Mesa Boogie 50+ Caliber problem

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.

Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...
__
Steve
.

Bob Mann

2007-02-14 15:21:02 UTC

On Wed, 14 Feb 2007 08:37:39 -0600, "Stephen Cowell"

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.
Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...

FWIW, that is exactly what happened to my F-50.
It wasn't completely gone but the heat from the tube caused the solder
on the resistor to let go.

--
Bob Mann
Help save trees. Wipe your ass with an owl.

Stephen Cowell

2007-02-14 15:24:32 UTC

"Bob Mann" <***@nowhere.com> wrote in message news:***@4ax.com...

...

Post by Bob Mann
FWIW, that is exactly what happened to my F-50.
It wasn't completely gone but the heat from the tube caused the solder
on the resistor to let go.

If this is so, then perhaps you could point out to us
where the resistor is in the amp, and the value of it.
This would go a long way to helping solve the problem.
__
Steve
.

Bob Mann

2007-02-14 16:23:27 UTC

On Wed, 14 Feb 2007 09:24:32 -0600, "Stephen Cowell"

Post by Bob Mann
FWIW, that is exactly what happened to my F-50.
It wasn't completely gone but the heat from the tube caused the solder
on the resistor to let go.

If this is so, then perhaps you could point out to us
where the resistor is in the amp, and the value of it.
This would go a long way to helping solve the problem.
__
Steve
.

Sorry, I just took it into the shop.
It was under warranty.

As I recall, the resistor was located quite close to the output tube
but they never said which tube actually went nor which transistor
"popped out".

--
Bob Mann
Help save trees. Wipe your ass with an owl.

sam booka X2

2007-02-14 17:45:12 UTC

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.
Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...
__
Steve
.

I did suspect that one of the output tubes has gone, slight milky haze
near the base, but I am without my tester. I was able to get a couple
Fender Sovtek 5881's to swap, but they didn't do the trick so I am here.
Give me a few more minutes and I'll have those pictures of the carnage up
on eSnips, and thanks for responding.

--
__________________________________________________________________
____________ ______ ____
/ ___/ _ / |/ / _ )/ __ \
/___ / // / / _ / /_/ /
|____/_--_/_/|_/_/____/\____/ Producer & Stocker of the Beer Fridge
|
---------------------------------------------------------------------
Saskatchewan Surf Association Keeper of the forbidden vowel, "z"

sam booka X2

2007-02-14 18:00:12 UTC

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.
Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...
__
Steve
.

In better light, I have it off the board... it is sorta brown black
coulda-been-orangeish-but-now-burnt-tan gold making it a 100 ohm... maybe!
:p Hang on... gotta get the camera... I can't type a thousand words that
fast...
The preamp schematic is at http://www.tubefreak.com/cal50pre.gif
I did suspect that one of the output tubes has gone, slight milky haze
near the base, but I am without my tester. I was able to get a couple
Fender Sovtek 5881's to swap, but they didn't do the trick so I am here.
Give me a few more minutes and I'll have those pictures of the carnage
up on eSnips, and thanks for responding.

Pictures are up...
http://www.esnips.com/doc/78cb098c-d3d1-4743-b8ed-222b0eb0c72f/DSCF0054
http://www.esnips.com/doc/09ac26ee-3fcf-48fa-b784-755e5248702b/DSCF0053

--
__________________________________________________________________
____________ ______ ____
/ ___/ _ / |/ / _ )/ __ \
/___ / // / / _ / /_/ /
|____/_--_/_/|_/_/____/\____/ Producer & Stocker of the Beer Fridge
|
---------------------------------------------------------------------
Saskatchewan Surf Association Keeper of the forbidden vowel, "z"

2007-02-14 18:54:34 UTC

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.
Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...
__
Steve
.

Pictures are up...
http://www.esnips.com/doc/78cb098c-d3d1-4743-b8ed-222b0eb0c72f/DSCF0054
http://www.esnips.com/doc/09ac26ee-3fcf-48fa-b784-755e5248702b/DSCF0053

Hi,

is the red lead connected to the pcb-pad of the resistor? It might be
point "A" in the schematic. Then it would be the "screen grid dropping
resistor" with 1500 in the scheme.

just a thought.

