Mark IV having issues

Hey all,

My Mark IV has been acting rather odd for a while. A few months ago (I haven't been home much to play it since I'm away for school), the amp completely fused out. I replaced the fuse and have been running it on a lower power setting, but, overtime, I noticed that the amp takes about 10 minutes to turn on and come to complete volume. Another issue is a large amount of crackling and hissing that's occurring. I've tried dealing with the tubes and such, but I'm not having any luck in identifying what is going on. Has anyone come across this before?

Thanks.

Replace the tubes.

The fuse acts as a protection device and typically blows when you have a shorting power tube (or rectifier tube in amps that have them). You say you've tried dealing with the tubes, but what does that mean?

Have you tried replacing the power tubes? What type of preamp tube troubleshooting have you done? The more info you can provide the better we can find a solution. Thanks!

Authorized Boogie said:

The fuse acts as a protection device and typically blows when you have a shorting power tube (or rectifier tube in amps that have them). You say you've tried dealing with the tubes, but what does that mean?

Have you tried replacing the power tubes? What type of preamp tube troubleshooting have you done? The more info you can provide the better we can find a solution. Thanks!

Click to expand...

I saw a video Mesa posted about helping to identify tube issues. You can tap the tubes and they make a ringing noise. Nothing happened when I did that. I even swapped the power tubes out for new ones and still nothing. I haven't gone through and replaced all preamp tubes at the same time, but I did rotate a new tube for each spot. Perhaps, it's all of them?

steeldragonjovi said:

Authorized Boogie said:

The fuse acts as a protection device and typically blows when you have a shorting power tube (or rectifier tube in amps that have them). You say you've tried dealing with the tubes, but what does that mean?

Have you tried replacing the power tubes? What type of preamp tube troubleshooting have you done? The more info you can provide the better we can find a solution. Thanks!

Click to expand...

I saw a video Mesa posted about helping to identify tube issues. You can tap the tubes and they make a ringing noise. Nothing happened when I did that. I even swapped the power tubes out for new ones and still nothing. I haven't gone through and replaced all preamp tubes at the same time, but I did rotate a new tube for each spot. Perhaps, it's all of them?

Click to expand...

Tapping tubes will only test for microphonics.

Did you swap out both pairs of power tubes with a new pair?

Tot trouble shoot the preamp tubes, take a new/known good 12AX7 and swap it into each preamp position, one position at a time. Test the amp in-between each swap to pin-point the tube that is potentially causing the issue.

Also, run a simple patch cable from the fx send to the fx return. If this helps, it indicates that the jacks need to cleaned - as they carry signal when nothing is plugged in. Simply spray contact cleaner on the tip of a 1/4" cable and excecise the jack 4-5 times.

You can find your nearest Authorized service center by using the search, here: http://www.mesaboogie.com/US/Dealers/locator/zip_search_r.php

Or, for a factory repair, please contact our Service Manager Rich Duvall at 707-778-6565, ext 324 for more info on service or to obtain a Return Authorization number.

steeldragonjovi said:

Hey all,

My Mark IV has been acting rather odd for a while. A few months ago (I haven't been home much to play it since I'm away for school), the amp completely fused out. I replaced the fuse and have been running it on a lower power setting, but, overtime, I noticed that the amp takes about 10 minutes to turn on and come to complete volume. Another issue is a large amount of crackling and hissing that's occurring. I've tried dealing with the tubes and such, but I'm not having any luck in identifying what is going on. Has anyone come across this before?

Thanks.

Click to expand...

Very typical of a tube amp that doesn't get turned on on a regular basis.

Try turning the amp ON, but leave it in STANDBY for an hour or 2. You might vigorously twist all the knobs back and forth while the amp is in standby. I'll bet you'll experience a lot less problems.