[misterc57]

I bought an old "TUSC CF 50", 50 watt guitar head. It uses (2) 6L6GC
power tubes. The TUSC CF 100 version uses (4) 6L6GC power tubes. It
appears that they share the same circuit board which is setup for (4)
6L6GC tubes.

Does anyone have a schematic for either head? I would like to find out
the voltage readings for the 6L6GC power tubes.

One tube was dead. I replaced a burnt resistor at pin 4 (4.6K ohm).
Then took the following DC voltage readings.

socket 1 - pin 4 reads 441V and pin 5 reads 50.2V
socket 2 - empty no tube on the 50 watt model
socket 3 - pin 4 reads 441V and pin 5 reads 49.7V
socket 4 - empty no tube on the 50 watt model

Based on tube data, do these seem right for a 6L6GC?

Thank you, Mark

[Phil Allison]

"misterc57" wrote in message
oups.com...

** Groper Alert !!


I bought an old "TUSC CF 50", 50 watt guitar head. It uses (2) 6L6GC
power tubes. The TUSC CF 100 version uses (4) 6L6GC power tubes. It
appears that they share the same circuit board which is setup for (4)
6L6GC tubes.

Does anyone have a schematic for either head? I would like to find out
the voltage readings for the 6L6GC power tubes.

One tube was dead. I replaced a burnt resistor at pin 4 (4.6K ohm).


** NO WAY is that resistor 4.6 kohms !!!!

Maybe YOU are colour-blind - 12 % of males are.

Measure the other similar resistor with an ohm meter.

Betya it is 470 ohms.




Then took the following DC voltage readings.

socket 1 - pin 4 reads 441V and pin 5 reads 50.2V



** Betya it is ** MINUS ** 50.2 volts !!


Based on tube data, do these seem right for a 6L6GC?


** Yep.



........ Phil

[Phil S.]

"misterc57" wrote in message
oups.com...
I bought an old "TUSC CF 50", 50 watt guitar head. It uses (2) 6L6GC
power tubes. The TUSC CF 100 version uses (4) 6L6GC power tubes. It
appears that they share the same circuit board which is setup for (4)
6L6GC tubes.

Does anyone have a schematic for either head? I would like to find out
the voltage readings for the 6L6GC power tubes.

One tube was dead. I replaced a burnt resistor at pin 4 (4.6K ohm).
Then took the following DC voltage readings.

socket 1 - pin 4 reads 441V and pin 5 reads 50.2V
socket 2 - empty no tube on the 50 watt model
socket 3 - pin 4 reads 441V and pin 5 reads 49.7V
socket 4 - empty no tube on the 50 watt model

Based on tube data, do these seem right for a 6L6GC?

Thank you, Mark


Pin 4 = G2; rated for 500v max, but some tubes will tolerate more and some
less. To be safe, stay below the max. What is voltage on pin 3 (plate)? I
assume on Pin 5 (grid) you mean the voltage is negative 50? Seems like this
should be more towards the mid 30's, but the real answer depends on the amp
and how much currrent the power tubes are pulling. Have you/do you know how
to check bias and calc static plate dissapation? Look for something about
that he http://aga.rru.com .

Just guessing here, but it could be that the amp had a burnt resistor
because it's not running properly. If so, this should be tended to.

[misterc57]

I am hear to learn...

What is Groper Alert?

You are right. I think I am color blind.

My meter says the resistors are

.460 K ohms

So the math is .460 X 1000 = 460 ohms.

I thought the color bands were yellow, blue, red. But I guess they are
yellow, blue, brown.

I pulled the matching resistor out of socket 4 on the board to use in
socket 1.

You also right about my readings at pin 5. They were MINUS, I had not
noticed until you mentioned it.

Thank you for all the clarifications and confirming the readings are in
spec.

- Mark


Phil Allison wrote:
"misterc57" wrote in message
oups.com...

