Starting a D'Lite
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Re: Starting a D'Lite
This is probably a stupid question but you did ground the HT center tap right?
Tom
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Re: Starting a D'Lite
Tom (when it comes to this stuff I am stupid)This is probably a stupid question but you did ground the HT center tap right?
Here's scan of the power transformer specs and here's how I have them hooked up
Primary 120 / 120 to the outlet
Secondaries
1st coil 640v, 250mA center tapped
Red 320v = one side of the rectifier
Black / Red center tap 160v = Bias
Red 320v = Other side of the rectifier
2nd coil 6.3v, 4.8A center tapped
Brown 3.15v = heaters
white / brown center tap = ground
Brown 3.15v = heaters
3rd Coil 5v, 3A
Yellow 5v = relays
Yellow 5v = relays
It seems to me that having all of my diodes be bad is unlikely, can anyone see a wiring issue that is evading me? Should the 640 center tap be grounded and the 6.3 center tap be the bias?
Thanks
Eric
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Re: Starting a D'Lite
The black/red and white/brown need to be grounded. I don't know why you have black/red liste4d as bias, it's not a bias tap. This xformer doesn't have a bias tap so you'll have to use one of the red legs to the bias supply and adjust the values of the resistors.
Re: Starting a D'Lite
+1 That transformer CT GROUNDED!! should give you 451V Plates.. Like Bob said that transformer doesn't have a bias tap so you will need to add one off the HT side of the sec.. Here is one Henry gave me that works fine you may have to adjust the 52k to ground but works great... Good LuckBob-I wrote:The black/red and white/brown need to be grounded. I don't know why you have black/red liste4d as bias, it's not a bias tap. This xformer doesn't have a bias tap so you'll have to use one of the red legs to the bias supply and adjust the values of the resistors.
Tony
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" The psychics on my bench is the same as Dumble'"
Re: Starting a D'Lite
that transformer doesn't have a bias tap so you will need to add one off the HT side of the sec..
you'll have to use one of the red legs to the bias supply
I apologize for my ignorance and I am grateful for the help.
I don't understand the quote above (HT=?). Do I take a tap from one of the 320v say from the junction of the secondary and the diode and run it into the bias supply. Wouldn't that give me 320v going into the bias when it wants to see 45v. So I would have to increase the value of the resistor from 470 ohm to ?
Thanks
Eric
Re: Starting a D'Lite
dreric wrote:that transformer doesn't have a bias tap so you will need to add one off the HT side of the sec..you'll have to use one of the red legs to the bias supply
I apologize for my ignorance and I am grateful for the help.
I don't understand the quote above (HT=?). Do I take a tap from one of the 320v say from the junction of the secondary and the diode and run it into the bias supply. Wouldn't that give me 320v going into the bias when it wants to see 45v. So I would have to increase the value of the resistor from 470 ohm to ?
Thanks
Eric
Yes..Do I take a tap from one of the 320v say from the junction of the secondary and the diode and run it into the bias supply.
The 56K resistor shunts AC to ground.. The lower the value Greater the drop..Bias supply's draw very little current.. Find the resistor value that gives you the 48v or close then hook up the cap.. You can also do a Marshall or Trainwreck style bias supply although I like this one the best not as spongy!!.. Good Luck..FWIW.. This supply was also used in Sundown amps..
Tony
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" The psychics on my bench is the same as Dumble'"
Re: Starting a D'Lite
HT I believe is a hold over from years gone by, it means High Tension or high voltage.
It usually refers to the secondary voltage of a tube amp power transformer.
I kind of thought maybe the center tap was not grounded correctly by your symptoms.
As others have said, your PT does not have a bias tap, so you have to create one from the 320v winding.
Tap off of it like shown and you should be good to go.
Remember that the bias voltage is NEGATIVE, so the diode and cap have to be reversed with the + towards ground for the bias diode and filter cap.
Don't forget to ground the white/brown center tap for the 6.3vac heater supply as well.
You can use the 5v tap to power your relays.
It usually refers to the secondary voltage of a tube amp power transformer.
I kind of thought maybe the center tap was not grounded correctly by your symptoms.
As others have said, your PT does not have a bias tap, so you have to create one from the 320v winding.
Tap off of it like shown and you should be good to go.
Remember that the bias voltage is NEGATIVE, so the diode and cap have to be reversed with the + towards ground for the bias diode and filter cap.
Don't forget to ground the white/brown center tap for the 6.3vac heater supply as well.
You can use the 5v tap to power your relays.
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Tom
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Don't let that smoke out!
Re: Starting a D'Lite
Also B+ refers back to the days when actual batteries were used to power tubes.
Here is a simple drawing for the bias circuit.
Remember that you will have to adjust the 56K to give the desired range of 20-45mv or ma bias on the 1 ohm resistors on the cathodes of the power tubes.
Here is a simple drawing for the bias circuit.
Remember that you will have to adjust the 56K to give the desired range of 20-45mv or ma bias on the 1 ohm resistors on the cathodes of the power tubes.
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Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Starting a D'Lite
Tom, Tony, TM, Bob & everyone else ......................
