Need to resurrect my HK Citation 22...

[Jim K]

Hello All:
My first post to this forum...glad to be in such capable company!!
I've owned a matched set of Harmon Kardon Citation 21 (preamp), 22 (200W/ch amp)
23 (FM tuner) since 1987, and for the most part, they have performed reliably and sound decent enough powering my homebrew speaker cabinets w/Seas drivers.

Unfortunately, the Citation 22 amp gave up the ghost whilst my family was celebrating Independence Day this year...the amp ran hot most of that day, and eventually the mini breaker on my surge strip tripped. A reset brought power back to the amp, but it never went fully back to its "green LED" operational mode.

Pulling the cover, it was apparent that one of its 250V/5A fuses had blown. After replacing the fuse and powering the amp on, one of its two power transformers hummed loudly for about one second, and the same fuse I just replaced blew again. Sounds like a blown transformer, correct?

I don't have the equipment to troubleshoot this any better than what I've described, but given the fact that it appeared to be the source of the hum, and it was noticeably warmer than the other transformer (even after just one second of power applied), makes me conclude there's a short in that transformer.

I was wondering if any of you concur that it <is> most likely a bad transformer, or if there are other components that need to be ruled out before I begin a hunt for a replacement transformer....which, by the way, is marked as follows:
Bando
5584-701555
BD21A3E-0001
BE11-HDI

Any suggestions, help, tips, or leads on where to pick up a replacement trans, would be most appreciated!!!
Thanks to all,
Jim Koeppel
Toms River, New Jersey, USA

[Giaime]

It's unusual that a tranny goes short. Check the power supply filter caps for shorts. But the most obvious and easy thing that could have happened is that you have some short output transistors. Check them all.

Good luck!

[anatech]

Hi Jim,
It sounds like you may have blown one channel (outputs + ? shorted). This is repairable. Do not reinstal another fuse or you may damage the power transformer. I would recommend you take this to a good shopo in your area. One that serviced HK under warranty would be preferred.

-Chris

[macchiajr]

Hi!
I'am almost shure that your HK will be OK after replacing its output transistors.
In order to check if this components are the real cause of your fault, you might check with a tester (very useful and unexpensive instrument) if they are short. (it means that a huge amount of current flow throug them, causing the overheating and the humming of the transformer ).
I hope it could help you.
Sorry for my bad english!

[Jim K]

Thanks to all for the replies thus far...
I will perform the additional troubleshooting you have suggested, and post back here in a day or two...

Jim K.

[anatech]

Hi Jim,
How much experience do you have with amplifiers (repairing)? If not a lot then send it in. It's the small stuff that will get you. I know several shops that can't do this right and they get paid to do this!

Anyhow, normally it's not just the outputs that go. It's very important not only what you put in, but how you install the repalcement parts.

No offense to macchiajr, but I have no idea how "he" can be so sure of the outcome with no addition info. Proceed with caution least you create an unrepairable amplifier.

-Chris

[Giaime]

And believe Chris, he knows what to do with beginners that try to repair their first amp... do you remember? That Marantz is still here and he's nicely driving a pair of AR28s in my system. But like my NAD more

[anatech]

Hi Giaime,
I had no doubt that they were. You should build a newer Marantz and compare them.

My main concern is that your Marantz was fairly tame, and you have a decent idea as to what comes next. A higher powered amplifier doesn't sit and smoke.... they go BANG ! No warning. So depending on what experience Jim has determines what he should do next. It would be cool if Jim can fix his own unit.

So when you gonna build something Giaime?

-Chris

[Giaime]

Originally posted by anatech
So when you gonna build something Giaime?

-Chris

Hi Chris! I just ended high school, and that one-tube radio that I built as a school project made me reach the highest peaks of school levels: 100/100 on the exams.
Photos here: http://img315.imageshack.us/img315/2...pertina7pp.jpg
http://img315.imageshack.us/img315/6611/host29lw.jpg
http://img315.imageshack.us/img315/5...icolare1ui.jpg
And me: http://img315.imageshack.us/img315/380/io4zz.jpg

Next project? I will enjoy the summer and maybe build some kind of tube amp kit like this http://www.elettronicanovarria.it/ca...Foto/kit1f.gif

(sorry for the OT people, but Chris is Chris )

[Jim K]

Gentlemen:
Well, after nearly five months, I found some time to troubleshoot this amp with a friend who is a very good electronics technician.
After some preliminary checks of the two power transformers on this dual mono amp, they both checked out OK. The individual power transistors on the right (defective) channel also appear OK, but there is a power rectifier (four pin, P/N D5Sb 40 73 ) that appears to be shorted across all four of its pins.
The left channel's rectifier appears to have acceptable resistance readings across its four pins. My next logical step is to replace the defective rectifier....but I cannot seem to find this part anywhere.
I have Googled the part number in every combination, checked electronics catalogs, but just can't seem to find any vendor that carries this part at all.
Any suggestions on how to purchase this item would surely be appreciated!!!!
I have attached a jpg photo file of the rectifier, if that will help...
Thanks for any assistance, suggestions, etc!!
Jim K.