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Old 8th March 2017, 10:11 AM   #231
diyAudio Member
Join Date: Jul 2010
Raindance. Try reading a little closer Stop with the Radiance.
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Old 8th March 2017, 11:05 AM   #232
diyAudio Member
Join Date: Jan 2011
oops! my bad
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Old 8th March 2017, 11:07 AM   #233
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Join Date: Jan 2011
Originally Posted by RobFreak View Post
I could use some EL34. Which ones do you have, sorry for asking such a vague questions, i bet you have TONS! ;-)

I will have a dig through some boxes for you shipping would be the killer as I am based in Australia
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Old 9th March 2017, 10:53 AM   #234
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Join Date: Jan 2011
I finished off the amp tonight, double checked the polarity of all caps and resistor values, isolation for terminals, continuity to all grounds. All looked good so I switched it on.

no smoke, no sparks, no smell!

I checked the voltages are measuring

AC input 236V
Rectifier 301V
Rectifier 5V
Heaters 6.1V
heater 3.2V
I forget the measurement after the choke but it was in range.

first thing I noticed these 6P3P tubes are NOISY when they heat up.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Problems so far.

right channel has no output
volume pot is wired backwards and absolute crap quality

both should be east to resolve and I will let it sing this weekend
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Old 9th March 2017, 06:20 PM   #235
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Join Date: Jul 2015
Smile Do "improved" version


Do upgrade as raindance suggest "improved" version #179

Look at schematic. Those 100R resistors in heaters should quieten 6P3P.

Change volume POT to ALPS Blue Velvet 100K as I suggested in post #186

Change cathode electrolytic capacitors to Panasonic FM, FC or other better quality.

Change power supply capacitors to better quality. Change grid capacitor 0.33uF to Hi-End audio capacitor.

Tell us the result
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Old 11th March 2017, 07:51 AM   #236
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Join Date: Jan 2011
Thanks big t,

much appreciated! nice to have the links in the same place.

one of the supplied 6P3P tubes was DOA so I replaced them with some 6N3C-E coin base NOS Reflektors I had and got the amp singing today. I also replaced the pot with a 100k alps and the hum is now ZERO.

I can say I am honestly very impressed with the sound, very natural and balanced.

After burning in for a few house I fiddled with the feedback loop and settled on 50k.

Raindance, you are right this thing runs HOT!! the transformer wires are rated at 130deg C and the core is 75deg after a few house of use. I will construct a simple step down and see if it runs cooler, a second transformer for the heaters is not out of the question. before hacking up the chassis I want to see how good i can get it to sound with basic changes. As you say I would not leave it unattended at the temps its running now.

Already ordered Russian PIO caps and some better resistors for a few $$$
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Old 18th March 2017, 08:24 AM   #237
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Join Date: Jan 2011
I swapped out the Chinese 6P3P power tubes with a pair of NOS Philco 6L6GA power tubes with a plate dissipation of 19W and swapped the Chinese 6N1 for a Vokshod 6N1P-EV. the amp sounds very alive and runs cooler? measured the power transformer before and it was running 75 degrees and now its steady on 50 degrees.

The amp is dead silent when switched on and then develops a hum that gets louder and louder after an hours use. (through the speakers)

probably need to replace the caps, but I am hoping the power transformer is not overheating or already cooked.
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Old 18th March 2017, 12:18 PM   #238
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Join Date: Jul 2015
By the way after 1,5 years of amlifier usage, got short in primary winding of the power transformer. It was always very hot. I used soviet 6P3S, 6N1P-EV and 5C4S. Tranformer price from China is around 85 EURO. Power transformer is made not acording "the rules". I think new replacement trafo will be the same very hot and got short soon. Maybe someone has experienced "the right" power trafo?
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Old 18th March 2017, 01:28 PM   #239
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Join Date: Mar 2017
Default Fuses at secondary winding

Hi, I'm going on to build up this amplifier and was wondering: there are no Fuses at secondary winding, is this ok?
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Old 31st March 2017, 12:52 PM   #240
Simbad is offline Simbad  United Kingdom
diyAudio Member
Join Date: Mar 2017
Hi, I've been a stalker for a while and really enjoying the help offered by the forum's members.

I received this amp kit as a birthday gift from my wife and can't wait to start the build. I'll be using the stock components that came with the kit so I have a reference when I start modifying with the suggested upgrades in this thread, capacitors, pot, tubes etc..
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