yet another 5e3 newb with startup problems....

[patrickshofner]

I've been working on my first build for the past several days.....a mojo 5e3 kit. I've finally got everything wrapped up. My problem is that I only get a very slight buzzing when the volume is at 10+, otherwise silence.

I've wired it per the triode electronics layout to have a standby instead of the ground switch that the mojo layout offers. all voltages are within spec. all grounds have continuity with the chassis. I'm stuck. I've attached some photos of my wiring in hopes that you veterans can spot an issue. My leads from the board are soldered on the bottom (in case you were wondering). OT primary wired straight to the standby switch.

[mort]

Are those bottom inputs touching the ground rail?

When I did my first amp, a 5e3 also, I forgot to put one of the jumper wires on the back of the board. Make sure to carefully check your wiring, and check for continuity between points at the ends of each wire lead.

[MWJB]

Can you give us dc voltages for the filter caps running L-R, and voltages for 12A#7 tubes pins 1, 3, 6 & 8 (easiest to read the 820ohm/1500ohm cathode & 56K/100K plate resistor eyelets on the board)

I trust you didn't isolate the input jacks from ground? How does your buss wire terminate, is it grounded at both ends?

It looks nice & neat when you wire the eyelets from behind, but unfortunately if you have an issue, none of us can see which wire connects to what.

[loudthud]

Did you hear clicks or buzzes when you measured the voltages at the tube pins? If yes, the amp and speaker are basically working. The problem is at the input jacks or a signal short at the volume pots. If not, the problem could be a short at the speaker jacks or in the speaker cable.

There are two types of phone jacks available and the terminals are in different order. If you just blindly followed a layout that wasn't designed with the same type jacks you have, they may not be wired correctly. On my profile page in the messages section there is a link to a thread with a resistance test for the input and speaker jacks.

[patrickshofner]

Sorry for the delay....my wife and I are trying to sell a house so I've spent the past couple days elbow deep in paint

I sincerely appreciate the help and I'm going to reply to each post one by one.

Are those bottom inputs touching the ground rail?

When I did my first amp, a 5e3 also, I forgot to put one of the jumper wires on the back of the board. Make sure to carefully check your wiring, and check for continuity between points at the ends of each wire lead.

I just check for continuity for each lead leaving the board with it's terminating point. all were good. including continuity between all grounds and the chassis.

[patrickshofner]

Can you give us dc voltages for the filter caps running L-R, and voltages for 12A#7 tubes pins 1, 3, 6 & 8 (easiest to read the 820ohm/1500ohm cathode & 56K/100K plate resistor eyelets on the board)

I trust you didn't isolate the input jacks from ground? How does your buss wire terminate, is it grounded at both ends?

It looks nice & neat when you wire the eyelets from behind, but unfortunately if you have an issue, none of us can see which wire connects to what.

From left (closest to PT) to right the voltages are the filter caps are: 376dcv, 330dcv, and 244dcv

voltages at V1: p1-126dcv, p3-1.9dcv, p6-132dcv, p8-1.9dcv
V2: p1-258dcv, p3-1.2dcv, p6-211dcv, p8-48dcv these were fine before tonight. frustrating! what would cause a high voltage at these pins? obviously i've screwed something up here.

Input jacks are grounded to the buss wire which terminates at a terminal strip bolted to the chassis. The opposite end is floating(?) but held up by the cap off the 3rd tone pot tab.

[patrickshofner]

Did you hear clicks or buzzes when you measured the voltages at the tube pins? If yes, the amp and speaker are basically working. The problem is at the input jacks or a signal short at the volume pots. If not, the problem could be a short at the speaker jacks or in the speaker cable.

There are two types of phone jacks available and the terminals are in different order. If you just blindly followed a layout that wasn't designed with the same type jacks you have, they may not be wired correctly. On my profile page in the messages section there is a link to a thread with a resistance test for the input and speaker jacks.

i think i have an error in my input wiring as well. at pin2 of v1, i have 33k ohms to ground with no input cable. channel 1 with cable in '1' have 1.04M ohm to ground, in '2' i have 67k ohm. from cable tip to ground it was 1.04M ohm on input 1 and 134k ohm on input 2. on channel 2, it's like there's nothing plugged in. my layouts have the channels wired the same so i did (or thought I did). i also have switchcraft j12a jacks for what its worth.

[MWJB]

From left (closest to PT) to right the voltages are the filter caps are: 376dcv, 330dcv, and 244dcv

voltages at V1: p1-126dcv, p3-1.9dcv, p6-132dcv, p8-1.9dcv
V2: p1-258dcv, p3-1.2dcv, p6-211dcv, p8-48dcv these were fine before tonight. frustrating! what would cause a high voltage at these pins? obviously i've screwed something up here.

Input jacks are grounded to the buss wire which terminates at a terminal strip bolted to the chassis. The opposite end is floating(?) but held up by the cap off the 3rd tone pot tab.

Only pin 1 of V2 is unusually high. Odd that it is higher than the supply voltage at preamp filter cap (244vdc). Either you have hooked it up to the B+/screen node, or you have the wrong value plate resistor.

I can see the tag strip at the input end, I can see the buss & cathode wires solderd to the ungrounded eyelets, just wanted to be sure the 2 outer tags were grounded. How are the volume pots grounded?