Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Jul Sun 05, 2020 6:05 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 923 posts ]  Go to page Previous  1 ... 16, 17, 18, 19, 20, 21, 22 ... 47  Next
Author Message
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 8:36 pm 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
Pbpix wrote:
john8750 wrote:
But, the voltage must be ok if the current is ok,



OMG... John... lol
I was not suggesting it was "wrong". or not "ok"

I just asked what it was.

Why did you think that if I simply ask you what voltage it reads on the cathode... why do you think that maybe I suspect it may be wrong or not ok???

I am just asking you to tell me what you measured.... NOT suggesting anything right or wrong.... lol



Sorry Peter. I did not have the measurement yet. I know it is important, but only looked for the B+ and cathode current.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 8:51 pm 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
Here are some voltages, and some problems.
AC supply volts 125.2
After 10 minutes
B+ 294 (surged to 410 at start up)
cathode current left channel V1 38ma V2 38ma
across 1ohm resistor right channel V1 37ma V2 37ma

cathode voltage left channel V1 22.56 V2 23.9
pin8 right channel V1 20.76 V2 14.51

All IC voltage are very close and should be no problem. But, the 470ohm 5watt for the 13volt supply gets very hot. Cant touch it. Would a sand type be better?
Attachment:
20180203_103024.jpg
20180203_103024.jpg [ 218.03 KiB | Viewed 805 times ]

Now, the CCS I had a problem with before, then cleared up, is the one with the 14.51volt reading. Although the current is correct. Don't understand that one.
No signal was applied yet.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 10:31 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22589
Location: Haledon, NJ, usa
You said: "cathode current left channel V1 38ma V2 38ma
across 1ohm resistor right channel V1 37ma V2 37m"
a

Wonder why the current measured is 1 ma more than that sensed across the 1 ohm resistor?

How did you measure the 38ma?
Is the 1 ohm sensing resistor a precision 1% type?

I don't know what you mean about "14v on the CCS but current is correct"?
..... maybe a weak tube?
Since -14v would be turning on the tube much harder than -22v
(-14v is 8 volts more positive than -22v.... Right?)
.... so maybe if you have a poor (low gain) tube so it requires 8v more positive grid voltage to turn it on enough to draw 37ma.

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Last edited by Pbpix on Feb Sat 03, 2018 10:36 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 10:35 pm 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
I just swapped the right channel V1 and V2 cathode CCs regulators. Found The low voltage problem stayed with the tube, not with the CCs. Don't know what could cause the low cathode voltage. Have good plate voltages, and screens, which are much less than the plate voltage. Remember, no signal input yet. Need to do some isolation troubleshooting.
I changed the 470ohm in the 13volt supply to a 20watt sand. Running ok now.
What could cause the low cathode voltage? Tube, OPT, that's all I can think of.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 10:40 pm 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
Pbpix wrote:
You said: "cathode current left channel V1 38ma V2 38ma
across 1ohm resistor right channel V1 37ma V2 37m"
a

Wonder why the current measured is 1 ma more than that sensed across the 1 ohm resistor?

How did you measure the 38ma?
Is the 1 ohm sensing resistor a precision 1% type?

I don't know what you mean about "14v on the CCS but current is correct"?
..... maybe a weak tube?
Since -14v would be turning on the tube much harder than -22v
(-14v is 8 volts more positive than -22v.... Right?)
.... so maybe if you have a poor (low gain) tube so it requires 8v more positive grid voltage to turn it on enough to draw 37ma.



UGH- those 1ohmers were installed a long time ago Peter. Before I understood the difference in carbon and precision resistors. I will measure the actual resistance of each. And get back to you.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 10:40 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22589
Location: Haledon, NJ, usa
Swap tubes

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 10:46 pm 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
Pbpix wrote:
Swap tubes



On my list, first thing Peter. probably the problem.
here is the 1ohm I used. Should I update?
Attachment:
1ohmers.jpg
1ohmers.jpg [ 132.81 KiB | Viewed 802 times ]

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 10:50 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22589
Location: Haledon, NJ, usa
Not for only a 1ma difference. .... But if you have a bunch of nice precision 1 ohmers laying around... it's nice to know in the future that measuring across an accurate resistor will report an accurate value.

I was suggesting you swap the tube on the 14v @38ma vs 22v@38ma situation to see if it goes away or follows the tube.

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 10:53 pm 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
Pbpix wrote:
Not for only a 1ma difference. .... But if you have a bunch of nice precision 1 ohmers laying around... it's nice to know in the future that measuring across an accurate resistor will report an accurate value.

I was suggesting you swap the tube on the 14v @38ma vs 22v@38ma situation to see if it goes away or follows the tube.




I will do that. My wife just got back from the car dealer with a brand new Buick. So, let me act all excited for just a minute.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 10:58 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22589
Location: Haledon, NJ, usa
john8750 wrote:
Pbpix wrote:
Not for only a 1ma difference. .... But if you have a bunch of nice precision 1 ohmers laying around... it's nice to know in the future that measuring across an accurate resistor will report an accurate value.

