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5E3 DIY problems...can you help?

4/26/2000 12:31 AM
rmike	5E3 DIY problems...can you help? Hi. This is my first DIY, so needless to say I haven't troubleshot an amp before. Its a tweed deluxe. I'll describe exactly what's happening--maybe it's diagnostic: Channel 1 is sounding great, but channel two (two input jacks on left) barely passes a signal (a little bit of guitar comes through), and it hums or fizzes and occasionally putts very quietly (motorboat?). The noise is affected by volume knob 2--i.e. it gets louder as you turn it up. Also, when in the working channel, hum/general noise can be introduced by turning up Volume 2 and to a lesser extent Tone. Is this normal? Anyway, when I touch the chassis or on/off switch while plugged into channel two, it quiets down some. Does this indicate some kind of ground problem localized to the second channel? I followed the layout pretty religiously and have checked all the joints before the volume pot. I'm wondering if something is grounding out the signal before the volume pot...or maybe a bad pot? Does anyone have any ideas? This is puzzling because it's only channel 2. mike

4/26/2000 12:31 AM

rmike

5E3 DIY problems...can you help?

Hi.
This is my first DIY, so needless to say I haven't troubleshot an amp before. Its a tweed deluxe. I'll describe exactly what's happening--maybe it's diagnostic:

Channel 1 is sounding great, but channel two (two input jacks on left) barely passes a signal (a little bit of guitar comes through), and it hums or fizzes and occasionally putts very quietly (motorboat?). The noise is affected by volume knob 2--i.e. it gets louder as you turn it up. Also, when in the working channel, hum/general noise can be introduced by turning up Volume 2 and to a lesser extent Tone. Is this normal? Anyway, when I touch the chassis or on/off switch while plugged into channel two, it quiets down some. Does this indicate some kind of ground problem localized to the second channel?

I followed the layout pretty religiously and have checked all the joints before the volume pot. I'm wondering if something is grounding out the signal before the volume pot...or maybe a bad pot?

Does anyone have any ideas? This is puzzling because it's only channel 2.

mike

4/26/2000 1:01 AM
Lee M.	I recently had a problem on my AX84 November. Tone controls weren't working right and were noisy indicating DC. Checked and rechecked my wiring and couldn't find anything wrong. Was getting ready to replace a tone stack cap and noticed that a wire going under the board seemed to be stuck on the cap lead poking thru the board. When I had put the board in place and clamped it down, the 1/8" or so lead sticking thru the board had pierced the insulation of that wire. I only mention this because sometimes all the wires can be in the right place and all the solder joints good and there's still a problem. Good luck. I built a 5E3 a year ago. It was my first DIY and it's a great little amp. Lee

4/26/2000 1:01 AM

Lee M.

I recently had a problem on my AX84 November. Tone controls weren't working right and were noisy indicating DC. Checked and rechecked my wiring and couldn't find anything wrong. Was getting ready to replace a tone stack cap and noticed that a wire going under the board seemed to be stuck on the cap lead poking thru the board. When I had put the board in place and clamped it down, the 1/8" or so lead sticking thru the board had pierced the insulation of that wire.

I only mention this because sometimes all the wires can be in the right place and all the solder joints good and there's still a problem.

Good luck. I built a 5E3 a year ago. It was my first DIY and it's a great little amp.

Lee

4/26/2000 3:19 AM
rmike	Update! Strangely enough, I was playing with the layout--specifically the lead coming off the plate of the 12AY7 comprising the first gain stage for the second channel (the problem channel) to volume 2. After a couple tries, I gave up. Then I came back an hour later, and, what do you know, it was fixed! Then, I tied that lead exactly where it was...plugged back in and everything worked...until I plugged into the #2 input of the second channel, at which point the symptoms all returned, in both jacks.... weird. Anyway, I'm now going to focus on the jacks, even though I rewired everything north of the first gain stage today already. mike

4/26/2000 3:19 AM

rmike

Update!

Strangely enough, I was playing with the layout--specifically the lead coming off the plate of the 12AY7 comprising the first gain stage for the second channel (the problem channel) to volume 2. After a couple tries, I gave up. Then I came back an hour later, and, what do you know, it was fixed! Then, I tied that lead exactly where it was...plugged back in and everything worked...until I plugged into the #2 input of the second channel, at which point the symptoms all returned, in both jacks.... weird.

Anyway, I'm now going to focus on the jacks, even though I rewired everything north of the first gain stage today already.

mike

4/26/2000 4:18 PM

Trace

quote:
"until I plugged into the #2 input of the second channel, at which point the symptoms all returned,
in both jacks.... weird."

It sounds like you could have a bad connection somewhere. I'd wiggle the wires with a test tone going into the amp. I'll bet you'll discover there's a faulty connection somewhere.

let us know how it goes!!!!
Trace

4/26/2000 4:32 PM
Troy	I'm glad you found the problem Mike! Did you use shielded cable from the inputs to the tube grids? This will help with noise! Sounds like you may have an oscillation creeping in from lead dress. Keep your grid wires as short as you can and lay them perpendicular to the plate wires. What did you end up using for trannies? Troy

4/26/2000 5:23 PM
rmike	Thanks for the advice, Trace! I'll take a look and use my plastic toothbrush "chopstick" probe to test things out. Unfortunately with band practice tonight and a show tomorrow and friday, it may not be till this weekend. Troy: I used a Fender repro BF deluxe OT and a Hammond 270EX PT. I measured -34 or -35 mA one of the 6V6s (from pin 8 of the rectifier to pin 3 of the 6V6). Running NOS Mazda 6V6s and two junk 12ax7s I had lying around (on an aside--I've already swapped tubes so the problems not correlated to this). I've got a boatload of 12A.. tubes to try, including AV7, AY7, AT7, AU7, and of course AX7. Will get back with details once I get the amp running perfectly, in a cabinet, and I get it out of my apartment to someplace I can crank it up! thanks for the interest guys. mike

4/26/2000 5:23 PM

rmike

Thanks for the advice, Trace! I'll take a look and use my plastic toothbrush "chopstick" probe to test things out. Unfortunately with band practice tonight and a show tomorrow and friday, it may not be till this weekend.

Troy:

I used a Fender repro BF deluxe OT and a Hammond 270EX PT. I measured -34 or -35 mA one of the 6V6s (from pin 8 of the rectifier to pin 3 of the 6V6). Running NOS Mazda 6V6s and two junk 12ax7s I had lying around (on an aside--I've already swapped tubes so the problems not correlated to this). I've got a boatload of 12A.. tubes to try, including AV7, AY7, AT7, AU7, and of course AX7.

Will get back with details once I get the amp running perfectly, in a cabinet, and I get it out of my apartment to someplace I can crank it up!

thanks for the interest guys.
mike

4/26/2000 5:59 PM

Rebel420

quote:
"I used a Fender repro BF deluxe OT and a Hammond 270EX PT. I measured -34 or -35 mA one of the 6V6s (from pin 8 of the rectifier to pin 3 of the 6V6). "

Those woud be my personal pick for iron in this amp

??? for ya... is your circuit completely stock, or did you modify it in some way? Also, IIRC, you said the amp goes dead when using channel 2, does that change with different settings of channel 1's volume? I don't have the amp in front of me, but if you wire the volume-1 pot incorrectly, when you turn it donw, you will in effect shunt channel 2 to ground before the driver stage. I know I may be talking elementary stuff, and may be overlooking something else simple (like a miwired jack etc), but just a suggestion *grin*

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