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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 9th September 2018, 04:22 PM   #1
dasa2131 is offline dasa2131  United States
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Location: Asheville NC
Default TSE - tried for the first time

Hello everyone,

Last night I tried firing up my TSE for the first time. I'm having several problems. At first I couldn't bias the right channel any higher than about 68mA (pot 12 was fully clockwise). Here's what the voltages looked like:

B+ 373
B- 240
Rt plate 172
Lt plate 174
Rt bias .684
Lt bias .704

I connected up some 8 ohm speakers and an MP3 player. I had to turn up the volume knob on the TSE to full and the MP3 player output volume to full before I could hear any sound. The music sounded anemic with almost no bass.

Then something happened. I don't know what I did other than constantly trying to adjust the plate voltages and try to keep the bias voltages around .70. The left plate voltage shot up to 376. I turned pot 20 all the way counterclockwise, but the left plate voltage wouldn't come down. Here are the readings:

B+ 386
B- 242
Rt plate 189
Lt plate 376
Rt bias .578
Lt bias .594

I just shut off the amp at this point. I couldn't smell or see anything that looked bad.

I using 300b tubes and Edcor XPWR131 power transformer and GXSE15-3.5k output transformers. I have removed R4 and replaced it with the Triad C14X choke. I also have the big round run capacitor installed in parallel with C5.

Sorry for the long post - any suggestions would be greatly appreciated!

Thank you,

Dave
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Old 9th September 2018, 07:37 PM   #2
w5jag is offline w5jag  United States
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Location: Arkansas
Quote:
Here's what the voltages looked like:

B+ 373
B- 240
Rt plate 172
Lt plate 174
Rt bias .684
Lt bias .704
I've not used 300B's before, but those numbers look OK to me.

Quote:
I had to turn up the volume knob on the TSE to full and the MP3 player output volume to full before I could hear any sound. The music sounded anemic with almost no bass.
Probably incorrect input wiring, possibly inadvertantly grounded. Pictures of all the connections from the input jacks, to the board, and any in between, might help someone identify the problem.

Quote:
Lt plate 376
Assuming this is the plate of the left 5842, and that it is an accurate measurement, I would suspect the left 10M45 current regulator has failed and is, essentially, a short. I'm not sure there is any other way to get the full B+ on the 5842 plate.

Win W5JAG
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Old 9th September 2018, 10:28 PM   #3
Evenharmonics is offline Evenharmonics  United States
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Your power transformer or output transformers should be reoriented to avoid magnetic coupling (possible hum).
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Old 10th September 2018, 08:56 AM   #4
PDL is offline PDL  United States
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Quote:
Originally Posted by Evenharmonics View Post
Your power transformer or output transformers should be reoriented to avoid magnetic coupling (possible hum).
Agreed +1
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Old 11th September 2018, 01:35 AM   #5
dasa2131 is offline dasa2131  United States
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W5jag,

I owe you a big thank you and a beer! I have ordered a few more of the 10M45's. Your comment about checking my wiring of input wiring lead me to discover I ordered (and soldered) the wrong resistors for R8 and R19. They are supposed to be 120k ohm, and I installed 120 ohm. I also made the same mistake for R15 and R26. I'm an idiot. I hope I didn't wreck my tubes.
I'm not really excited about removing the dead 3 pin 10m45, but I'll do my best. Any suggestions?

Thanks again,

Dave
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Old 11th September 2018, 05:25 AM   #6
w5jag is offline w5jag  United States
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Cut the dead part loose from its leads, then one at a time heat the stubs that are left with your soldering iron, and remove the stubs with needle nose pliers. If any solder is left, you can remove it with solder wick.

Tubes are hard to wreck, so I wouldn't worry much about them.

You're welcome!

Win W5JAG
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Old 13th September 2018, 01:05 AM   #7
TheGimp is offline TheGimp  United States
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Another option is a SOLDAPULLT desoldering tool.

The Original Deluxe SOLDAPULLT: EDSYN Inc.

Cut the lead off, heat it with a soldering iron, and suck it out.
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Old 13th September 2018, 01:28 AM   #8
dasa2131 is offline dasa2131  United States
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Mr. Gimp,

Thank you for replying - yes I have one of those. I haven't tried removing the 4 resistors and the two 10m45's yet, but I'll probably end up trying the solder wick and the soldapullt. By the way, I see you don't live too far from me - I'm in Mills River, NC (just a little south of Asheville).

Regards,

Dave
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Old 15th September 2018, 12:40 AM   #9
dasa2131 is offline dasa2131  United States
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I would love to get help from the experts! I replaced both of the 10M45's. I also put in the proper 120k ohm resistors for R8, R15, R19, and R26 (instead of the 120 Ohm resistors I foolishly installed).

When I fire up the unit, here's what I get:

R+ 421
R- 253
L Plate 172
R Plate 168
L Bias .555
R Bias .011

I can't bring up the Right bias voltage at all. I've tested with two different meters. I've tried swapping the output tubes - it doesn't follow with the tubes. I have the right bias trim pot turned all the way clockwise, and the voltage just doesn't rise. I confirmed this by playing some music - I hear nothing from the right channel. The left channel plays, but I can't get it very loud.

Any suggestions for what I should check?

Thank you,

Dave
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Old 16th September 2018, 12:48 AM   #10
dasa2131 is offline dasa2131  United States
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I got it working!!! Thank you George and everyone else that's responded to my dumb questions. It's playing now and sounds great. Here's what I measure:

R+ 383
R- 283
L Plate 174
R Plate 174
L Bias .698
R Bias .703

I ended up having to change out the MOSFETS (Q1 and Q2) and I also changed out R14 and R25 from 20K to 36K ohms.

Several people have told me I need to re-orient my power transformer so as not to cause a 60 Hz Hum. I'm using 99db efficient speakers and I hear absolutely no hum at all. As a result, I will not re-orient the power transformer.

At this point my only question is about R-. It's 283 VDC. Is this the right value? If not, how do I change it?

Thank you!

Dave
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