Problems with G5 Amp

Frank · Message non lu par **Frank** » 18 sept. 2006, 19:34

Hello !

My name is Frank and i´m from Germany. I´ve build the G5 a few months ago and now i´ve a Problem that i could not find yet

I´ve made a Master Volume Pot.My Problem is that when its turned to 8-10 (full up) the sound goes away if i pick the strings harder.When the Pot is turned all the way down and then again up,the sound is back.
The preamp is okay, it seems to be a problem in the output stage.
Does Anyone have a idea???

Thanks,
Frank

Message non lu par **McColson** » 18 sept. 2006, 20:21

Maybe your potar is dead, try to remplace it by a simple 1M (R17 on the schematic if you have place the master here). If the sound it's the same like when at 10 on your pot, it's not the pot.
So verify all your solders around the EL34, the wires...
Have you got some photos of the inside ?

Edit : Welcome Frank !!!

Message non lu par **PHILOU77** » 18 sept. 2006, 21:04

hello
when you built the G5 for the first time ? You had this problem or after ?

Frank · Message non lu par **Frank** » 18 sept. 2006, 21:33

McColson a écrit :Maybe your potar is dead, try to remplace it by a simple 1M (R17 on the schematic if you have place the master here). If the sound it's the same like when at 10 on your pot, it's not the pot.
So verify all your solders around the EL34, the wires...
Have you got some photos of the inside ?

Edit : Welcome Frank !!!

Thanks for the tips...
Hello McColson!
I´ve changed the Master Pot but its the same.I thought its a Ground Problem but i´ve checked it and it seems to be okay.
Is it possible that the OT is broken ? At the first Power on i forgot to connect the speaker.

It was only a moment, then i connected the speaker.
The soldering at the EL34 seems to be okay.Maybe i´ll take some Photos the next days.

Regards,
Frank

Frank · Message non lu par **Frank** » 18 sept. 2006, 21:37

PHILOU77 a écrit :hello
when you built the G5 for the first time ? You had this problem or after ?

Hello, its the second build of the Amp.The first time wasn´t very satisfing so i rebuild it.(the problem is that the first build worked fine

)

regards,
Frank

Message non lu par **McColson** » 18 sept. 2006, 21:51

Is it possible that the OT is broken ? At the first Power on i forgot to connect the speaker. Rolling Eyes

Yes It's possible !
Try to change the EL34 and after the OT if it's possible.

Frank · Message non lu par **Frank** » 18 sept. 2006, 21:58

McColson a écrit :
Is it possible that the OT is broken ? At the first Power on i forgot to connect the speaker. Rolling Eyes
Yes It's possible !
Try to change the EL34 and after the OT if it's possible.

Oups...
I´ve changed the Valve but it´s the same...
Do i really have to change the OT??? (it´s about 40 Euros

)
It´was really a short Time without the speaker.

Bye,
Frank

Message non lu par **McColson** » 18 sept. 2006, 22:15

Try to search before another solution but if the OT is dead, you will be dead too before finding the problem.

Have you the same voltage than the manual around the OT and the EL34 ?

Frank · Message non lu par **Frank** » 18 sept. 2006, 22:26

McColson a écrit :Try to search before another solution but if the OT is dead, you will be dead too before finding the problem.
Have you the same voltage than the manual around the OT and the EL34 ?

Hmm... i´m quite okay and not dead... but nearly

Okay , i´ll check the voltage and see if its okay.
I´ll reply tomorrow... I´m tired (maybe a little bit dead

)

Regards,
Frank

Message non lu par **vitriol82** » 18 sept. 2006, 23:10

When you play with your G5 at high level, is the OT really warm or hot?

Before testing the OT, when this one is dead , he's really dead and don't work at any power.

1- Take a look on your speaker jacks
2- Verify your impedance's configuration on the OT
3- Connect the speaker directly on the OT
4- Test with an another speaker

For the moment that's all I see.

Frank · Message non lu par **Frank** » 19 sept. 2006, 18:09

vitriol82 a écrit :When you play with your G5 at high level, is the OT really warm or hot?

Before testing the OT, when this one is dead , he's really dead and don't work at any power.

1- Take a look on your speaker jacks
2- Verify your impedance's configuration on the OT
3- Connect the speaker directly on the OT
4- Test with an another speaker

For the moment that's all I see.

Hello Vitriol82!

I decided to buy a new OT and some other Parts and build it up again

The OT isn´t hot or warm,
the speaker jack seems to be okay,
the impedance is correct,
the speaker is ok because it runs in another Amp perfectly,
It´s like McColson says im dead before i checked if the OT is dead,
if its not dead I can sell it trough Ebay... or I build another one

Thank you nevertheless,
Frank

Message non lu par **charpy** » 19 sept. 2006, 18:25

Hello frank,
your problem looks like a capacitor leakage in the tone stack. that could false the bias of the power tube. and the leakage may occur only when you have a peak of tension on the tone stack capacitors.

eventually try to change the coupling capacitor just before the tone stack. or and one more capacitor in serie with the first one.

Message non lu par **McColson** » 19 sept. 2006, 19:12

charpy a écrit : eventually try to change the coupling capacitor just before the tone stack. or and one more capacitor in serie with the first one.

Hey charpy there is no capa before the tone stack

Try to send your signal after your master to another poweramp (deconnect the junction between your master and the 5.6K grid resistor of the EL34).
If the sound is normal, that the poweramp the pb.

Message non lu par **Mikka** » 19 sept. 2006, 23:29

Maybe it's a broken down capacitor on C6.
That's what I feel.

best regards

Frank · Message non lu par **Frank** » 20 sept. 2006, 16:41

McColson a écrit :
charpy a écrit : eventually try to change the coupling capacitor just before the tone stack. or and one more capacitor in serie with the first one.
Hey charpy there is no capa before the tone stack

Try to send your signal after your master to another poweramp (deconnect the junction between your master and the 5.6K grid resistor of the EL34).
If the sound is normal, that the poweramp the pb.

Thank You All for your thoughts about my Problem, this forum is the greatest that i´ve been for a long while ! Great!

It maybe sound weird but, i´ve ordered some Parts from Tubetown to build the Amp again!

(including a new OT

)
I think they arrive tomorrow so i can build it maybe at the weekend.
As soon as possible i let you all know if its work or not !

And again thank you all for your hints and help!

Regards,
Frank