Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: MoparWade on June 28, 2016, 01:58:17 am
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Finished my circuitry for my first amp, a Twin Reverb. Everything seems fine so far but wanted to run it past everyone to make sure I am not missing something. For first power up I used a current limiter with no tubes in amp. On in standby no lamp, switched standby off and bulb in current limiter lit up just briefly but I assumed that was just the capacitors charging. Installed tubes and turned on, still on CL in standby, all filaments lit up and no activity from CL. Switched standby off and CL bulb lit up but only dimly and remained on, assumed that is normal. Have attached a couple pictures just because. If anything sounded wrong please let me know. Next step is to bias the tubes which I assume must be done without the current limiter?
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What size lamp?
Current is flowing in the bulb. It will get warm. How-warm depends on the relative Watts of the lamp and the amp. A 25W is too small to feed a Twin. I'd use 100W-200W to get near-normal voltages without risk of major fire. This is really just a net for major mistakes. At some point you have to lose the lamp and try the amp.
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Finished my circuitry for my first amp, a Twin Reverb. Everything seems fine so far but wanted to run it past everyone to make sure I am not missing something. For first power up I used a current limiter with no tubes in amp. On in standby no lamp, switched standby off and bulb in current limiter lit up just briefly but I assumed that was just the capacitors charging. Installed tubes and turned on, still on CL in standby, all filaments lit up and no activity from CL. Switched standby off and CL bulb lit up but only dimly and remained on, assumed that is normal. Have attached a couple pictures just because. If anything sounded wrong please let me know. Next step is to bias the tubes which I assume must be done without the current limiter?
Looks really nice... I'll be following you on this one. Nice clean work - good job
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What size lamp?
It's a 250W bulb. However, it's a 3-way bulb so I'm unsure as to whether it is appropriate for a current limiter.
Looks really nice... I'll be following you on this one. Nice clean work - good job
Thanks! That means a lot coming from someone who builds such beautiful amps.
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Sweet looking set up! Big project. I use a 300W bulb in my current limiter. I would think that you fire it up with the current limiter, watch for smoke then check voltages......when all that checks out, no need for the current limiter and then bias your tubes. That's what I did on my scratch supro. And, yep, fired that sucker up and quickly smoked a power rail resister due to a short.
Good luck!
Bart
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It's a 250W bulb. However, it's a 3-way bulb so I'm unsure as to whether it is appropriate for a current limiter.
When you put a 3-way bulb in a 1-way socket it becomes a 1-way bulb at the middle wattage rating..
So say the 3-way bulb is 50/200/250, it will now be a 200 watt bulb
Nice work, by the way!
:thumbsup:
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I use a 300W bulb in my current limiter.
That's way to big a wattage bulb for 1st turn on, for most amps 60w to 100w. The larger the wattage bulb the less protection it gives.