Mbira

Problem with one channel of my G9(fixed)
« on: November 23, 2005, 06:38:08 PM »
I can't figure this one out...HEREis the schematic.  One channel has much higher gain than the other.  When tracing the two channels, the signals are the same up till the grid side of R45 (by V2B)  after the plate, one signal is much more amplified than the other.  I have checked R30, R29, and changed out c12 and c13, but still no change.  Also switching the tubes does nothing.  Anybody have any ideas?

Thanks.
Joel
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com


moamps

Problem with one channel of my G9(fixed)
« Reply #1 on: November 23, 2005, 07:39:10 PM »
Check the C11 also.
Check also DC voltages on V2A cathode, V2B cathode and anode on both preamps.

Regards,
Milan

PRR

Problem with one channel of my G9(fixed)
« Reply #2 on: November 23, 2005, 07:52:55 PM »
Yes: C11, DC voltages, and also transformer wiring.

If it ain't that, it is something so oddball that we won't find it from afar, but you will smack yourself next week or next year when you finally find it.

Soeren_DK

Problem with one channel of my G9(fixed)
« Reply #3 on: November 24, 2005, 01:35:44 AM »
Also R24.. I made that mistage....
Quote from: idylldon
...it works like a champ and is as quiet as a mouse pissing on a cotton ball.

http://www.soundcloud.com/doctorsclub

Mbira

Problem with one channel of my G9(fixed)
« Reply #4 on: November 25, 2005, 01:26:59 PM »
ARGHHHH!!! :evil:  :evil:
I can not figure this out.  I have now replaced all caps in that section, checked all resistors in that section (I did check resistance while they were in-circuit)  Everything looks good.  Voltages are each equal.  Switched transformers nothing has helped.  I'm got some intuitive questions about the tube socket.  We'll see....

Joel
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com

ioaudio

Problem with one channel of my G9(fixed)
« Reply #5 on: November 25, 2005, 06:27:35 PM »
DI jacks - different levels?

unbalanced out: (right before the output transformer, after the 4.7µ/250v)-different levels?

regards, max

Corvus

Problem with one channel of my G9(fixed)
« Reply #6 on: November 25, 2005, 11:32:21 PM »
This may not help Mbira at all but I was very concerned about the difference in gain between the channels of my G9. Was soon diagnosed to the difference in input voltage when using a CD player as a signal source. G9 worked flawlessly. I did smack myself.

Quote from: "PRR"
If it ain't that, it is something so oddball that we won't find it from afar, but you will smack yourself next week or next year when you finally find it.

Mbira

Problem with one channel of my G9(fixed)
« Reply #7 on: November 26, 2005, 12:54:20 PM »
Quote from: "ioaudio"
DI jacks - different levels?

I'm not sure what this means?  The signals are equal up until R45 is feeding into the grid.  (They are equal at that point).  Basically it seems that grid to plate amplification is much less on one channel than the other at V2B.  Regardless of tubes, etc.  

Quote

unbalanced out: (right before the output transformer, after the 4.7µ/250v)-different levels?


Yup.

Pulling my hair out here.  I do have slightly different voltages on each grid and plate-I'll post those in a bit... Switched around tube sockets, rechecked resistor values-is it OK that I'm doing that in the circuit and not pulling out each resistor?  The 470u caps, I can't measure that high on my meter, but I have pulled them out and replaced them with others and the same problem....
Even switched front boards (with rotaries) around-no change
Damn...

Joel
 :evil:
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com

maxime

Problem with one channel of my G9(fixed)
« Reply #8 on: November 26, 2005, 02:59:43 PM »
just an idea..
try reheat the joints from r45 to the rest of signal flow...
cold soldered joints can give you big headaches..

