Re: UA 739
Have you used any of them in a Citation? I have a few myself. Prior to building new 16A driver boards from scratch, I thought I would get the amp running properly with the original boards and new outputs. The one that I am working on was a non-working Ebay unit at $49, one dead channel. The primary problem was shorted diodes in the power supply for the RH channel, quick and easy to fix. After the diodes were changed, the amp had substantial DC offset on the RH side, around 150-200mv, and could not be set, lots of drift, unstable and swinging positive to negative quickly when an attempt was made to zero it out. I left it sitting awhile, and while checking bias, goofed up and shorted an output to ground. It is now getting a full set of MJ15024 outputs, and I am replacing all electrolytics plus the UA739's. Per advice in another thread, the drivers will be MJ15024's as well, unless someone convinces me otherwise. I am curious if the Korean devices have any issues that may make them undesirable compared to original USA made Fairchild product.
vhinze said:
Have you used any of them in a Citation? I have a few myself. Prior to building new 16A driver boards from scratch, I thought I would get the amp running properly with the original boards and new outputs. The one that I am working on was a non-working Ebay unit at $49, one dead channel. The primary problem was shorted diodes in the power supply for the RH channel, quick and easy to fix. After the diodes were changed, the amp had substantial DC offset on the RH side, around 150-200mv, and could not be set, lots of drift, unstable and swinging positive to negative quickly when an attempt was made to zero it out. I left it sitting awhile, and while checking bias, goofed up and shorted an output to ground. It is now getting a full set of MJ15024 outputs, and I am replacing all electrolytics plus the UA739's. Per advice in another thread, the drivers will be MJ15024's as well, unless someone convinces me otherwise. I am curious if the Korean devices have any issues that may make them undesirable compared to original USA made Fairchild product.
btw, i noticed somebody was asking about an offset problem...... check the picture on page 5 of this thread. the pot near the metal can near the top of the board (the pot that is on the upper right) is the offset pot, the other pot on the lower center of the board is output bias. you should have very little trouble getting the offset adjusted to +/-5mv. once set, it should drift very little. if the amp isn't running hot, don't mess with the bias!!!!!!!
the amp has 500w worth of output devices and about 300w worth of power supply for each channel, but is (very conservatively) rated at 150w/ channel. it should happily do 250w/ch into 4 ohms, since it's also rated at 500w/8ohm bridged.
each channel has a separate power supply, so the normal power limitations of a stereo amp do not apply. this amp is essentially two monoblocks in one box.
the amp has 500w worth of output devices and about 300w worth of power supply for each channel, but is (very conservatively) rated at 150w/ channel. it should happily do 250w/ch into 4 ohms, since it's also rated at 500w/8ohm bridged.
each channel has a separate power supply, so the normal power limitations of a stereo amp do not apply. this amp is essentially two monoblocks in one box.
At the bottom of this site:
citation sixteen séries A
you will find the schematics, parts lst and PCB part placement drawings.
Hope this helps
Regards
James
citation sixteen séries A
you will find the schematics, parts lst and PCB part placement drawings.
Hope this helps
Regards
James
unclejed613 said:
I know of four basic versions. There was an original circuit configuration with early driver boards, built with or without LED Vu meters; there was the 16 series A with discrete circuitry for the driver boards, also with or without LED Vu meters. None had a volume control. The 16A had a silver pushbutton power switch, early amps had black toggle switches. Those with LED meters could be had with silver or with black faceplates. All had a main front panel that was black anodized. I guess that's all...
From a marketing perspective, HK offered a plain "purist" version of a couple of Citation products. Thus the 16 with or without meters, the Citation 17 preamp with EQ or the 17S with no tone controls at all.
Korean U739s
Yes, I have a C 16 running right now with the Korean devices, it's been in business for over a year with no problems and sounds fine, (to me). I installed the 739s in sockets I added to the original board. All electrolytic caps have been replaced, including the non polar electrolytics on the driver board. MJ15024s populate the heat sinks.
While I was at it I moved the 10 mfd 250 volt electrolytics to a position accros the 10K power caps instead of accross the rails on the heat sink. this is the same electrically according to the schematic, sparing the caps the heat they soak up in the stock setup and imporving airflow thru the heatsink chimney.
I also added a "hexafed" diode assembly I saw touted on eBay along with the additional filter caps this kit came with. The kit ran me about 80 dollars at the time, works fine too.
Yes, I have a C 16 running right now with the Korean devices, it's been in business for over a year with no problems and sounds fine, (to me). I installed the 739s in sockets I added to the original board. All electrolytic caps have been replaced, including the non polar electrolytics on the driver board. MJ15024s populate the heat sinks.
