5e3 build problem

[pontiacpete]

I've made mistakes a number of times with wiring up the input jacks. There's a link to Jims page on Weber's site that shows it clearly.

http://members.shaw.ca/house-of-jim/...ack_wiring.jpg
there's also a PDF called input wiring #2 that's helpful

Also, do you have the 6V6's grounded to the chassis? I don't see this. I forgot this on a BF super build I did and got no sound.
good luck! I'm sure you'll find the problem.

pete

[classyelf]

cheers pontiac pete, ill check out me jacks further. No i didnt ground them, there was no mention of this in the diagram? how would one go about grounding his 6v6's? grounding a certain pin?

tris

[pontiacpete]

Im certainly no expert, but if you check out the 5e3 schematic

Fender Amp Heaven Schematics - Tweed Blackface Brownface Silverface Bassman Champ Deluxe Princeton Super Vibroverb Reissue

there's a layout there that shows th e ground wire on pin1 and 2(?). Ive never see the inside of an 5e3, because 2, I believe, is one of the heater,,, but could that also have explained hummm issue you were having. [maybe someone else could chime in here and correct me]. I would try pin 1 ........

[mbratch]

Maybe I just can't see it in the pics, but it doesn't look like your PT has a low voltage center tap. I see the HV center tap, but not the LV. If that's the case, then you need a virtual center tap on the pilot light, a 100 ohm resistor off of each pilot terminal to ground.

Without it, you'll get big time hum.

[classyelf]

thanks mbratch, this has already been brought to my attention by loudthud though and I rectified the problem this morning. this fixed the loud hum i was hearing but I still get no audio from the guitar itself.

tris

I'm now thinking of rewiring a few components to match the triode electronics diagram completely and forget the standby switch, as I presently have everything wired to the ceriatone diagram (as it appeared to contain the same components as my triode kit and has only a few differences in the wiring; and I wanted a standby switch). Anyone think this is a good idea?

[mbratch]

Sorry, missed that.

[classyelf]

Some new findings, I was just about to have a look at the amp, and maybe start rewiring it to the triode diagram as i described above and I thought I'd try it out once more before hand. Fired it up and i can now get some audio from the guitar! allbeit very quiet, but its a start, I have to have the volume knobs no less than completely cranked to get any volume, but the sound i get, though quiet, has the tone of a cranked deluxe! lol sounded nice, but I could still talk over it. It got a little louder the longer I played but not much (I guess this was probably the tubes reaching their optimum temperature).

So the amp works, and sounds almost completely hum free, even with my strat! - I'm just not gettin anywhere near the volume I should.

I still have no idea what to do next though!

tris

[mbratch]

If it's behaving differently with no changes, I'd look around for a poor connection somewhere.

Regardless, I'd suggest checking voltages. Although the old 5E3 schematic doesn't label any voltages, the re-issue schematic at the Fender website does. They won't match exactly, but you should be in roughly the same range (e.g., if their schematic says 350V and you read 80V, you know something's wrong, but you might have 310V or 400V depending, and that might be OK). I assume you have a meter.

[loudthud]

Start with the voltages at the plus side of the three filter caps and then the voltage at each of the preamp tubes and 6V6s. Post those and someone here will be able to figure out where the problem is. Ofcourse be carefull to avoid getting a shock.

[classyelf]

cool will do loudthud, should I measure the voltage across the component or from the plus side to ground? and which pins should be meaured?

[loudthud]

Measure all voltages to ground. As before, use a clip lead or put the black lead in a hole in the chassis so you don't have to touch the probe or the chassis while taking readings. With one hand behind your back touch the tip of the red probe to the point where you want to measure. Be careful not to let the probe slip and short anything. The power will be on and dangerous voltages will be present.

On the 12AY7 pins 1,2,3,6,7 and 8. 3 and 8 are supposed to be connected together but measuring them gives us a guarantee that nothing strange is going on. Try to touch the probe on the socket terminal and not the wire soldered to it. On the 12AX7 pins 1,3,6,7 and 8. Pin 7 on that tube won't give a valid reading. On the 6V6s 8,3,4 and 5.

Note that some pins will read zero volts. This doesn't mean there is no reading, it means the reading is zero volts. It is prefectly normal.

