Hi,
I have DIYed 2 x EL34PP and both Monoblocs are having problems...
Monoblock 1 - Everything is ok except for sound being soft when power up. All voltage are consistent except for one going to output trans. The plate voltage to one of the optx is around 380v. Whereas the rest of the AN2, G1, G2 and CT are all around 430v. What could be the cause? Tried swopping in other tubes but its still the same. Have almost resoldered all joints but still cannot catch the problem.
Monoblock 2 - Getting a "zzzzzz" sound when power on. This is not the wrong phase hum as I have tried swopping the grids and plate from the power tube to the optx. All voltages look ok as in consistent. I can perpetually feel the power tranny producing the "zzzzz" sound and I am pretty sure thats the same sound I hear on the speaker. Have changed the wires to the power tranny but still the same. Also resoldered all joint. Could this be a case of the power tranny being faulty? If not then what else could be wrong. My filtering caps is 32uf+32uf 450v. When power on I am get a voltage of around 500v from the rectifier, could I have punctured the filtering cap?
Schematics is very much the same as http://www.diyaudio.com/forums/showthread.php?s=&threadid=12023&highlight=
Any helps would be appreciated.
rgds,
ed
I have DIYed 2 x EL34PP and both Monoblocs are having problems...
Monoblock 1 - Everything is ok except for sound being soft when power up. All voltage are consistent except for one going to output trans. The plate voltage to one of the optx is around 380v. Whereas the rest of the AN2, G1, G2 and CT are all around 430v. What could be the cause? Tried swopping in other tubes but its still the same. Have almost resoldered all joints but still cannot catch the problem.
Monoblock 2 - Getting a "zzzzzz" sound when power on. This is not the wrong phase hum as I have tried swopping the grids and plate from the power tube to the optx. All voltages look ok as in consistent. I can perpetually feel the power tranny producing the "zzzzz" sound and I am pretty sure thats the same sound I hear on the speaker. Have changed the wires to the power tranny but still the same. Also resoldered all joint. Could this be a case of the power tranny being faulty? If not then what else could be wrong. My filtering caps is 32uf+32uf 450v. When power on I am get a voltage of around 500v from the rectifier, could I have punctured the filtering cap?
Schematics is very much the same as http://www.diyaudio.com/forums/showthread.php?s=&threadid=12023&highlight=
Any helps would be appreciated.
rgds,
ed
ed said:
Monoblock 1-pull tubes out and measure resistances from CT to both anode taps-they must be in 5% max;
if that is not case-you have problem with OPT
Monoblock 2-did you measure current drawn from power xformer?
looks that you have somewhere excessive current draw,or somewhere bad electrolytic.
what do mean by
Whereas the rest of the AN2, G1, G2 and CT are all around 430v. What could be the cause? Tried swopping in other tubes but its still the same. Have almost resoldered all joints but still cannot catch the problem.
what is AN2,G1,G2 and CT
your cap is not design for the higher voltage. It is not right to run the cap close to its maximum surge rating of 500Volts and plus the el34 as one of the slowest turn on rate. Means the B+ is going to be higher than normal design for along time.
The caps could be making the zzz sound try to listen carefully i know mine made that sound even though they were rated very conservatily. But my design did not have the zzz sound from the speakers. you could check out my design at www.geocities.com/nickchua81
how long does this zzz sound last for? Could be your cap running in overvoltage when starts up and then go away after stabilizing.
Or it could be oscillation. Grid resistor to power tubes are good to stablize it or in the worse case use a small cap from grid to ground say 100pf or less to form a RC rolloff with the grid resistor
Your caps could be faulty aready as suggested by the other member and the other cap could possibly go then thus bring both voltage to opt to 380V
Whereas the rest of the AN2, G1, G2 and CT are all around 430v. What could be the cause? Tried swopping in other tubes but its still the same. Have almost resoldered all joints but still cannot catch the problem.
what is AN2,G1,G2 and CT
your cap is not design for the higher voltage. It is not right to run the cap close to its maximum surge rating of 500Volts and plus the el34 as one of the slowest turn on rate. Means the B+ is going to be higher than normal design for along time.
The caps could be making the zzz sound try to listen carefully i know mine made that sound even though they were rated very conservatily. But my design did not have the zzz sound from the speakers. you could check out my design at www.geocities.com/nickchua81
how long does this zzz sound last for? Could be your cap running in overvoltage when starts up and then go away after stabilizing.