Disclaimer
Be careful, with B+ "on" there are approx 450V available at this point
of the circuit. If you don´t know what you´re precisely doing, *don´t do
it* and rely to a tech. If you are a tech and I haven´t realized it, i
have to apologize.

regards

Jochen

sam booka X2

2007-02-14 19:20:10 UTC

Post by jh

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.
Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...
__
Steve
.

Pictures are up...
http://www.esnips.com/doc/78cb098c-d3d1-4743-b8ed-222b0eb0c72f/DSCF0054
http://www.esnips.com/doc/09ac26ee-3fcf-48fa-b784-755e5248702b/DSCF0053

Hi,
is the red lead connected to the pcb-pad of the resistor? It might be
point "A" in the schematic. Then it would be the "screen grid dropping
resistor" with 1500 in the scheme.
just a thought.
Disclaimer
Be careful, with B+ "on" there are approx 450V available at this point
of the circuit. If you donŽt know what youŽre precisely doing, *donŽt do
it* and rely to a tech. If you are a tech and I havenŽt realized it, i
have to apologize.
regards
Jochen

I'm no tech. The red lead was connected with the resistor to the now
scorched point on the board. The amp was unplugged and the caps all drained
when I took these shots. I held the components back in place for the
picture. There are two holes 1/16" apart in the PCB where the red lead and
resistor were attached, found soldered together as shown. The pad on the
PCB is/was torched.

It will be a month before I can get back to civilization. My IP is actually
a hughes.net satellite IP and shows the NOC in Germantown, Maryland, if you
were wondering why I just can't take it to the local tech.

Stephen Cowell

2007-02-15 04:26:49 UTC

"sam booka X2" <***@il.is.the.kitchen> wrote in message news:***@199.185.223.74...

...

Post by sam booka X2
I'm no tech. The red lead was connected with the resistor to the now
scorched point on the board. The amp was unplugged and the caps all drained
when I took these shots. I held the components back in place for the
picture. There are two holes 1/16" apart in the PCB where the red lead and
resistor were attached, found soldered together as shown. The pad on the
PCB is/was torched.
It will be a month before I can get back to civilization. My IP is actually
a hughes.net satellite IP and shows the NOC in Germantown, Maryland, if you
were wondering why I just can't take it to the local tech.

The resistor I'm looking at in the pic shows to be a 200ohm 5%2w...
red black brown gold. This is very much less than what is shown
in the schematic... the value read on the meter is much closer to
200 than 1500.

You're going to have to verify by ohming to nearby circuit
components... trace it out and *verify* that we are talking
about the screen dropping (as well as the rest of the pre!)
PS filter resistor.

You can replace it with what you found, what the schem shows,
or whatever you want, actually... they might have changed PT's
in mid-run and messed with this resistor, or something like that.
Anyway, a new set of finals and a new resistor and you should
be good to go... check bias of new finals, always.
__
Steve
.

Tony Hwang

2007-02-15 04:49:08 UTC

The resistor I'm looking at in the pic shows to be a 200ohm 5%2w...
red black brown gold. This is very much less than what is shown
in the schematic... the value read on the meter is much closer to
200 than 1500.
You're going to have to verify by ohming to nearby circuit
components... trace it out and *verify* that we are talking
about the screen dropping (as well as the rest of the pre!)
PS filter resistor.
You can replace it with what you found, what the schem shows,
or whatever you want, actually... they might have changed PT's
in mid-run and messed with this resistor, or something like that.
Anyway, a new set of finals and a new resistor and you should
be good to go... check bias of new finals, always.
__
Steve
.

Hmm,
If it is Sg drop resistor there shoud be more than one.
Tony

Tony Hwang

2007-02-15 05:04:02 UTC

Post by Tony Hwang

The resistor I'm looking at in the pic shows to be a 200ohm 5%2w...
red black brown gold. This is very much less than what is shown
in the schematic... the value read on the meter is much closer to
200 than 1500.
You're going to have to verify by ohming to nearby circuit
components... trace it out and *verify* that we are talking
about the screen dropping (as well as the rest of the pre!)
PS filter resistor.
You can replace it with what you found, what the schem shows,
or whatever you want, actually... they might have changed PT's
in mid-run and messed with this resistor, or something like that.
Anyway, a new set of finals and a new resistor and you should
be good to go... check bias of new finals, always.
__
Steve
.

