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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Thu 23, 2019 12:47 am 
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Got the remote volume control box working.
I connected the 100k pot that it has. Will have a knob. leave the Little Prince volume at 100% And mod the 807 input.
Sound seems good. But I will need more listening to make sure.
Remember, if its not exactly right but you cant hear it, then you cant hear it. :lol:
For the 9vac, I used the 12vac from the Little Prince through a 33ohm 5watt. Connected it went down to 9.3vac.
This is a cool addition, for the 'turn it down' wife. :roll:
Attachment:
remote.jpg
remote.jpg [ 230.49 KiB | Viewed 564 times ]

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Thu 23, 2019 4:46 am 
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john8750 wrote:
I hear that. :lol:


So, I made the wiring correction, simple. Connected through my 5902 power amp, and test speakers. 8)
Turned the amp on and, oh boy, no lady opera singing. Also, no sound at all. Now what :?:
Traced the signal up to the balance pot. Stops right there.
After checking everything, found the 500k pot was an audio type pot. :oops:
I replaced it with the correct type. :roll:
Wow :!:
Beautiful sound. Just awesome.
The bass pot needs to be rewired. It operates backwards. No big deal.
The MP3 boost circuit works.
I didn't notice any hum. But will pay attention. Hum pot is about 50%.
Do have a little open circuit hum in the phono selection. But the inputs are open.
Will do more tests.
I noticed that the 12SL7's run so cool I can keep my hand on them.
A very exciting project. The phono preamp, RIAA, could be omitted if it is not needed. That would cut the amp in half. Making a real nice control amp.
Use the best caps you have. No carbon composite resistors.
Attachment:
lpfinish3.jpg
Worth the trip down wiring error lane, eh? Super. Now you need to test the phono circuits.


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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Thu 23, 2019 8:42 pm 
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Flipperhome wrote:
john8750 wrote:
I hear that. :lol:


So, I made the wiring correction, simple. Connected through my 5902 power amp, and test speakers. 8)
Turned the amp on and, oh boy, no lady opera singing. Also, no sound at all. Now what :?:
Traced the signal up to the balance pot. Stops right there.
After checking everything, found the 500k pot was an audio type pot.
I replaced it with the correct type. :roll:
Wow :!:
Beautiful sound. Just awesome.
The bass pot needs to be rewired. It operates backwards. No big deal.
The MP3 boost circuit works.
I didn't notice any hum. But will pay attention. Hum pot is about 50%.
Do have a little open circuit hum in the phono selection. But the inputs are open.
Will do more tests.
I noticed that the 12SL7's run so cool I can keep my hand on them.
A very exciting project. The phono preamp, RIAA, could be omitted if it is not needed. That would cut the amp in half. Making a real nice control amp.
Use the best caps you have. No carbon composite resistors.
Attachment:
lpfinish3.jpg
Worth the trip down wiring error lane, eh? Super. Now you need to test the phono circuits.



Yes. Was real neat to be able to troubleshoot a problem using a signal gen.
Have a feeling the RIAA hum will go away with the bottom metal cover.
I just noticed that the treble pot is not acting correctly. What did I do now.
No doubt I will find the problem.

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Thu 23, 2019 8:45 pm 
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I need to finish work on my HK FM4 next. The FM3 requires constant correction on the tuning dial for about 20 minutes after powering up.

I bought this little kit, should be fun.
https://www.ebay.com/itm/Wireless-Stere ... 2749.l2648

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Fri 24, 2019 11:11 pm 
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Working on the bottom plate now. I will cut several holes in it, but cant find much heat producing areas. Even the power supply resistors are not so bad.
I have a set of feet, like for the 807, but smaller. Will post pics.