I was suggesting you swap the tube on the 14v @38ma vs 22v@38ma situation to see if it goes away or follows the tube.




I will do that. My wife just got back from the car dealer with a brand new Buick. So, let me act all excited for just a minute.

Is she Chinese? or does she want to be? ... or does she eat a lot of chop suey and chow mein... fortune cookies etc??
Buick is the best selling American car in China.

REF:
"American automakers are poised to sell more than 2.5 million vehicles in China this year. ... Indeed, through the first half of this year, GM has sold more cars in China (1.2 million vehicles) than in the U.S. (1.08 million)."

Ref
"The Buick brand is big in China, really big. In May Buick sold 100864 vehicles, up a whopping 61% compared with May 2015. Buick is the best-selling General Motors brand in China, followed by Wuling-Baojun, Chevrolet and Cadillac. Buick ..."

REF:
" Buick's popularity on the mainland is linked to China's last emperor and other historical leaders.
Sun Yat Sen, often referred to as the founding father of modern China, had one. And the two owned by Emperor Pu Yi reportedly became the first cars ever to enter the Forbidden City in Beijing. Unlike the emperor, Buick hasn't been branded as a relic of the past. "



REF:
http://www.businessinsider.com/why-chin ... ick-2013-4

REF :
http://money.cnn.com/2017/02/22/news/co ... index.html

Ref:
https://www.usatoday.com/story/money/ca ... /92363996/

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 11:57 pm 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
You guessed it Peter. Looking at the tubes, I found one with a mark on it. I must have marked it long ago and forgot.
I swapped all the tubes with a different brand.
Attachment:
20180203_140208.jpg
20180203_140208.jpg [ 105.8 KiB | Viewed 801 times ]


Now I get B+ 290
cathode volts----------RV1 22.59--------RV2 21.53---------LV1 16.74---------LV2 16.07
cathode current--------RV1 37------------RV2 38------------LV1 38-----------LV2 38
grid---------------------RV1 .4------------RV2 -.9------------LV1 -2.2----------LV2 -2.4

A lot of heat building up from the power resistors under the chassis. All power supply resistors get hot.
The opa604's for the right channel are warmer than the left channel.
No signal input yet.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 12:16 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22589
Location: Haledon, NJ, usa
Something wrong.
Why is left cathode and grid voltages so different from Right to get the same 38ma?

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 12:31 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 9664
Location: Texas. USA
john8750 wrote:
Pbpix wrote:
Swap tubes
On my list, first thing Peter. probably the problem.
here is the 1ohm I used. Should I update?
Attachment:
1ohmers.jpg

Ditch the carbon comp 1 Ohm resistors. They're only 10% and that assumes they're in spec and haven't drifted, which carbon comps are notorious for. Use metal film 1% (or better).


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 12:39 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 9664
Location: Texas. USA
john8750 wrote:
You guessed it Peter. Looking at the tubes, I found one with a mark on it. I must have marked it long ago and forgot.
I swapped all the tubes with a different brand.
Attachment:
20180203_140208.jpg


Now I get B+ 290
cathode volts----------RV1 22.59--------RV2 21.53---------LV1 16.74---------LV2 16.07
cathode current--------RV1 37------------RV2 38------------LV1 38-----------LV2 38
grid---------------------RV1 .4------------RV2 -.9------------LV1 -2.2----------LV2 -2.4

A lot of heat building up from the power resistors under the chassis. All power supply resistors get hot.
The opa604's for the right channel are warmer than the left channel.
No signal input yet.
How do you know "the CCS" is 38 mA when the 1 ohm is measuring differently?

What are you measuring the grid volts with? Something's wrong on the left channel if that reading is right. Grid volts shouldn't vary much from 0. Indeed, it CAN'T if the grid leak is grounded (and everything is working correctly). The makes me suspect the opamps are offset (or defective). Pull the opamps until you get the output tubes settled into correct readings.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 12:56 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22589
Location: Haledon, NJ, usa
" But, the 470ohm 5watt for the 13volt supply gets very hot. Cant touch it. Would a sand type be better?"

You've got a problem there too John.

Measure the voltage of each side of that 470 ohm resistor.
Or the dropp across it.
It should have about 33v of in input and 13 on the output.
That means it needs to drop 20v.
Flip designed it to devliver a max of 45ma even though the board requires only 35ma normally.

If your board is properly drawing only 35ma that leaves 10ma left to go through the Zener.

So if the 470 ohms has to drop 20v @ 45ma = .9 watts
triple = 3 watts....
so 3watts works and 5 watts is more than enough.

So you do NOT need a 20 watt resistor there.

If it's that hot... some-ting-wong

is the dropper cap 3.3uf?

.. so you must have a short drawing a lot more than 45ma.

