Newly Built 5F2a, Low and Bad Sound...

[Mandopicker]

I have found that doing a few basic things will help a great deal with the issues you are experiencing.

The idea is that choosing which components to ground together is perhaps more important than being tied to any particular "ground technique."

Try this...
Seperate the CT from all other grounds and and put it on its own transformer bolt...away from everything else. (Maybe with the Power Cord Ground if other options are limited.)

Also, I would connect the grounds of the first and second filter cap together and find another seperate place to ground them (maybe an OT transformer bolt near to that location.) Again, it is better to seperate these grounds from the filter caps that supplies the preamp tubes; which can be grounded at the input jack - with preamp tube cathode ground and tone volume controls.

And lastly, and you probably already know about this...that you make an Artificial CT for your Heater Supply by tying 2 x 100 ohm resistors to ground if your transformer does not already have a CT. * Doing this depends on how your Heater Supply is wired. If this is unclear you should look into this concept.

[tubeswell]

there is one more thing I think the other resistors are 1/4w they look really small though. I bought them from a local shop and told the guy they should be 1/2w. For them being 1/4w would affect the sound?

They could be 0.6W metal film resistors (which look really small) which have a breakdown voltage of something like 360V. If they are then should be okay as long as they are not having to drop exorbitant voltages. On the other hand if they are 1/4W, they will be okay in some places (like cathode resistors), but not as supply resistors.

Did you try swapping tubes?

[PFCnR]

"Is there any specific place for me to take a picture?"

The wiring of the power transformer, shwing how all leads are terminated.

The wiring of the tube sockets from above.

The wiring of the tone & vol pots & input jacks.

And a shot of the circuit board.

In the mean time, pull out the preamp tube, power up, how does this affect hum. If you still have hum with the power tube only installed, power down, pull it out and see what noise you get with just a rectifier.

As soon as my sister gets home i will take those pictures. She has a professional cam so i do not know to take a proper picture

I pulled out the preamp tube and run the amp there is no disturbing sound at all only a very low sound like which is similar to PT's sound but even lower than that. Also volume and tone has no affect on it. Same thing when i run it with only 5Y3 tube. Does that all mean there is something wrong with the 5751 tube? I think pictures will help us all better

[PFCnR]

They could be 0.6W metal film resistors (which look really small) which have a breakdown voltage of something like 360V. If they are then should be okay as long as they are not having to drop exorbitant voltages. On the other hand if they are 1/4W, they will be okay in some places (like cathode resistors), but not as supply resistors.

Did you try swapping tubes?

Unfortunately i do not have enough tube to try, i got only two 6v6, one 5751 and 5Y3. I am living in Turkey so finding them is really big problem i have order everything from the USA (except some resistors and circuit board and switches). If there is something wrong with the tubes that will cost me a lot

[PFCnR]

I have found that doing a few basic things will help a great deal with the issues you are experiencing.

The idea is that choosing which components to ground together is perhaps more important than being tied to any particular "ground technique."

Try this...
Seperate the CT from all other grounds and and put it on its own transformer bolt...away from everything else. (Maybe with the Power Cord Ground if other options are limited.)

Also, I would connect the grounds of the first and second filter cap together and find another seperate place to ground them (maybe an OT transformer bolt near to that location.) Again, it is better to seperate these grounds from the filter caps that supplies the preamp tubes; which can be grounded at the input jack - with preamp tube cathode ground and tone volume controls.

And lastly, and you probably already know about this...that you make an Artificial CT for your Heater Supply by tying 2 x 100 ohm resistors to ground if your transformer does not already have a CT. * Doing this depends on how your Heater Supply is wired. If this is unclear you should look into this concept.

Hello there,
I already have Artificial CT on my power tube ( pin 7 to pin 8 and pin 8 to pin 2) (100k 1W each).

By CT i assume you meant the HV CT and i have never tried that, and i can try everything at the moment to make it work better

[Bruce / Mission Amps]

Hello there,
I already have Artificial CT on my power tube ( pin 7 to pin 8 and pin 8 to pin 2) (100k 1W each).

By CT i assume you meant the HV CT and i have never tried that, and i can try everything at the moment to make it work better

Those two resistors should be 100 ohms not 100,000 (100K) ohms.
This is hard with out seeing it.... get some pictures and somebody will spot what is the matter very quickly I bet.

[PFCnR]

"Is there any specific place for me to take a picture?"

The wiring of the power transformer, shwing how all leads are terminated.

The wiring of the tube sockets from above.

The wiring of the tone & vol pots & input jacks.

And a shot of the circuit board.

In the mean time, pull out the preamp tube, power up, how does this affect hum. If you still have hum with the power tube only installed, power down, pull it out and see what noise you get with just a rectifier.

Here the pictures that you wanted to see. Hope you can see everything you wanted.

Pictures by canersahin - Photobucket

[Mandopicker]

I would also elevate that board so that it is sufficiently high enough that the wires on the bottom of the board do not touch the chassis.

A little bit of extra solder from one of those wires, particularly those that carry a lot of current, touching or even marginally close to touching, could induce noise.

Leave no stone unturned...good luck.

[PFCnR]

I would also elevate that board so that it is sufficiently high enough that the wires on the bottom of the board do not touch the chassis.

A little bit of extra solder from one of those wires, particularly those that carry a lot of current, touching or even marginally close to touching, could induce noise.

Leave no stone unturned...good luck.

What other options do i have for board? I will change the board for sure i am also not happy with it... Do you guys have any board layout for 5F2a?

[MWJB]

You have a deep chassis compared to a real 5F2A, shield the wires from input jack & vol tone pots to 5751 pins 2 & 7, ground shielding at one end only.

You don't want the heater wires routed back accross the PT, rewire them flat against the chassis wall, sweeping out & around the rectifier.