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Fri 24, 2019 11:22 pm 
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I walked into the shop this morning, wow, something burning hot.
It was the charger for the solar system.
The charger can handle 30amps. But needed a cooling fan.
I found a loose wire to the fan controller. The fan did not turn on. The charger got too hot and fried.
Daytime in the shop, all power comes from the cells. After the sun goes down, the battery supplies the power, through an inverter.
Easy fix..... 8)

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 2:01 am 
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The prince John has a hum. The hum is there independent of the volume level, or balance.
The hum pot has no effect.
Shorting the grid makes no difference.
Where should I look at the wiring?

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 2:01 am 
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john8750 wrote:
I walked into the shop this morning, wow, something burning hot.
It was the charger for the solar system.
The charger can handle 30amps. But needed a cooling fan.
I found a loose wire to the fan controller. The fan did not turn on. The charger got too hot and fried.
Daytime in the shop, all power comes from the cells. After the sun goes down, the battery supplies the power, through an inverter.
Easy fix..... 8)
Well, that sucks. A solar meltdown for the want of a wire, which caused the fan to fail, which caused.... Has sort of a Shakespearian ring, doesn't it?


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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 2:05 am 
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john8750 wrote:
The prince John has a hum. The hum is there independent of the volume level, or balance.
The hum pot has no effect.
Shorting the grid makes no difference.
Where should I look at the wiring?
The new or old Prince John, or both?

We really need to give the new one another name so we know what you're talking about.

What input and what grid? Are you testing the RIAA?

The first thing to check is your AC power.


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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 2:46 am 
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Flipperhome wrote:
john8750 wrote:
I walked into the shop this morning, wow, something burning hot.
It was the charger for the solar system.
The charger can handle 30amps. But needed a cooling fan.
I found a loose wire to the fan controller. The fan did not turn on. The charger got too hot and fried.
Daytime in the shop, all power comes from the cells. After the sun goes down, the battery supplies the power, through an inverter.
Easy fix..... 8)
Well, that sucks. A solar meltdown for the want of a wire, which caused the fan to fail, which caused.... Has sort of a Shakespearian ring, doesn't it?




Dammit Spock. Stop acting so human.

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 2:50 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
I walked into the shop this morning, wow, something burning hot.
It was the charger for the solar system.
The charger can handle 30amps. But needed a cooling fan.
I found a loose wire to the fan controller. The fan did not turn on. The charger got too hot and fried.
Daytime in the shop, all power comes from the cells. After the sun goes down, the battery supplies the power, through an inverter.
Easy fix..... 8)
Well, that sucks. A solar meltdown for the want of a wire, which caused the fan to fail, which caused.... Has sort of a Shakespearian ring, doesn't it?

Dammit Spock. Stop acting so human.

Most illogical :mrgreen:


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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 3:00 am 
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Flipperhome wrote:
john8750 wrote:
The prince John has a hum. The hum is there independent of the volume level, or balance.
The hum pot has no effect.
Shorting the grid makes no difference.
Where should I look at the wiring?
The new or old Prince John, or both?

We really need to give the new one another name so we know what you're talking about.

What input and what grid? Are you testing the RIAA?

The first thing to check is your AC power.




The new little prince, sorry, not the Prince John.
Name? I will put in my vote soon....
It seems like higher than 60hz.
I should shield inputs, unshielded so far.
Should I look at grounding?

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 3:07 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
The prince John has a hum. The hum is there independent of the volume level, or balance.
The hum pot has no effect.
Shorting the grid makes no difference.
Where should I look at the wiring?
The new or old Prince John, or both?

We really need to give the new one another name so we know what you're talking about.

What input and what grid? Are you testing the RIAA?

The first thing to check is your AC power.

The new little prince, sorry, not the Prince John.
Name? I will put in my vote soon....
It seems like higher than 60hz.
I should shield inputs, unshielded so far.
Should I look at grounding?
What input are you using? The phone, because I thought you already tried the tone amp and there was no hum.

Yes, the inputs should be shielded but that would generally vary with the volume.

Sure, check the grounding but without knowing what you're looking at I can't tell a thing.


