Musings on the State of the 5e3 Art in 2024

[lonote]

It's unfortunate and regrettable that such an unsuitable material is the default board substrate used for builders of Fender type amps.

Agreed.

If I were to intentionally do a vintage layout AB763, etc. I would likely use eyelets, but there is GR10 glass board stock available in 1/16" thickness that would be far better suited & still look nearly correct.

[lonote]

Any way to physically float/isolate the junction of the B+ feed to the 100K plate resistors?

[2tone]

I remember Ken Fischer telling me that the synthetic coating on modern push back wires could conduct stray voltages. I had a recent built amp with these and did measure several mv on the surface of these wires. Of course lots of old eyelet boards can at times conduct stray voltage..maybe it depends on the humidity?

[psb962]

Update: I moved the 68k resistors to the jacks, wired each pair direct to the 12AY7 grids, and the DC has completely gone from all 4 inputs.

Problem solved. Thank you all!

[psb962]

Next question I have to answer is whether to mod the tone control so that I can use it as a high cut without losing all the middle - and hence overdrive - that the standard tone control appears to do (due to its massive 4n7 capacitor).

This topic has been addressed both on the Robinette site https://robrobinette.com/5e3_Modificati ... _Cap_Value, and on Rondo's site (in great detail) http://www.recproaudio.com/diy_pro_audi ... ss_mod.htm.

I ran some simulations on LTspice using my model I posted and sure enough you can clearly see the tone control cutting highs and mids all the way down when the tone is below about 7. Replacing the 4n7 cap with a 680p cap appears to limit the high cut to 600Hz and up, which should be about right.

I overlooked this one when doing my build, but getting that overdrive while not having head sliced off by treble from a Jensen-like alnico speaker is important, right?

I would be grateful to hear from others who have tried this mod or have opinions about it.

[psb962]

Ok, next topic - sag.

These amps are renowned for sag when pushed hard at high settings. Does this mean the B+ drops due to excessive current draw? Has anyone every measured that?

If the B+ drops significantly it might be cool to have some sort of mod which lit an LED when the B+ drops below a certain level.

[St4rP0wd3r]

Just built this amp as my first project ever. I decided to go full throttle on the diy and sorted 100% of the parts myself, without starting with any kit.

I also used a blank chassis as I really don't like the facing-up style chassis and wanted all toggles on the faceplate. I finished it literally 20 minutes ago, so I didn't have much chance to play it yet, but result and the easiness to build it surprised me.

[LOUDthud]

Rock On !!!

[psb962]

Just built this amp as my first project ever. I decided to go full throttle on the diy and sorted 100% of the parts myself, without starting with any kit.

I also used a blank chassis as I really don't like the facing-up style chassis and wanted all toggles on the faceplate. I finished it literally 20 minutes ago, so I didn't have much chance to play it yet, but result and the easiness to build it surprised me.

I see you built in a bunch of mods from the start - like I did - with the screen resistors, rectifier diodes, filter cap bleed resistor, and power reduction. If it helps simplify things later on I find that having no standby switch works really well. Did you use separate cathode resistors and bypass caps on V1? I can't see any bridge across the cathode pins on V1.

[St4rP0wd3r]

I used separate bypass cathode resistors and caps for the lead and normal channels. Most tube wires are connected to the turrets below the board. I also didn't bridge the two options as the normal channel goes to V1 pin 8 and the lead to V1 pin 3.

[Mark]

On V1 I have 130V and 121V on the plates. However, the DC on the inputs remains even if I take the V1 tube out. So I don't think it's that.

Since I posted, I found a similar thread on here where the consensus was that the Mojotone eyelet board conducts(!), and plate voltage creeps across the board to the input resistors, which are soldered to the eyelet board. Recommendation was solder the resistors to the jacks and wire direct to V1 grids. Unless anyone can come up with other things I should check first, I guess I will have to go ahead and do that.

Unfortunately, seems that might explain it.

I have 2 late 70s Pro Reverbs with chronic conductive boards but they are nearly 50 years old & covered with wax, so they get a pass. Disappointing that is happening with brand new stuff.

Have you tried cleaning the boards and removing the wax. Lyle Caldwell claims it fixes the issue, though from my experience there was a slight amount of voltage conducting through the board.

[patrick620]

Wow. My first 5E3 "ish" build 20+ years ago was from cobbled parts and iron. I never got picky about an exact much of anything and it turned out great. Maybe I just got lucky. Looking back at these old pics I start to cringe knowing what I know now Cool thread. I will be watching and as always, continue learning. Thanks.

[lonote]

Have you tried cleaning the boards and removing the wax. Lyle Caldwell claims it fixes the issue, though from my experience there was a slight amount of voltage conducting through the board.

I had seen his videos & DID try cleaning, then deep cleaning, but no luck. They were really, really caked with wax & I could never eliminate the stray voltage, so I replaced the board (have only done one so far).

[ampdan]

I slapped this together with parts I had available for a local Blues Jam back line.JPG[/attachment].[attachment=1]IMG_2644[1].

[Colossal]

I slapped this together with parts I had available for a local Blues Jam back line.JPG[/attachment].[attachment=1]IMG_2644[1].

Dan,

Very nice looking build. What kind of carbon film resistors are those?