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Old 11th October 2010, 09:21 PM   #11
piero7 is offline piero7  Italy
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Forget the china FU 29, better the soviet GU29 but much better the 829B RCA! The anode caps comes from ebay. I tested the QQE030-20 but they are inadeguate...
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Old 11th October 2010, 09:58 PM   #12
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When my amplifier arrived one of the Chinese FU29s was smashed which is why I substituted the QQV06-40s (obviously QQV03-20s are a little underpowered). They worked fine for several months until the amplifier failed. In the meantime I had acquired some RCA 829Bs but I never got round to using them. When I have fixed the relay problem I will try them. Thanks for the advice.
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Old 26th June 2011, 03:37 AM   #13
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Hi All,

tdmax, did you ever find out wnat the problem was with your amp? I have an FU29 that looks slightly different to yours and the same resistor has burned out. the amp was running fine for 3 months and then just burned out one day.

occasionally the GU29 on the right would glow really hot even at low power levelsbut after turning it off and letting it cool down it would be fine again. but the last time it did this it made a really bad burning smell and I tool the cover off and found the same resistor burned!

Click the image to open in full size.


Click the image to open in full size.
( i replaced the FU29's) and re biassed the amp via the manufacturers reccomendations

the resistor is a 1k 2 watt. I can replace it but think it will just fry again as there must be a reason it fried in the first place. I would greatly appreciate help as I know very little about electronics.

Thanks!
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Old 2nd December 2011, 06:34 PM   #14
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I am getting one of these amps too. Anyone figure out where in the circuit the resistors are that fail and why they are failing? Is it the poor quality Chinese FU29 toobes or just poor quality Chinese parts... resistors, etc, an oscillation or instability of some sort? The Metal work to me is worth the price of the amp alone. And... gotta like those designation letters on the toobe anyway... FU! Of course one can rebuild that amp with really decent parts for about another USD ~$100.00 and use Russian GU-29 or real RCA 829 toobes instead so it is still a bargain and I like the use of the XX-29 toobes for output. Please keep posting when you guys find the issue and I'll let you know when mine arrives...

Also, there is a thread on another forum concerning this same issue and they have noted that two different PCB's main exist.... Some of you may already know about this thread.

Mark

Last edited by Mark Allen; 2nd December 2011 at 06:36 PM.
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Old 2nd December 2011, 06:47 PM   #15
GloBug is offline GloBug  Canada
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Yikes -$439 is pretty steep for metal work.
Maybe you can listen to it for a while first.
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Old 2nd December 2011, 07:12 PM   #16
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What would it cost you to have that metal work done in Canada or the US though...? Of course I intend to keep the amp whole and to help solve the issues with it if someone else doesn't beat me to it. I intend to take mine a step at a time and a few steps further and rebuild the amp with high end components...

This brings up another interesting point... Has anyone using this amp pre-conditioned your FU-29 toobes before using it? Having built a number of OTL amps over the years I can tell you that doing this can eliminate much of the internal arcing that OTL OP toobes suffer from, especially with the 6C33's... Try at least 80 hours with the toobe filaments only at normal filament voltage... You may find that it helps as this bottle is somewhat similar to the 6C33.

Mark
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Old 3rd December 2011, 12:10 AM   #17
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I solved the issue with my amp. it turned out to be one of the tube sockets not connecting with one of the pins properly. this was due to using NOS tubes and not cleaning the corrosion of the pins. it shorted the heateramd red plated one of the tubes

i replaced the resistor and replaced the output tubes with another pair of gu29's its been fine ever since.

I have thought about rewiring the amp point to point. it's a fantastc sounding amp with masses of power.
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Old 3rd December 2011, 03:22 PM   #18
saudara is offline saudara  Indonesia
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Dear all,

I am from Indonesia. I use FU29 in Fender 5F6A clone, it is much better compares to 6L6s.

Will try to build a stereo amp. using FU29, will post when it is done.

Here is the link of the Fender clone using FU29: Fender 5F6A_829B DIY.MP4 - YouTube
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Old 5th December 2011, 07:05 AM   #19
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Quote:
Originally Posted by Mark Allen View Post
I am getting one of these amps too. Anyone figure out where in the circuit the resistors are that fail and why they are failing? Is it the poor quality Chinese FU29 toobes or just poor quality Chinese parts... resistors, etc, an oscillation or instability of some sort? The Metal work to me is worth the price of the amp alone. And... gotta like those designation letters on the toobe anyway... FU! Of course one can rebuild that amp with really decent parts for about another USD ~$100.00 and use Russian GU-29 or real RCA 829 toobes instead so it is still a bargain and I like the use of the XX-29 toobes for output. Please keep posting when you guys find the issue and I'll let you know when mine arrives...

Also, there is a thread on another forum concerning this same issue and they have noted that two different PCB's main exist.... Some of you may already know about this thread.

Mark
I have a question... what is a "toobe"?
:P
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Old 5th December 2011, 10:17 AM   #20
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"Toobe" is an attempted phonetic transcription of the way Americans pronounce "tube". The final "e" is not required. Brits would pronounce it "tyoob" if we didn't call it a valve.
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