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PostPosted: Thu Jun 11, 2015 10:35 pm 
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Well, I've finally completed my tweed build and tested as recommended. Unfortunately some of my voltage readings are low. I took a chance and found that the amp does work but at a substantially reduced volume. Here are my voltage readings. Any help or advise would be welcome.

With rectifier tube installed - plate voltages as follows V1 pin 1 301 V pin 6 305 V, V2 pin 1 292 V pin 6 298 V, V3 490 V, V4 490 V

With all tubes installed - V1 pin1 22 V pin 3 0.32 V pin 6 20 V pin8 0.32, V2 pin1 35.3 V pin3 0.09 V pin6 38.1 V pin7 2.5 V pin8 3.9 V
V3 pin3 456 V pin4 53 V pin 8 2 V, V4 pin3 456 V pin4 53 V pin8 3.1 V

The amps does work, little to no hum or noise, volume is a fraction of expected. I also noticed that one of the 0.1 uf 400v caps reads 0 or close to it when all powered up, all other caps test for higher voltages. Not sure if this is significant.


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PostPosted: Fri Jun 12, 2015 8:02 pm 
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Check for bad connections to R22. Also make sure its value is 4.7K. Recheck all your wiring, solder connections and make sure all the right parts are in the right places. Looks like the the power supply is OK and the amp wants to work, but most of it isn't getting the voltages it needs.


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PostPosted: Tue Jun 16, 2015 11:09 am 
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Thanks for your response, I have verified R22 is correct value, I will go over everything again and retest as recommended and get back. Thanks!


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PostPosted: Tue Jun 16, 2015 7:28 pm 
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Just a long shot but when you verified R22 as 4.7k did you actually measure it, I only ask because a similar problem was recently reported by another builder where a 47k resistor was apparently in the kit by mistake, just wondering if the Red vs Orange bands are hard to see and being mixed up with 4.7k/47k

Similar issue here:
viewtopic.php?f=11&t=3927


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PostPosted: Tue Jun 16, 2015 10:47 pm 
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Joined: Thu Jun 11, 2015 10:17 pm
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Wow, you nailed it. A rookie mistake on my part. I just finished messaging Stephen, it's actually a 470k resistor, yellow violet YELLOW gold. Am I safe to assume this would cause my issue? I discovered this when I started my "check everything again" exercise. I started to investigate further on it's value when it became hard to get an actual reading from the resistor with my meter, intermittent readings that jumped around.


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PostPosted: Wed Jun 17, 2015 10:12 pm 
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All your voltages beyond R22 are way too low, so yes, that resistor being 100 times too big would account for that!

There are no 470K resistors in the standard amp. Looks like you received it by mistake. A red-yellow mistake is a bit more obvious than a red-orange one, but it can happen. And it's not just a rookie mistake, it can happen to the best of us!

You can save the 470K and try using it for the grid stopper mod on pin 7 of V2. You might find that improves the sound of the amp.


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PostPosted: Thu Jun 18, 2015 1:02 pm 
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Replacement resistor on it's way. I'll post with result of correct component when I install. Thanks!


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PostPosted: Wed Jun 24, 2015 2:03 pm 
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Prompt and exceptional service from Stephen, the replacement resistor arrived and was installed last night. Problem solved! The amps works beautifully! It really exceeded my expectations. I need more time to get acquainted but so far so good and very quiet at idle as well! Thanks to all who set me in the right direction, much appreciated!


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PostPosted: Sun Jun 28, 2015 12:04 am 
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Thanks everyone for chipping in to help! Good advice to measure parts before installing them

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