Citation12 repair!!

[ingvar ahlberg]

Rare visitor in my workshop!
Finaly I have had a HK Citation12 in for repair, no more than 32 years of service, so much for indestructabilty!! Actually just a case of dried out electrolytics.
By the way, I have designed boards to build Mr Pass ´s Mosfet modification from scratch, niceboard based on up to date components, any one want a pair to try send me a note.

Ingvar

[Jarno]

Hello Ingvar,

A friend of mine has a Citation 12, he has already stripped the pcb's and has asked me to find the necessary components. Now, for the most part I can find equivalents, but I'm still interested to see which components you chose (especially the semiconductors, of course).
Can you send me your partslist and schematic? I'll ask this friend of mine if he's interested in using new boards. How much do your boards cost?

Thanks,

Jarno

my email: Jarno dot verhoeven at planet dot nl

[ingvar ahlberg]

Hello Jarno.
Glad to hear that Your friend is doing this mod, it makes a really good amp.
I´ll send You my schematic and partlist during the day.
The semiconductors i use are:
Output devices IRFP264, very good.
Input stage 2SK872G, among the best there is, a bit hard to find.
Driver stage Zetex ZTX653 / ZTX753.

My boards are high grade FR4 with solder resist and silkscreen.
Cost is 10 Euro /pair, (mono board).

I also bias the output stage a bit higher than the original.

Pls let me know Your progress.

Ingvar

[Mark A. Gulbrandsen]

I converted about 30 Citation 12's to the Pass circuit back when I worked at the Hi-Fi repaor shop. Every customer was blown away by the improvement.

Mark

[ingvar ahlberg]

Hi Mark

Actually i think the Pass circuit is good enough to build from scratch.
With a really overzised powersupply and better cooling to allow higer bias it becomes even better.

Ingvar

[Nelson Pass]

I'm impressed. You can have a DIY logo without a submission.
All others without a submission have to pay A THOUSAND DOLLARS!

[Mark A. Gulbrandsen]

Ingvar,
I did crank up the bias for a couple of the customers. We did listening sessions back then with several of them. All of the customers agreed it was a remarkable improvement over the stock 12.

Mark

[ingvar ahlberg]

Mr Pass!
Submitting details:
For a start, here is the boards for the citation diy. I kept them very small to keep wires around the mosfets as short as possible.
The output devices ar mounted from underneat with the pins bent 90 degrees forward, this allows for a 4mm thick alluminium plate with corresponding holes for the transistors as distance wich makes a very tight assembly on the heatsink and the boards need not be secured any other way.

[Nelson Pass]

That's really cool, and makes me feel less guilty that I haven't
updated the Mosfet Citation (another back burner).

[Bob03]

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