• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

KA-7100 Q34 relay driver transistor

Captain Scary

Captain Scary

On Island Time
Did I put it in backwards?????

Relay comes on instantly at power up
and on power down relay takes a few seconds to
power off.

Friend dropped it off with a note that said it doesn't come on
for 20-30 minutes.
He was right about that.
I checked DC offset and had 7.4 and 20.2 Mv
so I swapped out the relay driver transistor
and away it goes,
except for it seems to work backwards?

Should I reinstall it 180 degrees?

TIA for any help.
Cheers,
Barry
 
Register to hide this ad
No,different transistor that was recommended
by several knowledgable AKers.
2N3904
I think the pin layout is different than the original?

New one is collector
base
emitter
looking from the bottom
so I'll have to figure out the original pin layout.

Unless there is something else amiss?
 
May have it now?
I have it installed C,B,E
and I think it needs to be E,C,B?

I'll do some more searchin tomorrow
after some brain cells rejuvenate to be sure
before I re-install it.................
 
Hi ecluser !!!
I havent been on here in a while...but I'll never, ever forget all your kind help you gave me fixing my KA-7100 via emails last summer !! Your the best !!
Thanks buddy !!
Captain Scary....good luck fixing your KA-7100...ecluser is really sharp and a great help with a similar problem I had....but I have since sold the amp.
 
Captain Scary said:
Did I put it in backwards?????

Relay comes on instantly at power up
and on power down relay takes a few seconds to
power off.
Click to expand...

If the base of your 2N3904 is connected to the relay, and the emitter is connected to ground, the relay will come on instantly at power up.

Test your transistor before a second trial...
 
IT LIVES!!!!

Thanks Dennis and ecluser for your support.

I picked up a new transistor on the way home from
work and installed it correctly this time.
Relay kicks on in 2 seconds and shuts down as it should on power down.

It is a sweet little amp.
I'll give it a good cleaning and call my friend to
come pick it up tomorrow.
It belongs to a friend of his father from Mass. or Conn.

Must be a nice guy as he gave my friend an SX-1980
for doing some work on his house.
 
Reviving this old thread, precisely because I neglected to replace the relay driver transistor while I had the amp torn apart for re-capping. :( In the picture embedded below (thanks, Leesonic!) I can't see Q34 anywhere. Is it on the same board as the relay, or somewhere else?

KA-7100second06.jpg
 
Following up on my own message, according to the service manual, it's on the amplifier board itself, on the bottom right corner of this picture, between C41 and the black wire designated '5':

KA-7100second03.jpg
 
Satisfyingly easy to replace. They really built these amps to be serviced, thank goodness. She's singing beautifully, once again.
 
You must log in or register to reply here.
Back
Top Bottom