MC2205 Love - Part 3

[Gregory]

Is an insulated backing needed?

One more consideration. Since the original fiberboard backing material in the Lamp Housing was probably used to help INSULATE the sheet metal wall from bulb heat, would it make sense to ADD a layer of fiber material between the fabricated aluminum reflector and the housing?

The reason for this concern is the TWO Meter PC boards are directly behind the lamp housing. That `light box´ gets mighty warm in just 45 minutes, and I'd not want to thermally stress the boards or their components.

The matter is worsened when the BLACK top cover is added. See below how the cover encloses the lamp housing while just clearing the Meter board tops.


Top trim cover encloses the lamp box and has vents, but doesn't shield the meter boards from heat.

Yes.. it does have vents but doesn't shield the meter boards in behind from heat. Is this of any concern? as now is the time to pull the housing (for the third time) and slip an insulating layer behind the flashing.


Views from the top

Here are a couple views from the top. A least one of the 2200uF capacitors are positioned close to the lamp housing. Another view shows where the front PC boards are generally located.


View looking down at the front PC boards.



View looking down at the voltage doubler caps.


I wonder if heat from the lamp box cooked one of those blue (formerly yellow) caps and degraded it causing Power Guard lamp trouble? After all it's been 30 or 35 years!! I firmly believe that it's HEAT that ruins electronics.


-Gregory

McIntosh owner for over thirty years.

[tony2]

Hello,
So what's goin'on since the last intervention ?

I live in France and own one since last year.
i love it but questionning myself about give him a second birth like you did.

Thank you for all this story and the clarity of your posts and informations.

See you all

[jdandy]

tony2.......Welcome to AudioAficionado.

Glad you found us. We have several members who live in France.

[Gregory]

Originally Posted by tony2

Hello,
So what's goin' on since the last intervention ?

I live in France and own one since last year.
I love it but questioning myself about give him a second birth like you did.

Thank you for all this story and the clarity of your posts and informations.

See you all

Tony.. the 2205 amplifier project was both enjoyable and very satisfying after completion. All of the `bugs´ have been fixed: burned out panel lamp, right channel cutting out, no RED Power Guard indication, only one GREEN Normal lamp lit, stiff SPEAKER rotary switch, oxidation of hardware, etc.

Now however, the LEFT power meter is dropping to zero at LOW output levels. It runs fine at medium to high outputs, so there is one more issue to solve. Otherwise.. I absolutely love the amp, and so goes the Title, 2205 Love. It's a takeoff from the title Ron C used for his C34V project. Yes.. I'm eyeing that C33 for some new caps too!

In summary I suggest the following. If it isn't broke, don't fix it!! (but you could always get inside for inspection.)


-Gregory

[Ron-C]

Heat around the meters is not an issue with 2205 amps. Look for a poor connection or bad solder for the meter problem.

Thanks,

[Gregory]

Originally Posted by Ron-C

Heat around the meters is not an issue with 2205 amps. Look for a poor connection or bad solder for the meter problem.

Thanks,

Thanks for the reply, Ron. This is not a contradiction but merely an observation. The lamp housing (as everyone knows) has round punched vent holes. There are also three groups of perforated `slots´ or vents in the top cover trim. See pic below:



MC 2205 front cover trim slots are just 0.077" from the cabinet underside. This is NOT in PANLOC detent, which is a bit further out.


Now.. with the amplifier inserted into the factory walnut case, there is only 0.077" clearance between the vent slots and the under-side of the wood. I noticed this when the amp was locked into its PANLOC position. The clearance to the Autoformers is only 0.060" and to the power transformer, even less at 0.043".

So.. it appears the airflow is restricted from the front lamp housing assembly with the amp inserted into its case. I may pull the 2205 out to the PANLOC detents if it's going to run more than an hour or two.

Next we'll have to see how `exposed´ the main heat sinks are in terms of airflow when in PANLOC detent position. After all.. we definitely want long trouble-free life.

Ron.. I'll send you a PM about the meter cutout troubleshooting thus far.


-Gregory

[Ron-C]

As long as the temp stays below 85 degree C you are safe and thousands of amps in the field have proved that over the last 40 years.
Did you put new power supply main caps in the amp yet?

Thanks,
Ron-C

[kmanusa]

My 2205 never seems to get hot at all. I do not use the walnut case, though.

I still have an intermittant left meter although mine just drops out entirely. When it does, cycling the speaker on/off switch always brings it back. I have replaced just about every cap and diode on the meter boards.

I have replaced all the output transistors and many signal path caps in both channels of the driver boards. I have replaced the input electrolytic caps (my amp is an older version w/o input board). Also replaced the main power supply electro caps. The amp works great but I never have solved the meter intermittant!

[Gregory]

Originally Posted by Ron-C

As long as the temp stays below 85 degree C you are safe and thousands of amps in the field have proved that over the last 40 years.

Did you put new power supply main caps in the amp yet?

Ron-C

Ron.. the filter caps are on the list of items to order. I may go all the way with a new panel glass if the meter repair confidence is high. Will the glass be fully prepared on the backside, etc? .. and there's the plastic bezel trim on the front side. Will need to research what adhesive to use, and how to align it perfectly.

BTW.. the link to the Filter Caps at Mouser is saved as a desktop icon. I believe this is the correct part:

36DX413G050DC2A Vishay/Sprague Aluminum Electrolytic Capacitors - Screw Terminal


-Gregory

[tony2]

Originally Posted by jdandy

tony2.......Welcome to AudioAficionado.

Glad you found us. We have several members who live in France.

Thank you and merry christmas to everybody.

So it works with no problem at all so you advise me Gregory not to go inside until something happens. I think i could have a better sound as new components would be put inside

So i keep it like that.

Do you think it is worth to replace the electrical plug and wiring with a bigger new one ?

See you all

Tony