My main tube amp...

Joined
Jun 12, 2010
Messages
2,492
Location
Willamette Valley
#1
A year or two ago I was fortunate enough to come across a McIntosh MC225. Only problem was it blew fuses when trying to power up. On the shelf it went for a later date.


In the meantime Local friend offered a trade for it that I bit on. As part of the trade we agreed that I'd replace the power supply and bias components and other key items later when he got them. He ended up getting a very nice AuthentiCap kit for the PS/Bias supply and I had a few Orange drops and a CL90 around to complete these areas. I installed, we turned it on and checked bias and voltage. Everything was dead on and solid. He took the amp home to enjoy.


While he had it he replaced the RCA's, the input pots and the .01uf input caps (with Orange drops). Things worked out and I ended up with the 225 back in my possession. This time it occurred to me that it's karma that I have this amp so I decided it would be best to replace the rest of the component in the amp.


I ordered Sonicap's to replace all the film caps in the amp. I used Blackgates for the two 100uf@10v caps. I replaced all the resistors with 1/2 watt, metal film, 1% resistors accept for the few 1 watt resistors which I replaced with metal oxide resistors that I matched. Ceramic caps were replaced with silver mica caps. Top Hat diodes and one previously installed 1n4007 replaced with Vishay UF4007's. I also bought a quad of new EH 7591's.


I finished replacing everything late last night. This morning I tubed the amp up and brought it up slowly on the variac. After letting it stabilize for a few minutes and not seeing any red plating tubes, I took voltage readings and checked bias. Bias was a solid -21vdc across all four tubes. All voltages were spot on. I took off the dummy loads and hooked up the test speakers. I brought it up but had no sound in the right channel. I quickly saw a resistor touching something it should not be, moved it and had sweet sound.


I've been listening to it most of the day and I have to say I've never heard my speakers sound so good. Excellent sound across the spectrum so far. Interested to see how things turn out with a few more hours on it. This one should be ready for the next 30 years or so...




















 

orange

Veteran and General Yakker
Joined
Jul 6, 2010
Messages
16,291
Tagline
Broken beyond repair but highly affable
#3
If they'd wink in random patterns it would be like Christmas. Nice work, Paul.
 

laatsch55

Administrator,
Staff member
Joined
Jan 14, 2011
Messages
56,244
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#5
Not a probnlem. i do have one serious inquiry----HOW IN GODS NAME CAN YOU WORK WITHIN AN AREA THAT NEAT????????????LOL
 
Joined
Jun 12, 2010
Messages
2,492
Location
Willamette Valley
#6
Not a probnlem. i do have one serious inquiry----HOW IN GODS NAME CAN YOU WORK WITHIN AN AREA THAT NEAT????????????LOL

No basement is one way...too hot til just last week to be out in the garage so I have to keep the area semi clean. Nothing worse than having to put everything up at night as it may be a few days til I get to it and I don't want lil'Jilly getting in it.....
 

Elite-ist

Administrator, (and straight-up pimp stick!)
Staff member
Joined
Jun 12, 2010
Messages
7,537
#9
Very nice history on your MC255, Paul. We have a few members here, who can do a decent job on repairing and restifying their vintage gear. I just didn't realize how many on this forum have such skills do undertake the detailed work I see posted.

Nando.
 

Pure_Brew

Veteran and General Yakker
Joined
Sep 2, 2011
Messages
1,854
Location
New England
Tagline
Coffee filters
#13
I want to build a tube kit really bad. But fixing up old things is fun too, and often cost effective.

....and I have Mac envy...
 

Skratch

Chief Journeyman
Joined
Dec 27, 2011
Messages
566
Location
Huntley Il.
Tagline
Life is short, so take your time
#14
There are a lot of vintage Dynaco out there, A lot of different upgrades for them. Their output trannies are some of the finest in their price range. Once they are upgraded they sound outstanding
 

Skratch

Chief Journeyman
Joined
Dec 27, 2011
Messages
566
Location
Huntley Il.
Tagline
Life is short, so take your time
#16
There a lot of upgrades from Triode electronics, Van alstine , Curio and welbourne Labs just to name a few that make great driver boards for the Dynaco's
 
Joined
Jun 12, 2010
Messages
2,492
Location
Willamette Valley
#17
There a lot of upgrades from Triode electronics, Van alstine , Curio and welbourne Labs just to name a few that make great driver boards for the Dynaco's
My favorite is from Poseidon, Shannon Sparks boards from over at DIYTube......I built up a pair of Mark III's that were great but could not hold a candle to this amp....
 

NavLinear

Veteran and General Yakker
Joined
Apr 12, 2012
Messages
5,653
Location
SoCal
Tagline
Survived the Thomas fire
#18
I must admit that the Mac's were lusted after when I was in the service and purchasing my first real audio hardware but a beer budget got in the way of something this nice. This is one beautiful amplifier and it shows the care you've given it. Almost makes me want to get a tube amp.

DDR in '76 - Checkpoint Charlie. When the train stopped traveling from Frankfurt to Berlin the East German soldiers were there waiting to surround the train at its arrival. The soldiers were standing at approximately 6 meter intervals with weapons drawn. They weren't facing the train but away from it with the intent of keeping the East Germans from hopping a ride to West Berlin and to freedom. Crazy times - not that these aren't - just different.
 
Joined
Jun 12, 2010
Messages
2,492
Location
Willamette Valley
#19
I must admit that the Mac's were lusted after when I was in the service and purchasing my first real audio hardware but a beer budget got in the way of something this nice. This is one beautiful amplifier and it shows the care you've given it. Almost makes me want to get a tube amp.

DDR in '76 - Checkpoint Charlie. When the train stopped traveling from Frankfurt to Berlin the East German soldiers were there waiting to surround the train at its arrival. The soldiers were standing at approximately 6 meter intervals with weapons drawn. They weren't facing the train but away from it with the intent of keeping the East Germans from hopping a ride to West Berlin and to freedom. Crazy times - not that these aren't - just different.
You should get a nice tube amp for sure!

The bus ride through East Germany to get to Berlin was a shock for a 17 year old kids from Missouri. Not that I wasn't expecting the "papers please" but the aisle of the bus filled with East German soldiers with submachine guns at the ready, the bus being surrounded and the mirrors, dogs and the likes did catch me off guard. And this was just going into East Germany at it's border of West Germany.

Being detained on the other side of the guard booth (between it and a huge wall with one single small door leading into East Germany) by a mountain of a woman in an East German military uniform with my "paperzzzz" in her hands had me actually scared. I was sure hoping that the State Dept would be able to get me out in a timely manner. Luckily, after some basic questions that I had the correct answers to I was allowed to spend the day in East Berlin.
 

orange

Veteran and General Yakker
Joined
Jul 6, 2010
Messages
16,291
Tagline
Broken beyond repair but highly affable
#20
I want to build a tube kit really bad. But fixing up old things is fun too, and often cost effective.

....and I have Mac envy...
Did you see link to the Dynakit auction I posted earlier this month?
 
Top