Random Acts of Stupidity

General discussion area for tube amps.

Moderators: pompeiisneaks, Colossal

Post Reply
Garthhog
Posts: 67
Joined: Tue Oct 14, 2014 9:03 pm
Location: McKinney, Texas
Contact:

Random Acts of Stupidity

Post by Garthhog »

Hi. my name is Ryan, and I'm an idiot.

I have been struggling with a distortion problem with an amp I have been trying to finish for a while. Ugly distortion at all volume levels, volume output was low. I suspected that I had damaged the output transformer because I had ran a rather strong signal through the amp without a resistive load or speaker cabinet attached, but wanted to go over everything else before declaring it to be so. My last step was to measure resistance across the primaries and THAT is where I found the funk... Turns out I wired the primary wrong and it was running like a Class A amp with power tubes that were pushing and pulling. I made a STUPID assumption about a wire color and should have known better. I wasted an EMBARRASSINGLY long amount of time on this.

So, any other builders want to step up to this mic? Just to help a bit, it starts like this... "Hi. my name is ***, and I'm an idiot."
Ryan Brown
Brown Amplification LLC
User avatar
jjman
Posts: 753
Joined: Sat Oct 06, 2007 2:33 pm
Location: Central NJ USA

Re: Random Acts of Stupidity

Post by jjman »

When I built my 1st amp it was about 23 years ago. It’s a 5F1 Champ circuit and there was only one problem. Huge hum that increased with the volume control. I had read about proper grounding but this chassis is so small I didn’t pay too much attention. And there were no websites related to amps back then, only usenet. After about 6 months it came to me one day. I had the CT of the HV winding connected directly to the safety ground lead of the power cord and floating via a wire nut. Then a jumper wire from the nut going to the far side of the chassis. Ground is ground right? I moved the CT to the filter ground area and no more hum. I had no idea that the CT flows current and thought is was merely a reference, like a heater CT.
If it says "Vintage" on it, -it isn't.
User avatar
pompeiisneaks
Site Admin
Posts: 4222
Joined: Sat Jan 14, 2017 4:36 pm
Location: Washington State, USA
Contact:

Re: Random Acts of Stupidity

Post by pompeiisneaks »

I've done too many to count, but probably the simplest was poorly wired input jacks where the connection to ground was close to the input resistors and touched them, shorting input to ground, took me hours of poking around to figure out why nothing came out. finally noticed it, and resoldered things much more 'solid' and away from one another and bingo, good to go :D
tUber Nerd!
User avatar
Winder
Posts: 201
Joined: Sat Nov 29, 2008 11:12 pm

Re: Random Acts of Stupidity

Post by Winder »

Traced a strange "swirly/fizzy" finish to notes on my Express for a couple of years, tweaking this ... changing that off and on/ever now and again. Always tested with the same Les Paul. Jacked a Double Cut in one day (single volume/tone) and the "anomaly" wasn't there. Turned out to be an issue with the wiring in the Les Paul. I've since returned the Wreck to stock. :oops:

Outside of amp building, as a young AF Lt. I once left the shorting clamps on the capacitor banks of a railgun power supply capable of dumping about 250,000 Amps at 500-700 Volts at a 1Hz firing rate. Had cameras rolling in the gun bay. Last thing I said to the machinist prior to hitting the fire button was ... "what could go wrong?" Building evac ... fire department ... yada yada ... :shock:

I had to clean and rebuild the cap banks. :lol:
User avatar
xtian
Posts: 6990
Joined: Mon Apr 19, 2010 8:15 pm
Location: NorCal
Contact:

Re: Random Acts of Stupidity

Post by xtian »

Oh, heck, I’ve shorted more than one solid state thingy by probing the wrong thing. FZZT! Toast.
I build and repair tube amps. http://amps.monkeymatic.com
ChopSauce
Posts: 1038
Joined: Wed Mar 15, 2017 12:08 pm
Location: So Paris, France

Re: Random Acts of Stupidity

Post by ChopSauce »

I've done too many too, especially considering I've built very few amps :wink:

Amazingly, it seems there's a part of who always witnesses my mistakes and points me (almost) straight to the trouble. I never built amps nearly as complex as a Dumble clone, though -
User avatar
norburybrook
Posts: 3290
Joined: Mon Jan 06, 2014 12:47 am
Location: London
Contact:

Re: Random Acts of Stupidity

Post by norburybrook »

Garthhog wrote: Sun Feb 18, 2018 9:21 pm Hi. my name is Ryan, and I'm an idiot.

I have been struggling with a distortion problem with an amp I have been trying to finish for a while. Ugly distortion at all volume levels, volume output was low. I suspected that I had damaged the output transformer because I had ran a rather strong signal through the amp without a resistive load or speaker cabinet attached, but wanted to go over everything else before declaring it to be so. My last step was to measure resistance across the primaries and THAT is where I found the funk... Turns out I wired the primary wrong and it was running like a Class A amp with power tubes that were pushing and pulling. I made a STUPID assumption about a wire color and should have known better. I wasted an EMBARRASSINGLY long amount of time on this.

So, any other builders want to step up to this mic? Just to help a bit, it starts like this... "Hi. my name is ***, and I'm an idiot."
I did exactly the same thing on my second ever build a JTM 45.

MC
rangdipkin
Posts: 24
Joined: Fri Feb 17, 2017 11:23 pm

Re: Random Acts of Stupidity

Post by rangdipkin »

Built one too many cathode biased amps, then built a fixed bias amp and wired the bias cap in backwards (negative pole to ground). She blew up, I saw my mistake and replaced it... and installed it backwards again.
User avatar
roberto
Posts: 1841
Joined: Tue Nov 27, 2007 4:45 pm
Location: Italy

Re: Random Acts of Stupidity

Post by roberto »

It's not my act, it's not on the electric/onic field, but worth to be read.

Today I've been contacted by the CEO telling me to verify what the technical department was doing about an air flowmeter.
The supplier (a worldwide leader on pneumatics) was telling to our techs that the flowmeter could only read liters per minute, and that caused internal troubles on the conversion to Nl/min. So I had to intervene.

Reading the manual, page 7, it says clearly "the flow of air flows on an hot surface". So the only thing that it can see is clearly the mass flow of air, not the flow nor the pressure nor anything else: I know the specific heat of the air and the heating power connected to the surface. Then there are three ways to show the values in liters per seconds: two are not standards I know, one is 20 Celsius degrees and 1 bar, so the Normal liters per minutes we are looking for.

Well, both the seller from the well known company and our technicians were saying the flowmeter can just see liters per minute, and not Normal liters per minute. No way to explain them how it's working and what it really can do.

I even tried to explain them that Normal liters doesn't give a volume, but a mass of gas, but they started saying that liters are liters, whatever letter you put in front if it. Well, white flag. Just call me when the accountimg will ask why we needed to add a pressure and temperature transmitter together with that massic flow meter. :roll: :lol:
User avatar
TUBEDUDE
Posts: 1656
Joined: Thu Jan 04, 2007 5:23 pm
Location: Mastersville

Re: Random Acts of Stupidity

Post by TUBEDUDE »

Hi my name is charles and I'm an idiot. I had a preamp tube string to wire up and somehow convinced myself to do the heaters last. Well it was about 2 AM and i wired all of them mostly all the way when it became apparent i was off one pin on all of them.
Now i always do the heaters first and never after 2300.
Tube junkie that aspires to become a tri-state bidirectional buss driver.
Post Reply