Rockster Lives!

Express, Liverpool, Rocket, Dirty Little Monster, etc.

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crafty1
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Re: Rockster Lives!

Post by crafty1 » Wed Feb 02, 2011 7:58 am

Hey Graham,

What brand of rectifier are you using? I did a build a while ago which used a GZ34 ( JJ ), 50/50uf on the plates and screens of the 6V6 pair.
Every time i turned it off Standby it would blow the fuse ( sounds similar to your problem ). What i did notice was that the rec tube was arcing inside and then the fuse blew. I checked the circuit and it was fine. I tried another JJ tube - same thing.

I then tried a TAD GZ34, no problem. Tried a Mullard and again no problem and have never had a problem since. I think that JJ must have had a bad batch of these tubes as i have read of other people suffering the same problem.

Amps that have high uf values ( 50uf and upwards ) do put heavy stresses on rectifier tubes upon start up. With the rocket based builds the rectifier sees a very high capacitance hurdle that it has to jump which can be too much for some current production tubes. Again i am assuming that you may be using a JJ GZ34.

Give the current TAD or Sovtek a try. I highly recommend any TAD Rec and power tubes. I have had excellent results with these tubes. ( Don't know about their pre amp tubes though?).

Hope this helps,

Rich

I

Beerman
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Location: Melbourne, Australia

Re: Rockster Lives!

Post by Beerman » Wed Feb 02, 2011 11:31 am

Hey Rich.
I do have a JJ GZ34, but this fault occurs even when the rectifier isn't installed.

I got some of the way through building a test rig for the PT this afternoon so I can check for draw (ammeter in series) on the primary and voltage on all the secondaries at the same time. Will probably knock that over on Friday - I'm out in the bush tomorrow.

Have also touched base with Daniel at AVAT who will look at it closer if required. But at this stage - contrary to my previous... - it looks like there is a short on the 5v winding.

How's your ZWreck settling in?
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Cheers and Beers.

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rawnster
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Re: Rockster Lives!

Post by rawnster » Wed Feb 02, 2011 7:01 pm

M Fowler wrote:Another way to wire the tone controls
+1

I wire the octal rocket tonestack like this:
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rooster
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Re: Rockster Lives!

Post by rooster » Thu Feb 03, 2011 12:11 am

Actually, Beerman, you are right to question the J/J GZ34. J/J did have a problem with their GZ34 - and plenty were shipped as I understand it. In my case, I ran thru 3 of these bad ones that actually worked briefly, and then failed. I purchased mine from Eurotubes and they made good on it which was nice. ....Well, the brain cells I lost trying to figure this out were never replaced, FWIW. :x But whatever, you know, buyer beware and all that.

J/J has corrected the problem which was vaguely described to me to be 'metallurgy problems', BTW, and as of 12/10 the new ones were in stock. To their credit, J/J tests these GZ34s in an amp before they sell them - a idea borne of necessity. ...This said, the 3 tubes I bought that failed passed this test. ?? The current one I picked up in December has been going strong for over 100 hours and that's with plenty of cycling on an amp running 460VDC - which leads me to conclude that all is good now.

FWIW, I think it was the Eurotubes company that pointed out the problem to J/J, and yes, they have a pretty close relationship with each other. How it is that other companies have continued to sell this tube while Eurotubes stopped for a while is kinda puzzling, eh?. For me in this case, I would say it's a benefit to work with a small and thoughtful company vs. the big boys who just stock the shelves.

Anyway, your problem is that tube, count on it. The brain cells will not come back, BTW..... :cry:
Most people stall-out when fixing a mistake that they have made. Why?

Beerman
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Location: Melbourne, Australia

Re: Rockster Lives!

Post by Beerman » Thu Feb 03, 2011 5:45 am

rooster wrote:Actually, Beerman, you are right to question the J/J GZ34. J/J did have a problem with their GZ34 - and plenty were shipped as I understand it. In my case, I ran thru 3 of these bad ones that actually worked briefly, and then failed. I purchased mine from Eurotubes and they made good on it which was nice. ....Well, the brain cells I lost trying to figure this out were never replaced, FWIW. :x But whatever, you know, buyer beware and all that.