Hmm,
If it is Sg drop resistor there shoud be more than one.
Tony

Hi,
My hunch, try a 1500 Ohm, 5W resistor.
Tony

Stephen Cowell

2007-02-15 14:43:32 UTC

"Tony Hwang" <***@shaw.ca> wrote in message news:8DRAh.983041$***@pd7urf2no...

...

Post by Tony Hwang
Hmm,
If it is Sg drop resistor there shoud be more than one.

This is the resistor that takes the place of a choke
in the PS filter string... not the final screen resistors.
__
Steve
.

Tony Hwang

2007-02-15 15:40:36 UTC

Post by Tony Hwang
Hmm,
If it is Sg drop resistor there shoud be more than one.

This is the resistor that takes the place of a choke
in the PS filter string... not the final screen resistors.
__
Steve
.

Hi,
That,s more likely. 5W 1500 Ohmish. According to the schematics.
Tony

sam booka X2

2007-02-15 18:03:04 UTC

Post by Tony Hwang

Post by Tony Hwang
Hmm,
If it is Sg drop resistor there shoud be more than one.

This is the resistor that takes the place of a choke
in the PS filter string... not the final screen resistors.
__
Steve
.

Hi,
That,s more likely. 5W 1500 Ohmish. According to the schematics.
Tony

Thanks guys. I wonder if this amp was modded to accomodate the KT66 6L6GC
tubes that it had in it when I got it used? There has been no change to the
resistors though where the bias voltage is hardwired to -47 V AFAICT
through ohming it out as per Steve's suggestions.

2007-02-15 15:37:32 UTC

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.
Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...
__
Steve
.

That resistor is located in the footswitch supply and provides power
to 3 of the 5 LDRs (LDR 1 - 3).
Your (in circuit?) measurement of "89.4" ohms tells me that it's not
burned open- (fwiw an open here would
disable the lead and mid-boost modes but would not disable clean, so
it is not the cause of your amp being
totally dead (if it is). The value should be 100 ohm. Let me ask you=>
the boogie foot switch has, (and needs to have),
some *internal* series resistance of (iirc) around 3.5K. You haven't
been a naughty boy and have been just using
"just any ol' foot switch, now have you? :-)

There's just about a bazillion boogies on the planet and properly
maintained, they are fine amplifiers.
Generally, the blokes running dissing them are old, stale Fender /
Marshall "parts changers"
who gave up on educating themselves beyond the 1950s and 1960s
designs. Be wary of these
types as you'll likely get your gear returned to you all jacked up and
worse off than when you
delivered it.

bk

sam booka X2

2007-02-15 18:24:38 UTC

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.
Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...
__
Steve
.

Yes I have. Simple on off. Ooooops. :p

Post by bk
There's just about a bazillion boogies on the planet and properly
maintained, they are fine amplifiers.
Generally, the blokes running dissing them are old, stale Fender /
Marshall "parts changers"
who gave up on educating themselves beyond the 1950s and 1960s
designs. Be wary of these
types as you'll likely get your gear returned to you all jacked up and
worse off than when you
delivered it.
bk

So at 89 ohms, it's still out of spec, and I should likely get a new one?
It still doesn't work in clean or lead when it is just resoldered to the
trace, and no FS is connected.

At any rate, I don't know why I use the FS as I generally have everything
set to work with the volume of my stock Strats to change the tone palette,
and leave the lead channel on. I'm kind of luddite when it comes to
effects, including the reverb which I leave zeroed. Which brings to mind,
will the reverb cause any troubles working without that spring?

2007-02-16 14:51:56 UTC

Since there is no power resistor with a sub-ten-ohm value on
your schematic (you posted two copies of the pwr amp, btw)
we need to verify what part of the amp the resistor is in.
Also check the colors again... a brown-black-silver-gold
resistor would be .1 or .2ohms, probably at 2watts (you didn't
tell us what kind of resistor... is it carbon comp? Metal film?)
Obviously there's not one in the schematic posted.
Tell us the components the resistor connects to. You have
probably lost an output tube, taking a cathode resistor with
it. Or, you've lost a zener and resistor for the EQ PS.
Post a picture of the burned resistor! That would help...
__
Steve
.

