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Old 15th May 2010, 08:05 PM   #11
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Do you have another rectifier tube (5AR4) to sub?
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Old 15th May 2010, 08:17 PM   #12
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Originally Posted by neonthecat View Post
Do you have another rectifier tube (5AR4) to sub?
no i'm afraid not
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Old 15th May 2010, 10:08 PM   #13
tomchr is offline tomchr  United States
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Some 5AR4's are prone to flash-over when run close to the max peak current rating (which I think is the case with the SimpleSE) -- even though they supposedly operate within the specified limits. I've used some Sovtek 5AR4's with good results. They seem pretty rugged.

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Old 16th May 2010, 02:04 AM   #14
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I have had 3 JJ 5AR4's blow but the Sovteks have held up fine so far. Blew them both on the SimpleSE and the TubelabSE.
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Old 16th May 2010, 02:31 AM   #15
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Originally Posted by proview1122 View Post
but then rectifier valve flashes bright and blown fuse (lots of swear words)... when fuse is replaced it powers up looks ok music starts to build up volume and then flash blown fuse probably about 10 seconds
Once a rectifier arcs over for the first time, it is virtually guaranteed to arc over again in the future. May as well just give up on it now, and stick it in the bin. You need a new rectifier, sorry.
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Old 16th May 2010, 04:41 AM   #16
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thanks for replies

the rectifier is in fact a JJ gz34s and was brand new! will order a Sovtek valve as per recommendation above
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Old 16th May 2010, 08:12 AM   #17
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just doing some testing
voltage at wall socket 248v

using test photos at Checkout pictures by Ty_Bower - Photobucket

thanks Ty it should maybe be a sticky


The electrolytic caps in the power supply I'm showing a final resistance of ~80K ohms = 76.2k
Check the 220K grid resistor on the 12AT7 (pin 2) = 217.7k (pin 7)=217.3k
Check the 220 ohm cathode resistor on the 12AT7 (pin 3) =220.5ohm (pin 8)= 202.6ohm
Check the 220K grid resistor on the power tube (pin 5). right=219.8k left 219.8k
Check the cathode resistor on the left power tube (pin 1)=566.3ohm pin 8 566.4ohm
Check the cathode resistor on the right power tube (pin 1)=570.3ohm pin 8 = 570.3ohm
Check the strapping from plate to screen. should be 100 ohms (pin 3-4) left 121.2ohm right 121.4ohm is this a bit high?
Check 12AT7 socket for 6.3 VAC heater voltage (pin 4 and pin5) =7.3vac same voltage on pin 2 of power tubes is this a bit high?
Check the rectifier for 5 VAC filament voltage (pin 2) = 6.1vac is this a bit high?
Check rectifier for HIGH VOLTAGE (pin 4) = 404.3vac (pin 6) 404.9vac


thanks
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Old 17th May 2010, 09:50 PM   #18
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any body any thoughts on the voltages above
new rectifier arrives tomorrow and I don't want to fry another one
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Old 18th May 2010, 12:42 AM   #19
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Quote:
Originally Posted by proview1122 View Post
Check the strapping from plate to screen. should be 100 ohms (pin 3-4) left 121.2ohm right 121.4ohm is this a bit high?
No problem here. I added an extra 250 ohms to the screens on mine. I was having issues with cheap tubes and glowing screens. The extra 250 ohms didn't fix my problem with the cheap tubes, but it doesn't seem to affect the normal operation with good tubes. I haven't bothered to take out the extra resistor. You won't hear any difference from the extra 20 ohms on yours.

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Check 12AT7 socket for 6.3 VAC heater voltage (pin 4 and pin5) =7.3vac same voltage on pin 2 of power tubes is this a bit high?
Check the rectifier for 5 VAC filament voltage (pin 2) = 6.1vac is this a bit high?
Check rectifier for HIGH VOLTAGE (pin 4) = 404.3vac (pin 6) 404.9vac
These seem a bit higher than I would like to see. They will come down a bit once you load up the windings (by plugging in the tubes). Still, these unloaded voltages seem higher than they should be. Sometimes cheap multimeters give bad readings on the AC scales. I checked the specs on the Edcor XPWR059 power transformer, and it does say it has a 240 volt primary. Odd.
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Old 18th May 2010, 06:12 AM   #20
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Originally Posted by Ty_Bower View Post
No problem here. I added an extra 250 ohms to the screens on mine. I was having issues with cheap tubes and glowing screens. The extra 250 ohms didn't fix my problem with the cheap tubes, but it doesn't seem to affect the normal operation with good tubes. I haven't bothered to take out the extra resistor. You won't hear any difference from the extra 20 ohms on yours.
that's good to know



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Originally Posted by Ty_Bower View Post
These seem a bit higher than I would like to see. They will come down a bit once you load up the windings (by plugging in the tubes). Still, these unloaded voltages seem higher than they should be. Sometimes cheap multimeters give bad readings on the AC scales. I checked the specs on the Edcor XPWR059 power transformer, and it does say it has a 240 volt primary. Odd.
Well the meter is a new its a true rms auto ranging al singing all dancing job and just to check I tried another meter and got the same results the PT was bought from edcor in the U.S. mains voltage here is high 248vac - 249vac as the supply transformer is only 10m away and I am first house on the line so does that may explain it?
will it be OK with the amp? is there any way of reducing the voltage or should I just ignore it.
cheers
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