J/J has corrected the problem which was vaguely described to me to be 'metallurgy problems', BTW, and as of 12/10 the new ones were in stock. To their credit, J/J tests these GZ34s in an amp before they sell them - a idea borne of necessity. ...This said, the 3 tubes I bought that failed passed this test. ?? The current one I picked up in December has been going strong for over 100 hours and that's with plenty of cycling on an amp running 460VDC - which leads me to conclude that all is good now.

FWIW, I think it was the Eurotubes company that pointed out the problem to J/J, and yes, they have a pretty close relationship with each other. How it is that other companies have continued to sell this tube while Eurotubes stopped for a while is kinda puzzling, eh?. For me in this case, I would say it's a benefit to work with a small and thoughtful company vs. the big boys who just stock the shelves.

Anyway, your problem is that tube, count on it. The brain cells will not come back, BTW..... :cry:
I'll cross that bridge when I come to it... at this point, I've not even installed the rectifier...
__________________________________________
Cheers and Beers.

Beerman
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Location: Melbourne, Australia

An update on progress

Post by Beerman » Mon Feb 14, 2011 7:30 am

I had my PT looked at by a local tranny manufacturer - he could find no fault with it, and was quite impressed with it's build quality.... he ran it for half an hour on his test rig, with all the secondaries loaded to 120% of spec, and it barely even warmed up...

Edcor trannies are the bomb!

Went back to my amp today, and found a wire clipping shorting the 5v winding at the rectifier socket... fresh eyes are a good thing.

Got the tranny back in, and went over all the PS connections... powered up... powered down etc... got quite excited when I saw that I had heaters glowing in all the tubes... took off the dummy load, and plugged in a speaker, plugged in a guitar, powered up again, slowly brought up the volume... and nothing... :(

Powered it back down and walked away.

Will come back to it tomorrow, and will measure voltages and post them.

Hopefully it's something simple.
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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Mon Feb 14, 2011 6:19 pm

Edcor trannies are great and the tone makes it worth getting them.

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RJ Guitars
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Re: Rockster Lives!

Post by RJ Guitars » Mon Feb 14, 2011 9:12 pm

No Sound has bit me a time or two... Twice now I caught myself wiring the auto shorting output jack wrong. Once I wired it wrong and first time I actually used an auto shorting jack for both speaker outputs... which of course doesn't work unless you have a cabinet plugged into both jacks.

I am confident that you'll get it squared away.

I am really pleased with the Edcor transformers, they are a good company making them one at a time and doing a nice job! It is also good to hear that they really did excellent under the 120% load test. They tend to be very conservative in their ratings!

rj

Ian444
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Re: Rockster Lives!

Post by Ian444 » Tue Feb 15, 2011 9:51 am

M Fowler wrote:Edcor trannies are great and the tone makes it worth getting them.
Right! Now you tell me, just after I ordered two Magnetic Components OPT's from Triode! ...Next time I'll try an Edcor, I just wish they'd sell them in black, that Gentian Blue is a bit out there...

Beerman, hang in there, it WILL be something simple...

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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Tue Feb 15, 2011 2:16 pm

Take the end bells off and paint or powder coat them black.

I like the blue.

Beerman
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Re: Rockster Lives!

Post by Beerman » Sat Mar 05, 2011 8:30 am

Got it sorted. Had the HT centre tap floating - looking over some other schematics I noticed that some amps use this as a standby - IE lifting it from ground mutes the amp.

Tied it to earth... It's Alive!!!

Sounding great as is. Will play a bit and tweak as required, but very happy with it as is. Gonna swing by my friend's studio tomorrow to give her a workout.

Running a JJ GZ34 for the rectifier.
A pair of XF3 Phillips EL34 outputs,
V1 is a Miniwatt 12ax7, V2 a Miniwatt 12au7 (with a bad triode), and V3 another old Miniwatt 12ax7.

Will post some pictures soon.

Will have to do something about a cabinet soon too.
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Cheers and Beers.

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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Sat Mar 05, 2011 2:50 pm

Nice line up of tubes in that bad boy, glad you got is running!

Mark

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RJ Guitars
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Re: Rockster Lives!

Post by RJ Guitars » Sat Mar 05, 2011 3:53 pm

Oi Mate... happy for you! Crank it up and let it rock, then send us photos and sound clips when you get the chance. rj

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