Harman Kardon Citation II Rebuild

[jackthehack]

This will get you down to 18 Hz and will match your Zebrawood build:

http://www.klipsch.com/na-en/products/p-312w-specifications/

 

[mayfly]

Folks,

I ordered up a bunch of replacement parts from Mouser two days ago.  Today, this arrived:

Everything in the order was perfect.  You folks in Texas should be proud that you have such a fine electronics distributor in your home state!  ccasion14:

 

[mayfly]

More news.  I removed the power tube sockets and 'A/C balance' pot from the A channel.  All are junk.

Here's a good shot of the heat damage with the sockets removed:

Heat is a very annoying thing.  It completely carbonized the insulation on several wires, to the point where they crumble when they are touched:

Replacement is the only way forward here.  Unfortunately, these wires were coming from the O/P and power transformers, which are potted.  That means time to splice:
First, cut the wires back to a point where they are not heat damaged (otherwise they'll be impossible to solder to as the melted insulation contaminates the wire.  Oh - I also cleaned up the chassis in this shot:

Then solder on the replacement wire.  Years of building amps with new transformers gave me a lot of wire ends to choose from in several colours:
Make your splice:

Then insulate the bejesus out of it.  I used two layers of heat-shrink. I might use more if I get more paranoid.

 

[Super Turbo Deluxe Custom]

You said it weighed about 70 lbs.  It would've been intersting to have an exact measurement before, then another after the rebuild.  It probably wouldn't have been a substantial difference because the case, the tubes, and mostly the transformers are the lion's share of the weight.  I wonder if the smaller caps shaved any weight off.

 

[Dan025]

It's a hifi, I think that kind of low end response is expected for hi fi equipment.  Gotta get a woofer to hear it!  :guitaristgif:

I know, but most subs I've seen have the low side of frequency resonse in the 30s Hz range.

can't hear it!
ya can certainly feel it though. think earthquake
old church organs had a low note that had like a 64' pipe. not sure if that is the right length but it resonated at 16hz or so they were often capped off do to it causing structural damage to the building.

anything that goes that low usually has passive radiators in place of ports, too much turbulence with ports.
i cant remember the company but there was a speaker that used a servo motor with a low moment of inertia that drove two opposed cones via a belt system. the box was huge and had many passive radiators.
they were used on rides at universal studios i think, and nasa used them for shuttle launch simulations.

looks like a nice peice you got there, i'm jealous. im a harmon kardon fan, i have only owned there entry level stuff but it blows the modern jap garbage away.

 

[Patrick from Davis]

You might look into teflon heat shrink tubing if you are worried about those solder joints getting frisky.  It should have a very high voltage rating.
Patrick

 

[mayfly]

More news.

While waiting for the sockets and capacitors from Antique Electronic Supply (which unlike Mouser seems to take forever to get here), I decided to test the windings of the output transformers to see if there were any shorts.

I did this by applying a 1V P-P (0.68 VAC) 1kHz signal to the output jacks, then measuring the resulting voltage on the primary windings.  Here's the results for the various speaker output taps:

O/P Tap	A Channel Primary	B Channel Primary
16 Ohms	9.80 VAC	9.80 VAC
8 Ohms	13.59 VAC	13.52 VAC
4 Ohms	18.53 VAC	18.34 VAC

I also did the same measurements at the UL taps with similar results.  This shows that not only are the output transformers functioning with no shorts, but they are fairly well matched as well.  So far so good.

 

[Return of Guitlouie]

Ok....so I've been watching this with interest.  VERY cool little project you have going there, Trevor.  But what the vinyl junkie in me must know is what are you going to run into this thing once you have it up and running? (please tell me he has some super cool turntable, please tell me he has some super cool turntable, please tell me he has some super cool turntable)

 

[Death by Uberschall]

Ok....so I've been watching this with interest.  VERY cool little project you have going there, Trevor.  But what the vinyl junkie in me must know is what are you going to run into this thing once you have it up and running? (please tell me he has some super cool turntable, please tell me he has some super cool turntable, please tell me he has some super cool turntable)

He has an iPod, he has an iPod , he has an iPod!!!  :icon_jokercolor: :headbang1: :icon_jokercolor: 

 

[Return of Guitlouie]

Ipod=weird digital compression.    Records=good analog compression.

 

[Super Turbo Deluxe Custom]

It's his new poweramp for his PA.  No more Bose.

 

[mayfly]

Welll, the first test source for this will likely be an iPod.  After that I've got a Rega Planar III turn table into a Manly Labs all tube turntable pre-amp. 

So you're both right!  :headbang:

Oh - and there is no freaking way I'm going to be lugging this monster to gigs!  :doh:

 

[mayfly]

More news.  Decided last night to work on the power supply.  I had chosen a set of 12-12 hexfred diodes for this project:

These are 'fast recovery' diodes that have low switching noise.  This hopefully will translate to less 120 Hz noise in the amp.  Unfortunately, whoever dreamed up the packaging for these suckers put the cathode on the exposed tab on the end.  Since these will be several hundred volts above ground, I decided to do the double heatshrink trick again:

I also figured I should use a bus bar for grounds, since soldering to the aluminum plate is guaranteed to make a bad connection.  I used 14 gauge copper:

The diode on the right is for the bias supply.

 

[MUYFUE]

It's all a mystery to me.  :tard:

Looks cool though. I KNEW there had to be SOMEBODY who understood all this gunk! I'm stupified, but interested.

 

[Alfang]

your gonna leave those diodes like that? your not gonna (heat)sink em?  just curious

 

[Death by Uberschall]

your gonna leave those diodes like that? your not gonna (heat)sink em?   just curious

I was thinking the same thing. Are you running a risk of them overheating without a base plate to absorb and dissipate the heat?

 

[mayfly]

Nah - at the current they will be running they should run cool w/o a heat sink.

I'll let you know if I'm proven wrong!

 

[mayfly]

for those who care, here's the data sheet on the FREDs:

ixdev.ixys.com/DataSheet/L187.pdf

These suckers are rated at 15A continuous with 35A peak (!).  In this amp they will see mA, so I'm not worried.

 

[Mor Paul]

Ok....so I've been watching this with interest.  VERY cool little project you have going there, Trevor.  But what the vinyl junkie in me must know is what are you going to run into this thing once you have it up and running? (please tell me he has some super cool turntable, please tell me he has some super cool turntable, please tell me he has some super cool turntable)

I'll need to check out your record collection when I check out your Bassman  :icon_thumright:

 

[mayfly]

Folks,

Just got the Antique Electronic Supply order.  The things in the foreground are the caps.

Now we are rolling!

and of course I could not resist picking up a T-Shirt at the same time