THANK YOU!
Eric
THANK YOU!
Eric
Re: Starting a D'Lite
Wasn't such a stupid question after all.Structo wrote:This is probably a stupid question but you did ground the HT center tap right?
Re: Starting a D'Lite
Hi guys
I made the bias supply as suggested. Now measuring (sans power tubes) from the wiper lug of the bias pot I have a range of -18.4 to -37.9 dc volts as I adjust the pot. I am unclear as to what the range should be ans whether I need to adjust the 56K resistor or if I am in good shape. Suggestions?
Grounding the center tap brought all the voltages up, in fact they are about 15 volts higher everywhere when compared to the d-lite voltage charts. Is this OK?
When I put in the power tubes, all controls on minimal settings "1" I get a loud high pitched whine, not leave the room loud but lets just say that I don't have to clean my ears tonight. The pitch of the whine changes as I manipulate the bias pot. Changing the settings on the volume, tone, OD and master doesn't affect the whine but the whine is affected by the presence pot; getting louder, changing pitch then going to a motor boat , aliens landing kind of sound.
All help is greatly appreciated
Eric
I made the bias supply as suggested. Now measuring (sans power tubes) from the wiper lug of the bias pot I have a range of -18.4 to -37.9 dc volts as I adjust the pot. I am unclear as to what the range should be ans whether I need to adjust the 56K resistor or if I am in good shape. Suggestions?
Grounding the center tap brought all the voltages up, in fact they are about 15 volts higher everywhere when compared to the d-lite voltage charts. Is this OK?
When I put in the power tubes, all controls on minimal settings "1" I get a loud high pitched whine, not leave the room loud but lets just say that I don't have to clean my ears tonight. The pitch of the whine changes as I manipulate the bias pot. Changing the settings on the volume, tone, OD and master doesn't affect the whine but the whine is affected by the presence pot; getting louder, changing pitch then going to a motor boat , aliens landing kind of sound.
All help is greatly appreciated
Eric
Re: Starting a D'Lite
Haven't read the whole thread so not sure if this is helpful but your current symptoms sound like you have the OT primaries reversed.
If so you will get positive feedback instead of negative....then you get oscillations like your hearing and presence control is in feedback network so I'd look there.
Typically, but not always (some odd irons out there) when your looking down into the amp with the rear panel towards you the blue OT lead goes to the pair or single power tube on the right side, the brown lead to the left side.
Good luck, HIH.
If so you will get positive feedback instead of negative....then you get oscillations like your hearing and presence control is in feedback network so I'd look there.
Typically, but not always (some odd irons out there) when your looking down into the amp with the rear panel towards you the blue OT lead goes to the pair or single power tube on the right side, the brown lead to the left side.
Good luck, HIH.
"...& I'm all out of bubblegum"
Re: Starting a D'Lite
Yep sounds like the old OT switch a roo.
If your OT primary wires are too short to reverse, you can reverse the wires that go from the power tube grids to the 220K .1uF on the board.
If your OT primary wires are too short to reverse, you can reverse the wires that go from the power tube grids to the 220K .1uF on the board.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Starting a D'Lite
Okay
+2 on backwards wiring. Seeing that I am such a pro at wiring a transformers I thought I'd show how it's wired before I trash something.
Here's the spec sheet. I thought I was wiring it so that I could switch between the two ohm ratings thus being able to switch between 6V6 and KT66.
So how ass backwards have I done this one?
Thanks
eric
+2 on backwards wiring. Seeing that I am such a pro at wiring a transformers I thought I'd show how it's wired before I trash something.
Here's the spec sheet. I thought I was wiring it so that I could switch between the two ohm ratings thus being able to switch between 6V6 and KT66.
So how ass backwards have I done this one?
Thanks
eric
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Re: Starting a D'Lite
Looks right to me.
I had my D'lite wired like that for a while but I never tried 6V6 in it.
So later I removed the switch but put in dual bias pots.
I like that arrangement and I can run tubes a bit closer together or as far apart as I want.
As far as the bias range, when I bias my 6l6 to 42ma the bias voltage is
-48v.
For 6V6 I think you want around 22ma? Can't remember.
You have a different PT so I can't advise what change you need to bring it closer to the range you need.
I think for 6V6 you need around -37v.
That would give 19ma on the cathodes.
Here is a D'lite 22 6V6 voltage chart. I suggest a range in bias between 18ma and 22ma.
I had my D'lite wired like that for a while but I never tried 6V6 in it.
So later I removed the switch but put in dual bias pots.
I like that arrangement and I can run tubes a bit closer together or as far apart as I want.
As far as the bias range, when I bias my 6l6 to 42ma the bias voltage is
-48v.
For 6V6 I think you want around 22ma? Can't remember.
You have a different PT so I can't advise what change you need to bring it closer to the range you need.
I think for 6V6 you need around -37v.
That would give 19ma on the cathodes.
Here is a D'lite 22 6V6 voltage chart. I suggest a range in bias between 18ma and 22ma.
You do not have the required permissions to view the files attached to this post.
Tom
Don't let that smoke out!
Don't let that smoke out!