Tubes are not glowing

zlib · 8808

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Offline zlib

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on: September 26, 2015, 11:49:27 PM
3 years ago I was a happy owner of Crack but one day left channel stopped working, then the other. I didn't solve the problem and left Crack for better times...
Some weeks ago I decided to revive my Crack but I found a lot of rust on RCA jacks and screws (ambient conditions were not very good). I changed RCA jacks, volume pot (Alps 100K) and headphones jack. Also I changed two large ceramic resistors (3K 10W) for another pair (3K9, 10W) and changed some wires to Oyaide 18 AWG. So, I disassembled my Crack and rebuilt it from scratch.
In previous topic we solved the resistance check problem: http://bottlehead.com/smf/index.php?topic=8417.0 Now I have another problem. When I turn it on the tubes are not glowing.
I checked power entry socket and power switch - they show signal from one side to another. The capacitors show some signs of life too (the values on my meter gradually change). So, where the problem might be? Is it power supply, bad tubes or something else? Is it safe to do a voltage check if the tubes don't glow?
« Last Edit: September 27, 2015, 12:00:55 AM by zlib »



Offline zlib

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Reply #1 on: September 27, 2015, 02:17:10 AM
Is it safe to check voltages if the tubes don't glow?



Offline kgoss

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Reply #2 on: September 27, 2015, 03:19:32 AM
Start with the resistance test.  If you pass that then move on to the voltage test.

Ken Goss


Offline Doc B.

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Reply #3 on: September 27, 2015, 04:15:59 AM
Since your first issue was resolved by resoldering a questionable connection I would suggest reflowing your solder joints with a hot iron one more time to make sure they are all conducting. Run the resistance check again, and then check voltages.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline Paul Birkeland

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Reply #4 on: September 27, 2015, 06:25:44 AM
Also I changed two large ceramic resistors (3K 10W) for another pair (3K9, 10W)
That's not a suitable replacement.

A voltage check will help locate the problem.

(The aftermarket headphone jack and volume pot with pins in conjunction with stranded wire will render your Crack very difficult to repair in the future)
« Last Edit: September 27, 2015, 06:28:03 AM by Caucasian Blackplate »

Paul "PB" Birkeland

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Offline zlib

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Reply #5 on: September 27, 2015, 07:11:44 PM
Here are my voltages. Please, be aware that I live in 230V country.

Terminal - voltage
1 - 220
2 - 240
3 - 0
4 - 240
5 - 220
6 - 0
7 - 0
8 - 0
9 - 0
10 - 0
11 - 0
12 - 0
13 - 230
14 - 0
15 - 240
20 - 0
21 - 240

A1 - 230
A2 - 0
A3 - 0
A4 - 0
A5 - 0
A6 - 230
A7 - 0
A8 - 0
A9 - 0

B1 - 230
B2 - 240
B3 - 0
B4 - 230
B5 - 240
B6 - 0
B7 - 0
B8 - 0
« Last Edit: September 30, 2015, 09:53:30 PM by zlib »



Offline zlib

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Reply #6 on: September 30, 2015, 10:04:53 PM
Looks like everybody are too busy to help me further (or my problem is too difficult)... Meanwhile I found bad joint at terminal 12 and resoldered it. Also one of the LEDs (from center to A8) looks dead (my meter doesn't show anything in either direction). Is this LED the source of my problem or is it just a result?

And some update on resistance check. I have 3.8K on terminals 7, 9, B3, B6 (because my big resistors are 3K9 10W, I guess). Is it fatal or not?
Also the resistance on terminal 13 doesn't change slowly like the manual says, it changes chaotically in both directions. Is it normal?



Offline Doc B.

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Reply #7 on: October 01, 2015, 05:36:51 AM
Once you make a change like fixing the bad solder joint at 12 it is time to remeasure your voltages and post any terminal voltages that are not to spec, as they have probably changed.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline zlib

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Reply #8 on: October 01, 2015, 06:08:48 AM
I remeasured voltages but they are the same as I posted earlier.

As you can see, I have nothing on terminals 7, 9, A3, A8, B3, B6 (but there must be something as manual says). The resistance check is OK now (with the exception of 3.8 KOhms on terminals 7, 9, B3, B6 instead of 2.9 KOhms - because of different resistors). And the LED from center A-pin to A8 looks dead (is it the source of all problems or is it just a result?)
« Last Edit: October 01, 2015, 06:16:46 AM by zlib »



Offline Paul Birkeland

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Reply #9 on: October 01, 2015, 06:27:19 AM
What is the AC voltage between power transformer terminals 4 and 5?  That is the origin of the voltage that causes the tubes to glow.  Without tubes glowing, you will have the symptoms you describe.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline zlib

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Reply #10 on: October 01, 2015, 06:40:28 AM
Meter shows something about 5.8 V between power transformer terminals 4 and 5.



Offline Paul Birkeland

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Reply #11 on: October 01, 2015, 06:41:42 AM
Now measure AC voltage between B7 and B8.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline zlib

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Reply #12 on: October 01, 2015, 06:49:42 AM
Between B7 and B8 I have 0.



Offline Paul Birkeland

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Reply #13 on: October 01, 2015, 11:18:53 AM
Ok, well, one of the two wires going from power transformer terminals 4 and 5 isn't making contact over there.  This can be a soldering issue or a broken wire.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline zlib

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Reply #14 on: October 01, 2015, 09:51:41 PM
Ok, well, one of the two wires going from power transformer terminals 4 and 5 isn't making contact over there.  This can be a soldering issue or a broken wire.

Thanks! That was the case! I attached the wire from power terminals 4 and 5 to B7 and B8 but didn't solder them at B7 and B8. Now the big tube glows but the little one doesn't. Only one LED glows and the other (at A8) doesn't.
Now the voltages at mentioned terminals are:
7 - 150
9 - 100
A3 - 0 (but the LED glows here!)
A8 - 80 (the LED doesn't glow here!)
B3 - 150
B6 - 100

The difference between 7 and 9, B3 and B6 may be because of the dead LED at A8? So, I just need to replace it and everything will work OK, right? Or do you see another problem in my voltages?