While I was at it I moved the 10 mfd 250 volt electrolytics to a position accros the 10K power caps instead of accross the rails on the heat sink. this is the same electrically according to the schematic, sparing the caps the heat they soak up in the stock setup and imporving airflow thru the heatsink chimney.
I also added a "hexafed" diode assembly I saw touted on eBay along with the additional filter caps this kit came with. The kit ran me about 80 dollars at the time, works fine too.
Citation Sixteen DC offset woes
I have recently developed a problem with my C16 amp,the model with the IC input stage. I noticed the VU lamp flickering on one channel at idle.
I've tried a new ua739, replaced the nonpolarized 10uF caps and switched the channel A and B boards. the problem travels with the B driver board.
I have VR 1 cranked all the way to the negative 10 volt rail and the DC offset won't go below 990 mV.
I suspect it may be one of the ceramic caps in the feedback network around the opamp. But what a pain to troubleshoot.
Anyone got wisdom to share?
I have recently developed a problem with my C16 amp,the model with the IC input stage. I noticed the VU lamp flickering on one channel at idle.
I've tried a new ua739, replaced the nonpolarized 10uF caps and switched the channel A and B boards. the problem travels with the B driver board.
I have VR 1 cranked all the way to the negative 10 volt rail and the DC offset won't go below 990 mV.
I suspect it may be one of the ceramic caps in the feedback network around the opamp. But what a pain to troubleshoot.
Anyone got wisdom to share?
Doesn't sound weird at all!
One of the first things I did when refurbishing the amp was scrub everything clean with 99% alcohol. The electrolytics on the driver board and elsewhere have been replaced and the amp ran well for over a year.
I did not mention in my previous post that the amp reproduces material ok, but there are rustling noises and an occasional pop,
not very loud though.
I tend to associate the noises with a defective cap. The ceramic caps are such low values, it's hard for me to see how to measure or test them definitively.
I also need to spend more time snooping around all the signal Q's on the driver board and look for good forward voltages.
One of the first things I did when refurbishing the amp was scrub everything clean with 99% alcohol. The electrolytics on the driver board and elsewhere have been replaced and the amp ran well for over a year.
I did not mention in my previous post that the amp reproduces material ok, but there are rustling noises and an occasional pop,
not very loud though.
I tend to associate the noises with a defective cap. The ceramic caps are such low values, it's hard for me to see how to measure or test them definitively.
I also need to spend more time snooping around all the signal Q's on the driver board and look for good forward voltages.
Solution to my bias problem
After studying the schematic and plotting the test points on the driver board layout drawing, I quickly found that the voltage on the emitter of Q1 was around 0.4 volt. The other four places I could measure this same voltage, Q2 and Q1/Q2 on the other board were at 0.7 volt. Guess I got a leaky Q1.
I got a handful of MPSU10s and 60s off eBay and measured the hFE. I took a U10 with a hFE of 74 and a U60 that measured 76 and stuck them in. (These puppies are going for $8.25 - $10.25 each.)
Perfect! The null current was easy to set to 9.5 mA and bias settled right down to the same value. Background noise is indistinguishable, even my wife can't hear anything! If you have the luxury, match the hFE of these babies and replace them in pairs.
Replacing R9 and R10 with a better resistor is a good idea. Newark part number 01H0111 is $2.15 apiece. 3 watt, 5% 3.9 kohm. Insulate the leads and leave them a little long to lift the resistor off the board.
After studying the schematic and plotting the test points on the driver board layout drawing, I quickly found that the voltage on the emitter of Q1 was around 0.4 volt. The other four places I could measure this same voltage, Q2 and Q1/Q2 on the other board were at 0.7 volt. Guess I got a leaky Q1.
I got a handful of MPSU10s and 60s off eBay and measured the hFE. I took a U10 with a hFE of 74 and a U60 that measured 76 and stuck them in. (These puppies are going for $8.25 - $10.25 each.)
Perfect! The null current was easy to set to 9.5 mA and bias settled right down to the same value. Background noise is indistinguishable, even my wife can't hear anything! If you have the luxury, match the hFE of these babies and replace them in pairs.
Replacing R9 and R10 with a better resistor is a good idea. Newark part number 01H0111 is $2.15 apiece. 3 watt, 5% 3.9 kohm. Insulate the leads and leave them a little long to lift the resistor off the board.
Re: UA 739
Hello Vhinze,
I am a newbie in here and i need some help with my Harman Kardon Citation 16. Due to a short circuit one of the channels suffers from DC drift now (but not constantly). Do you still have these µA739PC chips ? Maybe i need one to repair my HK Cit.16.
