I must be an idiot - need help
- Thread starter kach22i
- Start date
This morning's preliminary results of putting together a second system.
Detailed notes:
http://s184.photobucket.com/albums/x295/kach22i/Stereo/
Overall notes including an analysis diagram of both the Dynaco ST-120A and my large 100 watt Rotel HT amp.
http://s184.photobucket.com/albums/x295/kach22i/Stereo/
The music with set-up #3 dated 10/6/12 is incredible. I'm so relieved that my GRAFF tube pre-amp is okay, sounding better than ever with it's new Tungsram's.
I suspect there is a major impedance mismatch going on between the small 50 watt Rotel amp and the old Dynaco pre-amp. There is no place to ground the turntable on the Dynaco chassis, less hum left floating rather than wedged in a body joint, this too could be part of the problem here.
My next move is to substitute the large Rotel amp for the small Rotel amp. I have no idea why the large Rotel was doing the same thing as the ST-120A yesterday evening.
Then I'l open up the Dynaco ST-120A and look for something wrong.
Detailed notes:
http://s184.photobucket.com/albums/x295/kach22i/Stereo/
Overall notes including an analysis diagram of both the Dynaco ST-120A and my large 100 watt Rotel HT amp.
http://s184.photobucket.com/albums/x295/kach22i/Stereo/
The music with set-up #3 dated 10/6/12 is incredible. I'm so relieved that my GRAFF tube pre-amp is okay, sounding better than ever with it's new Tungsram's.
I suspect there is a major impedance mismatch going on between the small 50 watt Rotel amp and the old Dynaco pre-amp. There is no place to ground the turntable on the Dynaco chassis, less hum left floating rather than wedged in a body joint, this too could be part of the problem here.
My next move is to substitute the large Rotel amp for the small Rotel amp. I have no idea why the large Rotel was doing the same thing as the ST-120A yesterday evening.
Then I'l open up the Dynaco ST-120A and look for something wrong.
George, how does this bear on the 'lost channel' issue? Have you sorted that? Or is this all about a different set of components?This morning's preliminary results of putting together a second system.
Detailed notes:
http://s184.photobucket.com/albums/x295/kach22i/Stereo/
Overall notes including an analysis diagram of both the Dynaco ST-120A and my large 100 watt Rotel HT amp.
http://s184.photobucket.com/albums/x295/kach22i/Stereo/
The music with set-up #3 dated 10/6/12 is incredible. I'm so relieved that my GRAFF tube pre-amp is okay, sounding better than ever with it's new Tungsram's.
I suspect there is a major impedance mismatch going on between the small 50 watt Rotel amp and the old Dynaco pre-amp. There is no place to ground the turntable on the Dynaco chassis, less hum left floating rather than wedged in a body joint, this too could be part of the problem here.
My next move is to substitute the large Rotel amp for the small Rotel amp. I have no idea why the large Rotel was doing the same thing as the ST-120A yesterday evening.
Then I'l open up the Dynaco ST-120A and look for something wrong.
Yep, blown fuse in the large Rotel amp, may have happened when I pulled it out and rotated it last night. The amp was off when I did this, but a slight amount of chassis flex could have been all it took.
I'll check the ST-120A next, bet I find another blown fuse.
There could also be a root cause and not just coincidence, so I'll be proceeding carefully.
Good morning, kach22i. I just read about your issues here and the first thing that comes to mind is a compromised speaker cable. When you replace the fuses, before you hook up the original speaker cables back in, I would suggest trying the spare set out first and see if both channels are up and running. If the system is a go with that, do not attempt to place the original SC's back in the loop. If you have a digital or analog volt meter, ohm out both sets of speaker cables for continuity and shorting.
Tom
Tom
Great idea Tom, I have a Cen-Tech Digital Multimeter which I use to bias my tubes, but I've never used it to check speaker cables for continuity and shorting.
Is there a link to an easy step by step way to do this?
Maybe you could just walk me though it once.
Fused replaced, the big Rotel is planing both channels now on the secondary system.
I couldn't find any video that thoroughly and accurately showed you how to do this quickly, it would be quicker for me to just offer a step by step. First things first though. Let's verify that both speakers are up and running after the fuse replacement, using the spare set of SC's. If you can't produce sound out of both speakers with the spare set, then the issue resides upstream somewhere.
Tom
Tom
Tom, I've talked to a customer the local hi-end audio store, and the guy now repairing the Dynaco ST-120A amp output transistors (if proven to be the problem), and have a pretty good idea on how to test the speakers for shorts and the speaker wires and IC's.
I'll give you a shout if I run into problems.
I'll give you a shout if I run into problems.
Tom i had the same reaction last nite but George said he tried different speaker cables too.
