Search found 36 matches
- Wed May 30, 2012 1:03 am
- Forum: Technical Discussion
- Topic: Quad bias for simulclass operation
- Replies: 1
- Views: 515
Quad bias for simulclass operation
I am trying to implement quad bias controls on my 100 watt heads. Is this the right approach to do this. I would like to simulclass by mixing tube types as well. KT88, EL34, or 6L6. This is my working schematic. Will this work like this?
- Fri Jan 20, 2012 10:43 pm
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
Sound City update
Here is the completed amp. It sounds great and it sings nicely. My heaters are running about 6.9VAC. I left accomodations for dropping resistors. Should I drop it down of just leave it? I suppose I will leave it because it is at the +10% tolerance. The plates are running @ 520VAC. Love the tone. Sta...
- Mon Jan 16, 2012 2:59 pm
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
Sound City update
Had to be sure of the bias circuit before overhaul! I had planned on re-build anyway. The amp is gonna be a single channel with hi gain circuit. It is getting new caps, sockets, and new pots. I won't deny the bias circuit was a PITA! I will post pics when complete.
- Mon Jan 16, 2012 4:43 am
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
Sound City update
Well I will be utilizing the voltage doubler with separate bias controls for each tube. Pic 2 is the prototype bias circuit and pic 1 is the stripped version prior to rebuild. Should be a nice amp whem complete. I will be adding a presence control to it as well.
- Sun Jan 15, 2012 4:04 am
- Forum: Technical Discussion
- Topic: 1 uf phillips MKT 100V caps
- Replies: 4
- Views: 867
1 uf 100V
Found the Vishay substitute. Thank you for the help! Appreciate it!
- Sat Jan 14, 2012 11:10 pm
- Forum: Technical Discussion
- Topic: 1 uf phillips MKT 100V caps
- Replies: 4
- Views: 867
1 uf phillips MKT 100V caps
Does anyone know where I can find a source for these capacitors? Thanks
- Sun Jan 08, 2012 2:52 pm
- Forum: Technical Discussion
- Topic: Sound City 50+ partridge schematic
- Replies: 7
- Views: 3301
bias circuit
I have decided to keep stock transformer on 105VAC tap as it is and run a voltage diubler for the bias circuit. I will be dropping heater voltage a little bit to keep it with in tolerances. Thank you for all the great info on these amps!
- Sat Jan 07, 2012 1:45 pm
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
Updated bias circuit
I got this schem from another forum. Looks like a workable option. Voltage doubler.
- Sat Jan 07, 2012 3:17 am
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
bias circuit
Those readings were based on resistor changes. With the original schem 4.7K in place it is adjustable from -44 tp -42 or so. I will probably be tapping the HV and totally re-work the bias circuit.
- Fri Jan 06, 2012 5:35 am
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
increasing bias voltage
Appreciate the info. You are correct! I need to increase bias voltage to decrease bias current. Yes my 2 options are: Take it from HV tap or rectify the bias tap with full wave rectifier. Where could I find an example of these applications? Ex: schematics. Thank you for the help!
- Fri Jan 06, 2012 5:23 am
- Forum: Technical Discussion
- Topic: Sound City 50+ partridge schematic
- Replies: 7
- Views: 3301
Partridge Transformer
These are close, but no brown availiable- only 5 wires as stated
2 large - black and yellow
3 small - green, red, white
Power Tranny
Primary Windings
Grey- Tranny Shield
Black- Common
Orange- 105v
Brown- 115v
Yellow- 225v
Red- 245v
Partridge Mains transformer
TG9875
H2138H
2 large - black and yellow
3 small - green, red, white
Power Tranny
Primary Windings
Grey- Tranny Shield
Black- Common
Orange- 105v
Brown- 115v
Yellow- 225v
Red- 245v
Partridge Mains transformer
TG9875
H2138H
- Fri Jan 06, 2012 12:05 am
- Forum: Technical Discussion
- Topic: Sound City 50+ partridge schematic
- Replies: 7
- Views: 3301
Sound City 50+ partridge schematic
Well I would like to return to the original source of the problem here. Does anyone know where I can find original color codes of these 50 watt partridge output transformers. I know there are 5 wires leading to the input circuit. Large black and yellow - Small Green, White, and Yellow. Any info on t...
- Thu Jan 05, 2012 9:30 pm
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
Bias @ pin 5
I either check it with a weber bias rite meter or a fluke meter. I do not have the 1 ohm resistors on this amp. There are individual adjusters on each tube. It shouldn't matter as long as I bias each tube separately
- Thu Jan 05, 2012 9:27 pm
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
Re: Modifying bias circuit for lower current
The bias caps?
- Thu Jan 05, 2012 9:06 pm
- Forum: Technical Discussion
- Topic: Modifying bias circuit for lower current
- Replies: 24
- Views: 3852
Bias @ pin 5
Played with value of R43 went from 470R to 499K. The bias will not go below 74 to 80ma. The bias tap off the transformer is 33VAC. The readings @ pin 5 with no tubes installed is between .500 and -44 VDC. These voltages are obtainable by rotating bias adjusters. The schem shows a voltage of -36, but...