B+ on a superlite tmb
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B+ on a superlite tmb
Hello forum,
I am using resistors to decrease the B+ to 290 ish. I have already used the 'zener voltage dropping' method discussed on this site. But 4 zener diodes in series on the filter capacitor did not bring it down. So I used three 50 ohms resistors in series( 75 ohms 25 watt) soldered into B+ before it hit the rectifying diodes.
I turned on the amp and played for 10/15 secs, then powered off. On second power up, the amp has no sound. Is it possible that I might have fried the OT.
any suggestion and help is appreciated.
Thank you.
I am using resistors to decrease the B+ to 290 ish. I have already used the 'zener voltage dropping' method discussed on this site. But 4 zener diodes in series on the filter capacitor did not bring it down. So I used three 50 ohms resistors in series( 75 ohms 25 watt) soldered into B+ before it hit the rectifying diodes.
I turned on the amp and played for 10/15 secs, then powered off. On second power up, the amp has no sound. Is it possible that I might have fried the OT.
any suggestion and help is appreciated.
Thank you.
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- Bieworm
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Re: B+ on a superlite tmb
First.. what’s the B+ you start with before dropping it? I mean, how much do you intend to drop?
Second.. I find it very weird that the zeners don’t drop any voltage. Did you orientate them correctly?
Third.. resistors are not that great nor efficient to drop voltage at that position. I suggest to use an appropriate power transformer with the right voltage to start with.
No sound can mean a lot. But a fried OT is very unlikely. Can you post pics if the amp? Also, a voltage chart with the actual voltages would be very helpful
files/JMPGuitars_18_Watt_Superlite_TMB_ ... _Chart.pdf
Second.. I find it very weird that the zeners don’t drop any voltage. Did you orientate them correctly?
Third.. resistors are not that great nor efficient to drop voltage at that position. I suggest to use an appropriate power transformer with the right voltage to start with.
No sound can mean a lot. But a fried OT is very unlikely. Can you post pics if the amp? Also, a voltage chart with the actual voltages would be very helpful
files/JMPGuitars_18_Watt_Superlite_TMB_ ... _Chart.pdf
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Re: B+ on a superlite tmb
Correction:
"I turned on the amp and played for 10/15 secs, then powered off. On second power up, the amp has no sound. Is it possible that I might have fried the OT, because one end of B+ was not soldered. I soldered it back on. But still no sound, and very low voltage on filter capacitor.
any suggestion and help is appreciated.
"I turned on the amp and played for 10/15 secs, then powered off. On second power up, the amp has no sound. Is it possible that I might have fried the OT, because one end of B+ was not soldered. I soldered it back on. But still no sound, and very low voltage on filter capacitor.
any suggestion and help is appreciated.
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- Bieworm
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Re: B+ on a superlite tmb
If low voltage on filter cap you might wanna look at the rectifier or even the power transformer.
What’s the voltage measured across the HV winding?
Are you using a SS or a tube rectifier?
Pics of the guts would be helpful.
What’s the voltage measured across the HV winding?
Are you using a SS or a tube rectifier?
Pics of the guts would be helpful.
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Re: B+ on a superlite tmb
I got the amp up and running. My AC main: 122.7; B+ 311AC; 218DC & 206DC on Filter cap (used 5 zener diodes 30v, 5watt ) OT plate voltage on power tubes 212V.
preamp V1: pin1: 105; pin3: .75, pin6: 83.2
Preamp V2: pin1: 142; pin3: 28.6, pin6: 41.1
EL84: pin7: 212DC on both
the amp sounds clean and i get fair amount of overdrive with gain at max and vol at 2. I am happy how it sounds with this voltage setting.. I would like to hear from experts if these voltages are within safe limit.
Thank you.
preamp V1: pin1: 105; pin3: .75, pin6: 83.2
Preamp V2: pin1: 142; pin3: 28.6, pin6: 41.1
EL84: pin7: 212DC on both
the amp sounds clean and i get fair amount of overdrive with gain at max and vol at 2. I am happy how it sounds with this voltage setting.. I would like to hear from experts if these voltages are within safe limit.
Thank you.
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Re: B+ on a superlite tmb
That doesn't make sense. I'm assuming when you say B+ you actually mean the PT secondaries (311-0-311). B+ is the DC rectified voltage coming from your rectifier tube or diodes. Target B+ is 345VDC.
For voltage reference and comparison, look at the voltage documents in the downloads section.
Thanks,
Josh
For voltage reference and comparison, look at the voltage documents in the downloads section.
Thanks,
Josh
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Re: B+ on a superlite tmb
When you do the math based on his voltages he’s using a 225-0-225VAC or 0-225VAC secondary. But I’m afraid that will remain a mystery. OP doesn’t do the answering questions thingyJMPGuitars wrote: ↑Mon 01/01/24 7:25 pmThat doesn't make sense. I'm assuming when you say B+ you actually mean the PT secondaries (311-0-311). B+ is the DC rectified voltage coming from your rectifier tube or diodes. Target B+ is 345VDC.
For voltage reference and comparison, look at the voltage documents in the downloads section.
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Re: B+ on a superlite tmb
He said five 30V 5W Zener diodes to drop B+??
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Re: B+ on a superlite tmb
Right! In that case I still think he’d better use a suitable transformer. There is an awful lot of waste/heat thrown away
For my 6AQ5 amps I use a 250-0 VAC HT secondary transformer, and I still need to zener the B+ down like 25V
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Re: B+ on a superlite tmb
Yes, but we don't know what he's using. Even if the Zeners are poorly placed at ~50% efficiency, he's dropping around 75V. If they're after the first filter cap, that's 150VDC! Why?? Get the right PT, or set the right targets.
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