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Old 5th March 2020, 08:58 AM   #1
gorko1 is offline gorko1  Slovenia
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Default TSE II - problem with heater regulator

Dear friends,

Please help me to find the problem on my TSE II board (300B tubes)

- T1-GRN1 - T1-GRN2 - measuring 6,3VAC - OK
- jumper from 3-4 - OK
- R2=300R - OK
- R1=100R - OK
- IC3 orientation/soldered - OK
- D1 orientation/soldered - OK
- D5/D4 orientation/soldered - OK
- heater voltage on both 5842 sockets = 7,6VDC - OK
- heater voltage on 300B = 0 ( zerro) !!!
- MIC29502WT - input voltage on PIN2 = 7,6VDC - OK
- MIC29502WT - output voltage on PIN4 = 0 (zerro)
- changing MIC2902WT - still same problem !
- no smoke or anything suspicius, regulator temperature moderate
- HV = OK

I'm really lost here....

BR,
Goran
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Old 6th March 2020, 06:12 PM   #2
gorko1 is offline gorko1  Slovenia
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still nothing...I have resolder all points around regulator and still no voltage on output pin.....on input pin is 7,6vdc...

br,
Goran
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Old 6th March 2020, 10:44 PM   #3
MikeR is online now MikeR  United States
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Goran,

Wish I could help. Is there any dc voltage at the junction of R1 and R2? C3 looks to be oriented correctly, make sure there isn't a solder bridge on C3 that would short it to ground.
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Old 6th March 2020, 11:25 PM   #4
rayma is offline rayma  United States
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You should post the schematic here. A much better, close photo of both pcb sides is also needed.

Last edited by rayma; 6th March 2020 at 11:38 PM.
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Old 7th March 2020, 12:22 AM   #5
Tubelab_com is offline Tubelab_com  United States
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Quote:
You should post the schematic here.
Schematic is in post #1 here:

After a 14 year run, the TSE must DIE!

I don't see any obvious build errors.

The first thing I would do is to measure the resistance across the filament pins with no tubes installed. I get 400 ohms on my board in either direction after the readings settle. The pins are rather close to each other and it would be easy to create a short.
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Old 7th March 2020, 10:31 AM   #6
gorko1 is offline gorko1  Slovenia
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Hello Friends,

Look this nice solder bridge bettwen pins...
It made me almost nuts
Now is all ok ...5v on 300b heaters...
Huhhh...I will post finished amp on gallery soon...
Thank you all...

Goran
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Old 7th March 2020, 11:20 PM   #7
Evenharmonics is offline Evenharmonics  United States
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An old saying for carpenters / builders goes, "Measure twice and cut once." For solder heads like us, it's "Check twice and power up once."
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Old 1st April 2020, 07:57 AM   #8
gorko1 is offline gorko1  Slovenia
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Dear Frinds,

After few weeks of listening the TSEII I have still some problems.
I always had some felling that left channel is slightly louder than the
right channel....
Yesterday I have checked with fingers left channel 300B and to my surprise It was just slightly warm...no problem to hold fingers on it...
Right channel tube was very hot and you can burn your fingers easily...
I have immediately check the bias and It all looks ok... 80mA on both 300B and 174V on driver tubes... Then I swap the tubes from left to right and problem is still there on right channel. I have also measured V-out from amplifier with sinwave and I get 13,1VAC on left and 12,75VAC on right channel.
Do you have any idea what is wrong. Maybe bad mosfet ?



BR,
Goran
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Old 1st April 2020, 01:19 PM   #9
Tubelab_com is offline Tubelab_com  United States
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If the tubes are both set at 80 mA, and they are fed by the same power supply, then they must be dissipating the same amount of power, and therefore shedding the same amount of heat. Recheck the 80 mA now that the amp has run for a few weeks, since new tubes can drift around for a while. If they are the same, then there is probably some difference in the air flow or reflectivity in the area surrounding the tubes that explains the difference in glass temperature. The temperature on the glass can vary a LOT depending on where you touch it, be careful.

Quote:
I get 13,1VAC on left and 12,75VAC on right channel.
This is a channel imbalance of less than 3%, or 0.24 dB which isn't bad. The usual reasons for channel imbalance are component variations, usually the driver tubes or the volume pot (often rated at 10% or worse).

The 300B's contribute only a little of the total amplifier's voltage gain. The most gain comes from the 5842's, so this is where the imbalance lies.

Try swapping the 5842's to see if anything changes. A slight change in the plate voltage adjustment can affect the gain, so a few volts either way can improve the channel balance.
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Old 1st April 2020, 06:15 PM   #10
gorko1 is offline gorko1  Slovenia
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Quote:
Originally Posted by Tubelab_com View Post
If the tubes are both set at 80 mA, and they are fed by the same power supply, then they must be dissipating the same amount of power, and therefore shedding the same amount of heat. Recheck the 80 mA now that the amp has run for a few weeks, since new tubes can drift around for a while. If they are the same, then there is probably some difference in the air flow or reflectivity in the area surrounding the tubes that explains the difference in glass temperature. The temperature on the glass can vary a LOT depending on where you touch it, be careful.



This is a channel imbalance of less than 3%, or 0.24 dB which isn't bad. The usual reasons for channel imbalance are component variations, usually the driver tubes or the volume pot (often rated at 10% or worse).

The 300B's contribute only a little of the total amplifier's voltage gain. The most gain comes from the 5842's, so this is where the imbalance lies.

Try swapping the 5842's to see if anything changes. A slight change in the plate voltage adjustment can affect the gain, so a few volts either way can improve the channel balance.
Thank you George for datiled answer! With changing plate voltage on drivers I prfectly set the voltage on output and now is all ok...much more balanced sound... still one 300b much more hot...but donít care any more...its sounds perfect now...

BR
Goran
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