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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Wed 31, 2018 8:31 pm 
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Here it is at break time. If I have a problem with anything on the circuit board it could be a troubleshooting mess.
All commons are installed. Speaker circuits are in (up to the headphones)
All IC power circuits are in.
I guess the plate and screen tube connections will be next. Then Grid and cathode, CCS, then the tone circuit
Attachment:
20180131_110510.jpg
20180131_110510.jpg [ 202.96 KiB | Viewed 1245 times ]
pot wiring.
The transformer B+ connections, and CD inputs.
Its getting done.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Wed 31, 2018 10:26 pm 
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Seems like a odd reverse order John.
As I said yesterday.. I would think it best to first complete the 6v6 output transformer wiring completely and power supply along with CCS and opamps. Then you have a working amp.. right?
Then try the tone ckt & riaa etc.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Thu 01, 2018 2:39 am 
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Pbpix wrote:
Seems like a odd reverse order John.
As I said yesterday.. I would think it best to first complete the 6v6 output transformer wiring completely and power supply along with CCS and opamps. Then you have a working amp.. right?
Then try the tone ckt & riaa etc.



I will need the working tone circuit to test the amp. It is on the same circuit board with the CCS and preamp circuits. And interconnected already on the board.
No problem though. I have high hopes. Will test the CD player first.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Thu 01, 2018 7:12 am 
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A little confused about the output transformer wiring. Here is the transformer I have.
http://www.edcorusa.com/cxpp10-8k
Does this look correct? I seem to always wire Edcors backwards.
Attachment:
6v6%20pp%20amp%20change%20hw[1].png
6v6%20pp%20amp%20change%20hw[1].png [ 182.63 KiB | Viewed 1218 times ]

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Thu 01, 2018 7:31 am 
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john8750 wrote:
A little confused about the output transformer wiring. Here is the transformer I have.
http://www.edcorusa.com/cxpp10-8k
Does this look correct? I seem to always wire Edcors backwards.
Attachment:
6v6%20pp%20amp%20change%20hw[1].png

Yes the Edcor graphic matches the 6v6 print.
It isn't important which color sets you use for which tube exactly ... only be sure that you get the negative feedback correct. If not the amp will be louder when the FB wire is conneced instead of less loud as is correct.
If it's loud.. switch the FB to the other lead on the speaker side.

Note the little black phasing dots on the print. The dots show which ends are in phase.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 02, 2018 3:15 am 
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Now, look at the original schematic. I think I can see what confused me. Remember this, I am easily confused.
Attachment:
orig.png
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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 02, 2018 8:07 pm 
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Her she is. Ready for the smoke test, almost.....
The red circle indicates a possible problem. Doing a resistance check I found this CCS network about 600ohms at the output. The other three were much higher. Do I smell a damaged LM317 :?: probably.
Attachment:
20180202_103523.jpg
20180202_103523.jpg [ 197.88 KiB | Viewed 1189 times ]

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 02, 2018 10:11 pm 
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Check your wiring there.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 02, 2018 10:34 pm 
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Pbpix wrote:
Check your wiring there.



I will Peter. The only other component in the circuit is a 1000uf capacitor. The tubes are removed. There are two back to back caps there also, but the 3 other circuits read the same high Ks. I will find it. Points to a bad regulator.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 02, 2018 11:00 pm 
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I have a question. For the turntable there is a ground connection on the amp. Where does that post connect in the amp.
I am thinking, to the earth ground at the ac plug, and the metal cover over the RIAA amp. The chassis is wood. I have a ground at the power transformer, but not at the output transformers. Any ideas?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 1:09 am 
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john8750 wrote:
I have a question. For the turntable there is a ground connection on the amp. Where does that post connect in the amp.
I am thinking, to the earth ground at the ac plug, and the metal cover over the RIAA amp. The chassis is wood. I have a ground at the power transformer, but not at the output transformers. Any ideas?
What do you mean you don't have a ground at the OPTs? You better or the feedback won't work.

The turntable earth ground should be at the same place the amp ground is connected to earth, at the input jacks.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 1:51 am 
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Flipperhome wrote:
john8750 wrote:
I have a question. For the turntable there is a ground connection on the amp. Where does that post connect in the amp.
I am thinking, to the earth ground at the ac plug, and the metal cover over the RIAA amp. The chassis is wood. I have a ground at the power transformer, but not at the output transformers. Any ideas?
What do you mean you don't have a ground at the OPTs? You better or the feedback won't work.

The turntable earth ground should be at the same place the amp ground is connected to earth, at the input jacks.




