Simple SE + Edcor XPWR059 power problem - diyAudio
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Old 11th April 2011, 06:42 PM   #1
webby is offline webby  United Kingdom
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Unhappy Simple SE + Edcor XPWR059 power problem

Hi All,
My Simple SE has been running without a problem for about a year now, then a couple of days ago the fuse blew while listening to music after a few hours.
It has never done this before, now the fuse constantly blows (1A slow blow)
I tested the amp as follows
No FRED diodes. I use the 5AR4
XPWR059 wired for 240v

Blowing fuses suggests that something is shorted to ground,
checked for continuity;
The hot & neutral tabs of the IEC receptacle
Both tabs on the fuse holder
power switch

None of these indicate continuity, regardless of whether the power switch is open or closed.

Measured the XPWR059
The 6.3V winding 0.4ohm
The 5.0V winding 0.4ohm
The filter inductor (choke) & run cap not connected.

HT secondary coming from the power transformer.
The two red wires 25ohm

CXS8E 25-8-5K
Primary = 4.6Ohm
The secondary windings of the output transformer 0.7 ohm
primary 83 ohm.

So I disconnected all the XPWR059 secondary & Centre tap from the PCB, so the only connection is the power switch + Primary + red HV to my DMM.
I was expecting to test the HV then 6.3v & 5v.
Fuse blows!
Does this mean the power xformer is faulty?
I'm really scratching my head here, as it measures OK I think?
Any other tests I can do for the X59?
Many Thanks
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Old 11th April 2011, 08:57 PM   #2
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Random guess, but since this developed over time, do you have good grommets where your power tx is mounted? Maybe your mains leads are shorted.
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Old 11th April 2011, 09:10 PM   #3
chrisb is offline chrisb  Canada
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Location: victoria BC
Originally Posted by spopepro View Post
Random guess, but since this developed over time, do you have good grommets where your power tx is mounted? Maybe your mains leads are shorted.

FWIW, have you a spare rectifier tube to try? I had a problem with my SimplePP that had been working fine for quite a few weeks before it started blowing fuses randomly. It might run for a couple of days, then fail, then blow 3 fuses in a row on turn-on. To make a long story short it turned out to be a defective TAD GZ34 - replaced with Sovtek and it's worked like a charm for a couple of weeks now.

edit; my mistake not to read your full text - sounds like the issue might not be current draw on the secondary side

BTW, the Psvanne EL84 and 12AT7 are quite delightful in this amp - in basic pentode mode (unregulated screen supplies) the extra snap and "in your face" that some folks don't like about the tubes, but I don't detect, is very well suited to the system.
on hiatus

Last edited by chrisb; 11th April 2011 at 09:17 PM.
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Old 12th April 2011, 04:20 PM   #4
webby is offline webby  United Kingdom
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Location: england
Thanks for the replies.
I forgot to say the tubes are out at this stage, and the PCB is not connected.
Also the Xfrmr is removed from the chassis, free standing.
just using the switch,fuse & power connector.
I was checking for shorts on the leads.
Any further tests of the Xfrmr i can do to to determine if its faulty?
Many thanks
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Old 14th April 2011, 06:28 PM   #5
rknize is offline rknize  United States
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Can you measure the resistance of the other windings on the power transformer? It does sound like you have a short. How hot did it typically run?
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