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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 1:46 am 
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So John:
After you get the B+ down to 295 or 300v

Go back and measure the DC volts on each cathode. From the cathode to gnd.
It should be close to about 19v or 20v .... but ...NOT 25v.
as far as the +/- 20v supply goes.... we've got a 1uf dropper cap there.
So since we are feeding in 145v instead of 120v ... how much AC v do you measure feeding the rectifiers?
And then what is the DCv on the 1st 470uf filter cap before the 1k dropping resistor?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 4:34 am 
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I figured a resistance of 625.9ohms. That's for 300volt B+ at 100ma. The voltage feeding the 220ohm resistor is 365.
I am concerned that the B+ climbs very quickly to 412volts for about 10 seconds, then back down. The filters are rated for 400. Is that a problem?
I will get a new record of all voltages once the B+ is settled. I think a 620ohm is as close as I can get. But even at 20watt, the resistor gets hot enough to cook a hot dog. Would increasing that 5ohm help here?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 4:42 am 
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Pbpix wrote:
So John:
After you get the B+ down to 295 or 300v

Go back and measure the DC volts on each cathode. From the cathode to gnd.
It should be close to about 19v or 20v .... but ...NOT 25v.
as far as the +/- 20v supply goes.... we've got a 1uf dropper cap there.
So since we are feeding in 145v instead of 120v ... how much AC v do you measure feeding the rectifiers?
And then what is the DCv on the 1st 470uf filter cap before the 1k dropping resistor?




Of course the cathode voltages will drop with a 300v B+. I had 343v. Lets get the B+ in order first.
I will check all voltages. The 20v supplies are spot on.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 4:57 am 
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john8750 wrote:
I figured a resistance of 625.9ohms. That's for 300volt B+ at 100ma. The voltage feeding the 220ohm resistor is 365.
I am concerned that the B+ climbs very quickly to 412volts for about 10 seconds, then back down. The filters are rated for 400. Is that a problem?
I will get a new record of all voltages once the B+ is settled. I think a 620ohm is as close as I can get. But even at 20watt, the resistor gets hot enough to cook a hot dog. Would increasing that 5ohm help here?
"20 Watt" what? If that's a metal cased resistor that 20 Watt rating is HEATSINKED and at 25 C.

You're dissipating 6.2 Watt in it. That's why I suggested spitting between the two.

15 Sec shouldn't be a problem. At this voltage caps are usually rated for 50 V over max for 30 seconds.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 5:26 am 
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Flipperhome wrote:
john8750 wrote:
I figured a resistance of 625.9ohms. That's for 300volt B+ at 100ma. The voltage feeding the 220ohm resistor is 365.
I am concerned that the B+ climbs very quickly to 412volts for about 10 seconds, then back down. The filters are rated for 400. Is that a problem?
I will get a new record of all voltages once the B+ is settled. I think a 620ohm is as close as I can get. But even at 20watt, the resistor gets hot enough to cook a hot dog. Would increasing that 5ohm help here?
"20 Watt" what? If that's a metal cased resistor that 20 Watt rating is HEATSINKED and at 25 C.

You're dissipating 6.2 Watt in it. That's why I suggested spitting between the two.

15 Sec shouldn't be a problem. At this voltage caps are usually rated for 50 V over max for 30 seconds.




Its a sand resistor. What should I change the 5ohm to? When I had it at 50 ohms, neither the 220 or the 50 got so hot.
I am going for 300vB+. Is that good? Or 295?
Good news about the caps, had me worried.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 6:22 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
I figured a resistance of 625.9ohms. That's for 300volt B+ at 100ma. The voltage feeding the 220ohm resistor is 365.
I am concerned that the B+ climbs very quickly to 412volts for about 10 seconds, then back down. The filters are rated for 400. Is that a problem?
I will get a new record of all voltages once the B+ is settled. I think a 620ohm is as close as I can get. But even at 20watt, the resistor gets hot enough to cook a hot dog. Would increasing that 5ohm help here?
"20 Watt" what? If that's a metal cased resistor that 20 Watt rating is HEATSINKED and at 25 C.

You're dissipating 6.2 Watt in it. That's why I suggested spitting between the two.