Wiring is generally rather messy, plate wires (5751 pins 1 & 6) can be long & sweep around the tube socket. Grid wires (5751 pins 2 & 7, 6V6 pin 5) should be as short as possible...try and line up components with the tube socket pin that they connect to.

Wouldn't it be just as easy to use a pair of terminal strips to mount the parts, lose that circuit board.

[PFCnR]

You have a deep chassis compared to a real 5F2A, shield the wires from input jack & vol tone pots to 5751 pins 2 & 7, ground shielding at one end only.

You don't want the heater wires routed back accross the PT, rewire them flat against the chassis wall, sweeping out & around the rectifier.

Wiring is generally rather messy, plate wires (5751 pins 1 & 6) can be long & sweep around the tube socket. Grid wires (5751 pins 2 & 7, 6V6 pin 5) should be as short as possible...try and line up components with the tube socket pin that they connect to.

Wouldn't it be just as easy to use a pair of terminal strips to mount the parts, lose that circuit board.

Hello again,
After i read everything, i decided to rewire the amp to make it better, but this time i won't use circuit board because in here local shops only sell something similar circuit boards that i used. I just wanted to know would something like this work good? http://img233.imageshack.us/img233/4893/sk3003yo0.jpg

[tubeswell]

Hi Caner

Can you get mains-grade switch-panel from an electrical wholesaler near where you are? (Sort of like a formica for high voltages)

You would then be able to make your own boards using 4mm brass eyelets (from a building supply wholesaler) - like I do. (I use 3mm thick switchpanel and mount it off the inside of the chassis with spacer nuts).

These boards are very robust and cheap to make, and easily withstand high temperatures and high voltages. The only tools you need are a drill and bit and countersinker (for the eyelets), a fret saw and a file, and something like a nail punch to wriggle around in the back of the eyelets to flay the edges out once they are mounted on the board. The material cost of each board is about $15-$20

See the before and after pics of my most recent example

[PFCnR]

Hi Caner

Can you get mains-grade switch-panel from an electrical wholesaler near where you are? (Sort of like a formica for high voltages)

You would then be able to make your own boards using 4mm brass eyelets (from a building supply wholesaler) - like I do. (I use 3mm thick switchpanel and mount it off the inside of the chassis with spacer nuts).

These boards are very robust and cheap to make, and easily withstand high temperatures and high voltages. The only tools you need are a drill and bit and countersinker (for the eyelets), a fret saw and a file, and something like a nail punch to wriggle around in the back of the eyelets to flay the edges out once they are mounted on the board. The material cost of each board is about $15-$20

See the before and after pics of my most recent example

Hello guys,

Tubeswell your work very decent, however today i went to local shops i could not find any turret or eyelets for the circuit. So i bought a board which is similar to G10 (Garolite) but one side is completely copper faced. You can draw a path line on that copper field and after some chemical reactions you have the board. So i think i will give a try with the board that i bought today. It will look like a PCB but not a professional one and i will not draw all circuit on it. Will just paint the soldering points. I think it will be better than the circuit that i already had.

One more question: Can i use 5w 470R resistor instead of 1w one? The 5w that i have looks white and bigger. But that can affect the sound? If it does in a good or bad way?

If you want to see the board i can take some pictures.

Thanks.

[MWJB]

What about simple terminal strips (see Bluebell Audio, Hoffmanamps for examples)?

The circuit is so simple that you ony need a board/terminals for a few parts.

Main filter cap can go from rectifier pin 8 to PT bolt ground.

Screen supply cap can go from 6V6 pin 4 to PT bolt ground. 10K resistor sits between the "+" of these 2 caps.

6V6 cathode resistor & cap can go from 6V6 pin 8 to PT bolt ground.

12AX7 cathode resistors & bypass cap (pins 3 & 8) can go to solder tags under the tube socket bolts (not best practice, but I have seen $2K amps that do this, have done it myself on prototype builds with no problems).

Then you just need a few tags to mount 22k power supply resistor, 100K plate resistors, preamp filter cap "+" ("-" can go straight to input jack ground) & coupling caps (coupling cap from pin 6 12AX7 might even reach accross to 6V6 pin 5)?

If the parts are lined up with the tube socket pins that they connect to, then this can work even better than a typical eyelet board.

Yes, use 5W 470ohm resistor. It won't affect the sound - the 1W might only affect the sound by stopping the amp from working when it burns up.

[PFCnR]

What about simple terminal strips (see Bluebell Audio, Hoffmanamps for examples)?

The circuit is so simple that you ony need a board/terminals for a few parts.

Main filter cap can go from rectifier pin 8 to PT bolt ground.

Screen supply cap can go from 6V6 pin 4 to PT bolt ground. 10K resistor sits between the "+" of these 2 caps.

6V6 cathode resistor & cap can go from 6V6 pin 8 to PT bolt ground.

12AX7 cathode resistors & bypass cap (pins 3 & 8) can go to solder tags under the tube socket bolts (not best practice, but I have seen $2K amps that do this, have done it myself on prototype builds with no problems).

Then you just need a few tags to mount 22k power supply resistor, 100K plate resistors, preamp filter cap "+" ("-" can go straight to input jack ground) & coupling caps (coupling cap from pin 6 12AX7 might even reach accross to 6V6 pin 5)?

If the parts are lined up with the tube socket pins that they connect to, then this can work even better than a typical eyelet board.

Yes, use 5W 470ohm resistor. It won't affect the sound - the 1W might only affect the sound by stopping the amp from working when it burns up.

Well i was looking for terminal strips too from local shop today but i could not find any only thing i have found similar this:

http://www.volkanonline.com/images/p...5941_buyuk.jpg

Well soldering most of things to socket's pins wouldn't be too complex for debugging and finding errors?