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Post subject: Bassbreaker 18 30 Bias
Posted: Mon Mar 25, 2019 5:51 am
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Hi people
I am just retubing by bassbreaker 18 30,Is there any biasing required or is it set?
Any input would be great.
Thanks.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Mon Mar 25, 2019 6:24 am
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britpoper wrote:
Hi people
I am just retubing by bassbreaker 18 30,Is there any biasing required or is it set?
Any input would be great.
Thanks.


https://forums.fender.com/viewtopic.php?f=13&t=100205


Class A, EL84 power section; ; no need to bias, amp may sound better with bias check and adjust if needed


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Mon Mar 25, 2019 10:47 am
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stratele52 wrote:
britpoper wrote:
Hi people
I am just retubing by bassbreaker 18 30,Is there any biasing required or is it set?
Any input would be great.
Thanks.


https://forums.fender.com/viewtopic.php?f=13&t=100205


Class A, EL84 power section; ; no need to bias, amp may sound better with bias check and adjust if needed


Thanks for that.I will give it to my amp tec better to be safe.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Mon Mar 25, 2019 1:14 pm
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britpoper wrote:
stratele52 wrote:
britpoper wrote:
Hi people
I am just retubing by bassbreaker 18 30,Is there any biasing required or is it set?
Any input would be great.
Thanks.


https://forums.fender.com/viewtopic.php?f=13&t=100205


Class A, EL84 power section; ; no need to bias, amp may sound better with bias check and adjust if needed


Thanks for that.I will give it to my amp tec better to be safe.


Report what he have done.

Ask him you like to know ( for your file ) what was the original bias and what was EL84 plate's voltage
And what is the "new" bias with EL84 plate's voltage.

With these reading we/ you can lean a lot.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Sun Mar 31, 2019 1:43 am
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I replaced the tubes.
Really brought the amp to life.Set of sovtek power valves and jjs in the preamp.Very pleased with it, I wouldn't say its the quietest amp in the world but hell its loud.
Both channels are very usable.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Sun Mar 31, 2019 2:24 am
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britpoper wrote:
I replaced the tubes.
Really brought the amp to life.Set of sovtek power valves and jjs in the preamp.Very pleased with it, I wouldn't say its the quietest amp in the world but hell its loud.
Both channels are very usable.


You do by yourself or you see the tech ?
Did you ask him what is the bias now ? What was the bias before


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Mon Apr 01, 2019 1:40 pm
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Did it myself as the bias is fixed.
Thanks.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Tue Apr 02, 2019 8:59 pm
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britpoper wrote:
Did it myself as the bias is fixed.
Thanks.

:lol:

It is not a fixed bias, it is a cathode bias.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Wed Apr 03, 2019 2:54 pm
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Yes you are probably right. They have all failed.Hope the amp is not crocked.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Wed Apr 03, 2019 11:39 pm
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britpoper wrote:
Yes you are probably right. They have all failed.Hope the amp is not crocked.


You just did not know what we are talking about ; you amp and tubes are safe with this cathode bias amp.

While it is always advisable to check the bias when changing tubes, a cathode-biased amps in good condition, like yours, do not really need them.
If it was a fixed kiss, yes, absolutely.

Enjoy your amp.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Thu Apr 04, 2019 10:25 am
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Yes I understand lol.
I have put the old tired tubes back in and its working fine.
Thanks.


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Sun Apr 07, 2019 4:23 am
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Returned the tubes back to supplier.
Would have expected them to last more than 2 hours even without a bias check?


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Post subject: Re: Bassbreaker 18 30 Bias
Posted: Mon Apr 08, 2019 10:33 am
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It could toast the tubes in two hours if the bias isn't right.
I have emphasized before the critical nature of bias on an EL84.
These are smaller tubes than 6L6 or 6V6. The plate overheats easily and redplates with just a little too much current.
Further, Most of these EL84 amps don't have bias adjustment because its dial-a-bomb if yer not careful.
The factories, including Marshall and Peavey run the bias on the ragged edge of destruction to give them an agressive tone. Otherwise, these amps sound kinda cold. The factories almost always use low gain power tubes to keep the amps stable.
So suppliers get requests for low gain tubes a lot. This leaves a lot of high gain tubes left on the shelf. So what happens when you order tubes and don't spec a low gain? That's right, they reach for what's left. They send you a bomb in the mail. You put it in your amp and wonder why it went off.
You have to appreciate that when it comes to EL34 amps, the factories carefully select tubes that will last. You can now appreciate how fast they go when you select poorly.


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