15 Sec shouldn't be a problem. At this voltage caps are usually rated for 50 V over max for 30 seconds.

Its a sand resistor. What should I change the 5ohm to? When I had it at 50 ohms, neither the 220 or the 50 got so hot.
I am going for 300vB+. Is that good? Or 295?
Good news about the caps, had me worried.
The 5 ohm isn't doing much of anything because the transformer winding resistance is larger and taking the load. You might as well chuck it.

304 V (285 V plate + 19 V cathode) is the target voltage.

If the 50 Ohm gets the right B+ and, in your opinion, is cooler then go for it.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 6:54 pm 
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I think I got it about the best I can.
First, I swapped the primary and secondary of the PT. Output was 107vac. Not good.
Tried a third capacitor for the filter, B+ went up to 344volts. That's with a 220ohm resistor in addition to the 470. Removed the capacitor and changed the 5ohm to 10ohms. Close, but too much heat. So, I tried 3-220ohm 20watt resistors where the single 220ohm was. Heat is much less and B+ is 294.
All cathodes are 19-20volt, 25ma.
I noticed an unusual slight bit of static in the sound, only with the music. The only difference I could think of was the 22volts for the filament circuit. I got it up to 27volts and, static disappeared. I had to increase the dropper cap to exactly 9uf. You win that one Peter, dead on. So don't run the heaters on a lower voltage.
I got the exact B+ using Flips suggestion of a balance of the two PS resistors.
So, I will get the PS wired, need to wait for the 8uf cap.
The 20volt supplies are perfect. Input volts is 37.38. Drops 17volts across a 1K resistor to get 20volts, at 17ma.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 11:07 pm 
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john8750 wrote:
I think I got it about the best I can.
First, I swapped the primary and secondary of the PT. Output was 107vac. Not good.
Tried a third capacitor for the filter, B+ went up to 344volts. That's with a 220ohm resistor in addition to the 470. Removed the capacitor and changed the 5ohm to 10ohms. Close, but too much heat. So, I tried 3-220ohm 20watt resistors where the single 220ohm was. Heat is much less and B+ is 294.
All cathodes are 19-20volt, 25ma.
I noticed an unusual slight bit of static in the sound, only with the music. The only difference I could think of was the 22volts for the filament circuit. I got it up to 27volts and, static disappeared. I had to increase the dropper cap to exactly 9uf. You win that one Peter, dead on. So don't run the heaters on a lower voltage.
I got the exact B+ using Flips suggestion of a balance of the two PS resistors.
So, I will get the PS wired, need to wait for the 8uf cap.
The 20volt supplies are perfect. Input volts is 37.38. Drops 17volts across a 1K resistor to get 20volts, at 17ma.

The three 220 ohm resistors (660) we calculated last night. Right?
You said you needed to drop 65 volts... @100ma right? ...so we agreed that's 650 ohms... Right?
Then a few moments later you thought maybe you'd need to drop 70volts... right?
So 70v @100ma = 700 ohms.

Something doesn't sound right about why you got 344v with 3 caps and both the 220 + the 470 ohm resistor. Because 470+ 220 adds up to the SAME 690 ohms or similar to the 660ohms you have now with two caps.
Are you certain that you had 470 ohms and not 47 ohms?

To experiment a bit:
leave the 220 between the first two caps... then add a 3rd cap again but take the other two 220 resistors (440 ohms) and put it between the 2nd cap and add a third cap.
The resistance is EXACTLY the same... so remember... there's no magic here.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 11:42 pm 
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Pbpix wrote:
john8750 wrote:
I think I got it about the best I can.
First, I swapped the primary and secondary of the PT. Output was 107vac. Not good.
Tried a third capacitor for the filter, B+ went up to 344volts. That's with a 220ohm resistor in addition to the 470. Removed the capacitor and changed the 5ohm to 10ohms. Close, but too much heat. So, I tried 3-220ohm 20watt resistors where the single 220ohm was. Heat is much less and B+ is 294.
All cathodes are 19-20volt, 25ma.
I noticed an unusual slight bit of static in the sound, only with the music. The only difference I could think of was the 22volts for the filament circuit. I got it up to 27volts and, static disappeared. I had to increase the dropper cap to exactly 9uf. You win that one Peter, dead on. So don't run the heaters on a lower voltage.
I got the exact B+ using Flips suggestion of a balance of the two PS resistors.
So, I will get the PS wired, need to wait for the 8uf cap.
The 20volt supplies are perfect. Input volts is 37.38. Drops 17volts across a 1K resistor to get 20volts, at 17ma.

