5E3 Testing and troubleshooting

[Mojojtm]

Anyway I have installed the preamp tubes but...no shorts no smoke all good amp was on for about 10 mins.

The measurement at eyelet 39 was around 1.6 V DC when on the guide says it should be around 2.1 V DC

at eyelet 37 I got some strange value but I have to double check tomorrow as I stopped there , and I read 450 V DC when the guide says I should read 160V DC?

I am not 100% sure about that measurement so tomorrow I will confirm but if that would be correct what it means?

[martin manning]

The measurement at eyelet 39 was around 1.6 V DC when on the guide says it should be around 2.1 V DC

Likely that's the 12AX7 vs. 12AY7

at eyelet 37 I got some strange value but I have to double check tomorrow as I stopped there , and I read 450 V DC when the guide says I should read 160V DC?

Check that again. If 39 (cathodes, pins 3 and 8) are at 1.6, 37 and 36 (anodes, pins 1 and 6) should be close to 160. You're much better off referencing the socket pin numbers or the electrode names so people will know what you're talking about without reference to the StewMac diagram.

[Mojojtm]

I thought very strange that so far went all good, too good to be true.

I remeasured eyelet 39 1.6V DC
I remeasure eyelet 37 and I read 451V DC No Good!!!!!

I check the layout and there is a mistake, V1 socket is missing a jumper between pin 3 to 8 that must be probably the issue so going to rectify this part , (distractions while building the kit)

[Mojojtm]

Ok Martin

So I have added the jumper on V1 between pin 3 and 8

Now I can read eyelet 39 2.1 V DC this is correct spot on as per guide previously was 1.6 V dC

On 37 and 36 (anodes, pins 1 and 6) I can now read 274 V DC still too high?

I have rechecked all connections all seems good this time, the preamp tubes lit normal no smoke no arcing

Could be because I am using on both V1 and V2 the same 12ax7 ??

Also to take in consideration during this preamp testing only 5Y3 and the 2x 12ax7 are plugged in, the 2x 6V6 are not in, may that cause also this?

[sluckey]

Also to take in consideration during this preamp testing only 5Y3 and the 2x 12ax7 are plugged in, the 2x 6V6 are not in, may that cause also this?

It's time to plug in the 6V6s. Voltages will drop considerably when you do so.

[Mojojtm]

Also to take in consideration during this preamp testing only 5Y3 and the 2x 12ax7 are plugged in, the 2x 6V6 are not in, may that cause also this?

It's time to plug in the 6V6s. Voltages will drop considerably when you do so.

Thanks I really do appreciate your confirmation and reply.

I will proceed, I just feel unsecure, got some knowledge in my head but not enough manual and practical experience to come to a conclusion on my own

[Mojojtm]

ok I have added all Tube in

Now on eyelet 37 and 36 (anodes, pins 1 and 6) I read a much lower 137V (Should be 160) with 10% tolerability this is now maybe little too low????

eyelet 39 now reads around between 1.95 V DC this is more or less ok should be 2.1V DC it was like that without 6V6 in.

eyelet 28 I read around 295 V DC (according to guide should be 340V DC) , this is a little too low, maybe?

The Amp was on for 5 mins no arcing, no smoke or explosion, all tubes light lit, 5Y3 and 6V6s are getting very hot I think is expected

Thanks

[martin manning]

So I have added the jumper on V1 between pin 3 and 8

Now I can read eyelet 39 2.1 V DC this is correct spot on as per guide previously was 1.6 V dC

On 37 and 36 (anodes, pins 1 and 6) I can now read 274 V DC still too high?

Could be because I am using on both V1 and V2 the same 12ax7 ??

Also to take in consideration during this preamp testing only 5Y3 and the 2x 12ax7 are plugged in, the 2x 6V6 are not in, may that cause also this?

As you observed, the preamp voltages aren't determined until all the tubes are installed. The load current from the power tubes is many times what the preamp draws so they will strongly affect the preamp voltages by reducing the B+. Power stage voltages are not much affected by the preamp tubes, which is one of the reasons I prefer to start with the power tubes, as mentioned above. A 12AX7 will have different voltages vs. a 12AY7 at the same supply voltage, so don't worry about that. You should be getting sound now. I suggest getting a complete set of voltage measurements from all of the eyelets on the tube edge of the board and list them here.

[Mojojtm]

Sure let me do that and get back to you in here

[Mojojtm]

eyelet 26 41,5V DC
eyelet 27 291V DC
eyelet 28 247V DC
eyelet 29 200V DC
eyelet 30 45V DC
eyelet 31 97V DC
eyelet 32 50V DC
eyelet 33 200V DC
36 and 37 eyelet about 135V
39 1.9V DC

On some of the eyelet not sure why it depends how the probe tip touches the turret there is a variation maybe because I move the tip is difficult to get a steady number i notice this a bit more on eyelet 30 31 32 i think it depends on how I touch the turret using the probe tip , because of the wires on the way and the angles

Hope it all make sense the Amp has been now on for 15 mins no smoke all good only 5Y3 and 6V6 producing heat and that is expected I believe

[martin manning]

eyelet 26 41,5V DC
eyelet 27 291V DC
eyelet 28 247V DC
eyelet 29 200V DC
eyelet 30 45V DC
eyelet 31 97V DC
eyelet 32 50V DC
eyelet 33 200V DC
36 and 37 eyelet about 135V
39 1.9V DC

On some of the eyelet not sure why it depends how the probe tip touches the turret there is a variation maybe because I move the tip is difficult to get a steady number i notice this a bit more on eyelet 30 31 32 i think it depends on how I touch the turret using the probe tip , because of the wires on the way and the angles

Maybe flux on the eyelet is acting as an insulator.

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

You need to figure out why your 6V6's are running so hot. They will not last long like that... Are the plates glowing red? Is pin 5 at 0V? Is eyelet 18 (junction of 220k's) grounded?

[Mojojtm]

eyelet 26 41,5V DC
eyelet 27 291V DC
eyelet 28 247V DC
eyelet 29 200V DC
eyelet 30 45V DC
eyelet 31 97V DC
eyelet 32 50V DC
eyelet 33 200V DC
36 and 37 eyelet about 135V
39 1.9V DC

On some of the eyelet not sure why it depends how the probe tip touches the turret there is a variation maybe because I move the tip is difficult to get a steady number i notice this a bit more on eyelet 30 31 32 i think it depends on how I touch the turret using the probe tip , because of the wires on the way and the angles

Maybe flux on the eyelet is acting as an insulator.

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

You need to figure out why your 6V6's are running so hot. They will not last long like that... Are the plates glowing red? Is pin 5 at 0V? Is eyelet 18 (junction of 220k's) grounded?

According to the schematic eyelet 18 is not grounded, if I check pin 5 on any of the 2 6V6 there are some voltage around 40V pin 5 has a resistor, it is between pin 5 pin 6 of 6V6

[martin manning]

See jumper wire from 18 to 4.

[Mojojtm]

See jumper wire from 18 to 4.

Ok this is funny I actually followed the Mojotone when assembling the components on the board and there is no grounding jumper I will show you in a minute I cannot longer make screenshots for some odd reason

[martin manning]

Eyelet 18 must be at 0V one way or another.