'The Music Room'
'The Music Room'
TECHNICAL DIARY 2010
The precious few hours of free personal time I have left to work will be documented here. This part hopes to share my direct experiences as my restorations, D.I.Y. activities and repairs take form.
AIKIDO PREAMP OUTPUT CAPACITOR UPGRADE
The Mad Modman is onto a Russian Teflon and Oil capacitor thing, so he suggested that I try some in my DIY gear to see if they made a difference. Well I said "OK" and proceeded to warm up the Weller.
So here is the photo of the 0.47 uF Teflon Russian Military Capacitor upgrade. And wow, these thing put any of the fancies to total and utter shame.
Immediately the music became better. How, well the Bass performance is now up to par. Whenever I swap capacitors I listen for improvements at the frequency extremes first to see how they are behaving.
The midrange is very nice. So for a song, you can try these caps and see if they improve your musical experience.
These part are built like they were made to be installed inside a Missile. They don't have leads but have metal lugs.
Enjoy the photos... a bit blurry but the camera is a Casio and all of the photos it takes are out of focus even though it's an 8 Megapixel.. My SONY Cybershot from 2001 smokes the Casio dead, and it's only a 3.3 Megapixel, but it has Carl Zeiss optics,, ahhhh das ist wunderbar.
I also put 4x 0.22 uF of these in my KT88 Monoblocks and they also made a definite improvement over the Kimber Caps.
MESA BOOGIE .50 CALIBER COMBO AMPLIFIER
The Mesa .50 Caliber amp is but one example of how a PC board failed to age gracefully and how NOT to put together a guitar amplifier if you want it to become a classic design.
Looking at the heat damage, I can see that the heating problems are mostly located right at the point where the 9pin ceramic tube sockets are soldered to the board itself. Also most of the heat from the power tubes aged the board and caused it to degrade.
Also it is obvious that this board was worked on many times as it developed the symptoms of a sick and overheated PC board. Several repairs have lifted PC board traces and ruined the board, requiring jumpers.
The reason why we see this kind of damage is simple. The PC board is mounted inverted, the tubes facing down and the heat from all of the tubes rising up against the component side of the board.
You can clearly see the effects of this heating on the foil side of the board. The component side shows discoloration around the tube bases.
I called Mesa on the phone and they said that the PC board is not available any longer. Granted they were very courteous, helpful and empathetic.
The photos were taken by me during the repair process. You can almost smell the BBQ as you see what heat and moisture can do to a Mesa .50 Caliber PC board. I attempted to jumper all of the burned PC board traces, and the bias of the 6BQ5's continues to jump from -19 to -7.5, switching sides on my last attempt to find a better ground.
I gave-up and concluded that the amp needs a replacement PC board, no longer available. If the owner has the desire, I could re-wire this amp completely point to point by mounting the sockets directly to the chassis and implementing new sockets with covers for the 12AX7/12AT7 and spring loaded retainers for the 6BQ5's.
CLASSIC MARANTZ MODEL 7 PREAMPLIFIER AND MODEL 9 MONO-BLOCK AMPLIFIERS
In for repair a totally retro-classic vintage paired set of Marantz Tube equipment.
On order are a pair of Marantz 9 Main Power Supply capacitors.
(1) 40/40/40 uF/525 VDC CE Manufacturing FP plus (4) JJ 100uF/385VDC capacitors; 7/8" diameter.
I am tempted to spray these caps with some "Heat Resistant" Grey paint to maintain that original Marantz look.
Some people get really nervous about changing Marantz parts but wouldn't think twice about plugging these into the wall blind.... go figure.
Some Variac action is due and once they play, I will break them back into normal operation and finish any leaky cap or drifted resistor.
Once they are working, they will be up for sale.......................... any offers ????????????????????????????????????
