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I have three inputs going into the Sherwood - tuner, CDP, network player. I was listening to the CDP, all was going well. I turned on the network player. This also has an output of around 1.8volts. When it turned on, suddenly the volume went down about 30% and there is a low level type distortion. The music is there - but slightly distorted in the background and no longer clear.
Any suggestions? No pops, noises, smoke, smells. Just the sudden 30% loss of volume and loss of clear sound???? minor buzzy distortion.
charles
Follow Ups:
It was a faulty interconnect. For the life of me, how could it have gone with it just sitting there doing nothing (no movement)??????????
Think of any piece sitting on a shelf for years and then needing restoring before using. Or, the 1903 Curved Dash Olds, never used sitting in a barn that needs a frame off restoration. With old age things fall apart, go to heck, tend to be used less, less enjoyable to be used - so sayeth my wife when describing me.
Don Brian Levy, J.D.
Toronto ON Canada
Solder joints, crimps, you name it.
So I should be cleaning the tube sockets on my Mc240 once or twice/yr.?
I am going to DIY my next interconnects so that I know they will have good concretions.
Dave
You have more than one problem!
I had them at one time as a hot blooded kid but the doctor cured it with some shots.
Don Brian Levy, J.D.
Toronto ON Canada
Oops, "connections". The spellchecker did me in!
Dave
It was a faulty interconnect. For the life of me, how could it have gone with it just sitting there doing nothing (no movement)??????????Electronics is funny that way. You have to remember with cables,they get pulled in and out a lot and they develop breakages that up barely touching the connection they are supposed to be hook to.
When you get a chance,talk to Jim about some tubes for the output and phono section.You have Telefunkens in the linestage but changing the outputs and phono will take you on journey.
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 04/20/14
I have two setups, so LOTS of interconnects. While fishing through all the interconnects I decided this rats nest has to be straightened out.
Removed everything, replace cables to tube stereo - and guest what!!!! sounds fine.
I think it's a bumb interconnect or something along that line.
I'll look further later.
Get a hold of Jim McShane and get some output tubes.
Honest amplification is better than excessive 2nd order distortion anytime.
You really couldn't believe the tangle of wires back there. I MAY have had the network player split out to two sources - MAYBE!
charles
Charles
That is very a strong possibility and that probably changed loading of the input sources.Another thing you want to do if you haven't already is get yourself a can of Deoxit D5 and spray inside the pin holes of the tube sockets and then pull each tube in and out a few times to get it worked in..You had quite a bit of oxidation and I got a lot of it off but there is still some on there I couldn't get off and that is why it is good to clean those sockets every three months.It takes about 5 or 10min to do it all and it should be done to most every six months to guarantee best performance..You probably have something in your office that will work very nicely like denatured alcohol..Just draw it up in a 20 or 22 gauge syringe 3 ML and squirt it in each pin hole of the sockets.
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 04/19/14
Just a quick "voice of experience" note... alcohol is a great cleaner but make sure it's completely evaporated before "firing" things up!
I got a bit hasty once after cleaning an enclosed relay in an old 2-way radio. Put the can back on before the alc was dry. Relay switched B+ to the transmitter... the resulting fireball was small but certainly got my attention! Fortunately no damage...
Oh, and one hand behind your back while poking around energized circuits... something one may be careless about after working on a lot of low voltage stuff.
Obviously, as MS suggests, disconnect the network gizmo and see if the 'issue' is reversible.
If so, do you have something to buffer the output of the network thingy? E.g., pass its line-level output through a regular old (active) preamp to the Sherwood and see if it's OK. If you don't have a standalone preamp, you can try the tape outputs of an old receiver (with the input source set to the network player, of course). In some cases, the line-level tape outputs will just be a pass-through, with no buffering, so this might or might not be a good diagnostic.
