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Eico HF-30 rectifier problems

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Posted on April 8, 2015 at 12:44:03
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 Anybody having problems with JJ (?) EZ81 rectifiers?

I had a pair of HF-30s which seemed to be working fine. I sold them to my brother, and he has been using the amp for about a year. However, he has experienced several problems with rectifier flash over, which of course blows the fuse, and could certainly blow something else with any bad luck at all. The flash over (shorting within the tube?) occurs about 8-10 seconds after power-up, so I assume just as the tubes are starting to conduct.

I had completely recapped these amps before I sold them, and had gone through them checking resistor values and voltages. Everything was fine, output tubes drawing the correct current, etc. After my brother had the flash over happen the second time he took the amp to the local tech who checked it out and couldn't find anything wrong with it. He installed a new fuse and sent him on his way.

I have advised my brother to replace the two JJ rectifier tubes with new tubes, preferably not JJs. Hopefully that is the issue, though I have never had issues with other JJ tubes before. Has anybody else had issues with the JJ EZ81/6GA4?

 

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RE: Eico HF-30 rectifier problems, posted on April 8, 2015 at 14:50:21
Lee of Omaha
Dealer

Posts: 1800
Location: Omaha NE
Joined: September 8, 2006
 Is the flashover in one or both rectifiers? If it's in one it could be a slightly defective rectifier, and I'll bet it's from plate to cathode, as it sounds like it flashed when the B+ is fully charged and there is not yet conduction in the amplifying tubes (no load yet), so B+ voltage is at maximum.

I'm guessing slightly defective rectifier.

 

Rectifier octal socket?, posted on April 8, 2015 at 18:29:07
Mossback
Audiophile

Posts: 1871
Location: Washington, the State
Joined: November 17, 2001
 When rebuilding vintage gear I always replace the octal rectifier socket. How do they look?

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 00:48:12
Brian Levy
Audiophile

Posts: 2438
Location: Toronto
Joined: June 5, 2000
 I agree with the possible problem being traced back to the socket. It only takes a tiny piece of dirt or carbon track (quite common) between the pins, enough to make a voltage path or allow arcing. When these tubes were common we would dose them with carbon tet and mKe sure the sockets were absolutely clean and do the same with the entire tube, especially the base around the pins. Not sure what good cleaner(s) is available today or it there are better sockets available. When we replaced sockets, we always used a ceramic socket for the rectifier. A number of socket companies manufactured dedicated high voltage sockets but manufacturers generally did not use them, saving maybe $0.04 per unit. Not sure if there is a source for these any longer. Maybe the auction site or locate an old television. Those makers, especially the better b&w set makers tended to use the sockets more commonly. Lastly, there were solid state plug in substitutes for the tubes that did not exhibit flashback but as usual, there is controversy as to whether they affect the sound and so in a good or bad way. My take is that it should be no different than hard wiring a set of rectifiers when eliminating seleniums or a tube rectifier.
Don Brian Levy, J.D.
Toronto ON Canada

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 03:29:54
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 You have two amps..When you switch the rectifier tubes from the good amp to the bad amp,do they still flash? If so,the tubes are the issue but if not,your output tubes could be drawing excessive current on startup.When you recapped the amp,you didn't put over 80uf on the pair of the EZ81s did you?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

question?, posted on April 9, 2015 at 06:17:03
airtime
Audiophile

Posts: 11287
Location: Arizona
Joined: February 4, 2003
 Can you pull the output tubes as see if you still get a flash?

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 06:40:54
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 Thanks Michael. I was reluctant to suggest swapping the tubes to the other amp lest we get into a cascading series of damaged parts. Also, I believe the first cap in that amp is a 47uf. I don't know what the resistance of the secondary is (as I said, my brother has the amp now) but based on experience it is close to or higher than 150 ohms.

You are probably correct. He should either swap the good rectifiers to the bad amp or vice-versa.

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 06:47:11
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 Thanks Brian. The tech in Milwaukee actually suggested switching to solid state rectification also. In my experience that tends to jack up the B+ which I don't think is desirable, plus you have B+ on cold tubes issue. Good as a last resort.

I'll suggest my brother buy some deoxit and go to work on the sockets. Or maybe he'll want his tech to put in some new ones and be sure that's not the issue.

 

RE: Rectifier octal socket?, posted on April 9, 2015 at 06:49:16
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 Thanks for the suggestion. They looked fine to me. Neither of the amps appeared to have been heavily used. They are 50+ years old though.

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 06:49:58
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 I think it is just one of the rectifiers.

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 08:01:29
kintyre695
Audiophile

Posts: 975
Location: Toronto
Joined: September 6, 2003
 This is just a suggestion, but, if your brother had the amp in at the tech and the tech said it was ok, and now it doesn't work, shouldn't your brother be able to go back to the tech, and have him properly fix it? The tech should stand behind his work unless, it was something else that is wrong.

A variac would probably be a good idea if you are switching around tubes and working on the amp. Monitor the voltages going to the 1st cap and see what is happening.

Just an idea.

David

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 11:59:34
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 depends on if and/or how much he charged, if nothing, no, but most places charge an "operator ignorance" fee for those that work but the user did not know how to use properly. If he charged a small fee for inspection and determining if it worked, he should not be liable for a more expensive repair job that his actions were not responsible for. However if he did slipshod work, that may be a different thing. The point being, don't try to fuck your tech if he did honest work but the problem was something else, operator error or the like. I know way too many people think that techs, like everyone else in the world, are there to be at their beck and call and they abuse them, try to look at it from all sides...

 

RE: question?, posted on April 9, 2015 at 12:02:51
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Excellent point Charles..I was going to suggest that as well.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 12:19:47
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 it is an observation that the newly manufactured GZ34 cannot take the inrush current in many amps, one fix being to use a pair of diodes connected from the secondary to rectifier tube socket, this apparently inhibits flash-over. Michael can probably speak more to this, I know my Cary SLI-80 does that for the pair of 5U4 rectifiers, this is apparently an old ham trick to prevent tube rectifiers from being destroyed. Also, I believe that Dave Gillespie also recommends this for the chinese "firecracker" rectifiers, do a search here on AA or AK...

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 16:00:01
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Randy
The Eicos he has are the only ones that don't use the GZ34 rectifiers.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

EZ81 Not GZ34 my error, posted on April 9, 2015 at 16:55:32
Mossback
Audiophile

Posts: 1871
Location: Washington, the State
Joined: November 17, 2001
 Sorry I was confused thinking Eico HF35 not your amp that uses the EZ81's

 

RE: Eico HF-30 rectifier problems, posted on April 9, 2015 at 16:58:32
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 would that ham trick still be applicable to other tube rectifiers,noting that Dennis Had used it in the SLI-80, among others, Michael?

 

RE: Eico HF-30 rectifier problems, posted on April 12, 2015 at 12:17:05
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 Thanks for everyone's great suggestions. Working with my brother to get this resolved.
Gary

 

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