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A little help - Traynor YCV50 power
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10-21-2013, 12:35 PM
#21

jb
welder

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Originally Posted by dtsaudio

the spec is for measuring 350mV across the two
cathodes. page 9 of the service manual pdf file clearly states
this.

Originally Posted by dcole

notice the cathode resistors are shown as 2 ohm
resistors. The 350 mV level would give a very high plate
current.

Originally Posted by dtsaudio

You're absolutely right about the 2R resistors. They
should be 10R

Could you guys point me to where it
shows 350mV for bias across 2R resistors?
The current version from the
website ( http://traynoramps.com/downloads/servman/smycv50b.pdf )
shows 75mV across the 2R resistors. With approx. 410V at the plates, that
works out to about 15W dissipation at idle.
Maybe there was a typo on a
different schematic or different cathode resistor values?

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10-21-2013, 12:48 PM
#22

jb
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On closer look, I think you
guys are looking a 2 separate drawings, the old way was 350mV with 10R
cathode resistors, the newer version specs 75mV across 2R cathode resistors.

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10-21-2013, 01:09 PM
#23

drwow

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Originally Posted by jb welder

Could you guys point me to where it shows 350mV for
bias across 2R resistors?
The current version from the website ( http://traynoramps.com/downloads/servman/smycv50b.pdf )
shows 75mV across the 2R resistors. With approx. 410V at the plates, that
works out to about 15W dissipation at idle.
Maybe there was a typo on a
different schematic or different cathode resistor
values?

The previous version ("YCV50 Blue") of the
amp, or ( http://traynoramps.com/downloads/servman/smycv50blue.pdf
) on both page 9 and page 13.

It's important to note a few things:

- it's impossible to get any copy of older versions of service
manuals/schematics for any specific YCV amp from Traynor/Yorkville, even if
you "know somebody", they only keep the latest revisions (including
"discontinued" models).

- It's likely that unless you have a new amp
or the last revision of a discontinued model, what you look at on the pdf,
will not be exactly the same as the circuit/layout you're working
on.

- I suspect there's a few errors

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10-21-2013, 09:54 PM
#24

nonreverb

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I remember getting one of these
treasures in with serious bias problems due to the auto bias circuit being
totally whacked. I eventually reverted it back to a previous version without
the autobias and it worked perfectly...more importantly, the customer was
happy...

Originally Posted by allthumbs56

From the Owner's Manual;

"This
amplifier features Yorkville’s auto-balancing / auto-matching tube biasing
technology. As a result, when the time comes to replace the tubes in your
Yorkville amplifier, there is no need to pay a premium for a matched set –
nor does the bias need to be adjusted when you use a different brand. We
make no claims as to which brands of tubes might sound best, but with
auto-balancing / auto-matching, you are free to experiment without any need
for concern that the amplifier or tubes will be distressed. Please note that
auto-balancing / auto matching cannot fully compensate for different types
of tubes - 6L6/5881s versus 6CA7/EL34s, for example.
"

Marketing
Hoakum?

Fenders, Gibsons, Leslies and Hammonds
http://www.toneonwheels.com/

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10-22-2013, 01:28 AM
#25

drwow

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Originally Posted by nonreverb

I remember getting one of these treasures in with
serious bias problems due to the auto bias circuit being totally whacked. I
eventually reverted it back to a previous version without the autobias and
it worked perfectly...more importantly, the customer was
happy...

A few questions, if that's okay.

Do
you have copies of older service manuals, schematics, etc?
Which version
of the amp first came with the auto-balance feature?
How does the
auto-balance feature work?
How do you remove it?

BTW, we know each
other, ...long-time no see, brother.

~ R. Ewald

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10-23-2013, 01:24 PM
#26

jb
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Originally Posted by drwow

Do you have copies of older service manuals,
schematics, etc?
Which version of the amp first came with the
auto-balance feature?
How does the auto-balance feature work?
How do
you remove it?

Back in post #15 dcole posted a link
to a drawing showing the auto-match bias circuit. Complete (older) service
manual is available here: http://www.toomanyhelicopters.com/schems/Traynor_YCV40_Technical_Manual_w_Schem.pdf
It is for the YCV40, version 12.01, Dec.2005.
Here are the transistors
that sense the cathode current of each output tube and adjust the bias to
each tube independently
Here is how it mates with the output tubes (AS,BS to
cahtodes, A-,B- to grid feeds):
AS and BS sense the current through the cathodes, Q4 and Q5
adjust the bias voltage to the grids of the output tubes accordingly. You
should be able to remove the auto match circuit by changing it over to the
newer version schematic.