Or it could be oscillation. Grid resistor to power tubes are good to stablize it or in the worse case use a small cap from grid to ground say 100pf or less to form a RC rolloff with the grid resistor
Your caps could be faulty aready as suggested by the other member and the other cap could possibly go then thus bring both voltage to opt to 380V
Hi,
AN1, G1 is the Plate and Grid of the first EL34 and AN2 and G2 is the plate and grid of the 2nd EL34. CT is center tap where the B+ goes to.
I ever read some where that the Power Tranny having a "zzzzz" mean it working very hard. Which I guess there may be leakage some where. Is leakage likely caused by faulty caps?
Will try to get my hands on the filter caps that can handle higher voltages. My current filter caps are rates 450v but my supply is giving out 500v. I suspect that is the likely cause. Wlll change and post results.
thks,
ed
AN1, G1 is the Plate and Grid of the first EL34 and AN2 and G2 is the plate and grid of the 2nd EL34. CT is center tap where the B+ goes to.
I ever read some where that the Power Tranny having a "zzzzz" mean it working very hard. Which I guess there may be leakage some where. Is leakage likely caused by faulty caps?
Will try to get my hands on the filter caps that can handle higher voltages. My current filter caps are rates 450v but my supply is giving out 500v. I suspect that is the likely cause. Wlll change and post results.
thks,
ed
NickC said:
#1: Check the pass cap to tube 1, also make sure correct connections (components to the socket pins), also correct values.
#2: Change the filter cap (or just add another one in series with it, also add 2 shunt resistors, it's the fastest way to find out is it the problem with filter cap)
PS, for #1, did you check the cathode voltage on AN1? Is it much higher than AN2? If so, 100% sure defective coupling cap! If much lower, than check the cathode resistor/electrolytic cap...
#2: Change the filter cap (or just add another one in series with it, also add 2 shunt resistors, it's the fastest way to find out is it the problem with filter cap)
PS, for #1, did you check the cathode voltage on AN1? Is it much higher than AN2? If so, 100% sure defective coupling cap! If much lower, than check the cathode resistor/electrolytic cap...
Disconnect the circuitry from the power supply and see what the power supply rails look like: DC voltage, ripple. If that's OK, start tracing your wiring around the output stage.
Don't run excessively high voltages across supply electrolytics. This can be physically dangerous. They can fail explosively. If you've really got 500V running across 450V caps, STOP and replace them with something with at least 525V ratings before doing even one more step.
Don't run excessively high voltages across supply electrolytics. This can be physically dangerous. They can fail explosively. If you've really got 500V running across 450V caps, STOP and replace them with something with at least 525V ratings before doing even one more step.#1: Check connection with schematic and its correct. Swop in another coupling cap and still the same. Cathode voltage both at 33v. If no choice I will swop in the optx from #2.
#2: I will change the filter cap. But itst Sunday over here so got to wait till tomorrow. Or may swop in the filter cap from #1.
Advantage of have 2 of the same kind. I would be happy if at least one of the two is working.
#2: I will change the filter cap. But itst Sunday over here so got to wait till tomorrow. Or may swop in the filter cap from #1.
Advantage of have 2 of the same kind. I would be happy if at least one of the two is working.
DSummer said:
Well the shop that sells me the kit told me that it is more than enough. Did not know that the voltage from rectifier actually went above 500V. Too bad got to hunt for higher voltage ones tomorrow...
SY said:Disconnect the circuitry from the power supply and see what the power supply rails look like: DC voltage, ripple. If that's OK, start tracing your wiring around the output stage.
Hi,
It does happen that, when all else looks fine, one or more power tubes have an internal short causing a buzzz and making inductive comonents such as chokes and xformers vibrate.
The short will often be accompanied by a voltage drop once the tubes are drawing current.
It's just a thought though.
Cheers,
It does happen that, when all else looks fine, one or more power tubes have an internal short causing a buzzz and making inductive comonents such as chokes and xformers vibrate.
The short will often be accompanied by a voltage drop once the tubes are drawing current.
It's just a thought though.
Cheers,
Really doubt its the tube. I hae 6 x EL 34 and 4 x 12AX7 for swopping. Not unless problem is with the EF86.
fdegrove said:Hi,
It does happen that, when all else looks fine, one or more power tubes have an internal short causing a buzzz and making inductive comonents such as chokes and xformers vibrate.
The short will often be accompanied by a voltage drop once the tubes are drawing current.
It's just a thought though.