The three 220 ohm resistors (660) we calculated last night. Right?
You said you needed to drop 65 volts... @100ma right? ...so we agreed that's 650 ohms... Right?
Then a few moments later you thought maybe you'd need to drop 70volts... right?
So 70v @100ma = 700 ohms.

Something doesn't sound right about why you got 344v with 3 caps and both the 220 + the 470 ohm resistor. Because 470+ 220 adds up to the SAME 690 ohms or similar to the 660ohms you have now with two caps.
Are you certain that you had 470 ohms and not 47 ohms?

To experiment a bit:
leave the 220 between the first two caps... then add a 3rd cap again but take the other two 220 resistors (440 ohms) and put it between the 2nd cap and add a third cap.
The resistance is EXACTLY the same... so remember... there's no magic here.



That's a good experiment Peter. I will add the other cap for a test. I get scared watching the voltage climb above 400.
I will do that tomorrow. Shop is closed for the night.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Mon 12, 2018 11:51 pm 
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Wait a minute. Yes, the three 220ohm 20watt resistors made less heat separately. But still added up to about the same amount of heat as one single resistor did. So I replaced them with a 750ohm, 20watt. Ditched the 5ohm, wired straight to the first cap. B+ is around 290 and amp sounds good. Will need some venting. Just waiting for that 8uf cap. Will add a 1uf and a 100K resistor, drop it in, should be ready for the tone amp retrofit. Hotdang- Im making an amplifier :!:

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 12:04 am 
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john8750 wrote:
I think I got it about the best I can.
First, I swapped the primary and secondary of the PT. Output was 107vac. Not good.
Tried a third capacitor for the filter, B+ went up to 344volts. That's with a 220ohm resistor in addition to the 470. Removed the capacitor and changed the 5ohm to 10ohms. Close, but too much heat. So, I tried 3-220ohm 20watt resistors where the single 220ohm was. Heat is much less and B+ is 294.
All cathodes are 19-20volt, 25ma.
I noticed an unusual slight bit of static in the sound, only with the music. The only difference I could think of was the 22volts for the filament circuit. I got it up to 27volts and, static disappeared. I had to increase the dropper cap to exactly 9uf. You win that one Peter, dead on. So don't run the heaters on a lower voltage.
I got the exact B+ using Flips suggestion of a balance of the two PS resistors.
So, I will get the PS wired, need to wait for the 8uf cap.
The 20volt supplies are perfect. Input volts is 37.38. Drops 17volts across a 1K resistor to get 20volts, at 17ma.
What PS schematic for B+ are you using, because I can't make any sense what you're saying you've done.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 1:04 am 
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Hey John:
Remember last year I bought a passive tone cntrl board?
https://www.ebay.com/itm/Amplifier-Pass ... Swo0JWPArX

Here's the thred about it:
viewtopic.php?f=12&t=273358&start=1520

I think you bought it too.
I found a defect in that board and added the missing jumper.
Well it seemed to work nicely as a tone control ... but as a Baxandall ckt it loads down the signal somewhat so I had to boost the signal out of my mp3 player with the passive Radio-shack transformer amplifier.... then into the Baxandall then to the 6V6 amp.

But TODAY ... I was experimenting... and I switched out the NFB line on the 6V6 like we were talking about last night.
And it does seem to sound very nice even w/o the NFB.

And so... Yes of course it has more volume.... but with all that extra volume, I decided to see if I add the Baxandall tone amp after the Mp3 ... would I STILL need to boost the signal.... and the answer is ... no.... the Mp3 has enough to drive the Baxandall and the 6V6 w/o any additional boost.

