Powered up my build , found a couple of cold heater joints , 2 bad 12ax`s . But did get some nice tone , a little on the feeble side though as far as output , sounds like a 5 watt amp , very quiet , starts to break up/clip at about 8+ on the volume .
Voltages measured
B+1 = 343vdc
B+2 = 331vdc
B+3 = 258vdc
B+4 = 224vdc
B+5 = 220vdc
It looks like B+5 does not have very much current flow/load. Speakers used were some old 16ohm Celestions wired in series - I`ll change these to parallel for next test .
Macshaft wrote:Speakers used were some old 16ohm Celestions wired in series - I`ll change these to parallel for next test .
Any Ideas as to the low volume output ??
Not sure how many speakers you have, but even two 16 ohm speakers in series would be a net 32 ohms to the amp. That may be most of your volume problem right there. Time to rewire the speakers for sure.
Rewired the speakers to 8 ohm , then found no connection at V3 pin 6 , must have fallen asleep whilst finishing main board . lots of gain now , although I had the Kids going to bed so I couldn`t crank it up too much . Nice tone , but it starts to break up really early(3-4) and is fairly noisy (AC hum) I`ll work on rerouting some wiring to minimize hum . Wondering if my higher voltages are causing the early breakup??
Re-checked my voltages B+1 = 346 B+2 = 334 B+3 = 258 B+4 = 224 B+5 = 220vdc . At about "5" it really breaks up alot , and if pushed past 6-7 finally just cuts out(crackly fade to nothing) . never really gets much additional gain once past about "4" either . Increasing Cut control really adds a harsh brittle tone . At low volumes the tone is nice , but the bass and treble pots are at only 1 - 2 . cut at 1 or less .
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OK, I'll be the first to say it. Please don't take this the wrong way but the amp is a bit of a mess on the inside.
Part of the whole TW design is how the wires were routed (more so on the Exp & LP) and the effect they have on the amp. Not sure your grounding is all that neat either but I could be wrong. A lot of the crossed wires may not be the best layout for this amp.
The board is no doubt part of the problem. You're soldering to thin copper which may contribute to bad lead dress which can contribute to lots of problems.
The tube layout is a bit funky as well. Take a look at some of the better examples here and you should be in better shape for your next build. This odd layout makes it more difficult to help quell the problems you have indicated.
fzfwyv wrote:The tube layout is a bit funky as well. Take a look at some of the better examples here and you should be in better shape for your next build. This odd layout makes it more difficult to help quell the problems you have indicated.
Yeah, that's what I was wondering about in the other thread...
Glad you are making some progress on this... I really love the Rocket amp sound. I've built two iterations of the Rocket now and my voltages are are quite a bit lower than yours... For my 2nd iteration I used all VOX replacement transformers, JJ Can Caps, and the UR12 Variable Voltage Regulator (VVR2)... see the post at http://ampgarage.com/forum/viewtopic.php?t=6405
AllynMey has a Rocket build that I believe is supposed to be dead on to an original, maybe he will post his voltages for us to compare to. At this time I don't really know where everything out to settle in for sure, but I am quite pleased with the sounds I get.
I am thinking that the bias is way too hot with the voltages being too high , I am going to install 2 x 1 ohm resistors on R17 R18 so I can read the bias current , is this correct ??? . And I am also going to try a 1K 25W in series with the choke to try to pull down B+ a little more . I re-routed some more wiring and found a little less noise was the result as well as a little more gain . Still totally cuts out above 6-7 vol. and after playing for about a half hour it would cut out at only about 3-4 on the volume . Power tubes seem pretty hot to me , but I have never used EL84`s before
Macshaft wrote: I am thinking that the bias is way too hot with the voltages being too high , I am going to install 2 x 1 ohm resistors on R17 R18 so I can read the bias current , is this correct ???
Macshaft wrote: I am thinking that the bias is way too hot with the voltages being too high , I am going to install 2 x 1 ohm resistors on R17 R18 so I can read the bias current , is this correct ???
Aren't you running cathode bias?
Hey , I`m a really dumb newbie , the circuit is rocket A0 and yes it is Cathode bias , will it serve no purpose to check ?? My Rocket build parts list shows R17 R18 as bias resistors , sorry , I guess i am not to up on my tube theory .
Macshaft wrote: I am thinking that the bias is way too hot with the voltages being too high , I am going to install 2 x 1 ohm resistors on R17 R18 so I can read the bias current , is this correct ???
Aren't you running cathode bias?
Hey , I`m a really dumb newbie , the circuit is rocket A0 and yes it is Cathode bias , will it serve no purpose to check ?? My Rocket build parts list shows R17 R18 as bias resistors , sorry , I guess i am not to up on my tube theory .
You can still read current across those resistors. That is, you can read the voltage drop across those resistors and calculate the current.
If your amp is running too hot, you can change the value of the cathode resistors to drop the current. I cannot read what you have in there now - did you use the specified value or something lower?
Powered up my build , found a couple of cold heater joints , 2 bad 12ax`s . But did get some nice tone , a little on the feeble side though as far as output , sounds like a 5 watt amp , very quiet , starts to break up/clip at about 8+ on the volume . 
Re-checked my voltages B+1 = 346 B+2 = 334 B+3 = 258 B+4 = 224 B+5 = 220vdc . At about "5" it really breaks up alot , and if pushed past 6-7 finally just cuts out(crackly fade to nothing) . never really gets much additional gain once past about "4" either . Increasing Cut control really adds a harsh brittle tone . At low volumes the tone is nice , but the bass and treble pots are at only 1 - 2 . cut at 1 or less . 