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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 7:09 am 
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Thanks Flip.
Weird. I disconnected the house ground from the chassis. All hum stopped.
I will check the shop ground to the house panel. Sumthingwrong :?:
Would we be safe to not ground the chassis?
I know the NEC would not accept it.

The power amp I have connected has a wood chassis, 5902. A remarkable little amp.
So it has no ground connection.

RIAA still has a little hum. Need to shield inputs first.
A nice little boost for the MP3, works well.

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 7:35 am 
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john8750 wrote:
Thanks Flip.
Weird. I disconnected the house ground from the chassis. All hum stopped.
I will check the shop ground to the house panel. Sumthingwrong :?:
Would we be safe to not ground the chassis?
I know the NEC would not accept it.

The power amp I have connected has a wood chassis, 5902. A remarkable little amp.
So it has no ground connection.

RIAA still has a little hum. Need to shield inputs first.
A nice little boost for the MP3, works well.
When you said your solar system blew up and right after that said there's was hum in the amp. Hmm. Sounds suspicious, doesn't it?

Actually, this is a case of "been there, done that, got the t-shirt" and have watched a ton of other engineers get burned by the same thing. What is it? Check power. I could bore you for hours with "did you check the power" and "found it, the power was [insert various power faults]." My favorite is the technician who.... wait for it.... wait for it.... hadn't turned the unit on. (That was after chewing me a new one for asking "have you checked power?") :lol:

Could be a problem with the way you've grounded the case. Or a problem with how ground is running to the case (house/shop wiring). I don't know but if the ground is right then that can't 'cause' hum because it should be at the same potential as neutral. If it's 'causing' hum then it isn't and something is wrong. That's assuming you have all the audio equipment on the same outlet (breaker). Having them of different outlets (breakers) can cause hum because the ground wires are run separate (as are the power lines).

Or it could be shielding and then there's the known issue of no shields on the 12SL7s (we were hoping it wouldn't matter). But we know the circuit, when wired right, is hum free because the first one was.

Btw, if it's the tubes themselves we might could just build a perforated cage over the whole top, like the amps of old had.


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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sat 25, 2019 9:32 pm 
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When you said your solar system blew up and right after that said there's was hum in the amp. Hmm. Sounds suspicious, doesn't it?
Yes it does.

Actually, this is a case of "been there, done that, got the t-shirt" and have watched a ton of other engineers get burned by the same thing. What is it? Check power. I could bore you for hours with "did you check the power" and "found it, the power was [insert various power faults]." My favorite is the technician who.... wait for it.... wait for it.... hadn't turned the unit on. (That was after chewing me a new one for asking "have you checked power?") :lol:
All shop power checks out good. 1.2ohms between ground and neutral, acceptable.

Could be a problem with the way you've grounded the case. Or a problem with how ground is running to the case (house/shop wiring). I don't know but if the ground is right then that can't 'cause' hum because it should be at the same potential as neutral. If it's 'causing' hum then it isn't and something is wrong. That's assuming you have all the audio equipment on the same outlet (breaker). Having them of different outlets (breakers) can cause hum because the ground wires are run separate (as are the power lines).
Yes. The difference in this amp, from the first Little Prince is the inputs are grounded to the chassis, and also all inputs run to B- common. Seems that all is fine as long as the house ground does not touch B- common.

Should house ground need to connect to B-. I will insulate all inputs, and connect to B-. Connect house ground to the chassis only. And get back to you.

:arrow:

Or it could be shielding and then there's the known issue of no shields on the 12SL7s (we were hoping it wouldn't matter). But we know the circuit, when wired right, is hum free because the first one was.
Will shield all inputs, small job.

Btw, if it's the tubes themselves we might could just build a perforated cage over the whole top, like the amps of old had.

