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Old 12th October 2003, 07:07 AM   #11
ed is offline ed  Singapore
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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...

Quote:
Originally posted by SY
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.
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Old 12th October 2003, 11:37 AM   #12
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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,
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Old 12th October 2003, 01:26 PM   #13
ed is offline ed  Singapore
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Really doubt its the tube. I hae 6 x EL 34 and 4 x 12AX7 for swopping. Not unless problem is with the EF86.

Quote:
Originally posted by fdegrove
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,
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Old 12th October 2003, 01:34 PM   #14
ed is offline ed  Singapore
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Default 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,
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Old 13th October 2003, 05:35 AM   #15
effindi is offline effindi  Singapore
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Default wher did you get the kit from?

HI,

Where did you buy the kit from?

Push Pull monoblocks... sounds like kit from Martin Audio. Is it?

Regards,
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Old 13th October 2003, 10:34 AM   #16
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did you check the bias voltage for the the monoblocks. One could be pulling more current than the other or less
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Old 13th October 2003, 02:24 PM   #17
ed is offline ed  Singapore
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Default Re: wher did you get the kit from?

Yes its from Martin...

rgds,

Quote:
Originally posted by effindi
HI,

Where did you buy the kit from?

Push Pull monoblocks... sounds like kit from Martin Audio. Is it?

Regards,
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Old 13th October 2003, 11:11 PM   #18
effindi is offline effindi  Singapore
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Default 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.
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Old 14th October 2003, 12:53 AM   #19
ed is offline ed  Singapore
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Default 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...

Quote:
Originally posted by effindi
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.
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Old 14th October 2003, 07:17 PM   #20
DSummer is online now DSummer  United States
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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...
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