EVH 5150 III: 50 vs 100 watt

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marshallnoise
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Re: EVH 5150 III: 50 vs 100 watt

Post by marshallnoise » Sat Apr 20, 2019 1:55 am

Alright, I reran all of the voltage tests and the biggest problem I see is that TP44 I should have 263VDC and I am getting 32VDC.

This is the Phase Inverter V9 pin 6. I have swapped tubes and I had the same condition.

The only thing I can think of is that the Flame Proof 1W 100K resistor is shorted. When I measure it in circuit...I get OL. So that seems like its a bad resistor.

Once the amp cools down, I will de-solder it and test it out of circuit.

Getting there.

EDIT:
Yep, bad resistor. I will be installing a new one tomorrow morning and seeing if that fixes it!

marshallnoise
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Re: EVH 5150 III: 50 vs 100 watt

Post by marshallnoise » Sat Apr 20, 2019 5:19 pm

Ok, so I figured it out. The 100K resistor swap did the trick. Voltages back to normal.

I still had the hum as evidenced below.

https://www.youtube.com/watch?v=8Del8Jz9jbc

Then I did some tube swapping.

Still had the hum. But I was getting some mechanical noise from the power tubes. Not rattling but a vibration when I tapped the tubes. See below.

Boingggggg!
https://www.youtube.com/watch?v=Ta020uihZCc

I then grabbed another set of 6L6s and plugged them in. Noise gone!

:champ:

Still requires a 1A fuse instead of the 250ma fuse. But that's not a huge deal. I do think a full recap might be a good idea. Its not that old but I don't know the history of these caps or the amp. Gonna rock this amp this weekend at church and see what happens.

Oh, and the mod I settled on for reducing the channel 1 volume discrepancy between green and blue was R79 increasing to 47K. I tried R88 increasing to 380K and it REALLY screwed up the blue channel's tone. I always felt the blue channel was too much anyway so increasing the output on the green channel to match the blue did the trick. Yes, it overdrives faster, but for me, running channel 1 low on preamp gain gives me plenty of juice on blue and that leaves red for the heavy stuff!

Thanks for sticking with me on this!

J Saw
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Re: EVH 5150 III: 50 vs 100 watt

Post by J Saw » Fri Aug 16, 2019 4:17 pm

Hi all,
Thanks for having me. :)
Could someone please tell me which resistor is choke in a 50w el34 5150?
I'd like to do a choke upgrade/addition.
Thanks for any insight

J Saw
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Joined: Fri Aug 16, 2019 4:12 pm
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Re: EVH 5150 III: 50 vs 100 watt

Post by J Saw » Fri Aug 16, 2019 4:34 pm

Anyone know what resistor for choke addition?

marshallnoise
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Re: EVH 5150 III: 50 vs 100 watt

Post by marshallnoise » Sat Dec 21, 2019 10:40 am

I wouldn't use a resistor for a choke (I know people do), I would actually add a Marshall 50 watt actual choke. They are like 20 bucks or so.

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