/21/21 - I had to reflow the solder on the V3 heater pin 2. I noticed that the tube wasn't glowing when playing through the amp the other night. The amp sounded a bit off, and it looked like there was asymmetrical clipping from looking at recorded waveforms.

Difference in positive and negative parts of waveforms. 

I did not get a dropped voltage on V3 pin 3, but rather the full B+ of 378VDC at the time. I believe that this is a recent development, since both power tubes are typically glowing. It must have been a bad solder joint on the tube pin eyelet itself. I perhaps narrowly averted disaster before I blew the output transformer, or burnt out other components.

Once I verified continuity on all filament tube socket pins, I powered up took down all relevant voltages using a cheap Tenma multimeter. I will check the voltages again with a calibrated Fluke 289 meter.

Voltages measured at tubes.

B+ voltages 

My B+ measurement was lower this time around. Perhaps this means that there was a problem further back in time. The wall voltage was lower by 1VAC this time however. 

More 5E3 Head Progress

I found some time to finish drilling the Hammond chassis for my 5E3 head. I made some more mistakes (eg. a misaligned input jack), but it didn’t turn out too bad for a hand drilled chassis.

Drilled chassis for 5E3 head.

Progression of populating chassis hardware.

The location of the power transformer’s mounting holes were not as precise as I had liked. I was able to get everything to line up in the end.

Chassis with components mounted.

It may have taken a while to get the chassis drilled, things seem to be moving quickly. I am just about to be ready to start soldering wires onto the components.

Chassis with transformer wiring.

I am using a combination of reference documents to build the amp.

• Triode Electronics 5E3 Layout - for the wiring of the Classictone 40-18017 PT, which is equivalent to the 40-18066 that I am using.
• Metropoulos 50W Plexi Instructions - for the general workflow of wiring up heaters.
• Rob Robinette's 5E3 Page - general 5E3 theory of operation and tips to optimize layout/wiring.
• Mojotone 5E3 Kit Instructions - used as a double check for all connections.
• Trinity Tweed Amp Instructions - used as a general reference for 5E3 wiring.

Edit - 11/22/21 - I finished soldering the 120VAC wiring into PT primary. The color coding of the Classictone 40-18066 primary wiring is odd: the line connection is white and white-black, while the neutral is black and black-white. I had to double check the diagrams a few times.

AC input wiring into PT.

I shortened all of the transformer wiring, too hastily. I used a forum post in regards to the Classictone 40-18022 OT phase as reference, only to later find another forum post that contradicted the information.  I traced the 5E3 schematic and looked at the Mojotone instruction manual to double check, and it does look like I botched the wiring. I mistakenly ran the Yellow lead to V3 Pin 3, Green lead to V4 Pin 3. The diagram below is my proposed fix on the speaker jack side. 

Edit - 11/23/21 - I dressed the heater wiring based on typical Marshall-style layouts. My tube socket spacing is tighter than the average Plexi layout, so it was a bit of a nuisance to get done. It’s not as neat as I would like.

Edit - 11/29/21 - I ran all of the preamp wiring off the turret board side and soldered about half of those wires in. Once I have the turret board completely soldered, I will start trimming and routing the wiring onto the various tube sockets, pots, and jacks. 

I see why most 5E3 builds have heater wires installed above the tube sockets rather than along the chassis Marshall-style. The wires for V2 are located in the middle of the typical 5E3 board, while the tube socket itself is closer to one end of the chassis. I will soon commit and hope that I don't screw up the layout of the tube socket wiring.

5E3 turret board wiring progression.

Edit - 12/2/21 - I finished making all the connections to the chassis. I quickly did a continuity check on various connections to make sure that I didn’t have any routing errors. I fired up the amp through my Suhr Reactive Load.

I still need to drill a few holes for the vented cage that will sit above the chassis to complete the amp.

All connections soldered.

5E3 Lunchbox Head Continued

I’ve been dragging my feet to get started with my 5E3 head build. I finally put in a few orders with Valvestorm and Mouser to get the last few jacks and tube sockets needed for my 5E3 lunchbox amp. I had about an hour to get as much of the tedious drilling done.

Preparing the chassis with my layout.

