5E3 Testing and troubleshooting

[Mojojtm]

@Martin

Ok I found the mistake
Yes the grounding is missing on the Mojotone is not done underneath but from the turret board
In stewmac is underneath

Since I cannot dismount the board I was thunking to connect ground as per stewmac guide but rather than putting the ground wire jumper underneath the board I would solder a piece of wire from eyelet 4 to 9 and from 9 to 16

The eyelet 18 is already connected using yellow jumper to eyelet 4

[martin manning]

That should work. So the problem was neither 4 nor 9 were grounded? Mixing layouts is not a good idea unless you know exactly what you are doing.

[Mojojtm]

That should work. So the problem was neither 4 nor 9 were grounded? Mixing layouts is not a good idea unless you know exactly what you are doing.

I think problem is solved now eyelet 26 is 20V

eyelet 36 37 I get 169 V

eyelet 27 340 V

[martin manning]

That's better. Can you update this table with new voltages?

V3, V4 K eyelet 26 41,5V DC sch 20 (2x too high! Probably explains low voltages below)
B+1 and OT CT eyelet 27 291V DC sch 350
B+2, and 6V6 G2 eyelet 28 247V DC sch 320
B+3 eyelet 29 200V DC sch 245
V2b G eyelet 30 45V DC (ignore due to meter loading effect)
V2b K eyelet 31 97V DC sch 49
V2b A eyelet 32 50V DC sch 195
V2a A eyelet 33 200V DC sch 163
V2a K eyelet 35 ??? sch 1.3
V1b A 36 and 37 V1a A eyelet about 135V sch 128 125
V1a and V1b K 39 1.9V DC sch 2.0

[Mojojtm]

That's better. Can you update this table with new voltages?

V3, V4 K eyelet 26 41,5V DC sch 20 (2x too high! Probably explains low voltages below)
B+1 and OT CT eyelet 27 291V DC sch 350
B+2, and 6V6 G2 eyelet 28 247V DC sch 320
B+3 eyelet 29 200V DC 245 sch 245
V2b G eyelet 30 45V DC (ignore due to meter loading effect)
V2b K eyelet 31 97V DC sch 49
V2b A eyelet 32 50V DC sch 195
V2a A eyelet 33 200V DC sch 163
V2a K eyelet 35 ??? sch 1.3
V1b A 36 and 37 V1a A eyelet about 135V sch 128 125
V1a and V1b K 39 1.9V DC sch 2.0

I will by tomorrow thanks so far for the great help on this

[Mojojtm]

V3, V4 K eyelet 26 I get now 21,5V DC
B+1 and OT CT eyelet 27 I get now 347V DC
B+2, and 6V6 G2 eyelet 28 I get now 322V DC
B+3 eyelet 29 I get 255 V
V2b G eyelet 30 45V DC (ignore due to meter loading effect)
V2b K eyelet 31 I get now 44V DC
V2b A eyelet 32 I get now 208 V DC
V2a A eyelet 33 168V DC
V2a K eyelet 35 I now get 1.2V DC
V1b A 36 and 37 V1a A eyelet I get now 178 and 171 V DC
V1a and V1b K 39 1.3 V DC

I couldn't wait tomorrow

[martin manning]

V3, V4 K eyelet 26 I get now 21,5V DC 20.0
B+1 and OT CT eyelet 27 I get now 347V DC 350
B+2, and 6V6 G2 eyelet 28 I get now 322V DC 320
B+3 eyelet 29 I get 255 V 245
V2b G eyelet 30 45V DC (ignore due to meter loading effect)
V2b K eyelet 31 I get now 44V DC 45
V2b A eyelet 32 I get now 208 V DC 195
V2a A eyelet 33 168V DC 163
V2a K eyelet 35 I now get 1.2V DC 1.3
V1b A 36 and 37 V1a A eyelet I get now 178 and 171 V DC 128 125
V1a and V1b K 39 1.3 V DC 2

Schematic values are in red. Looks good. The differences on V1 are 12AX7 vs. 12AY7.

