Mark IIc clean channel problem

[adamc]

Hello everyone, this is my first post, sorry to ask for advice right off the bat. But I'd appreciate any help you can give me. I have a Mark IIc head that's having some issues. The lead channel sounds awesome but the clean channel sounds terrible. It has been sitting for about 10 years so it probably needs a cleaning, but I suspect it could also be a tube. It was in tough shape when I got it and all I have done with it so far is replace the power tubes (also about 10 years ago).

The clean channel has crunch no matter how I set it and the notes have no sustain.
I really never used the clean channel for anything before I stored it, I used the amp for recording on the lead channel only. Frankly I'm not even sure I have things set properly and I've never seen a manual for this amp.

Here are a few pictures of how I have the knobs set, as well as the tubes that were installed. It has 6L6's on the inside and EL34's on the outside. The preamp tubes haven't been replaced at all.

Thanks in advance for any help!

Adam

 

[adamc]

Thanks GTS, I will replace those EL34's. The tech I took it to back when I bought it installed those, he must've been confused about the 60/100 switch. Thanks too for the link and I'll try changing out the preamp tubes you suggested.

Adam

 

[JOEY B.]

In addition to what GTS stated, I will add:

Get a new quad of 6L6's for that amp. If I were trying for a good clean sound, I would push in the Volume1 and the Treble pots. The Bass pot can be pulled to fatten up a single coil guitar sound, but push it in for a humbucker equipped guitar, for sure. 8)

 

[>Photi G<]

Make sure the master knob is pushed in. Unlike the IIC+, the IIC's had a Gain Boost switch on the clean channel, to turn it into a crunch channel. Push the switch in. Everything else (except for the EL34's) looks fine. Give the amp a good cleaning too!

 

[adamc]

Thanks guys. I need to get some 6L6's before I troubleshoot further, and I guess I should get a couple of preamp tubes as well since they are suspect. I noticed in the link that GTS sent the manual suggests using an SPAX7 tube in the V1 socket. Is that still the standard practice? BTW, does Boogie still do the IIc+ upgrade? If so any idea what they charge? In the meantime I'm going to clean it up, it is really dirty. Thanks again for the comments.

 

[JOEY B.]

One other potential issue might be your reverb tank and or connections. If any of these are suspect it can lead to added distortion. If you put in the new tubes and the problem persists, turn down the reverb control and maybe disconnect the cables from the amp chassis. This is a known issue with the older Boogies. Good luck.