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Old 18th October 2008, 03:49 AM   #1
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Default New Build Power Up Advice

I'll be getting my OPT's for my Darling delivered in a couple of weeks and was wondering if ya'll could give some advice for the initial power up of my first DIY amp with HV? I have done some searching and found hints here and there, but nothing definitive. and in one spot.

Here is my line of thinking: Please correct me or make suggestions....

...Check, recheck, and check again wiring scheme......

1. No tubes inserted. Check that PT and filament trafo are not getting hot when mains power is supplied.
2. Insert all tubes except rectifier. Check filament voltages.
3. Make sure bleeder resistors (100K/2W) are installed across the 3 motor run caps in PS (or is one good enough?)
4. Insert rectifier (5Y3GT). Add 100W lightbulb in the hot leg of the mains before Power trafo.
5. Hook up a meter from B+ of each leg, right before OPT's, to ground to check B+ voltage after power up.
6. Insert some 8R/100W resistors across speaker outputs, or use some of my cheapo speakers as a load.
7. Insert shorted RCA plugs into RCA input jacks. NO SIGNAL.
8. Switch on amp from power strip and watch lightbulb. If it doesn't dim instantly shut off power.
If it dims, check meters quickly to see where B+ is. Don't let run more than 30 sec or so.
9. Power down. Smell for anything burning or burnt if it hasn't happened already.
10. Check cap voltages to see if they drained and visually inspect for anything burnt after checking that voltages are safe.
11. If all OK, hook DMM across cathode resistors,power back on and check bias voltages. If OK let run for 5-10 minutes and keep an eye on the plates, bias voltages, and B+ voltage.
12. Power down, make sure PS caps dare drained, and visually inspect again.
13 . If still OK, hook up mini CDP and see if the dang thing makes sounds that don't sound like crap.

14. Wish you had a Variac for this kinda stuff. Reminder to self--find one.
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Old 20th October 2008, 01:03 PM   #2
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Old 20th October 2008, 03:36 PM   #3
kevinkr is offline kevinkr  United States
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Sounds reasonable, a little more involved than I generally do.. You need to wait for the tubes to warm up. Initially the lamp will be very bright as the filaments are cold, as they warm up the lamp will dim, and then as it starts to draw plate current the lamp will brighten significantly - at this point measure your B+.. You will probably find it is rather low, but if present everywhere and no burning smells are evident you are probably ready to apply full supply voltage.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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Old 20th October 2008, 11:28 PM   #4
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Thanks for the advice, Kevin.

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Old 20th October 2008, 11:56 PM   #5
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My usual scheme is:
1. Wire primary power, check.
2. Wire voltage rectifiers, regulators.
3. Made preamp stages, tune them.
4. Connect one output stage, fine tune one channel.
5. Connect another channel output stage, fine tune it.
6. Connect speakers instead of dummy loads, listen and enjoy.
The Devil is not so terrible as his math model is!
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Old 21st October 2008, 03:06 PM   #6
Sherman is offline Sherman  United States
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For my first power-on I generally connect the power to an extension cord plugged into a switchable outlet across the room and turn on the power from there.
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