---I just luv it! ...What a great hobby we have! ...Searching for all type of solutions to our quest for absolution! :b
The problem here is that I first tried the old wires first (which blew the right channel fuse in the big Rotel before I knew it), then tried a second pair of speakers and fresh speaker wires a second time around with the fuse already blown (which I could not have known at the time).
A 100% fresh system with a third amp allowed me to test good working components one at a time and sort this mess out.
I sort of treated this like maleware or a computer virus, and needed a fresh computer to discover the faulty software/hardware.
---What doesn't make sense is that you did try another amp and the problem persisted!!!
...Too many burned (blown) fuses for my taste!
* George, you didn't do a good job first setting things up, and second explaining them with precision. ...No wonder you believe in ghosts!
...Too many burned (blown) fuses for my taste!
* George, you didn't do a good job first setting things up, and second explaining them with precision. ...No wonder you believe in ghosts!
If the speaker cable was compromised, then it blew the R or L channel out of the first amplifier. Upon hooking up the next amplifier, the same thing happened. With the third amp and a different set of SC's, no blown channel. When he tried the second set of SC's, the channel was already blown. Though it is always hard to diagnose issues over the net, this is what I have gathered as to what happened.
Tom
Moving the speaker cable may have either "fixed" the connection or shorted it. This would be impossible to tell externally, unless you had sound & just wiggled the connection on each end of the cable.
Lee
Lee
I admit i once had a similar problem...there was a leaky capacitor in one of my amps that people could not find. Meanwhile, whenever it would come back...slight buzzing would appear after a certain amount of time (and heat). Every hour or so for a few minutes...so annoying.
I ended up trying to switch cables L to R, etc...and then one day the amp would not turn on! i took it back...it turned on. I took it back...would not turn on...what?? Then i remembered there is a 2nd power switch in the back...if you bump it and it shuts off...well, you get the picture. Sometimes these little things can compound the real problem (in my case the leaky which someone eventually found and fixed.)
I ended up trying to switch cables L to R, etc...and then one day the amp would not turn on! i took it back...it turned on. I took it back...would not turn on...what?? Then i remembered there is a 2nd power switch in the back...if you bump it and it shuts off...well, you get the picture. Sometimes these little things can compound the real problem (in my case the leaky which someone eventually found and fixed.)
Yes, you have the big picture correct.
I took the afternoon off from my problems and also ran around to get the Dynaco amp fixed. The output transistors, two each side are not matching, the ones which blew had been replaced once before. I'm getting a price on updating both pairs, two different grade levels.
I have a date with my dust bunnies and dust mites today, it's long overdue. I'll also be checking all of my wires, IC's and of course the main speakers for shorts.
Here is a photo of the top of one of my HT amps, yes I feel ashamed but I had no idea it was like this under the shelf, darn cats.
Attachments
Good morning, kach22i. I don't recall you mentioning what pre you are using. Would it happen to be a tubed preamplifier? [The component that was in the rig when the channel was originally lost]
Tom
Tom
Tom, the original pre-amp was a GRAAF WFB One, it's tube with tube phono and it's working better than ever now thanks to some new tubes.
.........................................................................................................................................
I put my digital multimeter to use this morning and diagnosed the problem within a minute.
The root cause of the problem: the speaker wires as many suspected. However tarnish was the real culprit.
Please before passing any judgement take into consideration that I've tried in vain to prevent this problem from ever forming in the first place. I've tried two cleaners which had no affect. I've even considered sandpaper/emery cloth as a solution to remove this terrible blacking.
Background story: The original Nordost Z-Plug Banana's fractured because my speaker wire was about an inch too short, the right angle turn at each end was too much stress over a long period of time. The solution was to have the local Hi-End dealer put spade type terminal connections at each end. However these connectors tarnished turning black over a few years. When I went to the store and reported the condition they said that sounded strange. I asked for a recommend cleaner, they said they don't recommend liquid cleaners as they leave a residue which crystallizes and only causes more problems.
I've tried burnishing and rubbing with audio wipes, different audio approved cleaners, nothing has made a dent in the black coating.
Put the digital multimeter probes to the clean silver parts and get a good reading of about 7.6 Ohms when hooked to the main speakers. Connect directly to the speaker with the speaker wires detached and get a roughly similar number.
Put the digital multimeter black/ground probe to the clean silver part, and the red/positive probe to the blackened part and you cannot get a stable reading, it jumps all over the place at random and never settles down.
A picture is worth a thousand words........................here are a couple of thousands words.
http://s184.photobucket.com/albums/x295/kach22i/Stereo/
QUESTION: How do I clean these connections, and how do I keep them clean?
Yea, I've never seen anything like it either.
What aggravated this condition (in addition to the tarnish) is the solid brass spade to banana jumpers which I had to use to connect to the solid state Dynaco ST-120A amp. There has got to be a better and more secure way to connect to that amp. I'm open to suggestions. Space is tight and limited.
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