Thanks Tom and Tony
will check feedback/ presence ASAP.
BTW I never hook up the wire from the speaker jack to the NFB resistor until after install and bias up the output tubes and make sure the amp is functioning as it should.I'll usually connect it with an alligator clip to check it..This way if say your primary's are reversed your not trying to bias up your output tubes with + feedback taking place..Sometimes I like to play the amp first to see how it responds with no negative feedback before I decide on the exact value for the NFB resistor..
very cool tip Tony
every ones time is very much appreciated
Thanks
Darin
I killed 2 new F&T 200uf 300V, one actually popped...
replaced power tubes and caps(Illinois) and clicking stopped.
Wondering if a suspect power tube can cause caps to blow...?
it's up and running..voltages are good,PI is a little high 315V, will try and get this down to 300 or so...
but I still have the farting sound when I dig into notes...could this be preamp caps?
I might replace all preamp caps(F&T) with another brand.
This HRM style build is really playing hard to get...
Darin, glad you fixed your main issue, getting good at troubleshooting, soon we'll have a lot to learn from you!
On the farting issue, perhaps it would be good (so the guys can give you a better lead) if you specify if the problem arises playing clean or in OD. A small recording would do good too.
alvarezh wrote:Darin, glad you fixed your main issue, getting good at troubleshooting, soon we'll have a lot to learn from you!
On the farting issue, perhaps it would be good (so the guys can give you a better lead) if you specify if the problem arises playing clean or in OD. A small recording would do good too.
All the best.
Thanks alvarezh
not sure blowing things up counts as troubleshooting...
but I have learned so much from this forum, to try and learn
something new and help someone everyday is advice passed to me by my father and hopefully goes on with my boys...
As far as the farting...it's both in clean and OD, I can play soft and it's fine
but digging in on any note produces a loud farting clip sound
I will try and record a sample if possible
Thanks Tom
I have 5.6K's on the stoppers I may try some 6.2's
I might drop the PI caps to .05's
and I may up the NFB value of 4.7K to 6-10K
I hope these things can take me further towards a fix
A couple of other things to check - a faulty FX loop jack can cause the type of symptom you are hearing, can sound fine at low volumes but when you turn the amp up or dig in it will crackle and fart. Easiest thing to try is put a short cable in the loop and see if the problem goes away. If so, clean out the between the jack contacts with chemical cleaner or fine grit sandpaper.
A bad/cold solder joint can also cause similar symptoms, try just retouching all your joints or at least do a thorough inspection with a magnifier.
I'd try all the above before making any major changes to the amp or changing component values.
Bill www.sebagosound.com
wjdunham wrote:A couple of other things to check - a faulty FX loop jack can cause the type of symptom you are hearing, can sound fine at low volumes but when you turn the amp up or dig in it will crackle and fart. Easiest thing to try is put a short cable in the loop and see if the problem goes away. If so, clean out the between the jack contacts with chemical cleaner or fine grit sandpaper.
A bad/cold solder joint can also cause similar symptoms, try just retouching all your joints or at least do a thorough inspection with a magnifier.
I'd try all the above before making any major changes to the amp or changing component values.
Bill www.sebagosound.com
dcribbs1412 wrote:
Thanks Bill
I'll assume cable from the in to out?
Darin
Yes, that's correct. Since that seems to work, time to inspect and touch up those solder joints. I some times use a wooden stick to wiggle wires and components, this can expose a bad solder joint if applying pressure causes a crackle. Some times just pushing down on the circuit board can expose a bad solder joint in an eyelet.
Make sure to keep one hand in your pocket, I use a wooden chopstick as my prodding instrument. If you're not comfortable poking around in a live amp please don't try this, as the safety issues are many.
Bill www.sebagosound.com
dcribbs1412 wrote:
Thanks Bill
I'll assume cable from the in to out?
Darin
Yes, that's correct. Since that seems to work, time to inspect and touch up those solder joints. I some times use a wooden stick to wiggle wires and components, this can expose a bad solder joint if applying pressure causes a crackle. Some times just pushing down on the circuit board can expose a bad solder joint in an eyelet.
Make sure to keep one hand in your pocket, I use a wooden chopstick as my prodding instrument. If you're not comfortable poking around in a live amp please don't try this, as the safety issues are many.
Bill www.sebagosound.com
when I played it with the cable in the loop I still have the farting/cutting out
would this still be caused by the jacks?
BTW I touched up the joints also.
No, if it still happened with the cable in the loop then it's definitely not the jack contacts. Having touched up the joints, then I guess it's time for the real debug to start. Checking the bias of all the tubes is a good start. Can you post the plate and cathode values of all your preamp tubes. Should be in the ~200V+-20V range for the plates, and ~1.5V+-.5V for the cathodes.
Bill
Darin
Any way you can slave another pre amp into the output section of the amp?..This would help to narrow the source of the problem down to either pre amp or output..If you even have a loop handy you can use the return amp to drive the output section if you don't have another amp w/loop..
Get back with your results.. BTW I highly recommend working under a magnifying glass w/light as much as possible especially on the pre amp tube sockets and preamp switches..I pretty much use the glass through the entire build now and rarely have any soldering/connection issues anymore!!..Let the real fun begin!!..
Good Luck!!
Tony
" The psychics on my bench is the same as Dumble'"
