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Amplifier Problem - Revised Schematic
Re: Amplifier Problem - Revised Schematic
EADGBE wrote:
> OK, here is the schematic of the "good" channel, with voltage
> measurements indicated.
>
> I realize that some of the voltage indications are redundant, but I
> decided to "over-label" in the interest of clarity....
>
> http :// i240.photobucket,com /albums/ff58/eadgbe123/amplifier-good-channel.jpg
Are those the voltages you are NOW getting ?
Those look correct.
Graham
EADGBE wrote:
> OK, here is the schematic of the "good" channel, with voltage
> measurements indicated.
>
> I realize that some of the voltage indications are redundant, but I
> decided to "over-label" in the interest of clarity....
>
> http :// i240.photobucket,com /albums/ff58/eadgbe123/amplifier-good-channel.jpg
Are those the voltages you are NOW getting ?
Those look correct.
Graham
Re: Amplifier Problem - Revised Schematic
STOP THE PRESSES!
THE AMPLIFIER PROBLEM HAS BEEN *SOLVED* !!!!!!!!!!!!!!!!!!
SEE MY POST REGARDING THIS!!!!!!!!
MANY, MANY THANKS TO EVERYONE WHO OFFERED HELP, TIPS, AND
SUGGESTIONS!!!!!!!!!!!!!!!!!!!!!!!
STOP THE PRESSES!
THE AMPLIFIER PROBLEM HAS BEEN *SOLVED* !!!!!!!!!!!!!!!!!!
SEE MY POST REGARDING THIS!!!!!!!!
MANY, MANY THANKS TO EVERYONE WHO OFFERED HELP, TIPS, AND
SUGGESTIONS!!!!!!!!!!!!!!!!!!!!!!!
Re: Amplifier Problem - Revised Schematic
In article <300bf4d8-6b25-4fee-9536-1170843ae47d@e67g2000hsa.googlegroups,com >, EADGBE <hwbosshoss@comcast,net > wrote:
>
>STOP THE PRESSES!
>
>THE AMPLIFIER PROBLEM HAS BEEN *SOLVED* !!!!!!!!!!!!!!!!!!
>
>SEE MY POST REGARDING THIS!!!!!!!!
>
>MANY, MANY THANKS TO EVERYONE WHO OFFERED HELP, TIPS, AND
>SUGGESTIONS!!!!!!!!!!!!!!!!!!!!!!!
Maybe we can improve the design ?
greg
In article <300bf4d8-6b25-4fee-9536-1170843ae47d@e67g2000hsa.googlegroups,com >, EADGBE <hwbosshoss@comcast,net > wrote:
>
>STOP THE PRESSES!
>
>THE AMPLIFIER PROBLEM HAS BEEN *SOLVED* !!!!!!!!!!!!!!!!!!
>
>SEE MY POST REGARDING THIS!!!!!!!!
>
>MANY, MANY THANKS TO EVERYONE WHO OFFERED HELP, TIPS, AND
>SUGGESTIONS!!!!!!!!!!!!!!!!!!!!!!!
Maybe we can improve the design ?
greg
Re: Amplifier Problem - Revised Schematic
EADGBE wrote:
> STOP THE PRESSES!
>
> THE AMPLIFIER PROBLEM HAS BEEN *SOLVED* !!!!!!!!!!!!!!!!!!
>
> SEE MY POST REGARDING THIS!!!!!!!!
>
> MANY, MANY THANKS TO EVERYONE WHO OFFERED HELP, TIPS, AND
> SUGGESTIONS!!!!!!!!!!!!!!!!!!!!!!!
And the winner is...????
jak
EADGBE wrote:
> STOP THE PRESSES!
>
> THE AMPLIFIER PROBLEM HAS BEEN *SOLVED* !!!!!!!!!!!!!!!!!!
>
> SEE MY POST REGARDING THIS!!!!!!!!
>
> MANY, MANY THANKS TO EVERYONE WHO OFFERED HELP, TIPS, AND
> SUGGESTIONS!!!!!!!!!!!!!!!!!!!!!!!
And the winner is...????
jak
Re: Amplifier Problem - Revised Schematic
In article <bb9d022f-3212-41a4-b455-e8d7f6cbd09c@u69g2000hse.googlegroups,com >, EADGBE <hwbosshoss@comcast,net > wrote:
>On Apr 22, 10:34 am, zekfr...@zekfrivolous,com (GregS) wrote:
>>
>> Where did you get this diagram. Is it completely from scratch ?
>>
>
>Greg:
>
>No, it was copied, carefully, from the original schematic. I would
>have scanned the original schematic, but it is very fuzzy. I did
>check my schematic against the other channel's schematic, which was a
>bit clearer but did not have the expected voltages indicated, and was
>cluttered with the actual component values.
>
>I have checked, re-checked, and RE-checked the accuracy of my hand-
>drawn schematic, comparing it to the original, and there are no
>mistakes.
The emitter of Q204 has a strange DC path. The amplifier appears
non inverting. What is the voltage on Q204 collector ?
greg
In article <bb9d022f-3212-41a4-b455-e8d7f6cbd09c@u69g2000hse.googlegroups,com >, EADGBE <hwbosshoss@comcast,net > wrote:
>On Apr 22, 10:34 am, zekfr...@zekfrivolous,com (GregS) wrote:
>>
>> Where did you get this diagram. Is it completely from scratch ?
>>
>
>Greg:
>
>No, it was copied, carefully, from the original schematic. I would
>have scanned the original schematic, but it is very fuzzy. I did
>check my schematic against the other channel's schematic, which was a
>bit clearer but did not have the expected voltages indicated, and was
>cluttered with the actual component values.