[Mojojtm]

V3, V4 K eyelet 26 I get now 21,5V DC 20.0
B+1 and OT CT eyelet 27 I get now 347V DC 350
B+2, and 6V6 G2 eyelet 28 I get now 322V DC 320
B+3 eyelet 29 I get 255 V 245
V2b G eyelet 30 45V DC (ignore due to meter loading effect)
V2b K eyelet 31 I get now 44V DC 45
V2b A eyelet 32 I get now 208 V DC 195
V2a A eyelet 33 168V DC 163
V2a K eyelet 35 I now get 1.2V DC 1.3
V1b A 36 and 37 V1a A eyelet I get now 178 and 171 V DC 128 125
V1a and V1b K 39 1.3 V DC 2

Schematic values are in red. Looks good. The differences on V1 are 12AX7 vs. 12AY7.

Bingo thanks I really learnt a lot today thanks to you guys all and Martin that helped the most,

I will test tomorrow with a cabinet and a guitar, I am planning to build a Combo for it since that is what I am doing the most

[martin manning]

You're welcome, and glad it's all sorted out. Always exciting when a new build is brought up.

[Mojojtm]

You're welcome, and glad it's all sorted out. Always exciting when a new build is brought up.

Hey Martin

I would have been glad if everything worked but despite all measurement are ok today I plugged in a speaker cabinet 8Ohm
I plugged in a guitar on Normal channel 1

There are 2 jacks for the cabinet jack OT is 8Ohm if I plug on the first jack I get buzzy noise no sound the other jack doesn't produce noise neither sound nothing at all mute (silent)

I think the issue is on OT wire connections, there are 2 wires a yellow and green 0-8Ohm I believe the green is the 8Ohm? See connection on the jack?

The primary channel of the OT is as follows

See photo for OT

[martin manning]

You're welcome, and glad it's all sorted out. Always exciting when a new build is brought up.

I would have been glad if everything worked but despite all measurement are ok today I plugged in a speaker cabinet 8Ohm
I plugged in a guitar on Normal channel 1

There are 2 jacks for the cabinet jack OT is 8Ohm if I plug on the first jack I get buzzy noise no sound the other jack doesn't produce noise neither sound nothing at all mute (silent)

I think the issue is on OT wire connections, there are 2 wires a yellow and green 0-8Ohm I believe the green is the 8Ohm? See connection on the jack?

The primary channel of the OT is as follows

The DC operating point is all good, but there is an issue somewhere along the signal path, a bad or missing connection most likely. Re the speaker jacks, the first one has a shorting contact, so you must have a plug in there to get any sound. The second jack is only used if two cables are needed (second speaker is plugged in). You may have to reverse the output transformer leads if they ate not connected with the right polarity for the feedback loop. By the way, did you have a load connected to the output when you were testing with the output tubes installed?

To solve the signal path issue you could start by checking visually and verifying continuity between connections from the input to the power tube grids.

[Mojojtm]

You asked:

By the way, did you have a load connected to the output when you were testing with the output tubes installed?

"

What do you mean exactly if I had a speak connected with guitar or if I had Current Bulb limiter?

I had nothing connected only the Amp power cord plugged straight into the outlet but I had no speaker or anything else attached I didn't test any sound that day when I reported back all the DC values

[martin manning]

Yes, a speaker or a load resistor should be connected to the output when you power up with the output tubes installed. Your output was shorted, so hopefully no harm was done. From the StewMac assembly guide:

STEP 95
Test the 6V6 power tubes
With the amp unplugged, install the
6V6 power tubes.
Plug the speaker into the left speaker
jack. The other jack is for an extension
cabinet; if you plug the internal speaker
into it, you’ll get no sound.

IMO the author didn't make that point strongly enough.

[Mojojtm]

Yes, a speaker or a load resistor should be connected to the output when you power up with the output tubes installed. Your output was shorted, so hopefully no harm was done. From the StewMac assembly guide:

STEP 95
Test the 6V6 power tubes
With the amp unplugged, install the
6V6 power tubes.
Plug the speaker into the left speaker
jack. The other jack is for an extension
cabinet; if you plug the internal speaker
into it, you’ll get no sound.

IMO the author didn't make that point strongly enough.

Thanks ok today the speaker cab was plugged in the left speaker jack and is there that I get bu=zzy noise no sound, so for shorted it means wires polarity is wrong shall I invert the cables?

[martin manning]

You don't know that for sure yet, but since you are not hearing a loud squeal (positive feedback) they may be correct as they are. Leave them as they are for now, and look for the break in the signal path.