I committed to my layout and started drilling into the Hammond aluminum chassis. I immediately drilled the board mounting holes to make sure that I did not blow my measurements of the turret board. The board appeared to be laid out in metric units, while my layout was drafted in imperial units. My previous mounting hole layout was off by 1/32” for one of the turret board holes. I was fortunate to have a good fit when I committed to drilling.

Checking the turret board’s fit.

I moved onto punching the octal tube sockets with my Greenlee 1-3/16” hole punch, which went smoothly. By the end of the hour, I had drilled the pilot holes to punch the preamp tube sockets.

Punching the rectifier and power tube sockets.

I plan on finishing the preamp tube socket work next time. The top of the chassis has roughly the same amount of work as the front and rear panels combined. I am not looking forward to the Powercon drilling, since my punch (1-3/16”) is slightly bigger than the recommended connector hole diameter (1-1/8”). The holes for the mounting screws can get a bit too close to the connector hole, as it did on my Plexi build.

Edit - 10/22/21 - I haven't had access to an environment conducive to drilling for a while. I finished drilling the top and the rear sides of the chassis today. I was rushing through the process and made one of the output transformer mounting holes too large, which will have to be remedied with some additional washers. Drilling by hand went smoothly for the most part. The PowerCon chassis hole didn't turn out as well as I had hoped, but will be usable.

Top of drilled chassis,

Drilled hole for PowerCon connector.

I will need about half an hour to drill the front panel. Then the fun part comes with component mounting, and later the anxiety-inducing step of soldering.

To be continued.

5E3 Lunchbox Head Parts

I decided to pull the trigger on buying a power and output transformer for my 5E3 lunchbox head project after hearing that Classictone Transformers will cease operations after October 2020. I’ve used Classictone for my two other builds because of their upright project-style power transformers. I don't have the tooling to make a cutout for a laydown transformer, so I have only used upright power transformers so far.

 Classictone 40-18066 PT and 40-18022 OT

I did not come across any upright PT comparable to the 40-18066 that was in stock. The 40-18066 is an upright version of the 40-18017 laydown transformer, so I can use the Triode layout for transformer wiring reference. The 40-18066 does have a center tap for the 6.3V secondary, so I don't have to incorporate extra wiring to balance/elevate the heaters.

The 40-18022 is the standard 8kohm/8ohm 5E3 output transformer from Classictone.

Quick mockup of layout in CAD.

I bought the transformers before coming up with a layout this time. I had placed the PT and OT a little too close together on my Plexi build because I drilled the chassis before getting the transformers.

Hammond 1444-24 aluminum chassis taped up for drilling.

I need to buy some tube sockets, a Powercon connector, and I should be able to build this amp. I have already populated a turret board with Vishay metal film resistors, MKT1813 coupling capacitors, and F&T filter capacitors. I have decided to incorporate a negative feedback switch on an otherwise typical 5E3 build. I am thinking of using a 22k resistor and a 20k pot in series off the 8 ohm tap.

Double checking transformer layout prior to chassis drilling.

Incremental Progression on Amp Builds

I finally got all the components for the Marshall-inspired build. I had to reorder and redrill the chassis due to a mistake in the layout. 

Populated 1987 Turret Board

Populated 5E3 Turret Board

Hammond Chassis Laid Out for Drilling

Top View of Drilled Chassis

Fitting the cage to drill cage mounting holes

Power Transformer Mounting Holes

Output Transformer Mounting Holes

Plexi and 5E3 Turret Board Progress

As I upgraded some of the 2W metal film resistors to 3W on the 1987 turret board, I started populating a board for a future 5E3 head build that I have been putting off.

All passive components are now ordered except for the filter capacitors and a diode for the 1987 board. I am now considering installing a hi/low B+ voltage switch on the Plexi. I plan on using the 625V tap on the ClassicTone 40-18095 power transformer, but am thinking about utilizing the 690V or 560V taps.

The 5E3 will likely  be a straightforward build, with little or no modifications. Parts will be Vishay metal film resistors, Vishay MKT1813 and Cornell Dubilier 150 film capacitors, F&T filter caps, Cornell Dubilier silver Mica capacitors, and ClassicTone transformers.