Oops!

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Slowy
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Oops!

Post by Slowy »

Sometimes, I think I'm a monkey with a machine gun :roll:

I changed the valves in Optimus from 6L6 to 6DZ7. So far, so good.
Then in a moment of inspiration I replaced V1 with one of my old Mullard ECC83s

Switch on amp and Mullard explodes. Seriously, broken glass everywhere.
Today's job is to remove amp from chassis and visually check for circuit damage but I suspect I won't find anything.

No smoke or smell was present, the glass just shattered.
No fuses blown.

So what should I do? check there's no visual damage, replace the tube and switch on?
Or not?
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.

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Re: Oops!

Post by robthemac »

Slowy wrote: Mon Feb 06, 2023 8:50 am Sometimes, I think I'm a monkey with a machine gun :roll:

I changed the valves in Optimus from 6L6 to 6DZ7. So far, so good.
Then in a moment of inspiration I replaced V1 with one of my old Mullard ECC83s

Switch on amp and Mullard explodes. Seriously, broken glass everywhere.
Today's job is to remove amp from chassis and visually check for circuit damage but I suspect I won't find anything.

No smoke or smell was present, the glass just shattered.
No fuses blown.

So what should I do? check there's no visual damage, replace the tube and switch on?
Or not?
The preamp tubes should give a shit what's in the power section, right?
Jops wrote: Sun Sep 18, 2022 7:46 am Spring is the comic sans of reverbs anyway.

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Litterick
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Re: Oops!

Post by Litterick »

Assuming everything was working before you changed the valves, the problem was in the Mullard, not the amp. The Mullard was at V1, so it could not have been affected by the new valves. I would replace it and switch on (but first, I would put some protective material around the new replacement, in case I am wrong).

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Re: Oops!

Post by Jay »

You know the amp's maker. Why not ask him?

Was the replacement EeC83 pin compatible with what was there before?

Happy to check the voltages before you try a new valve

Anyway, one change at the time....
Go back to the 6L6 (after full visual inspection) and original V1. Check amp.
If it goes, you can start experimenting again, but read up on things first.
When faced with quality, I recognise it every time.

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Re: Oops!

Post by Slowy »

Jay wrote: Mon Feb 06, 2023 9:56 am You know the amp's maker. Why not ask him?

Was the replacement EeC83 pin compatible with what was there before?

Happy to check the voltages before you try a new valve

Anyway, one change at the time....
Go back to the 6L6 (after full visual inspection) and original V1. Check amp.
If it goes, you can start experimenting again, but read up on things first.
"You know the amp's maker. Why not ask him?"

Sadly Bill lost the circuit diagram. It was stored on an old hard drive. (Haven't you people heard of paper?!!!!!!)
Unlikely to be power tubes. I've switched them in and out several times with no issues; the amp is designed for this. The Mullard is the only new element.
Ah well, what could possibly go wrong........
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.

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Re: Oops!

Post by sizzlingbadger »

Probably a fault in the glass on the Mullard, try another tube, my guess, it will be fine.
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Re: Oops!

Post by clubhouse »

Dunno the specifics of the amp involved but a 6DZ7 is a twin power pentode. The incorporation of two pentode sections in one envelope makes it especially suitable for compact stereo systems. It’s essentially electrically equivalent to two EL84s in a single glass envelope…check substitution validation for the 6L6(G/GT/GB/GC/STR?) beam tetrode power valve.

Didn't even know there were twin pentode, single package valve types! I know of ECL types (triode/pentode combos) but twin pentodes...wow!

If it’s handling the 6DZ7 as a sub, it sounds like a cool as hell build…tres curious…care to share anymore about it, please? Is it substantially louder, compressed or quicker to break-up with a 6DZ7 than a 6L6? Do you change speaker loads to accomodate?

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Re: Oops!

Post by sizzlingbadger »

I'm not too sure the 6DZ7's will work that well as a direct plug-in replacement, depends on the original wiring on the socket I guess. If pin 1 & 5 (grids) are joined together and 3 & 6 (anodes) then it would run both pentodes in parallel, if not then only one pentode would be active.
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Re: Oops!

Post by Slowy »

sizzlingbadger wrote: Mon Feb 06, 2023 10:30 am I'm not too sure the 6DZ7's will work that well as a direct plug-in replacement, depends on the original wiring on the socket I guess. If pin 1 & 5 (grids) are joined together and 3 & 6 (anodes) then it would run both pentodes in parallel, if not then only one pentode would be active.
20230206_131833.jpg
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Pretty sure it's fine. :D
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.

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Re: Oops!

Post by Slowy »

clubhouse wrote: Mon Feb 06, 2023 10:13 am Dunno the specifics of the amp involved but a 6DZ7 is a twin power pentode. The incorporation of two pentode sections in one envelope makes it especially suitable for compact stereo systems. It’s essentially electrically equivalent to two EL84s in a single glass envelope…check substitution validation for the 6L6(G/GT/GB/GC/STR?) beam tetrode power valve.

Didn't even know there were twin pentode, single package valve types! I know of ECL types (triode/pentode combos) but twin pentodes...wow!

If it’s handling the 6DZ7 as a sub, it sounds like a cool as hell build…tres curious…care to share anymore about it, please? Is it substantially louder, compressed or quicker to break-up with a 6DZ7 than a 6L6? Do you change speaker loads to accomodate?
6L6, it sounds Blackface Fenderish with a bit more midrange; pretty tolerant and easy going.
6DZ7s give it much quicker transients. It seems more insistent, less inclined to compromise, snappier.
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.

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Re: Oops!

Post by Slowy »

As expected, no sign of smoke migration


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Looking inside, a couple of things stood out:

Not many builders protect the Capacitor connections this well.
20230206_131111.jpg
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And I love the power chord insulation used as spacers!
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20230206_131028.jpg (2.15 MiB) Viewed 1605 times
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.

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Re: Oops!

Post by robthemac »

Slowy wrote: Mon Feb 06, 2023 12:34 pm
And I love the power chord insulation used as spacers!

Heh.
Jops wrote: Sun Sep 18, 2022 7:46 am Spring is the comic sans of reverbs anyway.

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Re: Oops!

Post by RectifiedAmps »

Wow, it’s hard to imagine a situation where a preamp would be under enough electrical stress to explode. What was in V1 before? If it was an EF86 or some oddball valve, the mismatched pinout could’ve caused this, but just a guess really.

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Re: Oops!

Post by Slowy »

RectifiedAmps wrote: Mon Feb 06, 2023 1:02 pm Wow, it’s hard to imagine a situation where a preamp would be under enough electrical stress to explode. What was in V1 before? If it was an EF86 or some oddball valve, the mismatched pinout could’ve caused this, but just a guess really.
V1 was a Tung-Sol 12AX7.
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.

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Re: Oops!

Post by Slowy »

So I should put it all back together and turn it on, yes?
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.

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