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I have a 299 with no right channel. I used deoxit on the knobs and no change. I have the following plate and screen voltages on the 7189s:From front tube to back tube the readings are:
Pin 7 - 375v Pin 9 - 324v
Pin 7 - 375v Pin 9 - 315v
Pin 7 - 374v Pin 9 - 315v
Pin 7 - 374v Pin 9 - 314vAny ideas what might be ailing the right channel? Thoughts about what to try next?
On a related topic. I've subscribed to the Scott newsgroup but when I enter password it tells me it's invalid. I've sent three e-mails over the past month or soasking about this to the Scott moderator and have not gotten any response. Is the group defunct?
Follow Ups:
I have long ago passed on to my tech. to REPLACE all slide switches on Scott gear as well as most Fisher, FOR the very reason you describe.Original equipment slide switches were marginal quality to begin with and when in circuts as critical as being refered to there is no point in attempting or expecting flawless performance by just cleaning them.
This has been policy for the last 20 or 30 pieces of gear that I have had serviced and since, there has been no problems.
Before there were switch issues three times out of five.
Go figure!!
Hi,
It could be the Channel B pick up slide switch ( 2nd from the left). If the faceplate has shifted slightly to the left it will restrict the movement of that switch and it will not move far enough to the right. It just takes a little bit. Try loosening the nuts behind the control knobs and adjusting the faceplate. You may be lucky.
Larry.
Bob
We can safely assume that the output tranformer is most likley good at least from a primary stand point.You need to check and see if signal is getting thru your preamp to your amp stage on the right channel and tiny and dad are correct about the switches.
Next step is take out your preamp and driver tubes and spray deoxit in the sockets and pull the tubes in and out a few times.This has fixed many pieces of tube gear from radios to stereos to old tvs by doing this.
I have been replacing those slide switches regularly.
The weak link in my 299A are all those stupid slide switches. Have you tried using deoxit on them all as well?The one to look at in particular is the phase reversal switch which reverses the phase of the right channel, Jiggle it up and down and see if the right channel comes back. It's a switch worth bypassing.
Thanks for all your suggestions.What's the best way to deoxit the switches? They look pretty enclosed.
Just put the red director tube in the spray bottle and spray the switches directly on the contacts while turning them back and forth..
Did you try swapping preamp and driver tubes around?
I've swapped preamp, driver and output tubes, deoxited the switches and preamp and driver tube sockets. I'll check signal path from pre to amp. If the troubleshooting path seems to point to broken circuit, I may try to find a technician who would be better at locating the problem. I've looked to see if any resistors are broken but can't find any - beyond that I'm pretty much a blind man when it comes to circuitry.I'm relieved to hear that it is unlikely a bad transformer. Channel B sounds quite nice. Since I've gotten it that's all I've had. Anxious to hear what channel A sounds like.
With speakers (or headphones) connected & unit powered ON: A smallish-value capacitor (the lil' orange 0.01uf/400v metal film from Radio Shack will do) with one lead held between thumb & forefinger & the other lead touched to the control grid lug of each tube socket should produce a hum as heard from speakers (or headphones) if the stage is OK. IOW begin this procedure from the output & work back towards input one stage at a time to discover the stage that is not passing signal. When no hum is heard, thouroughly check that particular stage (tube & all supporting circut parts). BE CAREFUL, dangerous high voltage exists on nearby tube socket lugs. Discover schematics by inserting hhscott inbetween the ubiquitous www dot dot com.
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