If the problem persists after disconnecting the network player however, troubleshooting may be more arcane. My guess would be just one of those things; something jostled or impacted by the act of connecting up another source. Could be a loose tube, dirty socket, or control. Could be a speaker wiring anomaly, as Michael suggested. Could be a dodgy interconnect just metastable enough to cause a problem. Were it mine, I'd disconnect everything and reconnect piece by piece, determining whether the problem persists. If so, I'd then wiggle tubes, clean switches and pots, maybe start swapping preamp tubes... stuff like that.
all the best,
mrh
Try the CD player by itself and make sure your speaker terminals on the back of the amp are touching each other even slightly..Let me know.You also want to make sure that the speaker out terminals are not touching two different impedances because if you have no terminal on stranded speaker wires,one strand of wire can short against another terminal and give you major distortion.
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 04/18/14 04/18/14
the speaker terminals are OK - not touching
used the network player and cdp on another amp and they seem ok
tried using another input socket - same results
tried moving two of the tubes in the preamp phono section over to the line preamp section - no changes (but it could be two or more tubes??)
It sounds like a radio that can't tune into a station clearly. It plays music, but it has some sort of "buzz" to the instruments, not a buzz of it's own. the instruments are distorted, but no extra sounds or hums.
It happened when I had the CDP on and playing through the stereo. I turned on the network player that is connected to another input on the stereo (and not selected at that time) and it just suddenly got 20-30% quieter and "buzzy".
charles
charles
Look at your output tubes and see if any are glowing and did you change them..The output tubes were pretty old and one or two may have failed.
Make sure the slide switch on the back is set in the normal position and not the test position..
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 04/18/14
tubes are still the same and the switch is set to normal. I'll check tonight if any are glowing abnormally.
If the outputs went, wouldn't the sound have hum and not a low level distortion?
charles
If the outputs went, wouldn't the sound have hum and not a low level distortion?If one of the output tubes let go,you will get less than half of your power.Those tubes were quite old you had but they sounded good.I called and left you a message.
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 04/20/14
So they don't go with out a scream or anything nasty? Gee, I was expecting more from a blown output tube.
Can I visually see if one is dead?
charles
PS, I'll try and call tomorrow. I do appreciate your concern. Don't worry - old tubes do what old tubes do. Hey, they're ONLY 60 years old!
A tube can fail gracefully and just stop conducting. Better that than a short, by far. I have a pair of ASL Wave-8's that were playing happily one day. I heard a small, delicate "clink!" and one channel started doing exactly what you describe. The envelope had cracked, and it was obvious which tube it was because the getter was gone.You might have a set of 100-year tubes, but stats catch up to us all.
"LOL Those tubes should last a 100 years.Call me when you can."
ETA: 100 years x 365 days a year x 5 hours of operation a day is 182,500 hours. What tubes are those? Impressive life span, that.
Edits: 04/18/14 04/18/14 04/18/14 04/18/14 04/19/14 04/19/14 04/19/14
LOL
Those tubes should last a 100 years.Call me when you can.
Honest amplification is better than excessive 2nd order distortion anytime.
Since airtime seems to have solved the problem, I'll risk hijacking this thread with a question:
I'm measuring -18.5 volts at the grid of OP tubes, pin 2. This is after raising the value (resistance) of the bias supply R from 4.7Kohm to 5.6Kohm. Seems like I should be around -15V?
Also what current in mA should each 7189 draw? Can this be measured (the pair) at the 12ohm cathode resistors?
Peter
(as you can see, i made a little circuit board for the bias supply and phono filament circuit.)
Pete
You did a very nice job and I like your bias supply.I usually keep it at minus 16.5 to minis 18v..Minus 15 is way too low for this amp and the 7189s would be on fire.. Vg2 is higher due to the ultra linear transformer where as wired in pentode, Vg2 would be lowered to about 300v.
Leave it where you have it..This amp will produce about 22wpc with 7189s.
Honest amplification is better than excessive 2nd order distortion anytime.
Sounds like a problem for Mikey's expertise........
He has my S-5000 right now. I plan on running a S-2200 tuner, PS Audio Nuwave DAC, and a turntable.
Your problem may just be a tube. Start swapping left to right etc.... to see if the distortion follows.
........I was a vegetarian for 15 minutes... until the main course.
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