New tubes for my Liverpool

[Plague]

I'm hearing a "crackling" noise every now and then during practice.

At first I thought it was a bad cable or jack on my les paul but it is intermittent and seems to go away when I switch to my marshall.

My wreck has old hammond power tubes and two out of the three pre-amp tubes are old hammonds too. (1 groove tube pre-amp tube)

Question:

If I were to put a new set of power tubes in do I have to have someone bias the amp? I did not build it myself and really do not know too much about this matter.

2nd Question:

Does this sound like it could be something else besides power tubes? If so, what sort of trouble shooting might I do.

Thanks again for the help everyone!!

[fishy]

If its true to a Liverpool it will be cathode bias so it will not be necessary to rebias it.

If you have the opportunity of discussing it with the builder I would recommend that first off. They will know the amp better than you and can hopefully help out / fix it.

Some easy stuff without going inside the amp.....

You can check the tubes fit securely in the sockets and remove and insert the tubes a few times to clean the connection. Preamp and power tubes.
If you have known good tubes you can swap them out and see if it makes a difference. Pre and power.
Do the pots work properly?
Is it only after the amp warms up or straight away?
Does everything look mechanically secure?

I would also consider outside sources. Is there anything kicking in at the same time causing it....... AC for example. I tmight be as simple as incoming power.

[Plague]

If its true to a Liverpool it will be cathode bias so it will not be necessary to rebias it.

If you have the opportunity of discussing it with the builder I would recommend that first off. They will know the amp better than you and can hopefully help out / fix it.

Some easy stuff without going inside the amp.....

You can check the tubes fit securely in the sockets and remove and insert the tubes a few times to clean the connection. Preamp and power tubes.
If you have known good tubes you can swap them out and see if it makes a difference. Pre and power.
Do the pots work properly?
Is it only after the amp warms up or straight away?

Does everything look mechanically secure?

I would also consider outside sources. Is there anything kicking in at the same time causing it....... AC for example. I tmight be as simple as incoming power.

1.Pots are working properly.

2.I have some pre-amp tubes that are good laying around that I will try.

3.I only have three EL84's that are new right now though.

4.YES, the air conditioning is plugged in in the same room on its own surge protector and is a 10,000 btu AC. It does kick on and off during practice. There is also the 600w per side PA running for vocals and the bass head which is a solid state GK 450 watter or something like that.

5.YES, it seems to act up after its already warmed up.

6.I'll call the amp builder tomorrow morning and check whether its cathode bias or not.

7. Then I'll try to switch out the tubes and run some tests.


I'll check in afterwards!

Thanks so much.

Tyler