| rossdt |
In my new amplifier I use JJ GZ34 tube but I have
some problems. During the operation I noted sparks inside the tube. Why?
The PSU is very simple.
TA:
Vin=220 V rms;
Vout=450 V rms off-load;
8.7 ohm primary;
120 ohm half-secondary.
The following filter is a CLC filter (C=22 uF, L=20 H, C=33 uF).
Load: I(DC)= 200 mA
The temperature of GZ34 is about 110 - 120 degree.
Could you help me?
Thank you in advance.
Alessandro |
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| Trout |
| quote: | | In my new amplifier I use JJ GZ34 tube but I have some problems. During the operation I noted sparks inside the tube. Why? |
I have had that exact problem but ended up setting the tube aside and using a less desireable 5U4.
I did not know if it was just my particular tube, or a circuit issue, But either way, It has not happened since I switch, BTW, the 5U4 I used was a well seasoned ( about worn out) GE.
Trout |
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| burnedfingers |
| Could you try a resistor before the first cap or a smaller first cap to see if the problem stays or goes? |
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| kathodyne |
don't know if it helps in this case.....
try some resistors on both legs of the transformers secondary, before the rectifier... |
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| bembel |
Hi all,
I had the same problem with an EZ81, the first cap was to big (though smaller than datasheet Cmax), in fact electrolytic caps (especially old ones) are rated for -20% tolerance but on the other side +50%. the cap was in fact double its nominal value.I changed the cap and everything went fine.
I suggest that you measure your first cap, hope this helps |
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| Bas Horneman |
| Same here. I am not using the JJ's anymore. Instead I use Sovtek 5AR4/GZ34's which do NOT display that behaviour in the SAME circuit. I am very happy with JJ's other tubes...for example KT77...but their GZ34's are not kosher IMO. |
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| ivegotmono |
| quote: | | I had the same problem with an EZ81, the first cap was to big (though smaller than datasheet Cmax), in fact electrolytic caps (especially old ones) |
Me too, also EZ81s on eico HF81. I replaced the first caps in PS going to 40uf from 30uf and for several hours after cap replacement there were occasional sparks. Also a bad humm/hiss. It wen't away after a few hours and never came back.
The sparking was only minimal at it's worst.
Steve |
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| refference |
Hi Alessandro ,
Before you replace the tube , try these 2 tips :
1) Between one output tap of power transformer and
the pin 4 of GZ34 , put a wirewound 68 ohms x 5 W
resistor , do exactly the same , between another tap
and the pin 6 , with another 68 ohms x 5 Watts resis-
tor . BE SURE that you are making the output conne-
ction at the pin 8 .
2) Check the first capacitor ( 22 uf ) and the second capa-
citor ( 33 uf ) , if they don’t have any kind of leakage to
ground , DO THE SAME WITH THE CHOKE . Using a
ohm meter that can measure at least 20 Megaohms
If one or the two tips above , don’t solve the problem ,
replace the tube by another GZ34 , don’t use a 5U4 because
the voltage drop , inside the tube will be higher , and the
heater current rating is higher , too .
I hope it helps . Regards ,
Carlos |
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