I’m about to start up my first tube project, Tubelab SSE, on the bench. Without tubes except rectifier tube I get 500V. How much will B+ drop under load? Any tips for reducing B+ to more safe voltage?
Power: Hammond 374BX(375-0-375), transformer input at 230V
Wall socket: 235V
Choke 193L 5H(R 57 ohm) with extra 100ohm in serial
Rectifier GZ34
C1 47uF
D3,D4, TR1 in place
Next step is test with tubes and output with speaker load, right?
/ a tube noob
Power: Hammond 374BX(375-0-375), transformer input at 230V
Wall socket: 235V
Choke 193L 5H(R 57 ohm) with extra 100ohm in serial
Rectifier GZ34
C1 47uF
D3,D4, TR1 in place
Next step is test with tubes and output with speaker load, right?
/ a tube noob
Congratulations! 500 Vdc sounds about right for the unloaded power supply. (375x1.4=525, minus drop in tube rectifier ~500V.)
This is the peak voltage you will see before power tubes are conducting. What tubes are you using? Your B+ under load should be appropriate for the tubes you use, of course. Your power supply caps are 500V, right? What AC do you measure on the power transformer output specified for 375-0-375V?
Good luck with the rest of your startup procedure and then enjoy!
This is the peak voltage you will see before power tubes are conducting. What tubes are you using? Your B+ under load should be appropriate for the tubes you use, of course. Your power supply caps are 500V, right? What AC do you measure on the power transformer output specified for 375-0-375V?
Good luck with the rest of your startup procedure and then enjoy!
Puh, good to hear. Yes C1, C2 is rated 500V. I got 754V, 6.42V, 4.97V direct from the transformer
I have the 12AT7 and choice of EL34 or 6L6. Cathode resistors at default 560R.
Output transformer is Lundahls 2769 100mA, 4K7, 8ohm.
I hope all this is within the default margin?
I have the 12AT7 and choice of EL34 or 6L6. Cathode resistors at default 560R.
Output transformer is Lundahls 2769 100mA, 4K7, 8ohm.
I hope all this is within the default margin?
Looking at the GZ34 datasheet, it should drop around 60V when you draw 100mA.
It also depends on the resistance of the HT winding.
It also depends on the resistance of the HT winding.
sov,
Your voltages all sound right for being unloaded, just check again when your amp is playing music. The B+ then around 450 Vdc, and heaters a bit closer to 6.3 Vac. Your Lundahl LL2769 should be excellent performers for triode-connected EL34s or 6L6 types. (No UL, right?).
At first turn on with tubes use a variac if you have one, or light bulb current limiter such as (https://robrobinette.com/5e3_Modifications.htm#Light_Bulb_Current_Limiter)
I think you are ready for good music! Good luck!
Francois
Your voltages all sound right for being unloaded, just check again when your amp is playing music. The B+ then around 450 Vdc, and heaters a bit closer to 6.3 Vac. Your Lundahl LL2769 should be excellent performers for triode-connected EL34s or 6L6 types. (No UL, right?).
At first turn on with tubes use a variac if you have one, or light bulb current limiter such as (https://robrobinette.com/5e3_Modifications.htm#Light_Bulb_Current_Limiter)
I think you are ready for good music! Good luck!
Francois
@Parafeed813 , What is HT winding? I'm new to the lingo. Is it output transformer prim and sec resistance? If so, I will measure tonight. Looking att the simulation table I will reach at aprox 65-75mA.
@Francois G
I have no variac but will use a light bulb. I have used light bulb when powering upp firstwatt's but it didn't occurred to me to use it now. Thank you for reminding me. I have wired the Lundahls with no feedback or UL. Some photos are coming up later.
@Francois G
I have no variac but will use a light bulb. I have used light bulb when powering upp firstwatt's but it didn't occurred to me to use it now. Thank you for reminding me. I have wired the Lundahls with no feedback or UL. Some photos are coming up later.
For the record, voltage direkt from transformer without load:
Wall socket voltage: 235V
374BX 230V-input: 780V, 6.7V, 5.2V
374BX 240V-input: 746V, 6.4V, 5V
Wall socket voltage: 235V
374BX 230V-input: 780V, 6.7V, 5.2V
374BX 240V-input: 746V, 6.4V, 5V
The HT winding is the 750 volt winding on the power transformer.
The voltage readings you are seeing are typical for an amp with no output tubes. You will probably be at around 450 volts when tubes are installed. You can always use the 240 volt input for power up and then switch to the 230 volt connection if you need more B+ voltage.
The voltage readings you are seeing are typical for an amp with no output tubes. You will probably be at around 450 volts when tubes are installed. You can always use the 240 volt input for power up and then switch to the 230 volt connection if you need more B+ voltage.
Finaly I got some current but perhaps on the lower side. I could use power transformer 230V-input for a few volts more.
Suggestions for optimization? Lower resistors? A few more volts?
Cathode resistors 560 ohm: 29V
B+: 410V
GZ34, 12AT7, EL34
Images from a mad scientist desk, my wife's words. Don't call me scientist, I said. 🙂
Suggestions for optimization? Lower resistors? A few more volts?
Cathode resistors 560 ohm: 29V
B+: 410V
GZ34, 12AT7, EL34
Images from a mad scientist desk, my wife's words. Don't call me scientist, I said. 🙂
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I have a 60 uF motor run cap and a 100uF DC-link cap. Which would I choose? GZ34 says max 60uF capacitance, what does that mean?
It means that the capacitance before the choke (or resistor) should not be more than 60uF. After the choke you can add more.
This is to prevent exceeding the maximum cathode current on the charging peaks.
If you download and install PSUD2 you can visualize what happens when you change the first capacitor after the rectifier.
This is to prevent exceeding the maximum cathode current on the charging peaks.
If you download and install PSUD2 you can visualize what happens when you change the first capacitor after the rectifier.
Thanx @Parafeed813 that is interesting, I'll try to figure PSUD2 out. So generally, do you recommend 100uF for SSE?
@Tubelab_com, what do you think of good mA for EL34 or 6L6 and perhaps a good common?
@Tubelab_com, what do you think of good mA for EL34 or 6L6 and perhaps a good common?
Help me understand why I got B- instead of B+.
I have installed stuff in a chassi and now I get B-. Please guide me in search of what’s wrong. I do not dare to wait for meltdown.
Tubes are in place are glowing fine.
I have installed stuff in a chassi and now I get B-. Please guide me in search of what’s wrong. I do not dare to wait for meltdown.
Tubes are in place are glowing fine.
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Now I feel stupid.
🙂Your good observation was correct.
Is choke resistor with 3W OK?
B+ at 422V
V over RK at 30V
54mA Ik with EL34 is in the to-lower-part, right?
Aiming for 6L6-tubes
Should I go up in B+ or drop Rk?