Craig Sawyers

Because of the high cost of 2SC3381, why not replace with two separate transistors during fault finding? Two transistors on the same bit of silicon are only necessary to ensure thermal tracking (ie that the Vbe tracks with temperature)

Well, my latest errors have been (a) a solder bridge that vapourised two tracks on a pro power amp I was fixing. Um, re-fixing as it turned out; and ( missing soldering a component at all in the BH. I was so paranoid about the T2 I did a 100% solder inspection under a magnifier - and I still missed an unsoldered joint (so 99.95% inspection...)

That is bloody wierd. I'd really go back to basics. Pigtail the transformer leads into a bridge rectifier taped to the bench, and measure the rectified (ac) voltage - which will tell you if there is a problem with that particular winding. Connect up a 680uF cap and again see what it measures as smoothed ac. If all is OK, then there could be an interwinding short or something else peculiar in the way the -260V is generated from 300V using a dc offset from the -500V and -60V supplies. But again I'd go back to basics - even take the Tx out, and run each winding into a bridge screwed to a piece of wood (say), then add caps and see what the actual raw dc is from each of the three windings. Then check the voltage between each of the windings - they should be isolated. Birgir - do you have a megohm meter? The windings should be electrically well isolated to a rather high voltage. If there is an interwinding short, or low resistance, it should show up using a megohm meter with the voltage set to 500V. Do your transformers have interwinding insulation barriers?

That is a massive relief - that could have been really ugly in many different ways.

You've got that right Spritzer - tiredness (and booze) are never good partners to HV work

I've got a BH (not SE) and a T2. Anyone want to buy me a pair of SR009's so I can tell you what they sound like?

Jeez - sorry to hear that. I guess I got lucky with the power supply - it just fired straight up and hasn't missed a beat since. The amp - as most of you know - was a different kettle of fish entirely. It's got to be simple though - if the cap is roasting, and the rectifier bridge is OK - then it has to be the cap. Mislabelled and electrically in backwards. If that is the case, make sure the rectifiers haven't got cooked into the bargain. Try pulling the IXYS current limiters temporarily, and isolate the transformer, bridge and capacitor.

Um - how about filling in your profile so we have some idea who the hell you are?

Hey guys - happy birthday!

Al - have a great day! I'm drinking one for you right now.

In the UK they were call a Flexicurve. Green in colour IIRC. Yup still available - in the UK around £5 depending on length (isn't that true of so many things). But they seem to have changed to blue.

I want to live in Rochester! A fifth of a Gigabit per second - I had no idea that was possible. And "Sadly, most of the time I'm in my dorm on 100mbit ethernet" - well boo hoo.

I wondered too - but his profile says USAF, so it looks like he's at the sharp end.

OMG. I'd better start slowly softening my wife up as a long term strategy. I've just got to have a pair of those.

That is just great - I'll bet that kid is never picked on again! My son (many years ago) did something similar when he got fed up with being bullied and broke the kid's nose.

I decided to run the test at work having just downloaded a 530MB CD ISO image in a bewilderingly, jaw droppingly short time.

Check back through this thread for modifications on the power supply. In fact I think I posted a summary of mods, to wich KG added one or two I had forgotten.

Have a great one

Hear hear!

Given the third world speed I get at home, this is what I get at my desk at Leicester University: Zoom....

I'm not sure how many people have now got these running. Last time a poll was done, the count was 5 out of 22 having completed and were listening. Anyone like to volunteer a current number?

From what I've seen in the pics it is a wonder that this amp works at all!

Looks like it for DC http://hypertextbook.com/facts/2000/JackHsu.shtml To drive 100mA through the body at 700V rail to rail of a KGSS would need a body resistance of 7k. Typical hand to hand dry skin resistance can be way below that (a k or two) - and working with high voltage usually gives "sweaty palm syndrome", which makes the hazard even worse. Hence the excellent general advice of keeping one hand in the pocket at all times while taking measurements at modest levels.

I've just had a shudder moment. It looks to me like you are completely new to electronics - and the voltage inside any electrostatic amp is quite lethal. If you get it wrong, you can end up with many hundreds of volts with significant current capability from one hand to another - and that has a very high risk of stopping your heart. Please get someone to fix this for you - Justin already offered to do this if you sent it to him.

Anybody been in touch with Stax to see if they are OK there? They aren't too far from Tokyo, so would have been shaken around pretty badly.