Look at the bright side.At least they didn't ship you 100 ohms for your 100K.
If you are going to drop 55 volt at the power supply choke / inductor, you need to add up all the current from your tubes, The big users are the four 6550 power tubes at about 60mA (Plate&Screen). They should add up to be around 255ma for both channels. Use Ohms Law R = 55/0.255A or around 215 ohms. Use an adjustable 300 ohms 30W.
Flip a coin for your transformer conection. Most transformer tell you which end is which, yours don't. Just make sure you have enough wire length left if you need to switch around.
If you are going to drop 55 volt at the power supply choke / inductor, you need to add up all the current from your tubes, The big users are the four 6550 power tubes at about 60mA (Plate&Screen). They should add up to be around 255ma for both channels. Use Ohms Law R = 55/0.255A or around 215 ohms. Use an adjustable 300 ohms 30W.
Flip a coin for your transformer conection. Most transformer tell you which end is which, yours don't. Just make sure you have enough wire length left if you need to switch around.
@Alllensoncanon: mean of drop 55v: add serial adjustable 300ohm/30W with choke "rectifier -> capacitor -> choke -> adjustable -> capacitor" can adjust voltage?
i will read more to understand "Flip a coin for your transformer conection. Most transformer tell you which end is which, yours don't. Just make sure you have enough wire length left if you need to switch around." my bad english!
i will read more to understand "Flip a coin for your transformer conection. Most transformer tell you which end is which, yours don't. Just make sure you have enough wire length left if you need to switch around." my bad english!
On Power supply, See picture for suggestion on schematic changes and the type of adjustable resistor you can use. Notice the output stage power connection has been changed. Be Careful. Make sure you understand the changes before doing it.
On transformer, stay with your current connections. You have 50% chance of getting the negative feedback signal phase right. If not, switch the two red wire around.
On transformer, stay with your current connections. You have 50% chance of getting the negative feedback signal phase right. If not, switch the two red wire around.
Attachments
Don't adjust the resistor while power is on. Also make sure you discharge all the power supply filtering capacitors before touching anything.
**** High Voltage **** Adjust the resistor to the proper value before you put it on. The caps in this area can hold the high voltage for a long time. Discharge it before touching anything.
Thanks! I will try with your picture configuration.
With my PCB B+ to OPT at the 2nd capacitor, i will try draw schematics with PCB.
Can add series adjustable resistor on 355 VAC to drop down 300 VAC before SS&5U3C tubes.
I know High Voltage.
With my PCB B+ to OPT at the 2nd capacitor, i will try draw schematics with PCB.
Can add series adjustable resistor on 355 VAC to drop down 300 VAC before SS&5U3C tubes.
I know High Voltage.
@Alllensoncanon after replace 6550 G2 resistor with right 390R now B+ is 420V
6550 pin3 415V, pin4 413V, pin8 45V
6H9C pin2 232V
6H8C pin2-5 325V
If install P1-SG1 with pair 27ohm the sound like helicopter, now P1-SG1 with pair 32.3ohm Ok. If install feedback wire the speaker have oop oop with bass in out, now remove feedback wire the sound very good, is this negative feedback?
After heard 15min with laser thermometer all component is 45C but resister cathode so hot 110C. PCB and document: Cathode are 330uf parallel 680R/5W parallel 680R/5W, but in the first schematics install cathode are 2.200uf parallel 750R/7W parallel 750R/7W parallel 1.0uf/630v(nonpolar). How about the temperature of cathode resistor is normal?
http://www.diyaudio.com/forums/members/alllensoncanon.html
6550 pin3 415V, pin4 413V, pin8 45V
6H9C pin2 232V
6H8C pin2-5 325V
If install P1-SG1 with pair 27ohm the sound like helicopter, now P1-SG1 with pair 32.3ohm Ok. If install feedback wire the speaker have oop oop with bass in out, now remove feedback wire the sound very good, is this negative feedback?
After heard 15min with laser thermometer all component is 45C but resister cathode so hot 110C. PCB and document: Cathode are 330uf parallel 680R/5W parallel 680R/5W, but in the first schematics install cathode are 2.200uf parallel 750R/7W parallel 750R/7W parallel 1.0uf/630v(nonpolar). How about the temperature of cathode resistor is normal?
http://www.diyaudio.com/forums/members/alllensoncanon.html
The helicopter noise is "incorrect phase" negative feedback. To correct it, all you need is reverse the two red wires from the transformer primary. After that you can re-install the negative feedback resistor. You can also listen without the negative feedback resistor for a while. This way you can compare it with or without this resistor. Negative feedback is designed to give lower distortion and lower output impedance. Of course like everything else, there are side effects that you might or might not like.
The 6650 Cathode resistors generate 45V * 120mA = 5.5W of heat. Untouchable hot is normal.
The 6650 Cathode resistors generate 45V * 120mA = 5.5W of heat. Untouchable hot is normal.
I tried swap output OPT cable 0ohm to 8ohm and 8ohm to 0ohm, but when install feedback cable speakers oop oop with screen bass in&out, tried swap feedback cable same. Now no feedback cable only 1 cable output 0ohm to mass. Why??