Wow. That's me, confusion is my middle name and I do it well. I meant to say do I need to connect the transformer cans to ground. I do get the common and ground mixed up. Remember that the chassis is wood.
I will make an earth ground connection at the input jacks which is connected to amp common, and the phono ground lug.
The OPT's do connect to common. The amp is correct to the schematic.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 3:27 am 
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I just went back to working on the amp. All the CCS circuits read the same now. Don't know what the problem was.
So, I plugged in the tubes for the right channel. Powered up. Read the B+ at 343volts. All IC power is right up there.
Both cathodes on the right side drawing exactly 37ma. Now going shopping with the wife. I will next install the tubes for the left channel, and check the cathode current. So far, so good.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 8:21 am 
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john8750 wrote:
I just went back to working on the amp. All the CCS circuits read the same now. Don't know what the problem was.
So, I plugged in the tubes for the right channel. Powered up. Read the B+ at 343volts. All IC power is right up there.
Both cathodes on the right side drawing exactly 37ma. Now going shopping with the wife. I will next install the tubes for the left channel, and check the cathode current. So far, so good.

So far so good.
What voltage reading do you get on the 6V6 cathode @37ma

The data sheets indicate about 19v .... however when we had 25ma as idle current I was reading about 20v ... so it seems kind of odd to me that 19v would give 37ma.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 8:36 am 
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Pbpix wrote:
john8750 wrote:
I just went back to working on the amp. All the CCS circuits read the same now. Don't know what the problem was.
So, I plugged in the tubes for the right channel. Powered up. Read the B+ at 343volts. All IC power is right up there.
Both cathodes on the right side drawing exactly 37ma. Now going shopping with the wife. I will next install the tubes for the left channel, and check the cathode current. So far, so good.

So far so good.
What voltage reading do you get on the 6V6 cathode @37ma

The data sheets indicate about 19v .... however when we had 25ma as idle current I was reading about 20v ... so it seems kind of odd to me that 19v would give 37ma.



Are you figuring on a higher B+? I will continue testing tomorrow, and list all voltages.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 8:40 am 
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And the current allowed by the CCS is exactly 37.0ma. The B+ was 343 with only two tubes installed. Should drop lower with all 4 tubes running.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 8:41 am 
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john8750 wrote:
Pbpix wrote:
john8750 wrote:
I just went back to working on the amp. All the CCS circuits read the same now. Don't know what the problem was.
So, I plugged in the tubes for the right channel. Powered up. Read the B+ at 343volts. All IC power is right up there.
Both cathodes on the right side drawing exactly 37ma. Now going shopping with the wife. I will next install the tubes for the left channel, and check the cathode current. So far, so good.

So far so good.
What voltage reading do you get on the 6V6 cathode @37ma

The data sheets indicate about 19v .... however when we had 25ma as idle current I was reading about 20v ... so it seems kind of odd to me that 19v would give 37ma.



Are you figuring on a higher B+? I will continue testing tomorrow, and list all voltages.


35ma per tube = 70ma -19v

Class AB1 Amplifier
Source ........................................ RCA RC-29 - 1975
Plate Voltage ................................. 285 V
Grid No. 2 Voltage ............................ 285 V
Grid No. 1 Voltage ............................ -19 V
Peak Grid No. 1 Voltage........................ 38 V
Plate Resistance (approx) ..................... 65K Ω
Transconductance .............................. 3600 µMho
Plate Current (Zero Signal) ................... 70 mA
Plate Current (Maximum Signal) ................ 92 mA
Grid No. 2 Current (Zero Signal) .............. 4 mA
Grid No. 2 Current (Maximum Signal) ........... 13.5 mA
Load Resistance ............................... 8K Ω
Power Output (approx) ......................... 14 W
Total Harmonic Distortion ..................... 3.5 %

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 8:45 am 
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Didn't you read my question above?
"What voltage reading do you get on the 6V6 cathode @37ma"


So what voltage are you measuring on the cathode?
>>>Not the voltage drop across the 1 ohm resistor = cathode current

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 9:04 am 
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Pbpix wrote:
Didn't you read my question above?
"What voltage reading do you get on the 6V6 cathode @37ma"


So what voltage are you measuring on the cathode?
>>>Not the voltage drop across the 1 ohm resistor = cathode current



I did answer you and, said tomorrow I will list all voltages. The only voltage I read was across the 1ohm resistor, to figure the cathode current. I did not measure the cathode voltage. But, the voltage must be ok if the current is ok, and the B+ is correct.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 03, 2018 9:12 am 
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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

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