Ok the 5UA is in now - any my bias settings are off again. Where it was 73ma, now it's 54. I'm thinking I may want to have a convenient way of setting/measuring the bias.
I may have lost a little volume too... so hard to tell without doing a back to back measurement with a sound meter.
Happy 4th everyone !!!
I may have lost a little volume too... so hard to tell without doing a back to back measurement with a sound meter.
Happy 4th everyone !!!
oldmanStrat said:
I tried a 5U4 in my Simple SE. In the end, I went back to the 5AR4 mostly because I valued the slow startup. Here's my thread where I asked the question:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=129396
Here it is, just about finished. Believe it or not I haven't taken the finger prints off of the aluminum yet.
The only things not done are the sheet metal screws to hold the top down, and the motor run cap - but this amp sounds so good - and Lenny K is telling me so right now - that I'm not sure I need it.
Have to say the handles worked out great! so much easier to move it around.
The only things not done are the sheet metal screws to hold the top down, and the motor run cap - but this amp sounds so good - and Lenny K is telling me so right now - that I'm not sure I need it.
Have to say the handles worked out great! so much easier to move it around.
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PaulyT said:Very pretty! Your metal working skills are *way* beyond mine... my goal is simply to not have too many obvious dings and scratches around the holes.
It's mostly shiny
If I were to do it again, I'd turn the box upside down. If you want clean holes on top - put the cutting side of the punch on top and the wrench on the bottom. And keep the plastic on until the last hole has been cut. And besides, I purposely didn't show you the snafu's. Most are on the back (a good place to start) and the inside (but who cares?).I actually like my first build better - it has such a satisfying thunk when I turn on the power. And the metal box certainly get's warm! We're talking even the volume pot is a little warm to the touch...
But there is something about this amp...
looks like I spoke too soon...
after a few hours of operation last night the amp just quit. No AC light and the fuse was blown.
checked the board, nothing was burnt or any obvious damage. Ohmed out a few of the obvious candidates and everything looked good. I pulled all of the tubes - and blew another fuse.
I'm pretty sure its the power xfmr It looks like just plugging in the power cord is enough to blow the fuse (with the switch off). 
I'll confirm the diagnosis tonight.
after a few hours of operation last night the amp just quit. No AC light and the fuse was blown.
checked the board, nothing was burnt or any obvious damage. Ohmed out a few of the obvious candidates and everything looked good. I pulled all of the tubes - and blew another fuse.
I'm pretty sure its the power xfmr
It looks like just plugging in the power cord is enough to blow the fuse (with the switch off). I'll confirm the diagnosis tonight.
I hope it is not your transformer, that would be a bummer. If there is a short with the switch turned off, it might be your switch, your power socket, or your wiring in between these is shorting. If the switch is working and it is switched off, you should not be getting any power to your transformer - so it should not be the culprit.
Good luck finding the problem!
Chris
Good luck finding the problem!
Chris
The fuse is integrated into the IEC socket on the hot side. The switch is definitely functioning correctly.
Remember this was all working for days before it went poof.
The last experiment to rule out some odd issue with my wiring was to clip one of the primary xfmr leads off of the IEC socket.
With a new fuse - plugged in the power chord and I was able to see 120vac again. Flipped the power switch and the light came on. The light is part of the switch...
I'm going to confirm the fuse blowing with just the cord being pugged in... the more I think about it the less likely that is the case. If thats not it I'll be disconnecting the AC secondaries one at a time until it stops popping fuses. Hopefully I'll have enough.
Remember this was all working for days before it went poof.
The last experiment to rule out some odd issue with my wiring was to clip one of the primary xfmr leads off of the IEC socket.
With a new fuse - plugged in the power chord and I was able to see 120vac again. Flipped the power switch and the light came on. The light is part of the switch...
I'm going to confirm the fuse blowing with just the cord being pugged in... the more I think about it the less likely that is the case. If thats not it I'll be disconnecting the AC secondaries one at a time until it stops popping fuses. Hopefully I'll have enough.
Ty_Bower said:
I agree, only I can't find anything wrong with the PCB. All the tubes are out, and I've checked all the diodes. I looked for a short on the input and output of the heater reg - nada. No short between B+ and B- or B- to gnd. None of the windings without center taps are shorted to gnd. The primary isn't shorted to gnd either...
The fuse popping when I plugged in the power cord was a mistake. It was early and I'm guessing the coffee hadn't kicked in yet.
At this point all I can think of it the xfmr. Time to sacrifice some fuses...
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