Please Help Harmon Kardon surround amp power problem

Guest · Posted: Fri Jul 15, 2005 5:19 pm Post subject: Tested other transistors

Ive tested the other transistors and they all must have blown the c5358 that i replaced is ok but all the other three register 0 ill get some replacements and give it a try.

Guest · Posted: Fri Jul 15, 2005 5:50 pm Post subject: Toshiba A1986

Im having trouble sourcing the toshiba a1986 iv'e tried the suppliers where i got the c5358 but they have none in stock.

Do you know any other stockists ?

Thanks

Morrowrj · Joined: 14 Apr 2005 Posts: 29 Location: Pittsburgh, PA

Mcm stocks the part you need. check here:http://mcm.newark.com/NewarkWebCommerce/mcm/en_US/endecaSearch/searchPage2.jsp?x=14&Ntt=2sa1986&newSearch=true&searchtype=mfg&Nty=1&N=0&Ntk=gensearch&y=8

Good luck,
Robert

absorbentgnome · Joined: 30 May 2005 Posts: 51 Location: Cardiff, UK

It's unfortunate and expensive that all have blown Sad

Which ones have blown? Have a set of the 2SC5358 blown only, or a set of the 2SA1986 or both? Or random failures between the two?
Anyhow it sounds like you will have to get a full set of both for the whole amp.
Double check the smaller transistor pairs for faults as well because failure of the main output transistors can sometimes take out these as well. With a bit of luck they'll be ok.
Good luck. Smile

Guest · Posted: Thu Aug 04, 2005 11:07 am Post subject: Replaced all transistors

My transistors have finally arrived i've replaced all 4 and 2 further resistors that were connected to one of thne smaller transistors.

When i check the voltage on the transistor pins with a diode tester from ground it is different forn the other 3 banks of transistors. The voltage readouts seem to be the wrong way round.

example

Toshiba a1986 pin1 = 652mv for 1st 3 transistors 937mv for last one
pin3 = 987mv for 1st3 transistors 679mv for last one

It is the same for the toshiba C5358

It is as if they have been solderd in the wrong way round ( they havent )

Have you any idea what could cause this.

Thanks

GUEST · Guest

Hi,
It seems this expensive H/K AVR 430 and 630 model has a design problem. My receiver also started to shut down after 2 minutes of operation, it would turn on back again but it will shut down after 2 min and so on. When I turned the Multi room option and main amp off, it did not shut down after 2 min, instead it blew off my Rear left speaker, Well at least now i know why it was shutting down. Ther RL amp es bad, I also found the A1986 with an internal short circut (all pins read out 0 ohms) I have not tested C5358 yet. Thanks for posting this kind info, will be a lot of help to find transitors replacements.