The Boogie Board

Discussion Forum for Mesa Boogie Products
It is currently Tue Oct 17, 2017 11:51 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 3 posts ] 
Author Message
PostPosted: Sun Feb 19, 2017 12:15 pm 
Offline
Mark I

Joined: Wed Mar 27, 2013 7:28 am
Posts: 21
Hi guys,

My Mesa Boogie Studio Preamp sounds superb when I first turn it on and it does sound good for at least 20 minutes or so. After that, the lead tone changes in that the low end gets really undefined, I loose attack and bite.
Clean tone remains ok. I changed a lot of tubes, pretty sure it is not ear fatigue, I also have in my rack my JMP1 which does not do that.
Tubes being out of discussion, I would guess that a particular electronic part gets too hot and changes its characteristics. Any idea what is going on here? The preamp does sound out of this world when in parameters so to speak.
Thanks, Adrian


Top
 Profile  
 
PostPosted: Mon Feb 20, 2017 3:54 pm 
Offline
Mark I

Joined: Wed Mar 27, 2013 7:28 am
Posts: 21
In the mean time I installed a fan inside. Kept it on for 2 hours, no change in the sound, it is perfect.
I also talked to a friend of mine who knows electronics, he told me that the culprit may be a tantalum capacitor in the cathode bias that changes capacity because of the heat.
The fan is silent, no annoying noise. As I kept it on on the floor, I could smell the heat of the electronics inside. It's a pitty Mesa did not provide holes on the top of the unit to allow the heat to go up but I am happy with the present solution.
Not really roomy inside the preamp, I installed the fan to blow towards the back, the heat goes out through the holes in the back. But I had to take the reverb tank out, I don't use it anyway. However, it may be more efficient to blow the air through the lateral holes but I would need a very slim fan. I can find one but it will only work at 12 volts and I would need a separate source for it. The current fan works at 230 volts but it is kinda bulky.

No additional noise generated by the fan in the signal chain.
Cheers


Top
 Profile  
 
PostPosted: Tue Feb 21, 2017 2:36 pm 
Offline
Mark III
User avatar

Joined: Sun Mar 15, 2015 4:14 am
Posts: 163
Location: North Florida
Possibly a thermal conductive resistor or part of the PCB becoming comductive under thermal stress.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group