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sun 26, 2019 1:25 am 
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I isolated all inputs and connected to B-.
Ground still connected to chassis from house.
Powered on and got worse hum.
Connected ground to B- common. That damaged my MP3 player, now dead.
So, I need to do some thinking. Will compare it to the original Little Prince.
I will find it.

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sun 26, 2019 4:47 am 
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john8750 wrote:
I isolated all inputs and connected to B-.
Ground still connected to chassis from house.
Powered on and got worse hum.
Connected ground to B- common. That damaged my MP3 player, now dead.
So, I need to do some thinking. Will compare it to the original Little Prince.
I will find it.
Hum with B- isolated from earth ground is to be expected. With AC floating there's no reference to earth ground so it can be 'anything' but with leakages (assuming all leakages were equal) it'll probably settle to something around 60VAC, half the AC line.

Something is seriously wrong if connecting earth to B- blew your MP3 player. Sounds like somewhere earth isn't earth or neutral and hot are reversed.

"Yes. The difference in this amp, from the first Little Prince is the inputs are grounded to the chassis, and also all inputs run to B- common. Seems that all is fine as long as the house ground does not touch B- common." I can't make heads or tails of that. WHICH amp "is fine as long as the house ground does not touch B- common?" The first Little Prince has earth connected to chassis too; at least it's supposed to be.


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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sun 26, 2019 6:21 am 
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Flipperhome wrote:
john8750 wrote:
I isolated all inputs and connected to B-.
Ground still connected to chassis from house.
Powered on and got worse hum.
Connected ground to B- common. That damaged my MP3 player, now dead.
So, I need to do some thinking. Will compare it to the original Little Prince.
I will find it.
Hum with B- isolated from earth ground is to be expected. With AC floating there's no reference to earth ground so it can be 'anything' but with leakages (assuming all leakages were equal) it'll probably settle to something around 60VAC, half the AC line.

Something is seriously wrong if connecting earth to B- blew your MP3 player. Sounds like somewhere earth isn't earth or neutral and hot are reversed.

"Yes. The difference in this amp, from the first Little Prince is the inputs are grounded to the chassis, and also all inputs run to B- common. Seems that all is fine as long as the house ground does not touch B- common." I can't make heads or tails of that. WHICH amp "is fine as long as the house ground does not touch B- common?" The first Little Prince has earth connected to chassis too; at least it's supposed to be.




With the earth ground not connected to the chassis, no hum at all. The B- must connect to the chassis at the inputs, or lots of noise.
Would it work safely without the earth ground?
I don't yet understand whats going on.
The hot-neutral-ground is entering the amp correctly.
And the amp sound quality is great.

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 Post subject: Re: Another Little Prince- tube preamp
PostPosted: May Sun 26, 2019 7:44 am 
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john8750 wrote:
With the earth ground not connected to the chassis, no hum at all. The B- must connect to the chassis at the inputs, or lots of noise.
Would it work safely without the earth ground?
I don't yet understand whats going on.
The hot-neutral-ground is entering the amp correctly.
And the amp sound quality is great.
Will you PLEASE tell me WHICH preamp you're talking about.

The original Little Prince. It has, or should have because that's the way I said to wire it, earth ground connected to circuit ground (B-) at the inputs, because they're connected to the chassis. It works and doesn't hum.

Now, the 'new', 12SL7 Little Prince. The exact same thing should work, if it's the same thing.

No, it's not 'safe' with earth disconnected because if anything should fail (for example, the power transformer), there would be nothing to short it to earth. With transformer isolation B- needs to be connected to earth or else there's no reference to '0' (the 'earth') and it will HUM (unless the earth ground is connected through the input source). That it doesn't 'hum' when DISCONNECTED suggests to me you have it connected somewhere else and you're creating, at the very least, a ground loop when you connect 'earth', thereby making TWO connections to neutral/earth. And the fact it blew your MP3 player suggests to me one (or more) of those AC wires isn't what you think it is.

How do you know hot-neutral-ground is entering the amp correctly?


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