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Old 29th April 2013, 09:10 PM   #1
PJN is offline PJN  United States
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Default I need a little more advice on a Glassware Janus shunt regularor

Hi All,

I built a dual mono aikido line stage preamp a few months back powered by two Glassware Janus shunt regulator power supplies. After getting good advice here on a heater transformer. I had it up and running, both power supplied functioned properly and delivered the proper B+ and H+ voltages for the Aikido boards. The preamp it sounded excellent, and beat my SS pre by a wide margin. It had been running daily for about 3 months with no issues, but the other day I lost one channel, then the other. Upon checking I found that the both JJ 5Y3S regulator tubes were cold. There was 5 vac to the heater pins and 240 vac to the pins on the rectifier tubes, no B+ coming out, but the low voltage solid state H+ sides of the boards are working correctly. Everything appears normal, no burnt or discolored parts. I'm guessing that 3 months is a pretty short life for rectifier tubes, so before I go out and buy rectifier tube replacements is their anything that I should check that could be killing the tubes early ?

Thanks,

PJN
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Old 29th April 2013, 09:47 PM   #2
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Hi PJN

Please post some more details, pictures, PTs used, etc. Indeed, three months is very short life.

Erik
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Old 29th April 2013, 10:10 PM   #3
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I'm guessing too big of filter cap? A single 5Y3 should be able to run multiple Aikidos. Of course, being a shunt regulator, it sends some current to ground, maybe too much?
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Old 1st May 2013, 03:13 AM   #4
PJN is offline PJN  United States
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I'll post some pics when I get back in town this weekend.

PJN
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Old 5th May 2013, 03:05 PM   #5
PJN is offline PJN  United States
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Hi Everyone,

I took some pics of the build and the regulator tubes. Please note the strong mirroring on the tops of the tubes, it's much heavier on one side than the other. Is it possible that overheating could have caused the premature failures ? The top is well ventilated but does get warm.

PJN
Attached Images
File Type: jpg Top ventilation.jpg (169.3 KB, 161 views)
File Type: jpg Regulator tubes.jpg (141.0 KB, 160 views)
File Type: jpg Layout.jpg (152.4 KB, 161 views)
File Type: jpg PSU detail.jpg (145.1 KB, 159 views)
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Old 5th May 2013, 09:22 PM   #6
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Hi PJN,

I seriously don't know what the problem is, as everything looks alright. As such I will propose some things that may sound quite logical and you may have tested already, still...
- have you tested continuity (resistance with DVM) between pins 2 and 8 of the 5Y3? - you said the 5Y3's were cold, so probably filament is broken;
- without 5Y3 in their sockets, measure voltage AC between pins 2 and 8. Remember, from the top pins are mirrored in relation to the bottom. Do you measure 5VAC?
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Old 6th May 2013, 01:31 AM   #7
kevinkr is offline kevinkr  United States
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Frankly I would suspect the rectifier tubes themselves. The filaments have apparently opened up which IME has nothing to do with the load current they are delivering.

JJ rectifiers do not have a good reputation for longevity/reliability and I avoid them. In this case your best recourse might be to by some good NOS GE or similar 5Y3GT on eBay. They aren't expensive. (Ham fests are a good source as well if you can find a local one)

You should always have spare tubes, I always have at least several or more of any tube I use in my designs. Current production tubes often fail without warning and will leave you in a music free state if you do not have spares. NOS, or good used tubes may in many instances be better than current production.
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Old 6th May 2013, 12:18 PM   #8
PJN is offline PJN  United States
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Hi Guys,

Thanks for the input. I did test the voltages on the pins and they were fine, 5 VAC on the heater pins. It does appear that the filaments failed because there is some material floating around loose inside the tubes. I'll get some more tubes and give things another try.

PJN
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Old 6th May 2013, 12:47 PM   #9
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Quote:
It does appear that the filaments failed because there is some material floating around loose inside the tubes
I had stuff floating around in my JJ 5AR4...flashing and arcing..often...So I destroyed it. Bad tubes.

Also have material floating around in my JJ EL84. The EL84's still work fine.

Ergo: Don't use JJ Rectifier tubes.

Last edited by Bas Horneman; 6th May 2013 at 12:59 PM.
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Old 6th May 2013, 01:18 PM   #10
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Quote:
Originally Posted by PJN View Post
Hi Guys,

Thanks for the input. I did test the voltages on the pins and they were fine, 5 VAC on the heater pins. It does appear that the filaments failed because there is some material floating around loose inside the tubes. I'll get some more tubes and give things another try.

PJN
Hi PJN,

Both rectifiers going out at nearly the same time, as you describe, probably indicates some other problem in your circuit. I would be careful just plugging in new rectifier tubes, as they may well go poof on you.

I wouldn't expect both rectifiers to blow within a short time of each other. It's possible, but in my experience such things usually indicate another problem somewhere.

Since the original rectifiers didn't blow immediately, you can probably check the output current from the regulator boards, see if it's what you expect it to be.

Good luck.

Sam
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