The Citation 16A resurrection project

[taj]

I've inherited a great project. I was given a Harman Kardon Citation 16 chassis including power transformers; heatsinks with output devices and emitter resistors; and the protection relay PCB.

What I didn't get was the main "driver" PCBs -- the main amplifier circuit itself. And the amplifier was a plain-faced version which didn't come with those trademark V shaped LED arrays.

So my project will be to re-create the missing parts for this puppy based on the information contained in the service manual for the Citation 16A, the discrete version of this amplifier. I will create all the missing circuit boards and add the LED arrays for fun.

But I'm going to need help since I'm just learning electronics. Especially given the age of this circuit and its parts list. Hence the thread.


..Todd

[taj]

The first question that comes to mind is regarding some nomenclature in the parts list...

Many of the small signal transistors are labeled PNP GP or NPN GP. Does the GP just mean "general purpose" so that my pile of 2n5551/5401's will fit the bill?

And for the input differential pair (a nameless dual NPN job), will a pair of matched, thermally coupled 2SC2240's be adequate? They are low noise, linear...

..Todd

[taj]

By the way, I've created drawings for all of the PCB's for DIY board etching. They are PDF files meant for printing out and home etching, not Gerber files for professional manufacturing. All the boards are single sided.

I don't know how to use any of those PCB CAD programs. But I am a technical [computer] illustrator, so the drawings are quite satisfactory, and accurate since I traced the parts layout from the service manual (with a few minor tweaks here and there).

Anyone wanting the drawings is welcome to them. Just send me an email.

..Todd

[EchoWars]

I'm anxious to see how it goes...

[PB2]

Please post a link to the schematics.

Pete B.

[taj]

I intend to set up a web page eventually for this project with photos of the progress (or lack thereof) but it's not a priority, so email contact will have to suffice until then. If I do that, I will post a link.

The email button in DIYAudio should work. Or you can use...

100 amps at g mail dot com (with spaces removed and at/dot replaced appropriately).

..Todd

[taj]

Originally posted by PB2
Please post a link to the schematics.

Pete B.

Doh. (Note to self: Wake up, drink coffee, THEN read messages.)

Schematics are here...

Click me

..Todd

[PB2]

OK, you might notice that everything to the left of Q12 and Q13 operate at a reduced supply voltage of +/- 10V. This is not commonly done, and you might notice the unusual 2 stage VAS employed to get from the lower front end voltage to the full output voltage. Interesting that it is similar to the Tiger output stage that I have commented on in other threads.

They're running the front end at a reduced supply so that they can use lower voltage/power transistors better suited to the job.
My guess would be BC547C and BC557C for all in the front end.

Duals are discussed in this thread:
Matched PNP/NPN dual transistors

The fact that the emitters share a common pin should be a hint as to the correct device. This is a disadvantage since no emitter degeneration can be used. I prefer the LM394 but it is not what was used since the emitters do not share a common pin.

Pete B.

[PB2]

Looking at the design has me wondering if it is reliable and stable, as it is rather complex. I did a quick search, note the comment about being in the shop:
http://forums.audioholics.com/forums...p/t-11047.html


You might consider using a proven reliable design. Do you know if the output transistors are good?

Pete B.

[taj]

Hi PB2,

Interesting comments. Thanks.

I certainly have no concerns regarding the reliability of Citation 16's.

The stability of Citation 16's is, however, is a subject I'm not qualified to comment on, though I haven't heard of any oscillation issues with these. Anyone?

I haven't looked closely at my output devices or drivers yet, but they are easily substituted/replaced if need be, albeit in an all-or-nothing ($$) manner.

These amps have proven themselves to my satisfaction. They certainly aren't at Pass or Kress level, but they are a well-respected classic amp, and I'd love to rebuild this puppy for the nostalgia & fun of doing so.

We used to torture these things in our 70's garage band. I don't recall what they sounded like, but it wouldn't have been relevant anyway, since I believe it was driving old JBL phenolic diaphragm hi-mid horns and 15-inch low-mid cabinets. All fed horrid cover music by a bunch of 14-16 year olds, through $25 microphones and $150 mixers. I think the 'torture' applied to the drummer's parents upstairs too, who probably wanted their prized Citation 16 back in the Hi Fi cabinet where we borrowed it from.

..Todd