** Groper Alert !!


I bought an old "TUSC CF 50", 50 watt guitar head. It uses (2) 6L6GC
power tubes. The TUSC CF 100 version uses (4) 6L6GC power tubes. It
appears that they share the same circuit board which is setup for (4)
6L6GC tubes.

Does anyone have a schematic for either head? I would like to find out
the voltage readings for the 6L6GC power tubes.

One tube was dead. I replaced a burnt resistor at pin 4 (4.6K ohm).


** NO WAY is that resistor 4.6 kohms !!!!

Maybe YOU are colour-blind - 12 % of males are.

Measure the other similar resistor with an ohm meter.

Betya it is 470 ohms.




Then took the following DC voltage readings.

socket 1 - pin 4 reads 441V and pin 5 reads 50.2V



** Betya it is ** MINUS ** 50.2 volts !!


Based on tube data, do these seem right for a 6L6GC?


** Yep.



....... Phil

[misterc57]

438 Volts at pin 3 on both sockets.
441 Volts at pin 4
MINUS 50 Volts at pin 5

There appears to be a bias adjust knob on the board. I do have a probe
to test bias. Will check out the site you referenced

Thanks, Mark

Phil S. wrote:
"misterc57" wrote in message
oups.com...
I bought an old "TUSC CF 50", 50 watt guitar head. It uses (2) 6L6GC
power tubes. The TUSC CF 100 version uses (4) 6L6GC power tubes. It
appears that they share the same circuit board which is setup for (4)
6L6GC tubes.

Does anyone have a schematic for either head? I would like to find out
the voltage readings for the 6L6GC power tubes.

One tube was dead. I replaced a burnt resistor at pin 4 (4.6K ohm).
Then took the following DC voltage readings.

socket 1 - pin 4 reads 441V and pin 5 reads 50.2V
socket 2 - empty no tube on the 50 watt model
socket 3 - pin 4 reads 441V and pin 5 reads 49.7V
socket 4 - empty no tube on the 50 watt model

Based on tube data, do these seem right for a 6L6GC?

Thank you, Mark


Pin 4 = G2; rated for 500v max, but some tubes will tolerate more and some
less. To be safe, stay below the max. What is voltage on pin 3 (plate)? I
assume on Pin 5 (grid) you mean the voltage is negative 50? Seems like this
should be more towards the mid 30's, but the real answer depends on the amp
and how much currrent the power tubes are pulling. Have you/do you know how
to check bias and calc static plate dissapation? Look for something about
that he http://aga.rru.com .

Just guessing here, but it could be that the amp had a burnt resistor
because it's not running properly. If so, this should be tended to.

[Dave Curtis]

On 16 Oct 2006 19:07:25 -0700, "misterc57"
wrote:

438 Volts at pin 3 on both sockets.
441 Volts at pin 4
MINUS 50 Volts at pin 5

There appears to be a bias adjust knob on the board. I do have a probe
to test bias. Will check out the site you referenced

Thanks, Mark

Pin 3 (plate) should measure higher than pin 4 (screen grid).

-Dave

[Dave Curtis]

On Tue, 17 Oct 2006 05:52:31 -0500, flipper wrote:

On Tue, 17 Oct 2006 06:40:16 -0400, Dave Curtis
wrote:

On 16 Oct 2006 19:07:25 -0700, "misterc57"
wrote:

438 Volts at pin 3 on both sockets.
441 Volts at pin 4
MINUS 50 Volts at pin 5

There appears to be a bias adjust knob on the board. I do have a probe
to test bias. Will check out the site you referenced

Thanks, Mark

Pin 3 (plate) should measure higher than pin 4 (screen grid).

Depends on the components. Idle current through the OPT primary DC
resistance will cause a slight drop from B+ to the plate and then
there's idle screen current through the screen resistor, if it has
one, to B+. So a few volts might be correct.


-Dave

As I wrote that, I was wondering if he had tubes in it, and it turns
out he didn't. (Aha!)

-Dave