The YCS amps have a circuit with a
transistor across the bias trimpot. I'm not clear on exactly what it is
doing. The base of the transistor seems to be sensing the screen grid
voltage. The early versions of the YCS claimed to be able to run either 6L6
or EL34's, with the bias auto adjusting. Perhaps that is what this circuit
is doing.
Anyone familiar with this circuit please comment:

Originally Posted by drwow

it's impossible to get any copy of older versions of
service manuals/schematics for any specific YCV amp from Traynor/Yorkville,
even if you "know somebody", they only keep the latest revisions (including
"discontinued" models).

This statement is incorrect.
If you mean they only keep current versions on-line, then yes that is the
case.
But they certainly have older versions of the schematics. After
all, they have to work on the stuff themselves in their service dept. And I
can say that I have personally received older revision schematics that are
not found online. Perhaps you will need to verify that you are actually
working on a unit (serial #, board revision number etc.), but they have
schematics for older revisions. Within reason of course, there may not be
many versions available for extinct models.

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10-24-2013, 12:14 PM
#27

drwow

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Originally Posted by jb welder

Back in post #15 dcole posted a link to a drawing
showing the auto-match bias circuit. Complete (older) service manual is
available here: http://www.toomanyhelicopters.com/schems/Traynor_YCV40_Technical_Manual_w_Schem.pdf
It is for the YCV40, version 12.01, Dec.2005.
Here are the transistors
that sense the cathode current of each output tube and adjust the bias to
each tube independently
Here is how it mates with the output tubes (AS,BS to
cahtodes, A-,B- to grid feeds):
AS and BS sense the current through the cathodes, Q4 and Q5
adjust the bias voltage to the grids of the output tubes accordingly. You
should be able to remove the auto match circuit by changing it over to the
newer version schematic.

The YCS amps have a circuit with a
transistor across the bias trimpot. I'm not clear on exactly what it is
doing. The base of the transistor seems to be sensing the screen grid
voltage. The early versions of the YCS claimed to be able to run either 6L6
or EL34's, with the bias auto adjusting. Perhaps that is what this circuit
is doing.
Anyone familiar with this circuit please comment:

This statement is incorrect. If you mean they
only keep current versions on-line, then yes that is the case.
But they
certainly have older versions of the schematics. After all, they have to
work on the stuff themselves in their service dept. And I can say that I
have personally received older revision schematics that are not found
online. Perhaps you will need to verify that you are actually working on a
unit (serial #, board revision number etc.), but they have schematics for
older revisions. Within reason of course, there may not be many versions
available for extinct models.

I love being wrong,
it's an opportunity to learn something.

After my fourth attempt at
getting information out of Yorkville (w/ serial #, etc.) I got a reply from
Guy Beresford with the correct schematic for the earliest YCV50 version
(V.1).

For those interested:

Here's the bias circuit:

Sorry about those files, they didn't parse full size,
I'll fix it later...

Attached
Images

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10-25-2013, 10:33 AM
#28

jb
welder

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Originally Posted by drwow

After my fourth attempt at getting information out of
Yorkville (w/ serial #, etc.) I got a reply from Guy Beresford with the
correct schematic for the earliest

Glad to year you
got it sorted, Guy IS the man.

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10-25-2013, 07:55 PM
#29

nonreverb

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He is indeed...he just set me
up with the Hughes & Kettner Statesman Dual 6L6 schematic...I wouldn't
have touched this amp with a 10 foot pole without it.

Originally Posted by jb welder

Glad to year you got it sorted, Guy IS the
man.

Fenders, Gibsons, Leslies and Hammonds
http://www.toneonwheels.com/

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11-07-2013, 11:28 AM
#30

Adicted
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Any headway on the
cause?

Never mind,I saw the part about the bad tube in his
spares.

Having worked at L&M on lots of Traynors,I conclude the
design is just plain dumb,especially the standby circuitry.I told that to
Guy at Traynor and he spouts of about how brilliant it is. Really? A mosfet
circuit to drop voltage to the power tubes as a standby circuit?An auto bias
circuit? Why I ask?
Too much circuitry inside what should have been an
otherwise simple amp makes for tons of revisions as you can see by the
schematic changes and updates.
Simple is always best in my book.

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