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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Apr 12, 2013 5:33 pm
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Rock Star
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Location: Natural Bridge, Virginia
Final assembly and wiring of the chassis was completed today. :mrgreen:

I buzzed out all the wiring with my DMM and found no shorts or opens. Triple checked everything against the schematic and wiring diagram. As far as I can tell at this point, everything should be good to go.

Power up will take place tomorrow or Sunday. 8)

Here is the amp chassis from the front:

Image

Rear:

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Top:

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And the inside:

Image

I had to lengthen the yellow wire that connects V1's cathode bypass cap to the front panel switch because it was stretched tight once everything was assembled, but that was it.

Gonna be hard sleeping tonight. Like waiting for Santa Clause on Christmas morning. :lol: :lol: :lol: :lol:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Apr 12, 2013 6:12 pm
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Bill...Sure looks good. You got me laughing hard with the Christmas Morning Reference!

T2

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Apr 12, 2013 8:49 pm
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Rock Star
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Thanks. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Apr 12, 2013 10:47 pm
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Hey Bill, looks great! you sure got a lot done in your "down time". Bet it will sound amazing! Hows the healing process?

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 5:48 am
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Rock Star
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Bill, extremely well laid-out with excellent wire dressing & soldering. You'd make Lupe Lopez proud!

http://www.fenderforum.com/forum.html?d ... ber=590617

:D


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 6:39 am
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Rock Star
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Location: Natural Bridge, Virginia
BMW2002Ti wrote:
Bill, extremely well laid-out with excellent wire dressing & soldering. You'd make Lupe Lopez proud!

http://www.fenderforum.com/forum.html?d ... ber=590617

:D


Thanks. I have heard of Lupe. Maybe I should start sticking a piece of masking tape with my name on it in the amps I build. :lol: :lol: :lol:

Gonna be going "hot" with the amp in a few short minutes. 8)

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 7:27 am
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Just finished reading the entire thread.
On the edge of my seat !!!! :mrgreen:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 9:37 am
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Rock Star
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Location: Natural Bridge, Virginia
Power has been applied! Tubes not installed yet. I'm writing this near-real time as I do the initial checkout of things.

I got my first slight scare when I first connected everything up (speaker out to 8 ohm dummy load, power cord plugged in, bias probe sockets in place) and I flipped the power switch and then the standby switch. I thought I heard a slight crackle and noticed a wiff of something. I quickly shut power down and unplugged the power cord. A close exam of the circuit showed no evidence of anything burning. I decided the crackle was me moving around in my seat and the slight smell just the components having power applied for the first time.

So, I connected everything back up to measure the open circuit power supply voltages.

I got nothing. Nada. Zip. WTF?

Powered down, unplugged and flipped the amp over again. No AC out from the power transformer, except oddly the heater (the pilot light was lit). Checked the AC in at the outlet box and all was good. AC in to the amp looked good except even though I had 121 VAC across the hot lead and ground, there was nothing across the hot and common at the amp power socket. Hmmm. I checked to make sure I had the power socket wired correctly (I did), and reconnected the power cord to the amp. BINGO! I now had power across the hot and common leads at the power socket and 377 VAC from each red wire coming out of the PT to ground.

I then checked all the open circuit DC voltages directly at each power supply section as well as at each tube and found between 495 VDC and 500 VDC open circuit. Looking good.

Having an odd problem right now. When I install my bias probes, I am not reading any plate voltage on the power tubes.

DOH! I had the DMM set to the wrong voltage range. It's supposed to be set to the 2 VDC range because of the divider circuit in the probe socket that allows you to select between cathode current and plate voltage without changing scales.

Ok. Time to install the preamp tubes, one by one.

V1 installed: Heater lights. No explosions or flames.

V2 installed: Heater lights. No explosions or flames.

V3 installed: Heater lights. No explosions or flames.

Time for the power tubes. This is the big one. :lol:

V4/V5 installed: Heaters light. No explosions or flames.

Letting everything warm up for a few minutes before setting the power tube bias.

The initial bias has been set to 35 mA cathode current at 475 VDC plate voltage which works out to be about 33 mA plate current with an idle plate dissipation of 16 watts. Since the E34L is a 25 watt tube, that's 64% of maximum plate dissipation.