Come on guys! Are you going to just ~go~ with the above?
R261 is in the supply that I mentioned, but the post
above is only semi-accurate. Are you going to just "buy" my FS theory?
Let's look at the ckt. drawing and pick it apart? Maybe no one gives a
crap...
The FS supply, once rectified and filtered, stands at
about 8 to 10 Vdc. So you have that, R261(ldr led current limiting),
4 ldr leds in parallel with a 470 ohm and lastly, a switch closure.
Do you think that the resistor fried because of use of the wrong fs?
(Hint: the Boogie fs ~3.5K is to limit current for the *fs* led.)

Any potential around here anymore for ckt. discussion?
I fully expected to come back here this am & have
my butt kicked. :)

Ok.

bk

Stephen Cowell

2007-02-17 01:48:43 UTC

"bk" <***@hotmail.com> wrote in message news:***@j27g2000cwj.googlegroups.com...

...

Post by bk
Come on guys! Are you going to just ~go~ with the above?
R261 is in the supply that I mentioned, but the post
above is only semi-accurate. Are you going to just "buy" my FS theory?
Let's look at the ckt. drawing and pick it apart? Maybe no one gives a
crap...
The FS supply, once rectified and filtered, stands at
about 8 to 10 Vdc. So you have that, R261(ldr led current limiting),
4 ldr leds in parallel with a 470 ohm and lastly, a switch closure.
Do you think that the resistor fried because of use of the wrong fs?
(Hint: the Boogie fs ~3.5K is to limit current for the *fs* led.)
Any potential around here anymore for ckt. discussion?
I fully expected to come back here this am & have
my butt kicked. :)

Are you talking about the 680/330 resistor divider?
That would explain the 680ohm 2w in the picture.
__
Steve
.

sam booka X2

2007-02-17 10:35:07 UTC

Post by bk
That resistor is located in the footswitch supply and provides power
to 3 of the 5 LDRs (LDR 1 - 3).
Your (in circuit?) measurement of "89.4" ohms tells me that it's not
burned open- (fwiw an open here would
disable the lead and mid-boost modes but would not disable clean, so
it is not the cause of your amp being
totally dead (if it is). The value should be 100 ohm. Let me ask you=>
the boogie foot switch has, (and needs to have),
some *internal* series resistance of (iirc) around 3.5K. You haven't
been a naughty boy and have been just using
"just any ol' foot switch, now have you? :-)

I still care! :p

Post by bk
The FS supply, once rectified and filtered, stands at
about 8 to 10 Vdc. So you have that, R261(ldr led current limiting),
4 ldr leds in parallel with a 470 ohm and lastly, a switch closure.
Do you think that the resistor fried because of use of the wrong fs?
(Hint: the Boogie fs ~3.5K is to limit current for the *fs* led.)
Any potential around here anymore for ckt. discussion?
I fully expected to come back here this am & have
my butt kicked. :)
Ok.
bk

No butt kickin' here. I'm the patient... you guys are the surgeons! :p

sam booka X2

2007-03-16 21:22:59 UTC

I still care! :p

No butt kickin' here. I'm the patient... you guys are the surgeons! :p

An update with this thing...

It was the reverb spring that came off at one end and fell across the tube
pins that shorted the R261 resistor. All that stuff that was toasted was in
the reverb section. I wound up taking it to a fellow in Calgary, Canada,
Mike at Guitar Connections. He was referred by Guitarworks in Calgary, the
Mesa dealer there. All their Mesa stuff goes there.

He put some shrink wrap over the tube socket connections to prevent the
same thing from happening again, and fixed up the mess caused by the short.
It cost me about $50 US equivalent, including a checkup.

He says there will be no adverse effects from using a simple on/off
footswitch as was surmised by some. You just won't have an LED, but if you
can't tell, you are deaf anyways. I guess the LED is to freak people out at
gigs so you can blast them right out of the gate when you come off standby,
and wanna know which channel you have.