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 1:54 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
Men. You taught me about using carbon resistors. I built that amp before then. Wont happen again.
Got to agree about the 13volt overload. Because, tell you later.
So, I connected the MP3 to the CD inputs. Connected the shop test speakers, powered up.
Warmed up about 20 seconds, and had an un-Goddy screech from both speakers. Sounds like a mic-speaker feedback.
Opened the connection to the NFB circuits. That stopped the screech, and no sound now at all.
Turned the tone control pots up-down. Heard some squeeks here and there.
So I isolated the tone amp, cut the connections to the opa604's. Connected directly from MP3 to opa604 inputs.
Beautiful sound now from both speakers.
I will go back out and get the voltages shortly. Sure sounds good though.
The tone section must have a problem. I will check it for current drew. Voltage is right.
What about the NFB circuit? It causes an undesirable feedback. Can we be sure of that circuit being correct.
Thank you guys.......

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 2:00 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
Flipperhome wrote:
john8750 wrote:
You guessed it Peter. Looking at the tubes, I found one with a mark on it. I must have marked it long ago and forgot.
I swapped all the tubes with a different brand.
Attachment:
20180203_140208.jpg


Now I get B+ 290
cathode volts----------RV1 22.59--------RV2 21.53---------LV1 16.74---------LV2 16.07
cathode current--------RV1 37------------RV2 38------------LV1 38-----------LV2 38
grid---------------------RV1 .4------------RV2 -.9------------LV1 -2.2----------LV2 -2.4

A lot of heat building up from the power resistors under the chassis. All power supply resistors get hot.
The opa604's for the right channel are warmer than the left channel.
No signal input yet.
How do you know "the CCS" is 38 mA when the 1 ohm is measuring differently?

What are you measuring the grid volts with? Something's wrong on the left channel if that reading is right. Grid volts shouldn't vary much from 0. Indeed, it CAN'T if the grid leak is grounded (and everything is working correctly). The makes me suspect the opamps are offset (or defective). Pull the opamps until you get the output tubes settled into correct readings.



Good idea Flip. I will pull opamps and check further. I double checked the wiring very close, seems ok. Also, the NFB circuits are correct to the schematic, but have a problem. I will check on the gridleak to ground circuits. Wired yes, solder joint problem, knowin myself, I don't know.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 2:03 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 5327
Location: Los Angeles
Pbpix wrote:
" But, the 470ohm 5watt for the 13volt supply gets very hot. Cant touch it. Would a sand type be better?"

You've got a problem there too John.

Measure the voltage of each side of that 470 ohm resistor.
Or the dropp across it.
It should have about 33v of in input and 13 on the output.
That means it needs to drop 20v.
Flip designed it to devliver a max of 45ma even though the board requires only 35ma normally.

If your board is properly drawing only 35ma that leaves 10ma left to go through the Zener.

So if the 470 ohms has to drop 20v @ 45ma = .9 watts
triple = 3 watts....
so 3watts works and 5 watts is more than enough.

So you do NOT need a 20 watt resistor there.

If it's that hot... some-ting-wong

is the dropper cap 3.3uf?

.. so you must have a short drawing a lot more than 45ma.




That's a very good point Peter. Must be drawing mucho power to get that resistor that hot. I could use it to heat my entire shop. I will check it out.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 2:35 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22589
Location: Haledon, NJ, usa
If NFB causes loud screech... then you must have the NFB connected to the wrong speaker lead.
Reverse it and the speaker ground.

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 04, 2018 2:39 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 9664
Location: Texas. USA
john8750 wrote:
Good idea Flip. I will pull opamps and check further. I double checked the wiring very close, seems ok. Also, the NFB circuits are correct to the schematic, but have a problem. I will check on the gridleak to ground circuits. Wired yes, solder joint problem, knowin myself, I don't know.
The 'squeal' sounds like NFB is off the wrong side of the OPT secondary. Of course, it could also be a myriad of things if the opamps aren't wired/working right and you apparently have a problem there too. That's why I suggested wiring the amp up in stages, starting with the output tubes. That reduces the odds of problems compounding on you. For example, once the output tubes are settled then if they over current, or something else, when the opamp drivers are installed you know it's them and not the output tubes. But by, hail Mary, throwing all together it's a lot more difficult to know where the problem(s) is(are).

The 'hot' resistor on the tone amp supply might also be caused by the 3.3 uF cap being +50% on the tolerance side. Check the cap's actual value. Of course, it also might be a wiring problem with the tone chip causing it to pull excessive current but if that were the case I wouldn't expect to see the correct voltage on it because the supply simple can't provide more current than about 60 mA, even with a dead short across it, **IF** the cap is the right value. If the cap is on the high tolerance side of 3.3 uF, that being almost 5 uF, the dissipation of the 470 Ohm resistor shoots up to almost 4 Watt, which would get a 5 Watt resistor pretty warm, especially in a tight space.


Top
 Profile  
 
Post New Topic Post Reply  [ 923 posts ]  Go to page Previous  1 ... 16, 17, 18, 19, 20, 21, 22 ... 47  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: mcdmgb, Salguod and 13 guests



Search for:
Jump to:  


































-->


Privacy Policy :: Powered by phpBB