This is feedback schematics of PCB
Can i remove 220R resistor to mass, 220uf/50v capacitor. Replace 2Kohm series feedback with 200Kohm like with first plant schematics?
An externally hosted image should be here but it was not working when we last tested it.
Can i remove 220R resistor to mass, 220uf/50v capacitor. Replace 2Kohm series feedback with 200Kohm like with first plant schematics?
The 220 ohms resistor seems like it is just a backup loading from cases when the speaker are not hook up. I would remove it just because less is better.
Are you sure that the negative feedback compensation capacitor is 220uF and not 220pf ? In any event, I think your 1st choice of 200K is a better one.
Are you sure that the negative feedback compensation capacitor is 220uF and not 220pf ? In any event, I think your 1st choice of 200K is a better one.
Yes, i'm sure it is 220uf capacitor, in component list C2, C3. i mistake 220ohm is 200ohm to mass, R8, R9. R7,R10 is 2K parallet with C2,C3 (same with my brother's amp).
When i read component list have RF/15K*2 in last line, but i don't see in my brother's amp (OPT 35W output) my OPT output is 60W with detail
60W bile push - pull output transformer EI96 * 45
Model: OP964504
Core size: 32MM * 45MM
Winding method: 3 clip 2 section wound, with super-linear tap (43%)
Frequency response: 25HZ -20KHZ
Inductance (PP): L> = 90 H @ 500HZ
Primary impedance: 5K ohm
primary diameter: 0.25MM
Primary DC resistance: 140 ohms
Secondary impedance: 0-4 ohm-8 ohms (plus a group of 16 ohms, the price plus 20 yuan) 0-83-118T
Size: high 98MM wide 80 MM thick 99MM
Insulation treatment: dip insulating paint
Core material: imported Japan Z11 0.35MM thick insulation annealing film, stacked thickness 45MM.
Installation: vertical installation with side cover
Installation hole center distance: 65 × 70
Weight: 2.7KG
I thing, i need install series with feedback cable, what resistor need i install 15? 50K? 100K or 200K?
An externally hosted image should be here but it was not working when we last tested it.
When i read component list have RF/15K*2 in last line, but i don't see in my brother's amp (OPT 35W output) my OPT output is 60W with detail
60W bile push - pull output transformer EI96 * 45
Model: OP964504
Core size: 32MM * 45MM
Winding method: 3 clip 2 section wound, with super-linear tap (43%)
Frequency response: 25HZ -20KHZ
Inductance (PP): L> = 90 H @ 500HZ
Primary impedance: 5K ohm
primary diameter: 0.25MM
Primary DC resistance: 140 ohms
Secondary impedance: 0-4 ohm-8 ohms (plus a group of 16 ohms, the price plus 20 yuan) 0-83-118T
Size: high 98MM wide 80 MM thick 99MM
Insulation treatment: dip insulating paint
Core material: imported Japan Z11 0.35MM thick insulation annealing film, stacked thickness 45MM.
Installation: vertical installation with side cover
Installation hole center distance: 65 × 70
Weight: 2.7KG
I thing, i need install series with feedback cable, what resistor need i install 15? 50K? 100K or 200K?
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In the original schematic, two SS diodes are being used as the return path for the rectified DC because the transformer for B+ is not centre-tapped. The DIY version has 2 more diodes added to complete the bridge rectifier-- I've seen this done before with the intention of protecting the circuit in case the rectifier tubes short; perhaps that was the reasoning here. It should theoretically not impact the sound.
This schematic was taken from (or at least is identical to) the Bewitch 6550, which I am currently working on. An odd coincidence! 😱 If anyone has time, I have posted a question about this very circuit in my recent post.
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search some schematics, i know my feeadback missing 1 resistor series feedback, i will add 25Kohm (15K/35W - xxK/60W), right?
japanese 211 schematic
japanese 211 schematic
An externally hosted image should be here but it was not working when we last tested it.
The two schematics you posted are two totally different designs. I wouldn't try to mix them unless you know what you are doing and have better testing equipment.
Your amp have a phase splitter circuit right up to the input. The negative feedback placement is part of the front end. I would just follow your original schematic/design which just call for a 200K to 300K resistor with no capacitor.
Your amp have a phase splitter circuit right up to the input. The negative feedback placement is part of the front end. I would just follow your original schematic/design which just call for a 200K to 300K resistor with no capacitor.
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I was try install feedback resistor are 20K parallel 470pf (component list are RF/15K*2 (KT88) RF/10K (EL34), i thing 15K parallel 15K). Now speaker don't have any noise or hum when no input signal (without feedback speaker have hum 50Hz).
I will try some resistor feedback 10K, 10K+20K, 4.7K to test to have better sound. Can you explain the mean of value resistor feedback, high or low value resistor maybe make better? Thanks.
I will try some resistor feedback 10K, 10K+20K, 4.7K to test to have better sound. Can you explain the mean of value resistor feedback, high or low value resistor maybe make better? Thanks.
The ratio of feedback R over the input cathode resistor, RF/(R1+R2) or RF/(2.2K+100) determines the amount of negative feedback the amp will get. The smaller RF resistor is, the larger the feedback (aka: NFB). Note: More NFB is not necessary better. In your specific circuit, this NFB can effect the balance of your push-pull (phase splitter) circuit.
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