Anyways, if you like tube amps, check him out at 17th Ave and 17th St SW.
in Calgary. Lots of nice vintage Marshalls, HIWATT's, Fenders, and Ampegs
there in good repair to drool over or even buy if you can get them to part
with them... especially the HIWATT's and the Ampegs.

Bob Mann

2007-03-17 13:36:48 UTC

On Fri, 16 Mar 2007 21:22:59 GMT, sam booka X2

I still care! :p

No butt kickin' here. I'm the patient... you guys are the surgeons! :p

An update with this thing...
It was the reverb spring that came off at one end and fell across the tube
pins that shorted the R261 resistor. All that stuff that was toasted was in
the reverb section. I wound up taking it to a fellow in Calgary, Canada,
Mike at Guitar Connections. He was referred by Guitarworks in Calgary, the
Mesa dealer there. All their Mesa stuff goes there.
He put some shrink wrap over the tube socket connections to prevent the
same thing from happening again, and fixed up the mess caused by the short.
It cost me about $50 US equivalent, including a checkup.
He says there will be no adverse effects from using a simple on/off
footswitch as was surmised by some. You just won't have an LED, but if you
can't tell, you are deaf anyways. I guess the LED is to freak people out at
gigs so you can blast them right out of the gate when you come off standby,
and wanna know which channel you have.
Anyways, if you like tube amps, check him out at 17th Ave and 17th St SW.
in Calgary. Lots of nice vintage Marshalls, HIWATT's, Fenders, and Ampegs
there in good repair to drool over or even buy if you can get them to part
with them... especially the HIWATT's and the Ampegs.

I'll have to keep that in mind next time I am there.
Of course, I'll most likely be on the bike so that will help keep me
from buying anything.

--
Bob Mann
85 K100RS (traded for...)
04 FXD Stage 1(traded for...)
04 FLHTCUI 95" Stage 3

m***@yahoo.com

2007-02-15 02:37:55 UTC

oh shit here we go again
the reason the resistor burns is that the design
of this amp causes it to SELF DESTRUCT.
this amp should not only include an instruction
manual, it should include a fire extinguisher.
save time, call the paramedics now.

sam booka X2

2007-02-15 02:50:32 UTC

Post by m***@yahoo.com
oh shit here we go again
the reason the resistor burns is that the design
of this amp causes it to SELF DESTRUCT.
this amp should not only include an instruction
manual, it should include a fire extinguisher.
save time, call the paramedics now.

Hehe. It had great tone up until *then*. Maybe a little flabby in the
bottom, but what old gal ain't? :p

Is there any way it can be hacked to prevent this? Like where would a guy
start to put a fuse, and a bias trim pot, for example? I know Boogie says
"Fender says set this value for 52V... That's it!" when dismissing their
reason for not having a bias trim pot.

Tony Hwang

2007-02-15 04:51:06 UTC

Hehe. It had great tone up until *then*. Maybe a little flabby in the
bottom, but what old gal ain't? :p
Is there any way it can be hacked to prevent this? Like where would a guy
start to put a fuse, and a bias trim pot, for example? I know Boogie says
"Fender says set this value for 52V... That's it!" when dismissing their
reason for not having a bias trim pot.

Hi,
Installing a cooling fan is an option.
Tony

2007-02-15 16:31:51 UTC

99% of the time, the resistor burns / cooks solder joints
when an improper footswitch is used to toggle the lead / rhythm modes.

Same thing happens on JCM2Ks with R21.

sam booka X2

2007-02-16 05:42:33 UTC

99% of the time, the resistor burns / cooks solder joints
when an improper footswitch is used to toggle the lead / rhythm modes.
Same thing happens on JCM2Ks with R21.

I'm starting to think the reverb spring shorted across the pins of the tube
socket and took out something else.

I can hook an external amp to the direct effects send, still get no sound
from the input, but when I knock on the cabinet, I can hear it in the other
amp. Go figure! When I try the direct out to an amp and turn it up past
about 3, it will feedback around 400 hz. That's where I stand so far....

2007-02-16 16:09:45 UTC