Try it.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 2:18 am 
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Flipperhome wrote:
john8750 wrote:
I think I got it about the best I can.
First, I swapped the primary and secondary of the PT. Output was 107vac. Not good.
Tried a third capacitor for the filter, B+ went up to 344volts. That's with a 220ohm resistor in addition to the 470. Removed the capacitor and changed the 5ohm to 10ohms. Close, but too much heat. So, I tried 3-220ohm 20watt resistors where the single 220ohm was. Heat is much less and B+ is 294.
All cathodes are 19-20volt, 25ma.
I noticed an unusual slight bit of static in the sound, only with the music. The only difference I could think of was the 22volts for the filament circuit. I got it up to 27volts and, static disappeared. I had to increase the dropper cap to exactly 9uf. You win that one Peter, dead on. So don't run the heaters on a lower voltage.
I got the exact B+ using Flips suggestion of a balance of the two PS resistors.
So, I will get the PS wired, need to wait for the 8uf cap.
The 20volt supplies are perfect. Input volts is 37.38. Drops 17volts across a 1K resistor to get 20volts, at 17ma.
What PS schematic for B+ are you using, because I can't make any sense what you're saying you've done.



This one. But, my ac on the secondary is 145volts. You guys planed on 120volts. So it needed some changes.
What doesn't make any sense?
Attachment:
build.png
build.png [ 247.03 KiB | Viewed 426 times ]

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 2:23 am 
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Pbpix wrote:
Hey John:
Remember last year I bought a passive tone cntrl board?
https://www.ebay.com/itm/Amplifier-Pass ... Swo0JWPArX

Here's the thred about it:
viewtopic.php?f=12&t=273358&start=1520

I think you bought it too.
I found a defect in that board and added the missing jumper.
Well it seemed to work nicely as a tone control ... but as a Baxandall ckt it loads down the signal somewhat so I had to boost the signal out of my mp3 player with the passive Radio-shack transformer amplifier.... then into the Baxandall then to the 6V6 amp.

But TODAY ... I was experimenting... and I switched out the NFB line on the 6V6 like we were talking about last night.
And it does seem to sound very nice even w/o the NFB.

And so... Yes of course it has more volume.... but with all that extra volume, I decided to see if I add the Baxandall tone amp after the Mp3 ... would I STILL need to boost the signal.... and the answer is ... no.... the Mp3 has enough to drive the Baxandall and the 6V6 w/o any additional boost.

Try it.



Connect your amp to a CD deck and you will see the difference in input level.
The tone amp I use does have a little boost in it also.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 2:28 am 
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Here's a little thought for you Men. Is it possible to run the filaments through the same circuit as the B+? Has it been done using the power tube filaments?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 2:59 am 
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john8750 wrote:
Flipperhome wrote:
What PS schematic for B+ are you using, because I can't make any sense what you're saying you've done.
This one. But, my ac on the secondary is 145volts. You guys planed on 120volts. So it needed some changes.
What doesn't make any sense?
Attachment:
build.png
What didn't make any sense is I thought you were using my PS schematic. That explains it.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 3:39 am 
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Flipperhome wrote:
john8750 wrote:
Flipperhome wrote:
What PS schematic for B+ are you using, because I can't make any sense what you're saying you've done.
This one. But, my ac on the secondary is 145volts. You guys planed on 120volts. So it needed some changes.
What doesn't make any sense?
Attachment:
build.png
What didn't make any sense is I thought you were using my PS schematic. That explains it.




IC,IC. Sorry about the confusion. Just wanted to get the amp done and out of here. I have decided to go ahead, since the amp works perfectly, to add the tone control. Should have plenty of power to run the 13volt supply. Should be easy because you added it separately. But need to recondition it for 145v.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 3:45 am 
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Peter, I made up one of the CCS modules you use. Man, that's cool. Wish I would have done that. I may change them out, if I run out of things to do....

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 5:48 am 
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john8750 wrote:
Peter, I made up one of the CCS modules you use. Man, that's cool. Wish I would have done that. I may change them out, if I run out of things to do....

Good. Glad you like it.
It's certainly nice and compact that way. Isn't it? :-)

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Tue 13, 2018 6:17 am 
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Pbpix wrote:
john8750 wrote:
Peter, I made up one of the CCS modules you use. Man, that's cool. Wish I would have done that. I may change them out, if I run out of things to do....

Good. Glad you like it.
It's certainly nice and compact that way. Isn't it? :-)




Heck yes. What voltage caps did you use? I have 25-35-and 50. Used 35's just because of the size. Would use 50's otherwise.
I should have used 450's in the power supply. They are just a little taller than the 400's.

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