>
>I have checked, re-checked, and RE-checked the accuracy of my hand-
>drawn schematic, comparing it to the original, and there are no
>mistakes.
The emitter of Q204 has a strange DC path. The amplifier appears
non inverting. What is the voltage on Q204 collector ?
greg
Re: Amplifier Problem - Revised Schematic
GregS wrote:
> In article <bb9d022f-3212-41a4-b455-e8d7f6cbd09c@u69g2000hse.googlegroups,com >, EADGBE <hwbosshoss@comcast,net > wrote:
>> On Apr 22, 10:34 am, zekfr...@zekfrivolous,com (GregS) wrote:
>>> Where did you get this diagram. Is it completely from scratch ?
>>>
>> Greg:
>>
>> No, it was copied, carefully, from the original schematic. I would
>> have scanned the original schematic, but it is very fuzzy. I did
>> check my schematic against the other channel's schematic, which was a
>> bit clearer but did not have the expected voltages indicated, and was
>> cluttered with the actual component values.
>>
>> I have checked, re-checked, and RE-checked the accuracy of my hand-
>> drawn schematic, comparing it to the original, and there are no
>> mistakes.
>
> The emitter of Q204 has a strange DC path. The amplifier appears
> non inverting. What is the voltage on Q204 collector ?
>
> greg
Q204 is in a pretty simple DC feedback path with Q205 and the 207/8
combination. Its emitter currrent flows down through Q208 to ground.
The amplifier is non-inverting from the base of Q204, but inverting from
its emitter, which is where both the DC and AC feedback end up.
d
GregS wrote:
> In article <bb9d022f-3212-41a4-b455-e8d7f6cbd09c@u69g2000hse.googlegroups,com >, EADGBE <hwbosshoss@comcast,net > wrote:
>> On Apr 22, 10:34 am, zekfr...@zekfrivolous,com (GregS) wrote:
>>> Where did you get this diagram. Is it completely from scratch ?
>>>
>> Greg:
>>
>> No, it was copied, carefully, from the original schematic. I would
>> have scanned the original schematic, but it is very fuzzy. I did
>> check my schematic against the other channel's schematic, which was a
>> bit clearer but did not have the expected voltages indicated, and was
>> cluttered with the actual component values.
>>
>> I have checked, re-checked, and RE-checked the accuracy of my hand-
>> drawn schematic, comparing it to the original, and there are no
>> mistakes.
>
> The emitter of Q204 has a strange DC path. The amplifier appears
> non inverting. What is the voltage on Q204 collector ?
>
> greg
Q204 is in a pretty simple DC feedback path with Q205 and the 207/8
combination. Its emitter currrent flows down through Q208 to ground.
The amplifier is non-inverting from the base of Q204, but inverting from
its emitter, which is where both the DC and AC feedback end up.
d
Re: Amplifier Problem - Revised Schematic
On Apr 22, 11:29 am, zekfr...@zekfrivolous,com (GregS) wrote:
>
> The emitter of Q204 has a strange DC path. The amplifier appears
> non inverting. What is the voltage on Q204 collector ?
>
> greg
Greg:
The voltage at the collector of Q204 measures +11.09VDC.
On Apr 22, 11:29 am, zekfr...@zekfrivolous,com (GregS) wrote:
>
> The emitter of Q204 has a strange DC path. The amplifier appears
> non inverting. What is the voltage on Q204 collector ?
>
> greg
Greg:
The voltage at the collector of Q204 measures +11.09VDC.
Re: Amplifier Problem - Revised Schematic
"EADGBE" <hwbosshoss@comcast,net > wrote in message
news:7a5f62ce-00ec-4fac-84f3-838743faa613@e67g2000hsa.googlegroups,com ...
> In the interest of clarification, I have added some information to the
> schematic of the tape deck headphone amp that I'm having problems
> with.
>
> Some circuit paths are now labeled:
>
> http :// i240.photobucket,com /albums/ff58/eadgbe123/amplifier-1.jpg
>
> As always, the points at which voltage readings are marked with a star
> are NOT producing the voltage indicated. The +7V location is
> measuring 131mV instead. The other two points where a star is
> indicated are measuring between 20mV and 30mV (fluctuating slightly).
>
> I am starting to think that a circuit OUTSIDE of this circuit might be
> at fault, because NOTHING inside of this circuit seems to be
> faulty...but the darn thing still WILL NOT work.
I haven't read every follow up message but have you tried removing the
electrolytic caps and retesting the d.c.? I've seen the d.c. stability been
thrown off in many amps due to bad coupling caps.
Good luck.
--
David Farber
David Farber's Service Center
L.A., CA
"EADGBE" <hwbosshoss@comcast,net > wrote in message
news:7a5f62ce-00ec-4fac-84f3-838743faa613@e67g2000hsa.googlegroups,com ...
> In the interest of clarification, I have added some information to the
> schematic of the tape deck headphone amp that I'm having problems
> with.
>
> Some circuit paths are now labeled:
>
> http :// i240.photobucket,com /albums/ff58/eadgbe123/amplifier-1.jpg
>
> As always, the points at which voltage readings are marked with a star
> are NOT producing the voltage indicated. The +7V location is
> measuring 131mV instead. The other two points where a star is
> indicated are measuring between 20mV and 30mV (fluctuating slightly).
>
> I am starting to think that a circuit OUTSIDE of this circuit might be
> at fault, because NOTHING inside of this circuit seems to be
> faulty...but the darn thing still WILL NOT work.
I haven't read every follow up message but have you tried removing the
electrolytic caps and retesting the d.c.? I've seen the d.c. stability been
thrown off in many amps due to bad coupling caps.
Good luck.
--
David Farber
David Farber's Service Center
L.A., CA