I used the 10K dropping resistor with the bias pot. The settings I have now are fairly close to the low end of the pot travel (high end goes over 150 mA cathode current :shock: ) so I think I will swap the 10K resistor for the 27K which should give me something more in the middle of the pot travel. But for right now, I'm going to let things stabilize and then plug into the speaker cab to see if it makes any sound. So far so good.

She's plugged into the speaker cab now, impedance selector set to 8 ohms, volume turned all the way down, tone and presence set to 12 noon. Bright switch off, V1 cathode bypass cap connected.

Ok. Looks like things have come to an end for right now. When the amp was turned on, I was greeted with a moderately loud squeal that did not change with the volume control. To quickly trouble shoot, I decided to pull tubes. When I pulled V3 (PI), the squeal stopped. I put V3 back in and the squeal returned. So I next pulled V2 and the squeal went away. Plugged V2 back in and the squeal returned. Finally pulled V1. The squeal did not go away, so it looks like something with V2 or the circuit between V2 and V3. Gonna try another 12AX7.

Tried another 12AX7 which made no difference, but I did discover the source of the noise. I turned all controls except for the volume to the max. There was no squeal although I do have a fair amount of hum. I then turned each control individually from max to min going from bass to mid to treble to presence. There was no squeal until I got to the presence control. Turning the presence control down from max to min resulted in the squeal showing up at about 1:00 to 2:00 o'clock on the dial. Looks like I need to investigate the presence circuit and probably reduce the amount of feedback. Also need to look for the source of the hum although the amp is just sitting out in the open right now.

Wish me luck. :D

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Last edited by bluesky636 on Sun Apr 14, 2013 12:00 pm, edited 2 times in total.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 9:43 am
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bluesky636 wrote:

Gonna be going "hot" with the amp in a few short minutes. 8)


Bill........Bill........Bill, are you there? Oh I hope he didn't electrocute himself. :lol:

Seriously though, your build is looking pretty righteous. You think you'll be able to provide some sound samples when done? Would love to hear what it sounds like when its all done. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 10:06 am
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Rock Star
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Location: Natural Bridge, Virginia
socal323 wrote:
bluesky636 wrote:

Gonna be going "hot" with the amp in a few short minutes. 8)


Bill........Bill........Bill, are you there? Oh I hope he didn't electrocute himself. :lol:

Seriously though, your build is looking pretty righteous. You think you'll be able to provide some sound samples when done? Would love to hear what it sounds like when its all done. :D


Look above your post. I was writing in near real time as I worked and you posted before I finally did. :lol:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 10:09 am
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Rock Star
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Location: Natural Bridge, Virginia
Gotta leave shortly to get my hair cut, then my wife and friends are going out to dinner. Might not get back to the amp until tonight or tomorrow. Stay tuned for the next installment. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 11:05 am
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What ??? Wait !!!! :shock:
Awe man I wanted an in depth review of sweet tones !

I tell my wife that my Piedmont is like each note is dipped in gold and hung in the air
She just looks at me and does this :roll:

Tone Junkies unite !

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 12:36 pm
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blues bondsman wrote:
What ??? Wait !!!! :shock:
Awe man I wanted an in depth review of sweet tones !

I tell my wife that my Piedmont is like each note is dipped in gold and hung in the air
She just looks at me and does this :roll:

Tone Junkies unite !


:lol: :lol: :lol: :lol:

Yeah, We've all seen that look. :lol:

Art


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 1:38 pm
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Rock Star
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Location: Natural Bridge, Virginia
Ok. I replaced the 10K bias circuit resistor with the 27K. Definitely makes it easier to bias the power tubes. :D

I also did a little re-dressing of the heater wires to get them a little further away from things as well as the negative feedback wire (the yellow wire now seen running from the impedance switch along the board edge to the 100K feedback resistor) to get it away from the speaker output leads. The wire from the presence pot was also moved a little to get it away from under the eyelet board along with the other pot wires. Finally, I moved the PT wires a little. All grounds were re-verified. I'll see what happens later tonight. I have some thoughts if there are still problems.

Yesterday's wiring:

Image

Today's re-dress:

Image

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Apr 13, 2013 3:45 pm
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Bill again I miss the whole thing now your almost done tremendous job you've done with this. You ever think about going into electronics :lol: That looks great and very happy the foots coming along


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