Cheers,
Update
Monoblock 1 : Swopped Optx and coupling caps, still the same soft and distorted music when I crank volume high. Plate of EF86 measures 86v, plate of 12AX7 270 and 280 respectively. Plate of EL34 is 380 and 430 respectively.
Monoblock 2 : Swopped PS filter with Monoblock 1 and still the same. Changed the 22uf cap as well. Last suspect is the 10uf, will be doing that later. I think it may be due to certain faulty components resulting in a leakage and thus pulling a lot of current from teh Tranny. When the power tranny is working too hard then it creates the "zzzzzzz" sound??
Tired, got to take a break now.
rgds,
Monoblock 1 : Swopped Optx and coupling caps, still the same soft and distorted music when I crank volume high. Plate of EF86 measures 86v, plate of 12AX7 270 and 280 respectively. Plate of EL34 is 380 and 430 respectively.
Monoblock 2 : Swopped PS filter with Monoblock 1 and still the same. Changed the 22uf cap as well. Last suspect is the 10uf, will be doing that later. I think it may be due to certain faulty components resulting in a leakage and thus pulling a lot of current from teh Tranny. When the power tranny is working too hard then it creates the "zzzzzzz" sound??
Tired, got to take a break now.
rgds,
did that!
Hi,
I built those kit some 13 years ago and I still see the same kit being sold today.
The kit should sound very nice but I too was facing a humming sound from the speaker but due to no diyforum and internet at that time, I traded the kit back to them and bought a complete set of Thunder EL34 Push Pull amplifier which I am still using them today.
The hum problem was resolved by the lady and was eventually sold to some buyers back then.
One way is to spend a weekday ( take a day off from work! ) and spend a day time at their place to resolve the problem. It should be a small issue that can be resolved. Also if you are lucky, get the advice from the uncle. he is in the shop all the time.
Of course diyaudio will be able to guide you like they did with my the el84 amp.
Good Luck!
One other important factor... stay calm and control the frustration, it blocks an open mind to solve the problem.
Hi,
I built those kit some 13 years ago and I still see the same kit being sold today.
The kit should sound very nice but I too was facing a humming sound from the speaker but due to no diyforum and internet at that time, I traded the kit back to them and bought a complete set of Thunder EL34 Push Pull amplifier which I am still using them today.
The hum problem was resolved by the lady and was eventually sold to some buyers back then.
One way is to spend a weekday ( take a day off from work! ) and spend a day time at their place to resolve the problem. It should be a small issue that can be resolved. Also if you are lucky, get the advice from the uncle. he is in the shop all the time.
Of course diyaudio will be able to guide you like they did with my the el84 amp.
Good Luck!
One other important factor... stay calm and control the frustration, it blocks an open mind to solve the problem.
Re: did that!
I got it working but due to itchy fingers decided to change parts to better ones here and there and these probs surfaces Have worked on the monoblock for more than 10 months now. Don't think I will give up on these amps with that kind of effort. Have compete other projects and would like to close this one as a grand finale. but...
Still trying...
I got it working but due to itchy fingers decided to change parts to better ones here and there and these probs surfaces Have worked on the monoblock for more than 10 months now. Don't think I will give up on these amps with that kind of effort. Have compete other projects and would like to close this one as a grand finale. but...
Still trying...
effindi said:
Switched the tubes, switched the components, still have the same problem... Would it be the problem with tube sockets?
Check all the DC resistance at different points, like anode-gnd, cathode-gnd, grid-gnd (of course with power off and unplug the AC power cord) If possible, remove all those electrolytic caps and check with leakage. If not the tubes, the distortion problem seems like from the caps, most probably the cathode caps.
may be you can try to input a small signal in (from a signal generator, load with a resistor to output terminals) and check any voltage changes (anode, cathode and grid)
I have an experience with a defect 8 pins ceramic socket long time ago. Even it's new, problem solved after I changed the socket, may be you can try it in your last step. Hope you can solve the problems very soon...
Check all the DC resistance at different points, like anode-gnd, cathode-gnd, grid-gnd (of course with power off and unplug the AC power cord) If possible, remove all those electrolytic caps and check with leakage. If not the tubes, the distortion problem seems like from the caps, most probably the cathode caps.
may be you can try to input a small signal in (from a signal generator, load with a resistor to output terminals) and check any voltage changes (anode, cathode and grid)
I have an experience with a defect 8 pins ceramic socket long time ago. Even it's new, problem solved after I changed the socket, may be you can try it in your last step. Hope you can solve the problems very soon...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.