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Post subject: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Mon Jan 25, 2016 6:13 pm
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A buddies Super Champ XD had a 6V6 EH go spastic and good old R79 got very hot and deformed but allowed the PT to die instead of it doing its job as a sacrificial component.

Long story made short, we need a PT or is this now just a speaker cab ???

Ya I saw that TAD will build one for the value of the whole stink'n amp

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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 2:49 am
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R79 , the 1K, 2 watts resistor ?

Schematic here;
http://support.fender.com/schematics/gu ... ematic.pdf

Pt look not easy to find at low price
http://billmaudio.com/wp/?page_id=243


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 7:07 am
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Yes strattele52 R79 was cooked enough to change shape and make all its color bands turn black, however it did not break the circuit and now reads 1.7K
No tube glow, no pilot light assuming the worse :cry:

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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 8:24 am
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blues bondsman wrote:
Yes strattele52 R79 was cooked enough to change shape and make all its color bands turn black, however it did not break the circuit and now reads 1.7K
No tube glow, no pilot light assuming the worse :cry:


I understand you did not check power transformer ?

Cooked R79 ,mean you have a short circuit in the amp . Power Transformer may be good.

Did you check all the fuses ? Not with eyes but with meter.


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 8:54 am
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I went around the board and checked most resistors
Only the R79 "fuse" and the main fuse at the power cord connection and that fuse is OK
Is there any others hidden ???

I didn't find any shorts in the PT from ground to any of the legs there was always equal resistance at each color coded leg (wire) from the transformer so...... ???

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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 9:38 am
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If the amp heated up for any length of time, as the burnt resistor would suggest, its also likely that the PT heated up as well.
There is a thermal fuse inside the transformer that could have blown.
If the primary is open, you can do surgery on the tranny, check and replace the thermal fuse. Its a usually a white rectangular box, sometimes a bullet shape tube. with two bare silver color leads.
This makes it easy to track down as all the other leads coming out of the windings are coated red wires.
After you get the metal covers off and expose the windings, the fuse is located under a few layers of tape. An Xacto knife and tweezers works well, but be very careful about NOT nicking any windings.
The fuse is there to shut down the amp in case of transformer failure, but can also be damaged by an overloaded transformer from a different circuit failure..
Due to liability issues, a tech probably won't want to do this repair, but if there is no alternative available, its worth a shot.


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 10:37 am
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I won't even bother taking the PT apart,,, yet. What about internal fuses F2,3,4, and 5. I can't even find the pilot - led on the schematic? R79 blown because of shorted screen grid, or the filter cap after R79? You’re going maybe need new 6V6 tubes if screen shorted. Also ck. screen grid resistors. Have you tried to measured any pwr supplies voltages, before thinking PT is bad. Good luck.
I also own a Super Champ XD, not used at this time.


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 12:04 pm
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jackhammer wrote:
I . Have you tried to measured any pwr supplies voltages, before thinking PT is bad.
.



+1
That is what I already asked. :(


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 1:18 pm
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jackhammer wrote:
I won't even bother taking the PT apart,,, yet. What about internal fuses F2,3,4, and 5. I can't even find the pilot - led on the schematic? R79 blown because of shorted screen grid, or the filter cap after R79? You’re going maybe need new 6V6 tubes if screen shorted. Also ck. screen grid resistors. Have you tried to measured any pwr supplies voltages, before thinking PT is bad. Good luck.
I also own a Super Champ XD, not used at this time.


↑↑↑ This. Also, check the condition of all filter caps & rail resistors in main PSU, for thermal damage. If you need a PT, maybe this may work?

http://www.classictone.net/40-18027.pdf


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 3:47 pm
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Thanks guys
As I mentioned earlier one of his 6V6EH power tubes went south and caused this issue
R79 was my first jab at it as it was deformed and the color bands were charred, it now reads 1.65K instead of 1K
I have been testing all across the board and found no other crispy or out of spec parts so........

I have no power past the mains going into the PT so.....................
The slow blow fuse is fully operational

I'm betting the internal thermal fuse is smoked

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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 4:18 pm
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blues bondsman wrote:

I have no power past the mains going into the PT so.....................


Is this mean you have input voltage at the PT primary with no output voltage from PT with nothing connected at his secondary ?


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Tue Jan 26, 2016 5:40 pm
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stratele52 wrote:
jackhammer wrote:
I . Have you tried to measured any pwr supplies voltages, before thinking PT is bad.
.



+1
That is what I already asked. :(


Didn't mean to repeat your idea.

Thanks stratele52 for the schematic and all your posts.
I got caught up in the posts and reply without re-reading what everybody previously said.


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Wed Jan 27, 2016 2:42 am
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jackhammer wrote:
stratele52 wrote:
jackhammer wrote:
I . Have you tried to measured any pwr supplies voltages, before thinking PT is bad.
.



+1
That is what I already asked. :(


Didn't mean to repeat your idea.

Thanks stratele52 for the schematic and all your posts.
I got caught up in the posts and reply without re-reading what everybody previously said.


I agree and I'am happy you ask about the PT voltage . I'm waiting the answer.

IMO , this is the first test to do.


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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Wed Jan 27, 2016 5:16 am
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There are no measurements to take
secondaries are an open circuit
primaries brown to blue 6.3M ohms
and similar readings on the other primaries

I would say its a safe bet that the thermal fuse inside is toast and not real sure i would take the risk of trying to replace it and possible burning down my buddies house.

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Post subject: Re: Anyone ever find a replacement PT for Super Champ XD ?
Posted: Wed Jan 27, 2016 5:32 am
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Thank's for answer blues bondman . I should not read carefully your first post


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