Harman Kardon Citation A transistor help.

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Hi everyone,
I have a very nice Harman Kardon Citation A Solid State Preamplifier I bought from the original owner a short time ago. I recently started having problems with the left channel and using freeze spray have tracked the problem to a transistor (HKT-11-IND 323) in what appears to be a TO-18 package.

Unfortunately it looks to be either a repackaged third party or proprietary component as I can't find any information on it. There are (2) of these (HKT) transistors on this board and both having different ending numbers (323 and 10-3). There is also a third transistor which is an RCA 531-7403d VPYD3G (can't find any info on this one either). There is also a variable resistor which I assume is a bias adjust. There are a total of 11 of these boards with 7 of them being amplifier modules and 4 emitter follower modules.

My main concern is finding the replacement or equivalent of the aforementioned transistor. I've tried finding service manuals and Sams Photofacts but to no avail. I also contacted Harman International and spoke to a young man who was their "Senior" tech and he had no clue as to what I wanted. I suspect that he was born 20 years after this preamp was produced. I do have the schematic and the transistor numbers on the board are Q5316803, Q5316804 and Q5316864. Since the two are in sequence I figured they aren't going to be useful to me. I can email the schematic to anyone who can be helpful in ascertaining possible replacements. Any information on this preamplifier would be greatly appreciated.

Bruce
 
If all else fails, you might pull good right channel transistor and measure HFE.
At the very least, you would learn if the mystery transistor was NPN or PNP?
And measuring VBE drop can determine if a transistor that old could have
been germanium? ( I'm looking at a 2N1373 germainum in TO-18 as I type.)
 
Hi kenpeter and djoffe. Thanks for your suggestions. How should I post the schematics? They are a pdf file. Thanks.
I am very interested to the schematic. Can you send me the pdf? Perhaps I can convert for posting and can give you some advices.
My e-mail address. kirschner-hifi@tiefbasswiedergabe.de
Thank you very much.

I am also looking to the power schematic of the associated "Citation B".

looks your preamp like post #5 ? go to
http://www.diyaudio.com/forums/soli...ion-harman-kardon-citation-b-1963-1964-a.html
Harman Kardon Citation A ??(???)_??????-????-?????
 

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Hello Bruce,

I have a Citation A and i'm having the same problem as you. Could you send me the schematics? I live in Brazil and can't find it here.
My email is: :cop: email removed please use PM or forum email option.

Best regards,

John T.
 
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Note that the transistors in the Citation A are all germanium and are not easily available.
Sams photofacts for this model IIRC lists acceptable generic subs for the HK house numbers. When working well this is a very nice sounding pre-amplifier.

I used to service these units and it is possible to modify the unit to perform comparably with silicon transistors. (It is a lot of work however)
 
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Note that complementary pairs are used in the push pull follower cards and that the amplifier stage cards are compound-complementary amplifier stages. This was a sophisticated design and several different types were used.

Try to get a SAMS photofacts for this pre if you can find it - things will be 100% clearer.

You should try to replace all of them as they will all eventually fail. Electrolytics should be replaced as well, and there are lots of them.
 
Odd transistors

Any luck with this guys? I have kept mine going using NTE100,101,102,&103 at various points in the circuit. However, that transistor in the gain cards who's emitter connects to the -22.5V rail seems to be irreplaceable. It has a very high Vbe and seems to change with base current. The circuit will not work with any Ge or Si replacement here.... it has some internal magic which is unfamiliar to me! I have even tried changing Rb and adding Re. That isn't stable over temp, either. I used the one off the center channel as a spare.... now I need another. :( Any ideas what this device is? (PS I have schematics and a lot of experience with this unit if anyone needs some help)
 
Hmmm I hadn't thought about a zener. The setpoint of the transistor in question is easy to achieve and is stable over temp. However, it wreaks havoc on the intput transistor.... and nothing I have tried has kept it from a. not turning on at all b. motorboating c. saturating itself. Or if I get it right hot/cold, it won't stay. I can get it perfect at hot.... but then at cold, it's off and won't ever bias on as the unit warms up.
 
This module is a DC-coupled amplifier(we're talking module type II here,aren't we?) and as such it has to have all three transistors working correctly or you will get all sorts of trouble.
Q5 draws around 10mA at 12,5 V and that means 125mW over the transistor.Some heat will be generated here.

I would try to get all DC voltages correct.
 
Yeah I know. But, i can't get them correct over temp (over the entire temperature range) without the magic of that oddball transistor! The best I've been able to achieve using multiple pot's and some emitter feedback is to get it all perfect at hot. But, then at cold, leaving that setting, the input stage is just off (0 mA) and won't ever turn back on - even as the rest of the stuff warms up.

Trying to adjust it at cold is even more useless because it just won't stay.

I really would like to know what that little guy is! It's a similar situation on all the gain cards - albeit with different bias points. One thing I have not tried is using my emitter feedback setup in the type 3 cards which run more bias current in the input stage. Perhaps it would be more thermally stable. And, i could run the more finniky phono stage with the correct parts. But, I'm about ready to just dispense with both left and right type I cards and do something completely different. Really don't want to tho....
 
I have a friends "parts" Citation A in the shop right now. I used my Peak Component Analyser to scan the "mystery" transistor. I pulled (CAREFULLY) a good one from a module and scanned it. It checks as a 30 HFE NPN device. Now the fun part. A germanium device scans as a .2 to .3 volt diode when checked as a base to emitter junction only. Same as a collector to base junction only. The scanner says .73 volts on both junctions. It seems the mystery device may be a silicon device with very low HFE. Since the Citation B was the companion amplifier ( I own a working one), it is silicon devices. Maybe a silicon was snuck into the "A"! I have to find a device with low HFE. The silicon ones around here all go very high HFE (150 or higher).
Any thoughts?
 
I'll get the module schematic and take a picture and post it. The entire schematic is huge. All the gain modules are very close except for a few resistors and electrolytic values.
In most cases, open electrolytics account for the troubles in these units. There are a million of them!
 
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