It's a good idea to use the ohm meter function to verify continunity of the wires that are on the back side of the eyelet board. With the power off and the caps discharged (see below) simply touch one probe to the terminal at each end of a wire that is supposed to connect them. You may have left a wire off, broken a wire or connected one end to the wrong terminal. You meter may not read zero ohms but it should be less than 1 ohm.

To discharge the caps, turn the power off, unplug the amp, connect one end of a clip lead to the chassis and the other end to pin 1 of the 12AY7. Monitor the voltage at pin 3 of a 6V6 until it is below about 25V. This makes the amp safe and prevents damage to your meter.

[tubeswell]

(FWIW a tip for when measuring voltages; I use meter leads with small insulated alligator clips, and I clip the -ve lead to the edge of the chassis and then the +ve lead to the various parts of the amp I want to measure, turning the amp on and off and plugging it in and unplugging it between each measurement. For the pre-amp tubes, you can connect the +ve clip on the main board to the plate side of the plate resistors, or the cathode side of the cathode resistors etc (instead of at the socket pins, if you want to avoid accidentally shorting the pins with the 'gator clips. (Its a faggin' hassle, but I learnt my lesson in a jolty kinda way once upon a time). JM2CW)

[classyelf]

thanks guys, right got some results but they all seem to be very low? - especially as loud thud was saying to discharge the capacitors to a voltage below 25V when i wasnt getting anything near that let alone above?.

12ay7
pin-
1 - 1v DC
2 - 0
3 - 0
6 - 0.3
7 - 0
8 - 0

12AX7
pin-
1 - 0.7
3 - 0
6 - 0.6
7 - 0
8 - 0

Both 6v6's

8 - 0
3 - 0.35
4 - 0.25
5 - 0

Now all of these readings were slowly and exponentially decreasing, rather like the opposite of the increase you see in voltage when charging a capacitor alone. The readng was still present and decreasing when the amp was turned off for each one aswell and wasn't affectted at all when I turned the amp back on.

Can someone confirm from the single instruction in the PT diagram in post 1 that i'm meant to feed the 240V (after its been through the fuse and AC switch) into the white wire, and connect the black/white wire to the nuetral wire of the mains cable and then connect the white/black wire to the black?

thankyou all for your wise help as usual, tris

[tubeswell]

Hi there tris

Yep the mains 'active' (or 'phase') wire goes to the bottom of the fuse holder first, and then from the top of the fuse holder to the main switch, and then to the matching end of the PT primary. The 'neutral' (or 'return') wire goes straight to the other end of the same PT primary winding. The mains earth wire gets bolted straight to the amp's chassis.

The PT secondaries go to the other parts of the amp.

One end of the HT (or high voltage AC) secondary winding goes one of the rectifier anodes (pin 4 or 6) and the other end of the HT winding goes to the corresponding rectifier pin. The Centre tap for this HT winding goes to a grounding point on the amp chassis.

The 5VAC (rectifier) secondary winding goes (one side each) to pins 2 and 8 of the rectifier tube. The B+ wire comes off pin 8 of the rectifier and goes to the +ve side of the first filter cap. (The Output Tranny primary winding centre tap goes to the same +ve end of the first filter cap, and the two outer-ends of this primary go (one each) to the plate pins of the 2 output tube sockets (pin 3). The -ve side of the first filter cap should connect to the same grounding point at the HT centre tap for quietest operation. The first filtering resistor goes between the +ve end of the first filter cap to the +ve end of the 2nd filter cap. The +ve end of the 2nd filter cap also goes to both of the output tube screen pins (pin 4 of each output tube socket). The ungrounded end of the (big) 250R 5W cathode resistor goes to both output tube socket cathode pins (pin 8 on each socket). Pin 5 of each output tube socket is the control grid pin, and one each connects (via a separate wire each) to the junction of relevant coupling cap (which comes of the plate of the Phase inverter) and the 220k grid bias resistor. (How far back into the pre-amp should I go? - check what is there so far)

The 6.3VAC (heater) secondary winding goes (one side each) to each side of the lamp, and then (one side each) to pins 2 and 7 of the output tube sockets, and the one side to pin 9 and the other side to pins 4-5 (which are connected together) of each pre-amp tube socket. The 100R artificial ground resistors go one side each from (say) the lamp, to a ground point on the chassis.

[loudthud]

Classyelf, I think you got mixed up. Voltage readings are taken with the power on and resistance checks are taken with the power off. The amp made a hum at one point so I think it must be getting some power.