StrayCat

Problem with one channel of my G9(fixed)
« Reply #9 on: November 26, 2005, 03:09:56 PM »
(1)Check for cold solder joints at the (ff) voltage in at the tube sockets.
(2) I haven't looked in a while, are there polarity issues with the caps in the C11,C12,C13 locations?
(3) Were all you measurements +/- 1%- 5% or less?
(4)Look for any shorts with a 10 power magnifying glass.
(5) Are you using the High pass filter? HP section Caps C8 and C9 may be knocking off signal in different amounts or the HP section may be shorted. (6) Check that all the Lorlins are properly keyed.
(7) Is your output pot resistance Exactly the same or have you swapped them (1) left and (2)right? Both 47k LOG?



Hope this gives you some help or at least rules out basic stuff,

Cheers
Later
Chemira Music Studio


ioaudio

Problem with one channel of my G9(fixed)
« Reply #10 on: November 26, 2005, 03:15:11 PM »
sorry for my english...but you answered the question i intented to make :-)

from what you explain the problem seems around the srpp out stage. b+ differences up to +/- 10v shouldnt give a significant gain change.
i would suggest to rebuild the srpp stage.

Mbira

Problem with one channel of my G9(fixed)
« Reply #11 on: November 26, 2005, 03:29:29 PM »
Quote
(1)Check for cold solder joints at the (ff) voltage in at the tube sockets.

Did it.
Quote
(2) I haven't looked in a while, are there polarity issues with the caps in the C11,C12,C13 locations?

Checked, doublechecked
Quote
(3) Were all you measurements +/- 1%- 5% or less?

+-1%
Quote
(4)Look for any shorts with a 10 power magnifying glass.

I don't have that, but I checked with my ohm-meter set to the buzzer and checked all around the offending area.
Quote

(5) Are you using the High pass filter? HP section Caps C8 and C9 may be knocking off signal in different amounts or the HP section may be shorted. (6) Check that all the Lorlins are properly keyed.
(7) Is your output pot resistance Exactly the same or have you swapped them (1) left and (2)right? Both 47k LOG?

When I switch the whole front board between channels (with all the lorlins, etc) nothing changes...

Thanks for the ideas, though.  This sucks :sad:
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com

Mbira

Problem with one channel of my G9(fixed)
« Reply #12 on: November 28, 2005, 07:53:12 PM »
Still going batty on this...

Here are the voltages that I'm reading.  the 'good' tube is giving me these voltages on the pin #'s:
1-83.2v
2-0v
3-1.84v
4-.03v
5-11.59v
6-243.3v
7-83.4v
8-88.9v
9-5.6v

The 'bad' tube is giving me:
1-83.5
2-0v
3-1.71v
4-.02v
5-11.62v
6-235.0v
7-83.4v
8-89.0v
9-5.8v

Does this tell me anything?  I have now replaced R45, R28, R29, C12, C11, and C13 (of the bad section)

 :evil:  :sad:  :evil:  :sad:  :evil:  :sad:  :evil:  :sad:
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com

Mbira

Problem with one channel of my G9(fixed)
« Reply #13 on: November 29, 2005, 05:32:09 PM »
:guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :guinness:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:  :green:

Beers all around!!!!  I fed a signal straight into the grid and measured off the plate-same problems....Just for the hell of it, I disconnected the front pcb's and tried again.  All was good.  Didn't I switch out the boards before and found no change?  Of course I did!  I swear!  I looked at one board and there was a short :oops:   How I missed it I don't know...It was very late when I did the switch.  Bah anyway, all is good now.

Woohoo!
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com

gyraf

Problem with one channel of my G9(fixed)
« Reply #14 on: November 30, 2005, 05:54:54 AM »
:thumb:

 :grin:

Jakob E.
..note to self: don't let Harman run your company..

ioaudio

Problem with one channel of my G9(fixed)
« Reply #15 on: November 30, 2005, 09:18:39 AM »
glad to hear its working! where was the short located?

Mbira

Problem with one channel of my G9(fixed)
« Reply #16 on: November 30, 2005, 10:13:48 AM »
It was where the wires connect from the 10 pin molex onto the front board...

Thanks again guys.  This sounds awesome!

Joel
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com


 

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