Please get in touch with me !
With kind regards,
jan Slagman
The Netherlands
vhinze said:
Hello Vhinze,
I am a newbie in here and i need some help with my Harman Kardon Citation 16. Due to a short circuit one of the channels suffers from DC drift now (but not constantly). Do you still have these µA739PC chips ? Maybe i need one to repair my HK Cit.16.
Please get in touch with me !
With kind regards,
jan Slagman
The Netherlands
Need help for Citation16
I have 3 Citation16 amps-soon to go to 4 Citation16 amps...
Thanks to Pat at audionut66@comcast.net, I was able to fully rebuilt them.
Write to him & he will solve any issues you have with Citation16 amps.
I have 3 Citation16 amps-soon to go to 4 Citation16 amps...
Thanks to Pat at audionut66@comcast.net, I was able to fully rebuilt them.
Write to him & he will solve any issues you have with Citation16 amps.
Hello Citation 16,
Thanks for your input. I have been in touch with Pat already and he gave me some good advice and yes he has all the parts to repair my HK Cit.16
I owe two HK's the 16 and the 16a. My 16a was totally rebuild with first class components wayback in 1990.
My fellow technician already found the chips in Germany. Pat adviced me to look in Europe first because of the charges.
I bought my HK Cit.16a in 1978 and i used it with a pair of Infinty Q2 loudspeakers.
Lately i acquired the HK Cit.17S and the HK Cit.11. Real nice stuff !!!
See also one of my projects on:
http://www.hififorum.nl/index.php?topic=10420.0
This project was realized by my fellow technician Ruud Janssen
With kind regards,
Jan Slagman a.k.a. JBL freak
The Netherlands
Thanks for your input. I have been in touch with Pat already and he gave me some good advice and yes he has all the parts to repair my HK Cit.16
I owe two HK's the 16 and the 16a. My 16a was totally rebuild with first class components wayback in 1990.
My fellow technician already found the chips in Germany. Pat adviced me to look in Europe first because of the charges.
I bought my HK Cit.16a in 1978 and i used it with a pair of Infinty Q2 loudspeakers.
Lately i acquired the HK Cit.17S and the HK Cit.11. Real nice stuff !!!
See also one of my projects on:
http://www.hififorum.nl/index.php?topic=10420.0
This project was realized by my fellow technician Ruud Janssen
With kind regards,
Jan Slagman a.k.a. JBL freak
The Netherlands
Harman Kardon Citation 16
Hi folks,
In the end it pointed out a MPSU10 had gone. A German engineer told me the MJE340 is a perfect replacement for the MPSU10 and the MJE350 seems to be a perfect replacement for the MPSU60.
I thought this information might be of any help in case a MPSU10 or MPSU60 is hard to find or way too expensive.
With kind regards,
Jan Slagman
The Netherlands.
Hi folks,
In the end it pointed out a MPSU10 had gone. A German engineer told me the MJE340 is a perfect replacement for the MPSU10 and the MJE350 seems to be a perfect replacement for the MPSU60.
I thought this information might be of any help in case a MPSU10 or MPSU60 is hard to find or way too expensive.
With kind regards,
Jan Slagman
The Netherlands.
Check up
Hello Everyone, I have a Citation 16A that I am cleaning up, checked all the transistors and put fresh paste, the question I have is how to adjust the bias voltage VR2. If I understand correctly, I need to put the - lead on the + output terminal and the + lead in between the emiter of Q15 and the resistor R37 and adjust VR2 to have 10mV. Is that correct?
Thanks
BTW, nice forum.
Hello Everyone, I have a Citation 16A that I am cleaning up, checked all the transistors and put fresh paste, the question I have is how to adjust the bias voltage VR2. If I understand correctly, I need to put the - lead on the + output terminal and the + lead in between the emiter of Q15 and the resistor R37 and adjust VR2 to have 10mV. Is that correct?
Thanks
BTW, nice forum.
Citation 16a not able to adjust null
I found the drawing and replaced r10 and r26 because they are out of tolerance now I am at -.124 and -.040 mv respectively. I notice the voltage on one of the driver boards is -10.5 and +9.1 witch would explain the null pulled to the -. I gess I will replace the zeners cr3 and cr4 when I find them. Let me know if you think I am on the right track.
I found the drawing and replaced r10 and r26 because they are out of tolerance now I am at -.124 and -.040 mv respectively. I notice the voltage on one of the driver boards is -10.5 and +9.1 witch would explain the null pulled to the -. I gess I will replace the zeners cr3 and cr4 when I find them. Let me know if you think I am on the right track.
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