New tubes in Rectoverb combo - still having problems

[KuchDaddy]

Hello! I've been lurking here for a while, but this is my first post. Seems like some very cool people here. I have learned a lot!!

I play mostly acoustic, but my son is a metalhead and we recently purchased a Rectoverb series 1 combo from e-bay and we have been trying to troubleshoot a few issues with it.

The biggest issue it had was wacky microphonic squealing when using the efftects loop. The amp has (allegedly) brand new JJ tesla power tubes, but the preamp tubes were old, so we replaced all 5 of them with Electroharmonix 12AX7EH's with a balanced tube in the phase inverter position. That totally fixed the effects loop, which was nice, but we are still having other issues, which I still think might be tube related and I am wondering if we got some defective tubes.

The problems are:

1) VERY loud huming on the lead channel. This problem is intermittent and there seems to be no rhyme or reason as to when it happens.

2) General random noisiness, pops and crackles. Again this is intermittent and only on the lead channel, but seperate from the humming described above.

3) The reverb on the rhythm channel sounds like utter crap. Apparently the reverb tank didn't used to work at all until the previous owner replaced the reverb tank and cables with brand new ones. Now it works (I guess), but sounds bad.

I was wondering if any of you folks might have any ideas about what else to try before I take it to a shop. I guess it's possible that one or more of my new tubes are bad. Maybe I should have bought a spare to swap around.

Thanks in advance!!

 

[stokes]

Try wiggling each tube in its socket with the amp on and no guitar connected,put the volume as loud as you would if playing thru it.You are checking for loose and or dirty tube sockets.You are listening for noises when the tube is rocked.Check the clean setting too,it will be louder on the lead because of the extra gain.Since it is a used amp I would clean and retension the sockets,this could cause a lot of noise in a high gain amp.As for the reverb,do you know what repair was made to it?Are you sure it is the right tank?

 

[KuchDaddy]

Thanks for your help, I will check on the tubes when i get a chance. What is the best way to clean the tube sockets, compressed air? And I didn't even know you could retention the sockets. How do you do that?

As far as the reverb goes, according to the previous owner, the reverb did not work at all when he got it. He replaced the reverb tank with a new "Accutronics 9AB2A1B" tank from "Antique Electronic Supply". The companies web site says that this tank is used in "Fender and Mesa Boogie Amps", but I do not know for a fact that it is the OEM tank that comes in a series 1 rectoverb.

The sound of the reverb on the clean channel is as if everything you play is doubled very quietly by a very distorted guitar. Not appealing at all.


Again, thanks for your input.

 

[stokes]

To retension I use a dental pick,some people I've heard use heavy needles.Its just a mater of squeezing the female receptacle tighter in the socket.To clean them use contact cleaner,the stuff radio shack has is fine.I prefer the type that leaves no lubricating residue.Just spray some on the tube pins and work the tube in and out of the socket,in a circular motion.The reverb sounds like there is something wrong.Could be tubes could be the wrong tank,could be a grounding issue.Can you turn it off?I mean with a footswitch not just turning the knob down.If not disconnect your reverb cables from the chassis and see if the other noises go away.Reverb malfuntions can cause a lot of different symptoms.

 

[KuchDaddy]

Hey, I just thought of something. When I first got the amp, the power tubes were packed seperately and I had to install them. When I did, I noticed that one of them was so loose that I was afraid it would just fall out of the socket. Since the power tubes had those spring retainer thingies to hold them in, I thought maybe that it was OK and that they would be held in by the retainers. Maybe I should try to fix the tension in the powe tube sockets too?

 

[cesjr]

If I was a bettin' man I'd wager that's your problem right there. I had a similar problem with my Mark IV when I changed power tubes. The variation of pin diameters made my new tubes extremely loose. To the point where I was afraid one would fall out with a little vibration. I re-tensioned the tube sockets and the problem went away.

 

[stokes]

I have heard reports that the JJ tube pins were thinner than the standard size on other tubes.There was word that they have correected the problem,but you could have the older ones,I am sure there are still many out there being sold.I would also recomend checking the amp with the reverb cables disconnected at the chassis.As I said before reverb problems can cause a lot of different noises also,could be a combination of the sockets and the reverb.

 

[KuchDaddy]

Well, I cleaned and retensioned all the tube sockets and problems #1 and 2 are gone! Woohoo!!

I am still having reverb woes in the clean (rhythm channel). Apart from the reverb itself sounding distorted as described previously, I am experiencing the following problems when using reverb on the rythm channel.

1) Reverb cuts in and out. It seems to be sensitive to what I am playing, like certain notes tend to cut out or in more than others. I can kind of make it happen by playing certain phrases. Very annoying.

2) If I have the reverb "off" at the footswtich, I can still hear a little bit of reverb. It goes away if I turn the reverb know all the way down.

I am very thankful for the help I have received so far. If anyone has any reverb ideas, please chime in.
Thanks!

 

[stokes]

Good to hear some of your problems are solved.You describe the reverb problem being on the rhythm channel.Is it okay in the lead mode?Has it improved/changed since your first description in the previous post?The cutting in and out and the fact that you still hear some reverb with the switch off leads me to believe it is a grounding issue.I am not familiar with that particular amp,but if you can unplug the footswitch from the amp,try it and see if the problem goes away.If it does the contacts in the switch would be suspect.If not I think it may be a grounding issue in the circuit itself.If you call Mesa they may know of a problem that is common to that particular amp.

 

[KuchDaddy]

Thanks stokes!

If I unplug the footswitch, the reverb is "on" and I still have the problem.
The problem only exists on the rhythm channel, or at least it's more noticeable there with the clean tone. I will test it thouroughly on both channels so I know for sure and then give Mesa a call.